Guide to Preventing Parasites.pdf - Royal Canin Canada

GUIDE TO
PREVENTING
PARASITE INFECTIONS
COMPANION ANIMALS
Dr Alain Villeneuve, DVM, PhD
Professor of Parasitology
Faculty of Veterinary Medicine
University of Montréal
alain.villeneuve@umontreal.ca

GUIDE TO PREVENTING PARASITE INFECTIONS IN COMPANION
ANIMALS
Dr Alain Villeneuve, DVM, PhD, Professor of Parasitology, Faculty of Veterinary
Medicine, University of Montréal, alain.villeneuve@umontreal.ca
Parasites in our pets have been a major concern for a long time, especially after it was
realized that some of them are transmissible to humans. However, our knowledge of
these parasites has improved considerably over the past few years, and new species have
been described. Diagnostic methods are becoming increasingly sophisticated, more
powerful drugs are breaking into the market, and the prevalence rates seem to be on the
decline. This has led us to re-examine our entire approach in order to better adapt our
interventions. Organizations which bring together specialists from various health-related
fields have issued official recommendations that apply to the entire continent. However,
adopting them sometimes poses major challenges. This guide includes all the necessary
information for understanding the recommendations and adapting them to different
situations.
_____________________________________
Dr. Villeneuve received his DVM in 1978 and PhD in Parasitology in 1990 from the University of
Montréal, Québec. He is currently Associate Professor in the Department of Pathology and Microbiology,
Faculty of Veterinary Medicine, University of Montréal.
D.r Villeneuve is a member of many professional affiliations, including the World Association for the
Advancement of Veterinary Parasitology, the American Association of Veterinary Parasitologists and
the American Heartworm Society.
Last update: April 2008
2

Contents
1. Species reported in dogs and cats in Canada ………………………………... 4
2. Prevalence of the main species of parasites ………………………………… 6
2.1 Study results published in Canada ……………………………………. 6
2.2 Brigitte Guay’s study in 2004 ………………………………………… 8
2.3 Data obtained in our laboratory (2004 – 2006) …………….................. 10
2.4 Ticks …………………………………………………………………... 12
2.5 Zoonotic species ………………………………………………………. 14
3. Prevention ………………………………………………………………....... 17
3.1 Prevention or treatment? …………………………………………….... 17
3.2 The objectives of prevention ………………………………………….. 17
3.3 Current programs (CAPC) ……………………………………............. 18
3.4 A program tailored to our conditions …………………………………. 19
4. Diagnostic tools …………………………………………………………….. 22
4.1 Why use them? ……………………………………………………….. 22
4.2 Laboratory techniques ………………………………………………… 22
4.3 At-risk groups …………………………………………………............. 26
5 Drugs………………………………………………………………………… 27
5.1 How to read a label …………………………………………………… 28
5.2 A broad- or narrow-spectrum drug? …………………………………... 29
5.3 Drugs, parasites and treatments ………………………………………. 30
5.4 The residual effect……………………………………………………... 34
5.5 The effect against the different stages ………………………………… 35
5.6 Resistance to anthelmintics……………………………………………. 36
6. The case of heartworm …………………………………………………….... 37
6.1 Canine heartworm disease……………………………………………... 37
6.2 Feline heartworm disease……………………………………………… 41
7. The case of fleas …………………………………………………………….. 43
References …………………………………………………………………... 45
3

1. Species reported in dogs and cats in Canada
A number of species have been reported in dogs and cats in Canada. Since many pets
accompany their owners when they travel, it is now not unusual to also identify exotic
species from time to time. The following list does not, however, include these exceptional
cases, but only those species that are indigenous to our region.
Table 1. List of parasites indigenous to Canada
Protozoans
Specific to dogs Specific to cats In both dogs and cats
Trichomonas fœtus
Giardia spp.
Acanthomoeba spp. Entamoeba histolytica
Isospora ohioensis Isospora felis
Isospora canis Isospora rivolta
Isospora burrowsi
Cryptosporidium canis Cryptosporidium felis
Neospora caninum Hammondia hammondi Toxoplasma gondii
Besnoitia spp.
Hepatozoon americanum Cytauxzoon felis
Leishmania infantum
Trypanosoma cruzi
Sarcocystis cruzi Sarcocystis hirsuta
Sarcocystis tenella Sarcocystis arieticanis
Sarcocystis capracanis Sarcocystis gigantea
Sarcocystis miescheriana Sarcocystis porcifelis
Sarcocystis fayeri
Babesia canis
Babesia gibsoni
Flukes
Specific to dogs Specific to cats In both dogs and cats
Alaria canis Alaria marcianae
Alaria spp. Paragonimus kellicotti
Nanophyetus salmincola Methorchis conjunctus
4

Tapeworms
Specific to dogs Specific to cats In both dogs and cats
Diphyllobothrium spp.
Taenia hydatigena Taenia taeniaeformis
Taenia pisiformis
Echinococcus granulosus Echinococcus
multilocularis
Dipylidium caninum
Roundworms
Specific to dogs Specific to cats In both dogs and cats
Pelodera strongyloides
Strongyloides stercoralis
Ancylostoma caninum Ancylostoma tubaeforme Uncinaria stenocephala
Ollulanus tricuspis
Filaroides (Oslerus) osleri
Aelurostrongylus abstrusus
Angiostrongylus vasorum
Crenosoma vulpis
Toxocara canis
Baylisascaris procyonis
Spirocerca lupi
Toxocara cati Toxascaris leonina
Physaloptera rara
Acanthocheilonema
(Dipetalonema)
reconditium
Dracunculus insignis
Dirofilaria immitis
Trichuris vulpis Trichuris campanula
Trichuris serrata
Dioctophyma renale
Paersonema (Capillaria)
feliscati
Aonchotheca (Capillaria)
putorii
5
Trichinella spp.
Eucoleus (Capillaria)
aerophilus
Paersonema (Capillaria)
plica
Calodium (Capillaria)
hepaticum

Arthropods
Specific to dogs Specific to cats In both dogs and cats
Trichodectes canis Felicola subrostratus
Linognathus setosus
6
Ctenocephalides felis
Sarcophagidae (myiasis)
Calliphoridae (myiasis)
Cuterebra spp.
Ixodes scapularis
Ixodes cookei
Ixodes muris
Rhipicephalus sanguineus Dermacentor variabilis
Amblyomma americanum
Notoedres cati Sarcoptes scabiei
Demodex canis Demodex cati
Otodectes cynotis
Cheyletiella yasguri Cheyletiella blackei
Pneumonyssus caninum
2. Prevalence of the main species of parasites
Trombiculidae
First, it is important to know what the prevalence of the parasite species is in our region.
A few study results of the more common species were published in the past, and they
provide valuable information. For more recent data, we will use those obtained by Dr.
Brigitte Guay when working on her master’s degree and those obtained at the Diagnostic
Laboratory Service of the Faculty of Veterinary Medicine in Saint-Hyacinthe.
2.1 Study results published in Canada
The vast majority of the prevalence studies of canine parasites were published more than
25 years ago, specifically, between 1974 and 1979. Another was published in 1950. The
last two date back to 1986 and 1987. However, their results have little to do with our
current situation, since one of these studies was carried out in the far north of Québec, the
other carried out on samples taken in a recreational area. The data from these studies are
presented in the following table:

Table 2. Canadian studies of the prevalence of parasites in dogs
Region Prevalence (%) Reference
T.
canis
T.
leonina
Hookworm Trichuris n
Newfoundland 40 200 Mikhael et al., 1974
Nova Scotia 18 385 Mikhael et al., 1974
26.6 1.3 8 1.3 474 Malloy et al., 1974
12.7 0.6 181 Guallazi et al., 1986
N.-Brunswick 20 204 Mikhael et al., 1974
Québec 35 211 Mikhael et al., 1974
52.6 10.5 9.47 8.42 155 Choquette et Gélinas,
1950
43.5 12.5 4.6 239 Seah et al., 1975
34 11.4 2.5 1.2 332 Ghadirian et al., 1976
44 80 Desrochers et Curtis,
1987
Ontario 88 1000 Mikhael et al., 1974
24.1 6.8 10.3 7.4 1359 Yang et al., 1979
Manitoba 8-10 ? Mikhael et al., 1974
Saskatchewan 15 ? Mikhael et al., 1974
1.92 9.3 0.32 623 Anvik et al., 1974
Alberta 10 ? Mikhael et al., 1974
Nunavut 2.1 16.5 0 0.9 959 Unruh et al., 1973
Table 3. Summary of prevalence rates observed in dogs in Canada
Species Prevalence (%) Number of dogs Number of studies
Min-max Mean
Toxocara canis 1.92-88 30.8 6 322 13
Hookworm 0.32-12.5 7.25 3 363 7
Trichuris vulpis 0.6-8,4 3.8 3 699 7
T. leonina 1.3-44 10.1 3 982 7
Numerous prevalence studies worldwide have been published. Researchers have
compiled 54 studies covering some 42,000 dogs and obtained a mean of 15,2% of dogs
excreting Toxocara eggs, although the range was 0 to 93% (Glickman and Schantz,
1981). However, recent reports from university laboratories show a sharp decrease in
these figures.
Table 4. Parasite prevalence in samples submitted to American university
laboratories
Reference Prevalence (%) Year
7

T. canis Ancylostoma Trichuris
Greve and O’Brien, 1988 4.5 11.1 4.2 1988
Jordon et al., 1993 4.0 15.0 9.0 1990
Nolan et Smith, 1995 5.7 9.7 9.7 1993
In 1996, Blagburn and colleagues reported a prevalence rate of 14.54% in the United
States for Toxocara, 19.19% for Ancylostoma and 14.29% for Trichuris in dogs in
shelters located across that country. Because this is a large and recent study, it is often
cited as a reference.
Two studies have been conducted in cats, on in Nova Scotia, which involved 299 cats
(Mikhael et al., 1974), the other in Saskatchewan, which involved 52 cats (Pomroy,
1999). The prevalence rate of Toxocara cati was 25.1% in the former study and 26% in
the latter.
2.2 Brigitte Guay’s study in 2004
This study was carried out in April, May and June 2004. Fecal samples were obtained
from all dogs and cats taken to 31 veterinary facilities located in the province of Québec.
A total of 1,093 samples were obtained from dogs and 587 from cats. The tests were
performed in the laboratory of the Faculty of Veterinary Medicine at the University of
Montréal using the technique of centrifugation in a saturated zinc sulfate solution. The
animals sampled represent the group of animals receiving the best health care and the
least likely to have parasites. The prevalence rates for the parasite species found are
presented in the following table.
Table 5. Parasite prevalence in canine and feline fecal samples from Québec
veterinary facilities
Protozoans Prevalence (%)
Dogs Cats
Cryptosporidium spp. 3.0 0.5
Giardia spp. 4.2 0.5
Isospora spp. 5.3 3.4
Sarcocystis spp. 0.6 0.2
Helminths Prevalence (%)
Dogs Cats
Ancylostoma spp. 2.0 0.5
Toxocara spp. 3.2 4.6
Toxascaris leonina 0.3 0
Trichuris vulpis 0.6 0
8

Capillaria spp. 0.1 0.9
Taenia spp. 0.1 0.3
Alaria spp. 0.6 0
Arthropods Prevalence (%)
Dogs Cats
Cheyletiella spp. 0.1 0.5
Otodectes cynotis 0.2 0.5
Demodex 0 0.3
Trombiculidae 0.1 0
These data can be presented differently. Thus, 15.9% of the canine samples and 10,6% of
the feline samples contained at least one species of parasite. The range between
veterinary facilities was, however, quite wide: 5.1 to 52.6% for dogs and 3.3 to 47.6% for
cats.
Toxocara canis
- 10.2% of the puppies under 6 months of age were excreting eggs. In the dogs over one
year of age, the risk of infection was nearly ten times lower.
- The rate of infection in the males (3.2%) was slightly higher than that in the females
(3.0%), but this difference is not significant.
- The study did not find any differences in prevalence in the sterilized or unsterilized
animals over the age of 6 months.
- The use of drugs to prevent heartworm disease seemed to have a protective effect
against Toxocara.
- Even if only 3.2% of the samples contained eggs, there was considerable variation in
prevalence between different veterinary facilities, the range being 0.7 to 18.2%.
- The group with the most parasites included animals raised by private individuals
(15.4%). The rate of infection in these animals was more than twice that in the dogs at a
breeding facility (8.6%) or a pet shop (7.2%).
Toxocara cati
- 10.6% of the kittens under 6 months of age were excreting eggs. In the cats over the age
of one year, the risk of infection was nearly 15 times lower.
- The rate of infection in the females (5.6%) was slightly higher than that in the males
(3.7%), but this difference is not significant.
9

- The rate of infection in the cats over the age of 6 months that had been sterilized was
1.2%, whereas it was 8.3% in those that had not been sterilized.
- Although only 4.6% of the samples contained eggs, there was considerable variation in
prevalence between different veterinary facilities, the range being 0 to 33.3%.
- The most parasitized group included animals raised by private individuals (18.8%),
whereas this rate was only 4.7% in those at a pet shop and 13.6% in those from another
source, such as a shelter or a breeding facility, or that were simply found.
- Naturally, there was a higher rate of infection in the cats that were hunters (20%) than in
those that were non-hunters (3.6%).
Ancylostoma caninum
- Only 2% of the dogs were excreting eggs of this parasite.
- A slightly higher proportion of the dogs under the age of 6 months were infested (3.7%)
than the older ones (1.6%), but this difference is not statistically significant.
- Although only 2% of the samples contained eggs, there was considerable variation in
prevalence between different veterinary facilities, the range being 0 to 10.5%.
2.3 Data obtained in our laboratory in 2007
Our laboratory receives samples from animals hospitalized at our facility, from the
primary care clinic of the Small Animal Hospital, from a private company, and from
several veterinary facilities in the province. We received 206 samples from cats and 428
from dogs. We used the technique of double centrifugation of 2-g samples of fecal matter
in a saturated zinc sulfate solution.
10
Cats (%) Dogs (%)
Animals excreting parasites 18.9 33.6
Animals excreting zoonotic parasites 15.5 25.0
Puppies and kittens excreting parasites* 21.2 52.8
Puppies and kittens excreting zoonotic parasites* 18.5 40.3
* = Puppies and kitten under one year of age

Table 6. Parasite prevalence in samples of canine and feline fecal matter submitted
to the Diagnostic Laboratory Service of the Faculty of Veterinary Medicine in Saint-
Hyacinthe, 2004 - 2007
Species Prevalence in cats (n = 514) Prevalence in dogs (n = 1,152
Number % Number %
Isospora 42 8.1 132 11.4
Giardia 15 2.9 142 12.3
Trichomonas 2
Cryptosporidium 11 2.1 60 5.2
Toxoplasma 3
Sarcocystis 6
Alaria 7 0.6
Taenia 8 1.5 12 0.6
Diphyllobothrium 1
Dipylidium 3
Pelodera 1
Ancyl./Uncinaria 5 20 1.7
Toxocara 40 7.7 66 5.7
Toxascaris 14 1.2
Crenosoma 3
Physaloptera 1
Trichuris 1 15 1.3
Capillaria 9 1.7 1
Dirofilaria (mf) 8/287 2.7
Dirofilaria (Ag) 6/972 0.6
D. repens 2
Cheyletiella 6 1.1 1
Demodex 1 1
Otodectes 1
Adult animals are not immune to parasitic infections. Giardia was found in two 2-yearold
cats and in dogs aged 2, 4, 8 and 10 years; Cryptosporidium in dogs aged 5, 8, 10 and
15 years; and Toxocara in a 5-year-old dog. However, certain species are found more
predominantly in young animals.
Thus, in the dogs (2007):
Toxocara was found in 8.3% of those under the age of one year.
11

2.4 Ticks
Giardia was found in 27.2% of those under the age of one year.
Cryptosporidium was found in 10.7% of those under the age of one year.
Since 1990, the Laboratoire de santé publique du Québec has been offering Québec
residents a service for identifyng ticks found on humans and animals (LSPQ, 2005). A
number of specimens have been brought back from outside the province.
Table 7. Number and species of ticks submitted to the LSPQ (1990 – 2006)
Species Number %
Ixodes cookei 5 839 51,0
Ixodes scapularis 3 050 26,6
Dermacentor variabilis 1 236 10,8
Rhipicephalus sanguineus 624 5,4
Amblyomma americanum 245 2,1
Ixodes muris 147
Dermacentor albipictus 73
Haemaphysalis leporispalustris 39
The total number of specimens received has steadily increased over the years, although
we have not been able to determine exactly why. It could be that people are more aware
of ticks and detect them more often, but there may be other very important factors as
well, such as climate warming, an increase in the number of host populations, and
transport by migratory birds.
Table 8. Number of ticks submitted to the LSPQ from 1990 until 2007
Nb of ticks
2500
2000
1500
1000
500
0
1990 1993 1996 1999 2002 2005
12
Years

The total number of specimens from Québec submitted and identified as Ixodes
scapularis has followed the same upward pattern. From 1990 to 2006, slightly more than
89% of these specimens were found on animals, 71.2% of them on dogs and 28,7% on
cats.
Table 9. Number of Ixodes scapularis of Québec origin submitted to the LSPQ from
1990 until 2006
Nb of ticks
1200
1000
800
600
400
200
0
1990 1992 1994 1996 1998 2000 2002 2004 2006
The percentage of ticks carrying Borrelia burgdorferi was similar during the last few
years of the program, ranging from 8 to 15%. In addition, according to tests performed as
follow-up of certain cases, five Quebecers, 31 dogs and 13 cats were infected and
developed antibodies.
Table 10. Percentage of Ixodes scapularis of Québec origin that were carriers of
Borrelia burgdorferi
Nb of ticks
16
14
12
10
8
6
4
2
0
13
Years
1999 2000 2001 2002 2003 2004 2005 2006 220
Years

Table 11. Number of ticks submitted monthly to the LSPQ
Nb de tiques
Among the other species found on our pets, Rhipicephalus sanguineus purportedly
transmits Ehrlichia canis, Babesia canis, and other pathogenic agents, while
Dermacentor variabilis is considered the main vector of Rickettsia rickettsii, the etiologic
agent of Rocky Mountain spotted fever. The other species seem to have only minor
importance as vectors of pathogenic agents.
All the species of ticks found here have a similar development cycle. They eat only three
meals in their lifetime, each on a different animal, and the food they ingest during each of
these meals helps the next moult or egg laying after the female’s third meal. They climb
onto an animal and can take some time to get a suitable place before they bite and start
injecting their saliva and sucking blood. The meal lasts 3 to 14 days, and the ticks detach
only at the very end of the meal, at which point they fall to the ground. The sated female
will use the food in preparation for laying hundreds of eggs, which will take place a few
days later. Due to their method of feeding, which takes them from one animal to another,
and since ticks inject a large amount of saliva during their meals in order to get rid of the
fluids that were ingested, there is a strong potential for transmission of pathogenic agents.
2.5 Zoonotic species
450
400
350
300
250
200
150
100
50
0
1 2 3 4 5 6 7 8 9 10 11 12
One important argument for controlling parasites in our pets is the fact that the most
frequently encountered species are transmissible to humans. Too often, this is
unrecognized or ignored, but we should keep it in mind, especially knowing that children
are particularly at risk for infection, and since there are more and more people whose
immune systems have been weakened by various diseases.
14
Mois

Table 12. List of canine and feline parasite species that can affect human health
Parasite group Dogs Cats Condition(s) in humans
Protozoans
Cestodes
Nematodes
Arthropods
Cryptosporidium + + Diarrhea
Giardia spp. + + Diarrhea
Toxoplasma gondii - + Vary
Dipylidium caninum + + Vague gastrointestinal
disturbances
Echinococcus granulosus + - Pulmonary cysts
Echino. Multilocularis + + Hepatic cysts
Ancylostoma caninum + - Dermatitis, enteritis
Baylisascaris procyonis + - Erratic larval migration
(eyes, brain)
Dirofilaria immitis + - Pulmonary nodules
Strongyloides stercoralis + + Gastrointestinal
disturbances,dermatitis
Toxocara spp. + + Erratic larval migration
(eyes, brain)
Trichuris vulpis + - None
Cheyletiella spp. + + Dermatitis
Ctenocephalides felis + + Dermatitis
Notoedres felis + Dermatitis
Otodectes cynotis + + Dermatitis
Sarcoptes scabiei + + Dermatitis
Ticks + + Vary according to the agent
Trombiculidae + + Dermatitis
The number of cases of zoonosis in humans seems difficult to determine. Identifying such
infections proves challenging in most cases, and the lack of knowledge on the part of
most human health specialists is a major obstacle. Regular consultations with the
Diagnostic Laboratory Service suggest that zoonotic infections are quite common, despite
the fact that most people, including veterinarians, are under the impression that they are
rare. Such cases are simply misidentified or wrongly attributed to some other cause. We
can use the case of toxocariosis to illustrate the extent of the problem.
Only a few cases of human toxocaral infection have been reported in Canada (Table 8),
which seems to have reassured certain specialists (Fanning et al., 1981). However, the
15

clinical signs associated with such infections are quite vague and can be attributed to
various other causes. Furthermore, it is very difficult to confirm the diagnosis in the vast
majority of cases, unless one actually finds the parasites per se, for example, during a
biopsy. It is therefore not surprising that only the severest cases are identified. However,
serological studies give reason to suspect that a large proportion of the population
becomes infected (Embil et al., 1988). In the Halifax area, 14% of urban children under
the age of 15 years have a history of infection, as do 19.5% of rural children. Although
most of these infections are of no consequence, this is not true for others where vision
disorders are permanent. A study conducted in Alabama estimated the number of cases of
human ocular toxocariosis to be between 1 and 11 per 1,000 population (Maetz et al.,
1987). Another study from Ireland, using more restrictive criteria, estimated the
prevalence to about 1 per 10 000 population (Good et al., 2004).
Table 13. Cases of human toxocariosis reported in Canada
Number
cases
of Region Reference
27 Canada Tizard and Gyorkos, 1979
1 Saskatchewan Wong and Laxdal, 1958
1 Toronto McKee, 1957
1 Montréal Halal et al., 1975
7 Québec Perreault, 1978
18 Toronto Fanning et al., 1981
Fecal examinations in puppies and kittens are important for detecting protozoan
infections, which are very common at this age. Children in close contact with young
animals are at risk of infection. These animals should be screened and treated, when
possible, and strict personal hygiene measures should be imposed to prevent zoonotic
infections.
The table below gives a classification of zoonotic species based on the parasites’
pathogenicity, their contagiousness for humans, and their prevalence in animals. This
classification in quite arbitrary and is merely intended as a tool for targeting species that
pose a higher zoonotic risk.
Table 14. Classification of zoonotic species based on the relative importance
Species Pathogenicity
for humans
16
Transmissibility Prevalence
in animals
Total
score
Toxocara cati 3 5 5 13
Baylisascaris (skunks) 4 3 4 11
Baylisascaris (racoons)
5 1 4 10

Toxocara canis 4 3 2 9
Toxoplasma 5 1 3 9
Cryptosporidium 2 2 4 8
Strongyloides 4 3 1 8
Cheyletiella 1 4 3 8
Giardia 1 2 5 8
Sarcoptes 1 4 2 7
Ancylostoma 2 2 1 5
Fleas 1 2 2 5
Dirofilaria 2 2 1 5
Otodectes 1 1 3 5
Trichuris 1 1 1 3
Note : Each item is assigned a value of 1 to 5, with 1 being the lowest value.
3. Prevention
There is an important public health dimension to parasite infections that is too often
poorly defined. Many animal parasites produce elements that contaminate our
environment for prolonged periods of time and that are quite transmissible to humans.
Effective prevention should include the participation of different individuals at the
regional level, both ordinary individuals and pet owners. Health specialists have a special
role to play in educating people about the preventive measures that need to be taken.
Even if these measures often make good common sense, in many cases programs that
involve the use of drugs need to be implemented as well. It is important to have a good
understanding of which groups of animals are at risk and to take appropriate action.
3.1 Prevention or treatment?
Special attention should be given to an animal found to be infected or infested by
parasites. The treatments should be repeated at close intervals, first to rid the animal of its
parasites, then to restore it to health. As for prevention, its primary goal is to protect the
animal’s health and the health of those around it over the long term.
3.2 The objectives of prevention
The goals may differ according to the type of parasite. It is very difficult and probably
undesirable to protect an animal so that it never becomes infected with parasites, since to
achieve this, it would probably have to be medicated repeatedly and frequently. The
objective of a prevention program is a more long-term result: prevent parasites from
reproducing. This approach takes into account the fact that infections elements present in
the environment can persist fore very long periods of time, even years; that they are very
17

widespread, to the point that they are found wherever animals go; and that many animals
are never treated, especially stray cats. Our specific objectives are therefore:
To protect animal health;
To protect the health of the people around it;
To prevent parasites from laying eggs;
To use as few drugs as possible so as not to select resistant parasites;
To propose a practical approach for the animal’s owner.
Increasingly, we are abandoning the curative approach and using instead a preventive
approach to ensure that our pets do not become infected with parasites, and to provide a
healthy environment. We should bear in mind that our pets spend more and more time
indoors, in direct contact with different family members.
3.3 Current programs (CAPC)
The programs officially recommended by various organizations must take into account
all the possible differences encountered in a vast region, which means that users should
adapt the programs to their specific needs. Therefore, we cannot quote their
recommendations without first adapting them. The highlights of these recommendations
are as follows:
The first treatment is administered at the age of 3 weeks in cats and at the age of 2
weeks in dogs.
The treatment is repeated every other week up to the age of 9 weeks in cats and
up to the age of 8 to 12 weeks in dogs.
Cats and dogs are treated on a monthly basis up to the age of 6 months.
A nursing animal is treated at the same time as her puppies or kittens. Prenatal
transmission of larvae in a pregnant bitch can be prevented with a monthly
treatment protocol using certain macrocyclic lactones.
Adult animals are treated on a monthly basis, at regular intervals, or on the basis
of fecal examination results.
Fecal examination-based screening is done up to four times a year and at least
twice a year in young animals under the age of one year.
Year-round treatment for most parasites is strongly recommended for increasing
compliance with the programs and because many people travel with their pets.
Basic environmental sanitation measures should be taken.
18

3.4 A program tailored to our conditions
The program tailored to our conditions reflects the climatic differences and the
differences in the prevalence of parasites. There are only minor differences and the
reasons for them are discussed below. The program can be summarized as follows:
Dogs:
Cats:
Rationale
Treatment at the ages of 2, 4, 6, 8, 10 and 12 weeks.
Monthly up to the age of 6 months.
Treatment of a nursing bitch at the same time as her puppies.
Treatment on as-needed basis thereafter.
Once a month, starting at the age of one month.
Monthly up to the age of 6 months.
Treatment of a nursing cat at the same time as her kittens
On an as-needed basis thereafter.
Age at first treatment. When they are born, puppies already have parasites that travelled
through the placenta from the mother during the last trimester of pregnancy. The number
of parasites can be high. Treatment should be administered as soon as possible. It should
be administered before the age of 3 weeks because certain worms will start laying eggs in
puppies as early as 17 days of age. Treating at the age of 2 weeks seems reasonable,
given that the parasites are still small and that we do not want to treat too early so as not
to risk toxicity. Kittens are free of parasites when born, but their mother excretes a few in
her milk, which can constitute the offspring’s first source of infection. There is no rush to
treat, especially since the number of worms transmitted in this manner is very small.
Starting the treatment at the age of 4 weeks seems acceptable.
Time interval between treatments in unweaned animals. In puppies, the maximum
efficacy of treatments is often not achieved because of accelerated peristaltis and very
frequent diarrhea. There are many opportunities for puppies to become infected: through
their mother’s milk, by chewing on objects, and by exploring their surroundings. The lack
of immunity provides very poor protection against these multiple sources of infection.
Very often, the prepatency periods are much shorter in nonimmune animals. Thus,
Ancylostoma caninum completes its development in 12 to 15 days in puppies but will
take 26 days in adult dogs. In the case of Toxocara development, it takes 14 days in
puppies and 30 to 34 days in adult dogs. The treatment should be repeated every other
week for the first three months of life. In kittens, the lactogenic transmission of larvae
decreases with time, and there is better hygiene, but the mother may bring infected prey
19

to them. Nonetheless, in natural conditions, the parasite loads observed in cats are
generally very small and do not warrant aggressive treatment. Treatments repeated every
month seem sufficient, especially since the shorter prepatency period for Toxocara in 42
days.
Treatment of the mother during the lactating period. It is advisable to treat the mother
during the lactation period because she can easily become infected from her puppies or
kittens. She stimulates them to urinate or defecate and normally swallows everything that
is excreted. When a young animal ingests infectious stages, a certain portion of them
travel through the entire gastrointestinal tract and are excreted, often because of overly
rapid peristaltis. These parasites can then establish themselves in the mother. For reasons
of convenience, it is advisable to treat the mother and the young at the same time.
Monthly postweaning treatment. Weaning spells the end of a period during which
parasite transmission largely depends on the mother, specifically, through the excretion
of larvae in her milk. On the other hand, the young have already been treated on several
occasions and their immune system is gradually maturing to the point where it can protect
them against parasites. However, the games that they indulge in and their immense
curiosity still make them susceptible to ingesting infectious eggs present in their
environment. If free-roaming, the mother cat may, on a daily basis, bring back prey that
serve as paratenic hosts. The interval between treatments should then be adjusted to the
prepatency period of the most commonly encountered parasites.
Treatment in animals over the age of 6 months. The risk of infection in animals in this
age group is minimal, but it is still present. The prevention program is aimed at protecting
animals that are especially at risk for becoming infected and during periods when this risk
of infection is high. The length of the interval between treatments is base mainly on the
length of the prepatency period of most parasites. During the winter, the risk of new
infections is low or even nonexistent. It is then possible to increase the interval between
treatments.
Screening tests. It is advisable to perform a large number of stool tests. This is even
essential in animals under the age of one year. A fecal examination during the first visit
to the veterinarian is a must. It would be wise to have it repeated at least once or twice
during the first year. Zoonotic agents are especially common in animals in this age group,
and humans are often in very close contact with these animals. In animals on a prevention
program using a broad-spectrum product, the test can be performed shortly before the
first treatment or toward the end of the program, provided you wait at least six weeks
after the last treatment. In an animal weakened by illness or that is exposed to infection as
a result of its activities, an annual examination would be desirable, even during the
deworming program, if necessary.
However, you should not stop from having a fecal examination done just because a pet is
on a deworming program. No drug can protect an animal from all parasite species, not
even the broad-spectrum drugs (see following table). The term “broad-spectrum” might
20

seem very reassuring, but at best, less than half of the common parasite species will be
susceptible to such a drug.
Table 15. Canine parasite species that exhibit little of no susceptibility to treatment
with pyrantel (which is considered a narrow-spectrum drug)
Cryptosporidium, Giardia, Isospora
Dipylidium, Taenia
Strongyloides, Dirofilaria, Trichuris, Capillaria
Fleas, Sarcoptes, Cheyletiella, Demodex, Trombiculidae, tiques
Note : Only a high percentage of Ancylostoma, Uncinaria, Toxocara and Toxascaris can be eliminated.
Measures in addition to treatment. The importance of such measures relies on the fact
that many parasites, especially in young animals, are transmissible to humans but can
seldom be treated pharmacologically. It will be recalled that cryptosporidiosis affects
some 15% of puppies under the age of 3 months and the giardiosis affects 25% of
puppies under the age of 6 months, according to the data obtained in our laboratory. The
drugs used against certain frequently encountered parasites cannot provide total control
over these infections in all cases.
Complementary measures for minimizing parasite infections in animals and
humans:
Remove feces from your environment on a daily basis and dispose of it in a trash
can.
Observe appropriate personal hygiene practices, such as washing your hands
before meals.
Keep children’s sanboxes covered when they are not in use and protect the places
they frequent most often.
Wear gloves when gardening.
Give pets enough food so that they do not turn to hunting.
Fence in your yard to keep out stray and wild animals.
Keep skunks and racoons away by not leaving any trash cans outside and by
blocking the underneath of sheds so that they cannot take refuge there.
It is difficult, if not impossible, to decontaminate soil. You should only replace
the top 15 cm, since eggs stay at the surface.
Limit the places where the pet can defecate.
Encourage those around you to take these measures.
Pay close attention to animals that eat dung or feces.
21

4. Diagnostic tools
4.1 Why using them?
Fecal testing has lost a bit of its popularity over the past few years, which iscompletely
unjustified. Declining parasite prevalence, together with the use of a low-sensitivity
technique, has led many veterinarians to perform fewer tests or to falsely believe that
parasites have disappeared. We should use relatively sensitive techniques to convince
ourselves of the importance of prevention.
Why perform a fecal examination?
To diagnose a sick animal.
For screening purposes in a healthy animal.
To determine the most appropriate drug.
To determine the parasite load and decide if treatment is necessary.
To check that a given treatment is effective.
Screening is very important, especially when the clinical presence of parasites in an
animal is not very manifest but nonetheless results in significant contamination of its
environment and, possibly, transmission to humans.
4.2 Laboratory techniques
Recent studies have shown that centrifugation techniques are more sensitive than
flotation techniques (Dryden et al., 2005). The CAPC even recommends completely
abandoning flotation as a fecal examination method (CAPC, 2005).
In a controlled la boratory trial, we observed that centrifugation increased the number of
eggs recovered on a microscope slide by a factor of 10 to 15 compared to simple
flotation. The preferred saturated solution used in this technique is zinc sulfate, with
double centrifugation. It is the most effective solution for separating protozoans, such as
Giardia, Cryptosporidium and Isospora, from fecal matter. Little debris floats, yet this
technique is sensitive enough to detect the presence of heavier eggs, such as those of
Toxocara and Trichuris, and most of the eggs of others parasites, except perhaps those of
Taenia. On the other hand, Taenia eggs are rarely present in the feces of infected animals
(see Table 16). Ideally, the density of the saturated zinc sulfate solution should be 1,18.
22

Table 16. Egg density varies according to the species (David and Lindquist, 1982)
Toxascaris leonina 1,055
Ancylostoma caninum 1. 055
Toxocara canis 1, 090
Toxocara cati 1, 100
Trichuris vulpis 1, 145
Taenia spp. 1, 225
Table 17. Technique of double centrifugation in zinc sulfate
Materials
_______________________________________________________________________
15 mL centrifuge tubes
Zinc sulfate solution
50 mL beakers or any other similar containers
Tap water or distilled water
Tea strainer
Microscope slides and cover slips
Wooden applicator sticks
Horizontal of fixed-angle centrifuge
Procedure
_______________________________________________________________________
1. Take a 1 or 2 g sample of feces, taking care to include the mucus, if any is
present.
2. Carefully dissolve the sample in 12 mL of tap water, then filter through a tea
strainer to remove the larger pieces of debris.
3. Pour the filtrate into a centrifuge tube. Centrifuge at 1 500 rpm or at the speed
recommended for urine (the lowest speed) for 10 minutes.
4. Gently discard the supernatant (the parasite elements are in the pellet).
5. Add approximately 10 mL (or 2/3 of the tube) of zinc sulfate solution. Use a
wooden applicator stick to resuspend the pellet. Fill the tube up to about 1 cm
from the top.
6. Centrifuge at 1 500 rpm or the equivalent for 10 minutes.
7. Gently remove the tube from the centrifuge and place it vertically in a rack. Add
zinc sulfate solution by letting it flow slowly down the side of the tube so that it
does not disturb the film on the surface of the liquid (parasitic elements float to
the surface). Add enough solution to obtain a meniscus and place a cover slip on
the surface. Wait 10 minutes.
8. Transfer the cover slip to a microscope slide and examine the entire slide under a
10X objective.
23

________________________________________________________________________
Note 1. Zinc sulfate in available from Anachemia (No 98440-380; Price: 80$ for 2 kg) or from other
suppliers. Add 450 g of zinc sulfate to a litre of distilled water and shake it until dissolve. Also, FECADRY
II can be obtained from CDMV (No 14496; Price: 19$ for 3.8 litres).
Note 2. If you use a horizontal centrifuge, you can skip step 3 by filling the tube in such a way to obtain a
positive meniscus and placing a cover slip on top of the tube. After the tubes are properly balanced, they
can be centrifuged.
Table 18. Comparaison of prevalence rates obtained by necropsy and by zinc sulfate
flotation in 2,737 dogs and 1,480 cats at a New-Jersey shelter (Lillis, 1967)
Species Prevalence (%) Sensibility (%)
Nécropsie Flottation
Dogs
Ancylostoma 72 63 87,5
Toxocara 22 11 50,0
Cats
Trichuris 75 65 86,6
Taenia 25 15 60,0
Dipylidium 28 1 3,5
Toxocara 55 45 81,8
Taenia 33 19 57,5
Dipylidium 10 0 0
This study used flotation, which is less sensitive than centrifugation, as the fecal
examination technique. However, because of the very high prevalence, the parasite loads
were probably high as well. Nowadays, the low prevalence rates observed certainly does
not account for such high sensitivity. On the other hand, parasites, at least certain species,
are considered prolific, which gives us some assurance with regard to sensitivity.
Table 19. Number of eggs or parasitic elements produced per female per day
Toxocara spp. 200 000
Ancylostoma caninum 16 000
Trichuris 2 000
24

Table 20. Recommended techniques for determining canine and feline parasite
species
Protozoans
Most species Centrifugation in zinc sulfate solution
Trichomonas, Entamoeba Direct smear in a drop of saline
Giardia Direct smear in a drop of saline, centrifugation
Cryptosporidium spp. Direct smear in a drop of sugar solution, centrifugation,
Prospect T
Babesia Blood smear
Flukes
Most species Sedimentation, centrifugation in zinc sulfate solution
Tapeworms
Most species Examination of segments found in feces, sedimentation,
centrifugation
Roundworms
Most species Centrifugation in zinc sulfate solution
Pelodera Skin scraping, Baermann technique
Strongyloides Baermann technique, culture on blood agar, centrifugation
Ollulanus Examination of vomitus
Filaroides Bronchoalveolar washing
Aelurostrongylus,
Crenosoma
Baermann technique
Dirofilaria,
Blood filtration, commercially available kits
Acanthocheilonema
Dracunculus Inoculation of the skin wound
Trichinella Muscle biopsy
Dioctophyma,
Urinalysis
Paersonema plica,
P. feliscati
Arthropods
Most species Direct examination, skin scraping, fecal examination
25

4.3 At-risk groups
Knowing which groups are at risk can help us target our deworming efforts as an adjunct
to fecal testing. The main at-risk groups are as follows:
Young animals under the age of 6 to 12 months (first exposure to parasites,
immature immune system, inadequate hygiene).
Pregnant and lactating females (significant stress, hormone imbalance negatively
affecting the immune system).
Adult hunters (prey-dwelling parasites that are ingested do not migrate into the
host’s tissues and are less exposed to its immune system).
Adult males (particularly susceptible to certain species).
Animals raised in groups (significant stress associated with noise and social
interactions; abundance of a wide range of infectious agents).
Animals from poorly-kept kennels or catteries (they have been exposed to many
species of parasites, some of which persist in the animals’ tissues).
Animals on prolonged corticosteroid therapy (immunosuppressive effect).
Animals that have undergone major surgery.
Animals suffering from malnutrition (weaker immune system).
Very old animals.
Animals with diabetes (immunosuppression).
Stray animals.
Animals kept in a highly contaminated environment.
Animals that travel to areas where there is a higher risk of infection.
Animals entered in shows and competitions.
Animals taken to dog parks.
Animals that eat dung or feces.
The following table indicates the risk of parasite infections associated with different
activities. This classification is quite arbitrary and is merely intended as a tool for
targeting dogs and cats at higher risk for such infections.
Table 21. Risk factors for parasite infections in dogs, by parasite species
Species Âg
e
Season Kennel* Yard Wildlife Parks Cottage South Show
s
Coccidia > Y ++ + + +
Cryptosporidium > Y ++ + +
26
Hunting

Giardia > Y ++ + +
Taenia = ++ + ++
Dirofilaria = July-Aug + ++ + ++ +
Toxocara > Y + + + + + +
Ancylostoma = + + + + ++ +
Baylisascaris = + ++ ++ +
Trichuris = + + +
Puces = May-Oct + + + ++ +
Cheyletiella = ++ ++
Sarcoptes = + + +
Otodectes > Y ++ +
Trombiculidae = July-Sept ++ +
Cuterebra = Summer ++ +
Lice =
Ticks = Spring-
Fall
* = Poorly-kept kennels
Y = young animals
27
+ + ++ ++
Table 22. Risk factors for parasite infections in cats, by parasite species
Species Age Season Cattery* Yard Wildlife Shows Hunting
Coccidia > Y ++ + + +
Cryptosporidium > Y ++ +
Giardia > Y ++ +
Taenia = ++ ++
Dirofilaria = July-Aug + ++ +
Toxocara > Y + + + ++
Ancylostoma = + + + +
Fleas = May-Oct + + + +
Cheyletiella = ++ ++
Otodectes > Y ++ +
Trombiculidae = July-Sept ++
Cuterebra = Summer ++
Lice =
Ticks = Spring-Fall + ++
* = Poorly-kept catteries
Y = young animals
5. Drugs
There are now many antiparasitic drugs and they are not all the same. It is therefore
important to study them carefully so that you use them properly.

5.1 How to read a label
The label on a given drug contains various information provided by the pharmaceutical
company. This information has been examined and approved by the government
authorities. To properly understand this information, you need to know which
requirements and limits were met. In addition, these rules have changed over the years,
with the result that drugs marketed at different times may be labelled in accordance with
different standards.
For example, with regard to indications, the species listed are those that have been
investigated in studies demonstrating greater than 80% efficacy. Those that are not listed
have generally not been investigated in any studies for various reasons, often because the
species are rare, or studies have shown them to have poor efficacy. Independent scientific
literature can fill these gaps.
There are good clinical-practice guidelines for studying the effects of drugs on
companion animal parasites (WAAVP; VICH, 2002a et b). In general, for approval
purposes, the company must submit two or three studies, with or without controls
(controlled or critical), to demonstrate a drug’s efficacy.
More specifically, a study with controls (a controlled test) involves two groups of six
infected animals. One of the groups is treated with the study drug, while the other
receives a placebo. One to two weeks after treatment, all the animals are sacrificed and
necropsied. The efficacy for each species and for the study is calculated by means of the
following formula:
Mean number of parasites in the controls – mean number of parasites in the treated animals
________________________________________________________________________________ X 100
Mean number of parasites in the controls
In a study with no controls (a critical test), the animals involved serve as their own
controls. The animals are treated, but their feces are gathered one to three days prior to
treatment and during the seven days that follow it. The animals are necropsied seven days
after the infection. However, this type of study is reserved for free parasites in the
intestine. The efficacy for each species and for each individual animal included in the
study is calculated by means of the following formula:
Number of parasites expelled
_____________________________________________________________________ X 100
Number of parasites expelled – number of parasites remaining in the intestine
For approval purposes, clinical trials are considered more as safety studies than efficacy
studies.
28

Special terminology is used on labels. Thus, a drug used as a “treatment” for a particular
species of parasite means that the company has conducted two or three studies each
showing greater than 90% efficacy in eradicating worms of that species. A drug used as a
“therapeutic aid” for a particular species will have been investigated in studies showing
less than 90% but more than 80% efficacy in eradicating worms of that species. And, a
drug used as “prevention” against infection by a particular species of parasite will first be
administered to the animal, which is then exposed to the infectious agent. Studies then
show that no parasite successfully infected the animal. Lastly, a drug used for the
“treatment and control” of infections by a particular species of parasite eliminates more
than 90% of the parasites when administered the first time, while subsequent
administrations (in the case of products intended for monthly administration over six
consecutives months) keep parasite loads at low levels.
5.2 A broad- or narrow-spectrum drug?
It seems clear that using broad-spectrum drugs is more beneficial for preventing parasitic
infections and infestations. One main argument is that these drugs provide protection
against ectoparasites in animals that are not confined indoors. Animals generally develop
little resistance with age, opportunities for infestation come up regularly, and most of
these parasites are transmissible to humans. On the other hand, protection against internal
parasites may seem less necessary, but in most of our regions, heartworms, fleas, and
certain gastrointestinal parasites constitute a real threat. Younger is the animal, more we
use broad-spectrum drugs.
5.3 Drugs, parasites and treatments
This section provides drug information in tabular form. Despite all the care taken in
making these tables, some mistakes may have occurred. Please refer to the label on each
of these drugs to confirm the information presented here.
Table 23. List of parasites and their treatment (the drugs that have not been
approved are marked with an asterisk; the dose at which a given drug is effective
may vary)
Parasite Generic name
Acanthamoeba spp. (post-mortem diagnosis)
Acanthocheilonema (Dipetalonema)
reconditum
(not required)
Aelurostrongylus abstrusus Fenbendazole*, ivermectin*
Alaria spp. Espiprantel*, fenbendazole*, praziquantel*
Ancylostoma spp. Fenbendazole, febantel, ivermectin*, milbemycin, moxidectin,
oxibendazole, pyrantel
Babesia spp. Fenbendazole*, ivermectin*
Baylisascaris procyonis Fenbendazole*, ivermectin*, moxidectin*, milbemycin*,
pyrantel*
29

Besnoitia Diminazene (Berenil), phenamidine (Ganaseg)
Calodium (Capillaria) hepaticum (pseudoparasitism)
Calliphoridea (myiasis) Ivermectin*, macrocyclic lactones*
Cheyletiella spp. Ivermectin*, lime sulfur*, milbemycin*, sélamectin*
Crenosoma vulpis Fenbendazole*, ivermectin*, milbemycin*
Cryptocotyle Epsiprantel*, fenbendazole*, praziquantel*
Cryptosporidium spp. Paromomycin*
Ctenocephalides felis Imidacloprid, lufenuron, methoprene, nitenpyram, pyrethrins,
selamectin
Cuterebra spp. (surgical removal), ivermectin*
Demodex spp. Amitraz, ivermectin*, milbemycin*, moxidectin*
Dioctophyma renale (surgical removal)
Diphyllobothrium spp. Epsiprantel, praziquantel
Dipylidium caninum (fenbendazole not effective), epsiprantel, nitroscanate,
praziquantel
Dirofilaria immitis Diethylcarbamazine, ivermectin, melarsomine, milbemycin,
moxidectin, selamectin
Dracunculus insignis (surgical removal)
Echinococcus spp. Praziquantel
Entamoeba Metronidazole*
Eucoleus (Capillaria) aerophilus Fenbendazole*, ivermectin*
Felicola subrostratus Imidacloprid*, lime sulfur*, selamectin*
Filaroides (Oslerus) osleri Ivermectin*
Giardia spp. Febantel*, fenbendazole*, metronidazole*,
Hammondia
Isospora spp. Sulfadimethoxine, toltrazuril*
Linognathus setosus Imidacloprid*, ivermectin*, lime sulfur, permethrines, selamectin*
Mesocestoides Epsiprantel*, praziquantel*
Methorchis conjunctus Epsiprantel*, praziquantel*
Multicepts Epsiprantel*, praziquantel*
Neospora
Notoedres cati Ivermectin*, lime sulfur*, selamectin*
Ollulanus tricuspis Fenbendazole*, pyrantel*
Oncicola canis Fenbendazole*?
Otodectes cynotis Ivermectin*, milbemycin, selamectin
Paersonema (Capillaria) feliscati Fenbendazole*, ivermectin*
Paersonema (Capillaria) plica Fenbendazole*, ivermectin*
Paraganimus kellicotti Fenbendazole*, praziquantel*
Pelodera strongyloides Ivermectine*, lime sulfur*, milbemycin*, selamectin*
Physaloptera rara Fenbendazole*, ivermectin*, pyrantel*
Pneumonyssus caninum Ivermectin*
Sarcocystis spp. (none)
30

Sarcophagidae (myiasis) Ivermectin*
Sarcoptes scabiei Ivermectine*, lime sulfur*, milbemycin*, selamectin
Spirocerca lupi Fenbendazole*
Spirometra mansonoides Epsiprantel*, praziquantel*
Strongyloides stercoralis Fenbendazole*, ivermectin*, nitroscanate*
Taenia spp. Epsiprantel, fenbendazole*, nitroscanate, praziquantel
Ticks Amitraz, DEET, permethrins
Toxascaris leonina Fenbendazole, ivermectin*, milbemycin, moxidectin, nitroscanate,
piperazine, pyrantel
Toxocara canis Fenbendazole, ivermectin*, milbemycin, moxidectin, nitroscanate,
piperazine, pyrantel, selamectin**
Toxocara cati Fenbendazole, ivermectin*, milbemycin, moxidectin, nitroscanate,
piperazine, pyrantel, selamectin
Toxoplasma gondii Clindamycin*, pyrimethamine-sulfadiazine*,
Trichinella spp. Albendazole*, fenbendazole*?
Trichodectes canis Imidacloprid*, lime sulfur*, permethrins, selamectin*
Trichomonas Ronidazole*, metronidazole*, fenbendazole*
Trichuris spp. Febantel, fenbendazole, ivermectin*, milbemycin, pamoate
d’oxantel
Trombiculidae Lime sulfur, macrocyclic lactones*, pyrethrins
Uncinaria stenocephala Fenbendazole*, ivermectin*, moxidectin, nitroscanate, piperazine,
pyrantel, selamectin*
* = use not approved; ** = help to the control
Table 24. Liste of drugs and their indications
Trade name Parasite
Advantage Fleas, lice*
Advantage Multi Ancylostoma, Demodex, Dirofilaria immitis, fleas, lice*, Otodectes, Sarcoptes,
Toxascaris leonina Toxascaris leonina, , Toxocara, Trichuris, Uncinaria
Antirobe Toxoplasma
Baycox* Isospora (coccidia)
Capstar Fleas
Cestex Dipylidium, Taenia taeniaeformis, T. pisiformis, T. hydatigena
DEET Fleas, flies, lice, repellent for mosquitoes, ticks and trombiculids
Defend, Active 3,
Zodiac
Fleas, flies, mosquitoes, ticks
Droncit Dipylidium caninum, Echinococcus granulosus, E. multilocularis,
Diphyllobothrium, Mesocestoides, Taenia taeniaeformis, T. pisiformis, T.
hydatigena, T. ovis
Drontal Ancylostoma tubaeforme, Dipylidium caninum, Echinococcus granulosus, Taenia
taeniaeformis, Toxocara cati
Drontal Plus Ancylostoma caninum, Dipylidium caninum, Echinococcus granulosus, E.
multilocularis, Diphyllobothrium, Mesocestoides, T. pisiformis, T. hydatigena, T.
ovis, Toxascaris leonina, Toxocara canis, Trichuris vulpis, Uncinaria
31

stenocephala
Filaribits Dirofilaria immitis, ascarids
Filaribits Plus Dirofilaria immitis, Ancylostoma caninum, Toxocara canis, Trichuris vulpis
Flagyl* Giardia, Trichomonas, Balantidium,systemic and enteric anaerobic bacteria
Heartgard Dirofilaria immitis
Heargard Plus Dirofilaria immitis, Toxocara canis, Toxascaris leonina, Ancylostoma caninum,
Uncinaria stenocephala
Immiticide Dirofilaria immitis (adults)
Interceptor Baylisascaris*, Crenosoma*, Dirofilaria immitis, Ancylostoma caninum, A.
tubaeforme, Toxocara canis, T. cati, Toxascaris leonina, Trichuris vulpis,
Demodex*, Sarcoptes*, Pneumonyssus*
Ivomec* Ancylostoma caninum, Aelurostrongylus, Cheyletiella, Demodex, Dirofilaria
immitis, Eucoleus aerophilus, Filaroides (Oslerus) osleri, Otodectes,
Pneumonyssus, Sarcoptes, Strongyloides, Toxocara canis, T. cati, Trichuris
vulpis, Uncinaria stenocephala
Lopatol Ancylostoma caninum, Dipylidium caninum, Echinococcus granulosus*, Taenia
hydatigena*,T. multiceps*, T. ovis*, T. pisiformis, Toxocara canis, Toxascaris
leonina, Uncinaria stenocephala
Milbemax Dirofilaria immitis, Ancylostoma tubaeforme, Toxocara cati, Dipylidium caninum,
Taenia taeniaeformis, Echinococcus multilocularis
Milbemite Otodectes cynotis
Mitaban Demodex, ticks, (not effective against fleas)
Panacur, Safeguard* Ancylostoma caninum, Eucoleus aerophilus*, Filaroides hirthi*, Paragonimus
kellicotti*, Taenia pisiformis, Toxascaris leonina, Toxocara canis, Trichuris
vulpis, Uncinaria stenocephala
Pipérazine Ascarids
Program Fleas
ProHeart Ancylostoma caninum*, Dirofilaria immitis, Toxcascaris leonina, Toxocara
canis*, Uncinaria stenocephala*
Pyran, Pyr-a-Pam,
Strongid*
Ancylostoma caninum, Toxascaris leonina, Toxocara canis, T. cati, Uncinaria
stenocephala, Physaloptera*
Pyr-a-Pam Plus Ancylostoma caninum, Toxascaris leonina, Toxocara canis, Trichuris vulpis,
Uncinaria stenocephala, Physaloptera*
S-125 Isospora, enteric bacteria
Tribrissen Toxoplasma
Revolution Dermacentor, Dirofilaria immitis,fleas, lice*, Otodectes, Rhipicephalus,
Sarcoptes, Toxocara canis**, T. cati
Sentinel Ancylostoma caninum, Dirofilaria immitis, fleas, Toxascaris leonina, Toxocara
canis, Trichuris vulpis
* = use not approved; ** = help to the control
32

Table 25. List of drugs and their main characteristics
Drug Trade name Formulation Animal Minimum age
for treating
Amitraz Mitaban Topical Dogs 16 weeks
Preventic Collar Dogs 16 weeks
Clindamycin Antirobe Tablets Dogs, cats N.A.
Diehylcarbamazine Filaribits Tablets Dogs 8 weeks
Diehylcarbamazine +
oxibendazole
Filaribits Plus Tablets Dogs 8 weeks
Epsiprantel Cestex Tablets Dogs, cats 7 weeks (cats)
Fenbendazole Safeguard* Drench Dogs, cats 2 weeks
Panacur Granules Dogs, cats* 2 weeks
Imidacloprid Advantage Topical liquid Dogs, cats 8 weeks (cats)
7 weeks (dogs)
Advantage
Multi
Topical liquid Dogs, cats 8 weeks (cats)
7 weeks (dogs)
Ivermectin Ivomec* Topical Dogs, cats 8 weeks
Oral Dogs, cats 8 weeks
Injectable Dogs, cats 8 weeks
Heartgard Chewables Dogs, cats 6 weeks
Ivermectin + pyrantel Heartgard Plus Chewables Dogs, cats 6 weeks
Lufenuron Program Oral Dogs, cats 6 weeks
Injectable Cats Weaned
Melarsomine Immiticide Injection Dogs N.A.
Metronidazole Flagyl* Tablets Dogs, cats N.A.
Milbemycin Interceptor Tablets Dogs, cats 2 weeks
Milbemite Topical Dogs, cats 2 weeks
Milbemycin + lufenuron Sentinel Tablets Dogs 2 weeks or
>1kg
Milbemycin + praziquantel Milbemax Tablets Cats 6 weeks
Methoprene Ovicollar Collar Dogs, cats N.A.
Moxidectin ProHeart Delayed
injection
Advantage
Multi
33
Dogs 6 months
Topical liquid Dogs, cats 8 weeks (cats)
Nitenpyram Capstar Tablets Dogs 4 weeks or >1
kg
Nitroscanate Lopatol Tablets Dogs 2 weeks
Permethrins Defend, Active
3, Zodiac
Topical Dogs 8 weeks
K9-Advantix Topical Dogs
Piperazine Many Tablets Dogs, cats 2 weeks
Praziquantel Droncit Tablets Dogs, cats 6 weeks

Praziquantel + febantel +
pyrantel
Injectable Dogs, cats 6 weeks
Drontal Plus Tablets Dogs, cats > 1 kg
Praziquantel + pyrantel Drontal Tablets Cats 4 weeks ou >1
kg
Pyrantel Pyran Tablets Dogs, cats 2 weeks
Pyr-a-Pam Tablets Dogs, cats 2 weeks
Strongid* Drench Dogs, cats 2 weeks
Pyrantel + oxantel Pyr-a-Pam Plus Tablets Dogs
Selamectin Revolution Topical liquid Dogs, cats 6 weeks
Sulfadiazine S-125 Tablets Dogs, cats N.A.
Toltrazuril* Baycox* Drench Dogs, cats 3 weeks
5.4 The residual effect
The residual effect of drugs has almost never been tested in pets. In herbivorous animals
kept on a pasture, it is relatively easy to approximately calculate the length of this period.
If the infection pressure is high, fecal samples are taken from the animals every week or
every other week. The animals are treated at the beginning of the period, and the interval
between when parasite egg-laying disappears and the reappearance of eggs in the feces is
calculated. Then we simply subtract the prepatency period from the calculated period to
obtain the duration of the residual effect.
Another way to do this, with experimental infections, is to treat the animal and infect it
after a determined period of time. Thus, administering infective Uncinaria larvae to dogs
treated 18 days earlier with moxidectin did not cause any infection in the animals (Epe,
2004). It can thus be conclude that, in experimental conditions, moxidectin persisted for
18 days in the animals at a concentration high enough to protect them against Uncinaria
infections. However, it would be risky, to say the least, to extrapolate this conclusion to
any other species of parasite, as long as it has not been investigated in a specific
experiment.
However, the duration of this residual effect is important in term of flea prevention.
Efficacy studies have carefully calculated this duration. For example, 27 days after
administering selamectin to a dog at a rate of 6 mg/kg of bodyweight, it was infested with
100 fleas. Seventy-two hours later, the animal’s coat was combed with an appropriate
instrument to find every living flea that was still present on the animal. Ninety-eight
percent of the fleas had disappeared (McTier et al., 2000). It can therefore be concluded
that the duration of the residual effect of selamectin against fleas is greater than 27 days.
However, the limits of our definition of “residual effect” should be spelled out
beforehand. We will thus need to determine the cutoff below which we consider that the
drug loses its efficacy. A number of products presently in use exhibit a residual effect
lasting approximately a month.
34

There is another type of study that provides certain information about Toxocara in an
indirect manner. These studies involve administering macrocyclic lactones to pregnant
and nursing bitches in order to observe the protective effect of this program on their
puppies. In the last trimester of pregnancy and during nursing, tissue larvae reactivate and
find their way to the fetuses and puppies by crossing the placenta or as a result of being
excreted in the colostrum and milk. Thus, the protective effect of macrocyclic lactones
can be evaluated by comparing the parasite load in treated puppies with that in control
puppies. Such studies have been conducted with doramectin, ivermectin and selamectin,
with convincing results (Payne and Ridley, 1999; Payne-Johnson et al., 2000; Schneider
et al., 1996). The residual effect and the effect of periodic treatments on this protection
conferred to puppies has not been evaluated separately, but this is a useful approach in
the context of a prevention program.
5.5 The effect against the different stages
It is relatively easy to determine the efficacy of a given substance against the adult stage,
and the techniques for doing this are well-known. For the larval stages, one must bear in
mind that there are two forms of larvae, migrating and hypobiotic. It is important to
carefully distinguish between “inhibited, quiescent, hypobiotic, or encysted larvae” and
“developing larvae”. The former are often encysted in cells or tissues, their metabolism is
at a minimum, and they exhibit little activity. The latter dwell in tissues or even in the
lumen of organs (liver, blood vessels, intestines, or respiratory tract), have a very high
level of metabolism, and are active. It is easy to imagine that drugs will not necessarily
have the same efficacy against these two different types of larvae, given their location,
their different levels of metabolism, their different surface antigens, and so on.
Previously, this matter was important with regard to drugs that exhibited little intestinal
absorption. Nowadays, most of the drugs used (macrocyclic lactones, benzimidazoles)
pass into the bloodstream and can thus exert their effect on the larval forms. However,
only fenbendazole administered at 150 mg/kg/day for three days has demonstrated a high
level of efficacy against Toxocara canis larvae encysted in tissues other than the central
nervous system.
The supply of migrating larvae probably continues, even after all the sources of infection
have been eliminated. The reactivation of inhibited larvae seems to be a continuous
phenomenon with Toxocara and Ancylostoma. This would explain the reactivation of
larvae in the last trimester of gestation, for example. Using a drug that has no effect
against larvae leaves in place parasites that will start laying eggs relatively early, that is,
before the end of the known prepatency period of that particular species. On the other
hand, using a drug that exerts an effect against migrating larvae will prevent the parasites
from laying eggs for a period of time equal to the prepatency period, but no longer.
Lastly, using a drug that exerts a residual effect lasting 18 days against a given species of
parasite may increase, by an additional 18 days, the interval between treatments for this
parasite. Therefore, the main advantage of using a drug with a residual effect is to enable
us to increase the intervals between treatments. On the other hand, the use of these drugs
can promote resistance, at least in theory, mainly as a result of the exposure of parasites
to the decreasing doses at the end of the between-treatment interval. However, the dose
35

equired to destroy parasites varies according to the species, and increasing the intervals
between treatments is limited by the parasite species that is the least sensitive to the drug.
Thus, for many drugs, the effect against fleas does not seem to persist beyond one month,
which limits the length of the interval for more-sensitive parasite species, for which
longer intervals can be used. For instance, ivermectin destroys third- and fourth-stage
Dirofilaria larvae at a dose of 6 μg/kg and first-stage larvae at a dose of 50 μg/kg, but has
little of no effect on adult parasites, even at a dose of 200 μg/kg.
5.6 Resistance to anthelmintics
Since antiparasitic drugs are being used more and more commonly and on a wide-scale
basis, many people wonder if we might be creating resistance problems. However, very
few publications have reported such a problem. A first case was reported in a 9-week-old
puppy with a hookworm load that was high enough to be life-threatening. The puppy was
treated twice in three weeks with pyrantel pamoate. The fecal examination performed a
few days after the second treatment still showed considerable egg excretion (Jackson et
al., 1987). It is known that anthelmintics are less effective in highly parasitized animals.
This is probably due more to the fact that these drugs are poorly absorbed than to a
resistance phenomenon. The other two cases reported concern greyhounds, animals that
need to be dewormed against Toxocara and Ancylostoma every two to three weeks for
years (Ridley et al., 1994). In one case, pyrantel pamoate had zero efficacy in two
puppies and 81.6% efficacy in two others. In the other case, the mean efficacy of this
drug was 83.84% in five dogs, which, overall, is acceptable and statistically
nonsignificant. Recently, in a clinical trial performed in Australia, the pyrantel pamoate
efficacy was only 25.7% against Ancylostoma caninum experimentally infected dogs
(Kopp et al., 2006).
There is very likely no basis, at least in the short term, for fearing resistance in parasites
that affect our pets. There are several reasons for this. Resistance usually develops in
animals kept in a relatively closed environment, such as horses, poultry and sheep. It
develops in herds kept on the same pasture or in the same pen and is generally limited to
this environment. And, resistance develops in parasites with relatively short generation
times, such as coccidia, trichostrongyles, and cyathostomes.
Dogs and cats are seldom kept in such conditions. Drugs are used on a wide-scale basis
but often for preventive purposes only, when there are no parasites. Therefore, selection
pressure on parasites is negligible. This is especially true for heartworms and fleas. If
ever the parasite produces resistant offspring, they will first have to contend with
environmental conditions such as freezing in the winter and dry weather and sunshine in
the summer, which will kill most of them. The few survivors ingested by a suitable host
will be targeted by the animal’s immune system, which may encyst them, with the result
that most of them will not produce any offspring. Another factor that can come into play
is the wide variety of drugs used to destroy parasites: fenbendazole, macrocyclic lactones
(ivermectin, milbemycin, moxidectin, selamectin), nitroscanate, pyrantel pamoate, and
piperazine. Rotating drugs in a given region is therefore already being done. Lastly, since
animals in a given region constitute a highly differentiated group, if only because of
36

eed and place of birth, we can expect considerable genetic variety both in them and in
the parasites.
Determining if there is a fecal egg count reduction is one of the techniques generally used
to determine if there is a resistance phenomenon (Wolstenholme et al., 2004). The animal
is dewormed, and egg output is evaluated at the time of treatment and two weeks later.
The decrease should be at least 90%. This approach may not be suitable for all animals,
drugs, or parasite species. Puppies naturally infected with Toxocara were treated with
piperazine. Necropsy showed that 86% of the parasites had disappeared, despite a
statistically nonsignificant fecal egg count reduction (Fisher et coll., 1994).
6. The case of heartworm
6.1 Canine heartworm disease
AHS : The official recommendations of the American Heartworm Society are available
on its website and in Veterinary Parasitology (2005; 133 : 255-266). Here are the
highlights of interest to Canada:
- In most parts of Canada, the peak period for infection in limited to the months of July
and August. It can be slightly longer than three months in the southernmost areas of
Ontario and about two months in the other provinces. This period was determined on the
basis of meteorological data (Slocombe et Surgener, 1997) and seems to cover the
transmission season.
- Dogs should be screened at 7 months postinfection if blood concentration techniques
are used or at 9 months if serological tests are used. Serological tests can detect an
infection form the fifth month following infection, but maximum sensitivity in animals
with a small worm burden and in those protected by the administration of macrocyclic
lactones is achieved only after nine months. Therefore, blood filtration tests should be
started in April or May and serological tests only in June. Performing a test before this
period yields information not on the previous season, but instead on the year before,
which makes it of little value.
- A positive antigen test should always be confirmed, especially in animals at low risk for
infection. An unconfirmed positive result cannot be cited as a reason for starting
adulticide treatment.
- Blood concentration techniques are used to identify animals that serve as reservoirs of
infection.
- Prophylaxis should be initiated no later than the age of 8 weeks during an infection risk
period.
37

- In animals that are unprotected during the transmission season and that might be
harbouring parasites aged 10 weeks or older, monthly treatment for an entire year should
be initiated immediately.
- A lack of efficacy has been reported for all the macrocyclic lactones used in canine
heartworm disease prophylaxis. An annual screening test is therefore strongly
recommended.
- For adulticide treatment, it is strongly advisable to administer a first dose of
melarsomine, followed four to six weeks later by two doses separated by a 24-hour
interval. This protocol lowers the risks inherent in the treatment.
- Microfilaricide treatment is initiated as soon as a diagnosis is made. Milbemycin seems
to be the drug with the greatest microfilaricidal effect. After the fist dose is administered,
the dog should be monitored because of the risk associated with the death of a large
number of microfilariae. Major reactions were observed in dogs whose microfilaria count
had been estimated to be as low as 5,000 per millilitre of blood (30 to 40 microfilariae per
microscope field at x10 magnification in the filtration test). The reasons for initiating this
treatment before administering an adulticide are to reduce the number or circulating
microfilariae, to eliminate the migrating third- and fourth-stage larvae, and to reduce the
adult worm mass by inhibiting the female’s reproductive system. In addition, it is not
known how effective melarsomine is against larvae aged 4 months or less. The risk of
thromboembolism during subsequent adulticide treatments will be reduced accordingly. It
is advisable to delay adulticide treatment for six months.
- The long-term use (12 months) of a macrocyclic lactone is beneficial in animals that are
infected but that display no clinical signs and have very few or no radiologically
documented pulmonary lesions and few or no microfilariae. Ivermectin seems to give the
best results in such cases, mainly because if its long-term lethal effect on young adult
worms. However, this approach does not seem to bring about improvement in chronically
infected animals with major clinical signs. If this type of treatment is administered to
such an animal, it is important to do a follow-up two or three times a year.
- Certain macrocyclic lactones now have a residual effect that makes them more
effective, but for now, it is not advisable to lengthen the interval between treatments.
Additional comments
Annual screening test for all dogs: It has been shown that drugs cannot provide 100%
protection against heartworms. This is probably the only reason why the AHS has called
for a shorter interval between screening tests. Before applying this measure to all dogs,
one should take the following points into consideration. Even a low parasite load can lead
to the appearance of microfilariae in the blood and permit transmission of the infection,
which goes against the main objective of our intervention. If infection occurs, it will, in
all probability, be by a small number of worms, which do not constitute a threat to the
38

infected animal’s health. Since infection pressure is low in our region, very few animals –
in absolute value – receiving preventive treatment will be infected.
According to postal surveys carried out in Canada in the past, the number of animals
infected despite preventive treatments (including those cases where people forgot to
medicate their animals for several months) was about 1 dog in 10,000. By way of
comparison, and according to the surveys, the prevalence of heartworm disease in
unprotected dogs was approximately 1 or 2 cases per 1,000. This would work out to a low
percentage of 0.1 to 0.2% of dogs that could be infected due to incomplete drug efficacy.
Therefore, there really is no deed to change our current practice with regard to our
regions and to our animals, if they never venture into highly enzootic areas.
Greater emphasis should be placed on the annual screening test in certain animals. The
following groups, which are considered to be at greater risk, might serve as a guide to
making this decision:
Dogs that travel to enzootic areas, such as the eastern half of the United States or
any coastal area anywhere in the world.
Dogs that live in an area of Canada considered enzootic because one or more
cases were detected there in previous years.
Dogs that live in rural areas.
Dogs that spend a lot of time outdoors.
Before initiating a second season of prophylaxis.
If there is reason to believe that one or more doses have been missed.
What type of test should be used? Our objective in using a diagnostic test is to identify
infected animals in order to treat them and to prevent transmission of the infection to
other animals. It is important to treat animals with health problems or microfilaremia.
Occultly infected animals might be identified by antigen testing but will, in all likelihood,
be treated like noninfected animals. The number of cases of occult infections in an area of
very low endemicity, such as in Canada, will always be extremely low. That equals to
about one-fourth the number of microfilaremic cases, or 0.02% of all dogs. Therefore,
blood concentration techniques make it possible to identify animals that are transmitting
the infection, and animals manifesting clinical signs will undergo a battery of tests in any
event. In conclusion, blood concentration techniques enable us to achieve our objectives
just as well as antigen tests. However, this applies only to areas where the prevalence is
extremely low, which is the case with most areas in Canada.
Should one continue to take preventive measures? The postal survey enabled us to
closely monitor the situation in Canada, despite the problems associated with the survey.
We have now abandoned this approach and are using instead web-based voluntary
reporting. This very practical tool worked well in 2004 and 2005, but it is obvious, with
39

the current data gathered in 2006, that there is general disinterest. This is unfortunate, for
the direct result of this state of affairs is to believe that the prevalence of heartworm
disease is on the decline, which has certainly not been demonstrated. If we are not
convinced of the importance of our program, it goes without saying that we will do less
of it. It was mentioned earlier that, as in epidemiological studies carried out in other
models, if we can protect a large percentage of the population, then a large proportion of
other animals would be protected as well. For instance, if was pointed out that
vaccinating a large percentage of animals in a given population stops a potential epidemic
and thus protects the nonvaccinated animals. I do not find this reasoning valid for
heartworm disease because of the presence of a large reservoir that we can do nothing
about – wild canines. More than ten years ago, the proportion on infected coyotes in
Monteregia was around 10%, and it has probably increased since then. Interestingly, most
dogs found to be infected over the past several years were living in rural areas, which
underscores the strong likelihood of wild canines being the current source of infection.
There are two other arguments that underscore the importance of our program. If we look
closely at the situation with the infection in the Hudson/St-Lazare area, west of Montréal,
we realize that it is impossible to eradicate the infection once it is present in a given area
(see Table 26). It was estimated, with the veterinarians working at the time of the
epidemic, that approximately 10 to 20% of the dogs in this municipality were infected.
Dogs are still becoming infected there 20 years later.
Table 26. Number of cases of canine heartworm disease reported in the Hudson/St-
Lazare area
Number of
cases
120
100
80
60
40
20
0
83 85 87 89 91 93 95 97 99 1 3
40
Years

Table 27. Number of cases of canine heartworm disease reported in Canada in the
annual postal survey
Number of
cases
1600
1400
1200
1000
800
600
400
200
A last argument that might convince us to take preventive measures is the possibility of
this parasite infecting humans. Many people become infected but destroy the parasite
without experiencing any ill effects. However, other people develop a pulmonary nodule
measuring 2 to 3 cm in diameter following the death of the parasite in a pulmonary
artery. About half of these people will experience clinical signs and symptoms
bothersome enough to prompt them to seek medical attention. More than 180 cases have
been reported in the literature for the United States alone, and one woman in Ontario was
recently found to be infected. In all likelihood, a number of infected individuals will
never be identified, which suggests that this figure could be much higher.
6.2 Feline hearworm disease
0
76 78 80 82 84 86 88 90 92 94 96 98 0 3 5
The official recommendations of the American Heartworm Society are available on its
website and in Veterinary Parasitology (2005; 133: 267-275). Here are the highlights of
interest to Canada:
- Although cats are susceptible to heartworm infection, they are more resistant to it than
dogs. The usual burden encountered consists of one or two worms, and there are fewer
than six in most cases.
- The mosquitoes known to be the most important vectors prefer to feed on dogs, which
could explain, in part, why there is a lower prevalence of infection in cats. However,
mosquitoes of the genus Culex, which are very common in urban areas, have no
preference in this regard.
41
Years

- The prevalence of feline heartworm disease is thought to be 5 to 15% of that observed in
unprotected dogs in the same area.
- Microfilariae sometimes appear in the blood of infected cats. They appear in the blood
more than 195 days postinfection and can be detected there for a period of about one
month. The lifespan of the adults has been estimated at two to three years.
- Intimal proliferation of the arteries harbouring the parasites is usually localized. Since
there are very few worms, collateral circulation is adequate to prevent pulmonary
infarction. However, clinical signs, often diagnosed as asthma or allergic bronchitis,
develop around the third and fourth month postinfection, then disappear.
- Diagnosing heartworm disease in cats is difficult and requires the use of several different
techniques. They are used mainly in cats manifesting clinical signs suggestive of
heartworm disease and, less often, for screening purposes.
- Only D. immitis has been reported in cats. Its presence can sometimes be detected by
blood concentration techniques.
- Serological tests showing the presence of antigens become reactive 5.5 to 8 months
postinfection and can only detect the presence of female worms. According to a study
involving shelter cats, approximately 50 to 70% of infected cats have at least one female
worm. Tests showing the presence of antibodies are able to detect both males and females
as early as two months postinfection. However, their sensitivity is reportedly between 32
and 89%. It seems that the antibody titer decreases as the worm matures and that it is higher
in infected animals displaying clinical signs.
- The radiological signs are the same as in dogs. There is a subtle increase in the diameter
of the main lobar and peripheral pulmonary arteries. These changes are especially visible in
the ventrodorsal view and particularly in the right caudal lobar artery. Such changes are
reported in about 50% of cats suspected of being infected, based on their history and
clinical signs. They are therefore encountered less often than in dogs.
- The worm or worms can be visualized echocardiographically, provided they are in the
large vessels. Because of their very large size, if the worms are more than 5 months old, the
likelihood of their being in these large vessels is rather high.
- An annual or biennial follow-up is done for cats that are infected but that display few
clinical signs. In such cases, it is advisable to allow time for a spontaneous cure. Prednisone
can be used in animals with radiologically documented lesions. Adulticide treatment should
be used as a last resort. Ivermectin administered at a dose of 0.024 mg/kg once monthly for
two years reduced the parasite load by 65%. When the worm dies, the release of antigens
can cause an anaphylactic-type reaction.
42

- In cats, prophylaxis can be achieved with a macrocyclic lactone. Given the small number
of microfilariae present, there is no need to test these animals before medicating them.
Screening involves both the antigen test and the serological test.
- Prophylaxis should be initiated no later than the age of 8 weeks during an infection risk
period.
Comments: Because of the high pathogenicity of heartworms in cats, especially since they
can cause an anaphylactic-type reaction, prophylaxis in at-risk animals is quite important.
On the other hand, the prevalence in Canada is too low for this to constitute a valid
argument. The approach differs form that for dogs, mainly because screening is not as
important. Clients should be well-informed so that they can make an informed decision.
Table 28. Number of cases of feline heartworm disease reported in Canada in the
annual postal survey
Number of
cases
40
35
30
25
20
15
10
5
7. The case of fleas
0
76 78 80 82 84 86 88 90 92 94 96 98 0 2 4
How transmission occurs. Very little transmission occurs through simple direct contact
between animals. It occurs more readily through exposure to newly emerged fleas, for
instance, when an animal is taken to a place outdoors frequented by stray dogs. Certain
wildlife could act as a reservoir, in particular, skunks, racoons and wild canines. More
than 50 animal species have been found to be naturally infested with cat fleas.
Treatment season. If an animal is found to be infested with fleas and if flea eggs have
very likely been left inside the home, it would be advisable to initiate monthly treatment
for a period of at least five months. For prophylaxis in an animal that is free of fleas but
which is at risk of becoming infested, it would be a good idea to initiate treatment early,
that is, in early June or perhaps even in early May. If ever the animal becomes infested
43
Years

efore the treatment program is started and infests the inside of the home, the program,
because of its length, will eradicate these fleas in the months that follow.
When a man weighing more than 75 kg walks on a carpet containing cocoons, he causes
the emergence of 31% of the fleas after a single pass and 100% of them after the fifth
pass (Silverman et Rust, 1985). Studies have shown that during the summer, 90 to 95% of
fleas emerge between the 28 th and 35 th day and only a few between 35 th and 60 th day.
According to American studies, all fleas hatch within five months. However, European
authors have observed sporadic emergences up to 50 weeks after the start of pupation.
Fleas survive the winter only on infested animals or in places that are very well protected
against the cold. For a cat that roams outdoors, even in the winter, consideration might be
given to placing it on a year-round treatment, as it could take refuge in a flea-infested
shelter and bring some back into the home.
Flea products act quickly. Fleas jump onto animals and take a first blood meal almost
immediately, on average, within 30 seconds (Cadiergues et coll., 2000; Dryden et Rust,
1994). Mating takes place after the meal, and the female starts to lay eggs one to two
days later. Egg production is rather low during the first three days (Thomas et coll.,
1996).
Table 29. Details on antiflea agents for dogs and cats
Substance(s) Trade name(s) Formulation(s) Mechanism of
action
44
Action
Pyrethrins Several Powder, spray, etc. Sodium channels Adulticide
Permethrins* Defend, etc Topical Sodium channels Adulticide
Methoprene Ovicollar, etc Collar, spray Larvicide Growth inhibitor
Lufenuron Program
Sentinel
Imidacloprid Advantage,
Advantage
Multi
Tablets, injectable Larvicide Inhibits hatching
Topical Blocks
acétylcholine
receptors
Nitenpyram Capstar Tablets Blocks
acétylcholine
receptors
Adulticide
Adulticide
Selamectin Revolution Topical GABA antagonist Adulticide
Substance(s) Minimum age
for treating
Onset of action Duration of
residual effect
Pyrethrins 8 weeks Minutes Days < 1980
Permethrins* 8 weeks Minutes to 72 hours 4 weeks 1980
Methoprene No mention Slow 7 to 12 months 1994
Lufenuron 6 weeks (cats)
6 weeks (dogs)
Slow 32 to 45 days 1994
Year launched

Imidacloprid 8 weeks 2 to 12 hours 4 weeks 1997
Nitenpyram 4 weeks 30 minutes to 6
hours
45
36 hours (cats)
24 hours (dogs)
2000
Selamectine 6 weeks 12 to 36 hours 4 weeks 2000
* = The use of permethrins in cats can lead to severe poisoning
Recommendations:
Animals that go outdoors, even for brief periods of time, should be treated
prophylactically to protect them during the period from early June to late
November.
Treating the inside of a home in which an infested animal lives is not indicated,
unless there are very young children or someone with an allergy, the animal is
allergic, there are a large number of fleas, or the occupants cannot tolerate fleas
being there. In such cases, the services of an exterminator may be used.
One or more fleas may persist on a treated animal without this having to cast
doubt on the product’s effectiveness. All the available products will take a certain
amount of time before they kill a flea that jumps onto a treated animal. This is of
more concern if the animal’s environment is still infested.
An allergic animal will benefit from the use of any flea product, provided the
parasite load decreases both on the animal and in the environment within a
reasonable amount of time.
Acknowledgements
The author would like to thank Pfizer Animal Health for their support in the production,
printing and distribution of this document.
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