Guide to Preventing Parasites.pdf - Royal Canin Canada

More documents

Recommendations

Info

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
Page 1 and 2: GUIDE TO PREVENTING PARASITE INFECT
Page 3 and 4: Contents 1. Species reported in dog
Page 5 and 6: Tapeworms Specific to dogs Specific
Page 7 and 8: Table 2. Canadian studies of the pr
Page 9 and 10: Capillaria spp. 0.1 0.9 Taenia spp.
Page 11 and 12: Table 6. Parasite prevalence in sam
Page 13 and 14: The total number of specimens from
Page 15 and 16: Table 12. List of canine and feline
Page 17 and 18: Toxocara canis 4 3 2 9 Toxoplasma 5
Page 19 and 20: 3.4 A program tailored to our condi
Page 21 and 22: seem very reassuring, but at best,
Page 23 and 24: Table 16. Egg density varies accord
Page 25 and 26: Table 20. Recommended techniques fo
Page 27 and 28: Giardia > Y ++ + + Taenia = ++ + ++
Page 29 and 30: Special terminology is used on labe
Page 31 and 32: Sarcophagidae (myiasis) Ivermectin*
Page 33 and 34: Table 25. List of drugs and their m
Page 35: There is another type of study that
Page 39 and 40: infected animal’s health. Since i
Page 41 and 42: Table 27. Number of cases of canine
Page 43 and 44: - In cats, prophylaxis can be achie
Page 45 and 46: Imidacloprid 8 weeks 2 to 12 hours
Page 47 and 48: HALAL F, Lampron F, Viens P. 1975.

Guide to Preventing Parasites.pdf - Royal Canin Canada

Create successful ePaper yourself

Delete template?

Save as template?