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Questions and Answers Surrounding the 2012-2013 Outbreak of Cattle Anaemia
Associated with Theileria orientalis.
Summarised by Katie Hickey, Adviser, Animal, Marine and Food Response Team, Investigation
Diagnostic Centres and Response Directorate, Ministry for Primary Industries.
Classification of Theileria According to the World Organisation for Animal Health
(OIE):
Genus Theileria, Family Theileriidae, Order Piroplasmida, Subclass Piroplasmia, Phylum
Apicomplexa.
• Theileriae are obligate intracellular protozoan parasites that infect both wild and domestic
Bovidae throughout much of the world
• Some species also infect small ruminants
• They are transmitted by ixodid ticks, and have complex life cycles in both vertebrate and
invertebrate hosts
• There are six identified Theileria spp. that infect cattle; the two most pathogenic and
economically important are Theileria parva and Theileria annulata
• T. parva occurs in Eastern and Southern Africa and causes East Coast fever (ECF or
Corridor disease)
• T. annulata causes tropical theileriosis (TT), also known as Mediterranean theileriosis and
occurs in North Africa, southern Europe and Asia
• T. lestoquardi is the only species of economic significance infecting small ruminants, and it
occurs in the Mediterranean basin, North Africa and Asia
• Most Theileria species are confined to Asia or Africa corresponding to the geographical
distribution of their vector ticks, except for the worldwide distribution of the apathogenic T.
buffeli.
What is the distribution of the Theileria orientalis in other countries?
T. orientalis has been recognized in New Zealand cattle since 1982 and is known to be
present in Australia, Japan, and other Asian countries as well as in Turkey, the UK, France,
Spain and the USA.
T. orientalis belongs with the T. sergenti/ T.buffeli group of Theileria parasites. The
taxonomic status of this group has been debated for many years. Based on Major Piroplasm
Surface Protein (MPSP) and 18S Rdna sequences, studies have designated these parasites
as the T. sergenti/ T. buffeli/ T. orientalis group of benign Theileria.(Kamau et al 2011)

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What is known about the cattle tick- Haemaphysalis longicornis?
General Features:
The New Zealand cattle tick, Haemaphysalis longicornis (H. longicornis), is reported to have
been introduced into Australia from Japan. H. longicornis is likely to have been present in
New Zealand from near the beginning of the 20 th century (possibly around 1908). Before the
introduction of the Stock Act 1908, there was unrestricted importation of livestock into New
Zealand from Australia, with the potential of bringing disease that had been acquired through
Australia’s own importations from other countries.
The cattle tick H. longicornis occurs in a number of countries bordering the western Pacific.
It is a three-host tick, larva (from the egg), nymph (emerging from the engorged larva) and
adult (emerging from the engorged nymph). The New Zealand strain is parthenogenetic, so
only females are found. The tick has a low level of host-specificity, feeding on a wide range
of mammals and birds. Each stage feeds for around 4 days (larva) or 7-10 days (nymph and
adult) dropping to the ground when fully engorged and moults days or weeks later,
depending upon temperature. Unfed ticks can survive for around 12 months without feeding.
The cattle tick assumes considerable importance in New Zealand, because it is the only
exotic tick that has established here which has an economic impact. It causes production
losses in cattle, deer, sheep and other livestock, as well as deaths, and infests endemic
animals such as kiwi and other birds.
Distribution of H. longicornis in New Zealand:
There has never been a comprehensive survey to describe the locations where the cattle
tick is found. The distribution described here is a culmination of reports to Allen Heath, and
from veterinarians in the field. The cattle tick can be found throughout much of the North
Island, numbers are sparse down through the Hawkes Bay and Wairarapa as well as in the
Manawatu. The most southern limit for the tick on the East Coast of the North Island is near
Pirinoa in the Wairarapa, and areas of sand-dunes a little further to the south appears to be
the southern limit of the tick on the west coast of the North Island.
In the South Island H. longicornis has been found in Tasman and Golden Bay. Other South
Island records include Motueka, Takaka and in Marlborough north of the Wairau River
(Heath et al. 2011). There is recent confirmation that ticks are not found on the West Coast
of the South Island. The cattle tick was briefly introduced into Southland some years ago
and was eradicated by strict monitoring and surveillance and dipping. There were only two
properties involved, so eradication was achievable.
What is the period between tick infestation, parasitaemia and clinical disease i.e. how
long from tick bite to anaemia?
Sporozoites of T. orientalis are transmitted in the saliva of a feeding adult ticks and nymphs,
so could be entering the host within minutes of full attachment and commencement of
feeding. Schizonts can appear in the host within 3 days of infection. There is no transovarial
transmission so each tick stage must acquire its own Theileria organisms to become
infected, but transstadial transmission (from tick stage to tick stage as larva moults to nymph
and nymph to adult) also occurs.

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The pathogenesis of the Theileria orientalis group species (T. sergenti/ T. buffeli/ T.
orientalis) has not been described in any detail however, generally Theileria is first seen in
peripheral blood approximately 2-3 weeks after infestation with vector ticks. The effect of
Theileria orientalis group parasitised erythrocytes on haematological parameters (blood
haemoglobin and HCT) precedes the appearance of the parasite by 4-6 days (Yagi et al.
1991). In an infected animal there are two peaks in parasitized red blood cells. The second
peak, occurring 1-2 months after infection, is associated with the severest clinical signs of
anaemia (Kawamoto et al. 1991).
When is the correct time to start tick prevention programs? Does treating early
reduce risk of needing to treat adult ticks later?
There are two critical times to treat livestock against ticks that will reduce the numbers of
ensuing tick lifecycle stages, but the timing does not necessarily always match farm
management practice. Dipping (including spray and pour on acaricides) between July and
August will hit nymphs that have overwintered. Once may not be enough; it depends upon
the persistence of the product used. Nymphs once fed, will become adults, so reducing
nymphal numbers early reduces subsequent adult numbers in October through December.
Another critical time is when larvae are active, between February and March. By reducing
their numbers there will be fewer nymphs to overwinter (nymphs arise from fed larvae) and
so next season there should be fewer ticks.
Treatments in months outside these principal activity times will only target a small number of
ticks and so will not be as effective in bringing subsequent numbers down. Maximum activity
of each stage is compressed into a relatively short space of time, hence the critical treatment
periods.
There is of course no reason why stock cannot be treated when adults are active (October
to January), as this will reduce the numbers available to lay eggs, however, larger ticks may
be harder to kill because of the dose of insecticide needed to affect them (dependant on
product used) and as noted above, if the stage that leads to adults is hit hard, then treatment
for adults becomes less necessary.
The problem with relying on dipping alone is that there is a continuum of tick activity that
demands more than one treatment of stock over the tick activity season to ensure that most
questing ticks get into contact with treated stock. That is another reason for two treatments
within a relatively short period (Heath pers comm May 2013.)
Cattle ticks are almost impossible to eradicate from a property by chemical treatment alone
because they are on and off the host in a week and live in pasture for many months. The
ticks can also survive on native animals. Chemical control combined with pasture
management is the most effective method of minimizing the tick population.
What about suggesting treating all new stock with tick treatments before introducing
them to the rest of the herd?
When bringing cattle from known Theileria areas you risk introducing Theileria to the rest of
your herd if ticks are present on that animal or in the environment. Treating cattle that are to

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be introduced should help reduce the chance of spread to the rest of the herd. However
parasitaemic animals can still result in spread to cattle if there are ticks present on your
property.
Will herds build immunity to Theileria? Will the incidence of the disease decrease
over time in those farms that are already T. orientalis Ikeda positive?
Herd immunity will develop after exposure to the parasite. Whether disease will continue to
be evident clinically in a herd will be dependant on previous exposure to the Theileria,
colostral immunity, tick populations, as well as rates of infection. The health status and
additional stresses on the herd will contribute to development of disease. Some years there
will be no problems and other years there will be, as has been the case since T. orientalis
was first recognised in New Zealand in 1982. Herd immunity may be slow to develop. One
herd under investigation still has anaemia after being diagnosed with Theileria eight months
ago (albeit at a low prevalence.) There may be specific aspects of the climatic, tick and
production system characteristics in New Zealand which require further study. The
dynamics of these variables will effect what we see next season.
Figure 1: Conceptual model of the relationships between infection challenge by ticks,
disease incidence case fatality and antibody prevalence in tick-borne disease
infestations (L’Hostis and Seegers 2002)

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Is it correct to assume that there is no disease issue in meat or dairy products derived
from affected animals?
There is no disease issue in meat or dairy products from affected animals. There are no
human health risks or food safety risks associated with Theileria orientalis.
Is the main concern with Theileria the effect it has on cattle herd productivity?
Yes, the main concern is a production issue; there is the possibility of decreased milk
production, increased abortion, and a decrease in pregnancy rate. We may not see the full
effect of the impact, of a new strain of Theileria orientalis in New Zealand, on production for
a year or more.
Ticks alone can cause disease, how can you differentiate between disease caused by
Theileria and disease caused by ticks alone?
Ticks elicit a host response when their mouthparts pierce the host’s skin. While feeding, the
tick injects saliva into the host, causing a variety of unfavourable reactions. These reactions,
together with blood loss, may adversely affect livestock productivity and may in themselves
occasionally result in death, particularly in tick-naïve animals and when tick burdens are high
and animals are further stressed. Current epidemiological investigations of the outbreak of
anaemia are elucidating the relationship of Theileria infection and morbidity.
When are cattle at most risk of Theileria infection?
Cattle are susceptible to Theileria infection during times of stress, for example:
• Peri-parturient depression of immunity.
• When suffering from concurrent disease.
Can Theileria be transmitted iatrogenically?
Infections of Theileria in herds will be sustained by a combination of the enduring character
of Theileria infections in individual cattle, and the presence of a competent population of
ticks infected with Theileria. Transmission amongst cattle will primarily occur via ticks
feeding. However mechanical transmission of blood from an infected animal to an uninfected
animal can also result in the uninfected animal becoming infected. Small amounts of blood
that may be present in vaccination needles may be sufficient to cause infection. In New
Zealand, it may also be possible that the stable fly could potentially transfer Theileria
infection.
If Theileria was spread via needles or flies in the continued absence of ticks, the disease is
unlikely to be maintained in the host population in that particular herd.

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Acknowledgments:
Thank you to Allen Heath for providing the references on Haemaphysalis longicornis:
“The role of ticks and biting flies in the transmission of theileriosis.” Allen Heath 2013.
Cane R (2010). Profile: Haemaphysalis longicornis Neumann, 1901. New Zealand
Biosecure, Entomology Laboratory. Available at:
http://www.smsl.co.nz/site/southernmonitoring/files/NZB/Ha%20longicornis%20Profile.pdf
And thanks to Kevin Lawrence, Andrew McFadden, Zhidong Yu, Richard Norman and
Stephen Cobb for their contribution.
Other references:
http://www.dpi.nsw.gov.au/biosecurity/animal/info-vets/Theileria
James MP, Saunders BW, Guy LA, Brookbanks EO, Charleston WAG, Uilenberg G (1984).
Theileria orientalis, a blood parasite of cattle. First report in New Zealand. New Zealand
Veterinary Journal. 32, 154-156.
James MP (1984). Theileria orientalis in Northland cattle. Surveillance 11(3), 18-19.
Kamau J, de Vos AJ, Playford M, Salim B, Kinyanjui P, Sugimoto C (2011). Emergence of
new types of Theileria orientalis in Australian cattle and possible causes of theileriosis
outbreaks. Parasites and Vectors 22, 1-10
Kawamoto S, Takahashi K, Onuma M, Kubota S, Nejo H, Kurosawa T, Sonoda M (1991).
Rebound phenomenon of parasitemia in splenectomized calves primarily infected with
Theileria sergenti. J Vet Med Sci. Feb;53(1):127-8.
L’Hostis M, Seegers H (2002). Tick-borne parasitic diseases in cattle: Current knowledge
and prospective risk analysis related to the ongoing evolution in French cattle farming
systems. Veterinary Research 33, 599-611.
McFadden AMJ, Rawdon TG, Meyer J, Makin J, Morley CM, Clough RR, Tham K, Mullner P,
Geysen D (2011). An outbreak of haemolytic anaemia associated with infection of Theileria
orientalis in naive cattle. New Zealand Veterinary Journal, 59, 79-85.
The World Organisation for Animal Health, technical disease cards:
http://www.oie.int/fileadmin/Home/eng/Animal_Health_in_the_World/docs/pdf/THEILERIOSIS_FINAL.
pdf
Yagi Y, Ito N, Kunugiyama I (1991). Decrease in erythrocyte survival in Theileria sergentiinfected
calves determined by non-radioactive chromium labelling method. J Vet Med Sci.
Jun;53(3):391-4.