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<strong>Questions</strong> <strong>and</strong> <strong>Answers</strong> <strong>Surrounding</strong> <strong>the</strong> <strong>2012</strong>-<strong>2013</strong> Outbreak of Cattle Anaemia<br />
Associated with Theileria orientalis.<br />
Summarised by Katie Hickey, Adviser, Animal, Marine <strong>and</strong> Food Response Team, Investigation<br />
Diagnostic Centres <strong>and</strong> Response Directorate, Ministry for Primary Industries.<br />
Classification of Theileria According to <strong>the</strong> World Organisation for Animal Health<br />
(OIE):<br />
Genus Theileria, Family Theileriidae, Order Piroplasmida, Subclass Piroplasmia, Phylum<br />
Apicomplexa.<br />
• Theileriae are obligate intracellular protozoan parasites that infect both wild <strong>and</strong> domestic<br />
Bovidae throughout much of <strong>the</strong> world<br />
• Some species also infect small ruminants<br />
• They are transmitted by ixodid ticks, <strong>and</strong> have complex life cycles in both vertebrate <strong>and</strong><br />
invertebrate hosts<br />
• There are six identified Theileria spp. that infect cattle; <strong>the</strong> two most pathogenic <strong>and</strong><br />
economically important are Theileria parva <strong>and</strong> Theileria annulata<br />
• T. parva occurs in Eastern <strong>and</strong> Sou<strong>the</strong>rn Africa <strong>and</strong> causes East Coast fever (ECF or<br />
Corridor disease)<br />
• T. annulata causes tropical <strong>the</strong>ileriosis (TT), also known as Mediterranean <strong>the</strong>ileriosis <strong>and</strong><br />
occurs in North Africa, sou<strong>the</strong>rn Europe <strong>and</strong> Asia<br />
• T. lestoquardi is <strong>the</strong> only species of economic significance infecting small ruminants, <strong>and</strong> it<br />
occurs in <strong>the</strong> Mediterranean basin, North Africa <strong>and</strong> Asia<br />
• Most Theileria species are confined to Asia or Africa corresponding to <strong>the</strong> geographical<br />
distribution of <strong>the</strong>ir vector ticks, except for <strong>the</strong> worldwide distribution of <strong>the</strong> apathogenic T.<br />
buffeli.<br />
What is <strong>the</strong> distribution of <strong>the</strong> Theileria orientalis in o<strong>the</strong>r countries?<br />
T. orientalis has been recognized in New Zeal<strong>and</strong> cattle since 1982 <strong>and</strong> is known to be<br />
present in Australia, Japan, <strong>and</strong> o<strong>the</strong>r Asian countries as well as in Turkey, <strong>the</strong> UK, France,<br />
Spain <strong>and</strong> <strong>the</strong> USA.<br />
T. orientalis belongs with <strong>the</strong> T. sergenti/ T.buffeli group of Theileria parasites. The<br />
taxonomic status of this group has been debated for many years. Based on Major Piroplasm<br />
Surface Protein (MPSP) <strong>and</strong> 18S Rdna sequences, studies have designated <strong>the</strong>se parasites<br />
as <strong>the</strong> T. sergenti/ T. buffeli/ T. orientalis group of benign Theileria.(Kamau et al 2011)
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What is known about <strong>the</strong> cattle tick- Haemaphysalis longicornis?<br />
General Features:<br />
The New Zeal<strong>and</strong> cattle tick, Haemaphysalis longicornis (H. longicornis), is reported to have<br />
been introduced into Australia from Japan. H. longicornis is likely to have been present in<br />
New Zeal<strong>and</strong> from near <strong>the</strong> beginning of <strong>the</strong> 20 th century (possibly around 1908). Before <strong>the</strong><br />
introduction of <strong>the</strong> Stock Act 1908, <strong>the</strong>re was unrestricted importation of livestock into New<br />
Zeal<strong>and</strong> from Australia, with <strong>the</strong> potential of bringing disease that had been acquired through<br />
Australia’s own importations from o<strong>the</strong>r countries.<br />
The cattle tick H. longicornis occurs in a number of countries bordering <strong>the</strong> western Pacific.<br />
It is a three-host tick, larva (from <strong>the</strong> egg), nymph (emerging from <strong>the</strong> engorged larva) <strong>and</strong><br />
adult (emerging from <strong>the</strong> engorged nymph). The New Zeal<strong>and</strong> strain is par<strong>the</strong>nogenetic, so<br />
only females are found. The tick has a low level of host-specificity, feeding on a wide range<br />
of mammals <strong>and</strong> birds. Each stage feeds for around 4 days (larva) or 7-10 days (nymph <strong>and</strong><br />
adult) dropping to <strong>the</strong> ground when fully engorged <strong>and</strong> moults days or weeks later,<br />
depending upon temperature. Unfed ticks can survive for around 12 months without feeding.<br />
The cattle tick assumes considerable importance in New Zeal<strong>and</strong>, because it is <strong>the</strong> only<br />
exotic tick that has established here which has an economic impact. It causes production<br />
losses in cattle, deer, sheep <strong>and</strong> o<strong>the</strong>r livestock, as well as deaths, <strong>and</strong> infests endemic<br />
animals such as kiwi <strong>and</strong> o<strong>the</strong>r birds.<br />
Distribution of H. longicornis in New Zeal<strong>and</strong>:<br />
There has never been a comprehensive survey to describe <strong>the</strong> locations where <strong>the</strong> cattle<br />
tick is found. The distribution described here is a culmination of reports to Allen Heath, <strong>and</strong><br />
from veterinarians in <strong>the</strong> field. The cattle tick can be found throughout much of <strong>the</strong> North<br />
Isl<strong>and</strong>, numbers are sparse down through <strong>the</strong> Hawkes Bay <strong>and</strong> Wairarapa as well as in <strong>the</strong><br />
Manawatu. The most sou<strong>the</strong>rn limit for <strong>the</strong> tick on <strong>the</strong> East Coast of <strong>the</strong> North Isl<strong>and</strong> is near<br />
Pirinoa in <strong>the</strong> Wairarapa, <strong>and</strong> areas of s<strong>and</strong>-dunes a little fur<strong>the</strong>r to <strong>the</strong> south appears to be<br />
<strong>the</strong> sou<strong>the</strong>rn limit of <strong>the</strong> tick on <strong>the</strong> west coast of <strong>the</strong> North Isl<strong>and</strong>.<br />
In <strong>the</strong> South Isl<strong>and</strong> H. longicornis has been found in Tasman <strong>and</strong> Golden Bay. O<strong>the</strong>r South<br />
Isl<strong>and</strong> records include Motueka, Takaka <strong>and</strong> in Marlborough north of <strong>the</strong> Wairau River<br />
(Heath et al. 2011). There is recent confirmation that ticks are not found on <strong>the</strong> West Coast<br />
of <strong>the</strong> South Isl<strong>and</strong>. The cattle tick was briefly introduced into Southl<strong>and</strong> some years ago<br />
<strong>and</strong> was eradicated by strict monitoring <strong>and</strong> surveillance <strong>and</strong> dipping. There were only two<br />
properties involved, so eradication was achievable.<br />
What is <strong>the</strong> period between tick infestation, parasitaemia <strong>and</strong> clinical disease i.e. how<br />
long from tick bite to anaemia?<br />
Sporozoites of T. orientalis are transmitted in <strong>the</strong> saliva of a feeding adult ticks <strong>and</strong> nymphs,<br />
so could be entering <strong>the</strong> host within minutes of full attachment <strong>and</strong> commencement of<br />
feeding. Schizonts can appear in <strong>the</strong> host within 3 days of infection. There is no transovarial<br />
transmission so each tick stage must acquire its own Theileria organisms to become<br />
infected, but transstadial transmission (from tick stage to tick stage as larva moults to nymph<br />
<strong>and</strong> nymph to adult) also occurs.
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The pathogenesis of <strong>the</strong> Theileria orientalis group species (T. sergenti/ T. buffeli/ T.<br />
orientalis) has not been described in any detail however, generally Theileria is first seen in<br />
peripheral blood approximately 2-3 weeks after infestation with vector ticks. The effect of<br />
Theileria orientalis group parasitised erythrocytes on haematological parameters (blood<br />
haemoglobin <strong>and</strong> HCT) precedes <strong>the</strong> appearance of <strong>the</strong> parasite by 4-6 days (Yagi et al.<br />
1991). In an infected animal <strong>the</strong>re are two peaks in parasitized red blood cells. The second<br />
peak, occurring 1-2 months after infection, is associated with <strong>the</strong> severest clinical signs of<br />
anaemia (Kawamoto et al. 1991).<br />
When is <strong>the</strong> correct time to start tick prevention programs? Does treating early<br />
reduce risk of needing to treat adult ticks later?<br />
There are two critical times to treat livestock against ticks that will reduce <strong>the</strong> numbers of<br />
ensuing tick lifecycle stages, but <strong>the</strong> timing does not necessarily always match farm<br />
management practice. Dipping (including spray <strong>and</strong> pour on acaricides) between July <strong>and</strong><br />
August will hit nymphs that have overwintered. Once may not be enough; it depends upon<br />
<strong>the</strong> persistence of <strong>the</strong> product used. Nymphs once fed, will become adults, so reducing<br />
nymphal numbers early reduces subsequent adult numbers in October through December.<br />
Ano<strong>the</strong>r critical time is when larvae are active, between February <strong>and</strong> March. By reducing<br />
<strong>the</strong>ir numbers <strong>the</strong>re will be fewer nymphs to overwinter (nymphs arise from fed larvae) <strong>and</strong><br />
so next season <strong>the</strong>re should be fewer ticks.<br />
Treatments in months outside <strong>the</strong>se principal activity times will only target a small number of<br />
ticks <strong>and</strong> so will not be as effective in bringing subsequent numbers down. Maximum activity<br />
of each stage is compressed into a relatively short space of time, hence <strong>the</strong> critical treatment<br />
periods.<br />
There is of course no reason why stock cannot be treated when adults are active (October<br />
to January), as this will reduce <strong>the</strong> numbers available to lay eggs, however, larger ticks may<br />
be harder to kill because of <strong>the</strong> dose of insecticide needed to affect <strong>the</strong>m (dependant on<br />
product used) <strong>and</strong> as noted above, if <strong>the</strong> stage that leads to adults is hit hard, <strong>the</strong>n treatment<br />
for adults becomes less necessary.<br />
The problem with relying on dipping alone is that <strong>the</strong>re is a continuum of tick activity that<br />
dem<strong>and</strong>s more than one treatment of stock over <strong>the</strong> tick activity season to ensure that most<br />
questing ticks get into contact with treated stock. That is ano<strong>the</strong>r reason for two treatments<br />
within a relatively short period (Heath pers comm May <strong>2013</strong>.)<br />
Cattle ticks are almost impossible to eradicate from a property by chemical treatment alone<br />
because <strong>the</strong>y are on <strong>and</strong> off <strong>the</strong> host in a week <strong>and</strong> live in pasture for many months. The<br />
ticks can also survive on native animals. Chemical control combined with pasture<br />
management is <strong>the</strong> most effective method of minimizing <strong>the</strong> tick population.<br />
What about suggesting treating all new stock with tick treatments before introducing<br />
<strong>the</strong>m to <strong>the</strong> rest of <strong>the</strong> herd?<br />
When bringing cattle from known Theileria areas you risk introducing Theileria to <strong>the</strong> rest of<br />
your herd if ticks are present on that animal or in <strong>the</strong> environment. Treating cattle that are to
<strong>Page</strong> | 4<br />
be introduced should help reduce <strong>the</strong> chance of spread to <strong>the</strong> rest of <strong>the</strong> herd. However<br />
parasitaemic animals can still result in spread to cattle if <strong>the</strong>re are ticks present on your<br />
property.<br />
Will herds build immunity to Theileria? Will <strong>the</strong> incidence of <strong>the</strong> disease decrease<br />
over time in those farms that are already T. orientalis Ikeda positive?<br />
Herd immunity will develop after exposure to <strong>the</strong> parasite. Whe<strong>the</strong>r disease will continue to<br />
be evident clinically in a herd will be dependant on previous exposure to <strong>the</strong> Theileria,<br />
colostral immunity, tick populations, as well as rates of infection. The health status <strong>and</strong><br />
additional stresses on <strong>the</strong> herd will contribute to development of disease. Some years <strong>the</strong>re<br />
will be no problems <strong>and</strong> o<strong>the</strong>r years <strong>the</strong>re will be, as has been <strong>the</strong> case since T. orientalis<br />
was first recognised in New Zeal<strong>and</strong> in 1982. Herd immunity may be slow to develop. One<br />
herd under investigation still has anaemia after being diagnosed with Theileria eight months<br />
ago (albeit at a low prevalence.) There may be specific aspects of <strong>the</strong> climatic, tick <strong>and</strong><br />
production system characteristics in New Zeal<strong>and</strong> which require fur<strong>the</strong>r study. The<br />
dynamics of <strong>the</strong>se variables will effect what we see next season.<br />
Figure 1: Conceptual model of <strong>the</strong> relationships between infection challenge by ticks,<br />
disease incidence case fatality <strong>and</strong> antibody prevalence in tick-borne disease<br />
infestations (L’Hostis <strong>and</strong> Seegers 2002)
<strong>Page</strong> | 5<br />
Is it correct to assume that <strong>the</strong>re is no disease issue in meat or dairy products derived<br />
from affected animals?<br />
There is no disease issue in meat or dairy products from affected animals. There are no<br />
human health risks or food safety risks associated with Theileria orientalis.<br />
Is <strong>the</strong> main concern with Theileria <strong>the</strong> effect it has on cattle herd productivity?<br />
Yes, <strong>the</strong> main concern is a production issue; <strong>the</strong>re is <strong>the</strong> possibility of decreased milk<br />
production, increased abortion, <strong>and</strong> a decrease in pregnancy rate. We may not see <strong>the</strong> full<br />
effect of <strong>the</strong> impact, of a new strain of Theileria orientalis in New Zeal<strong>and</strong>, on production for<br />
a year or more.<br />
Ticks alone can cause disease, how can you differentiate between disease caused by<br />
Theileria <strong>and</strong> disease caused by ticks alone?<br />
Ticks elicit a host response when <strong>the</strong>ir mouthparts pierce <strong>the</strong> host’s skin. While feeding, <strong>the</strong><br />
tick injects saliva into <strong>the</strong> host, causing a variety of unfavourable reactions. These reactions,<br />
toge<strong>the</strong>r with blood loss, may adversely affect livestock productivity <strong>and</strong> may in <strong>the</strong>mselves<br />
occasionally result in death, particularly in tick-naïve animals <strong>and</strong> when tick burdens are high<br />
<strong>and</strong> animals are fur<strong>the</strong>r stressed. Current epidemiological investigations of <strong>the</strong> outbreak of<br />
anaemia are elucidating <strong>the</strong> relationship of Theileria infection <strong>and</strong> morbidity.<br />
When are cattle at most risk of Theileria infection?<br />
Cattle are susceptible to Theileria infection during times of stress, for example:<br />
• Peri-parturient depression of immunity.<br />
• When suffering from concurrent disease.<br />
Can Theileria be transmitted iatrogenically?<br />
Infections of Theileria in herds will be sustained by a combination of <strong>the</strong> enduring character<br />
of Theileria infections in individual cattle, <strong>and</strong> <strong>the</strong> presence of a competent population of<br />
ticks infected with Theileria. Transmission amongst cattle will primarily occur via ticks<br />
feeding. However mechanical transmission of blood from an infected animal to an uninfected<br />
animal can also result in <strong>the</strong> uninfected animal becoming infected. Small amounts of blood<br />
that may be present in vaccination needles may be sufficient to cause infection. In New<br />
Zeal<strong>and</strong>, it may also be possible that <strong>the</strong> stable fly could potentially transfer Theileria<br />
infection.<br />
If Theileria was spread via needles or flies in <strong>the</strong> continued absence of ticks, <strong>the</strong> disease is<br />
unlikely to be maintained in <strong>the</strong> host population in that particular herd.
<strong>Page</strong> | 6<br />
Acknowledgments:<br />
Thank you to Allen Heath for providing <strong>the</strong> references on Haemaphysalis longicornis:<br />
“The role of ticks <strong>and</strong> biting flies in <strong>the</strong> transmission of <strong>the</strong>ileriosis.” Allen Heath <strong>2013</strong>.<br />
Cane R (2010). Profile: Haemaphysalis longicornis Neumann, 1901. New Zeal<strong>and</strong><br />
Biosecure, Entomology Laboratory. Available at:<br />
http://www.smsl.co.nz/site/sou<strong>the</strong>rnmonitoring/files/NZB/Ha%20longicornis%20Profile.pdf<br />
And thanks to Kevin Lawrence, Andrew McFadden, Zhidong Yu, Richard Norman <strong>and</strong><br />
Stephen Cobb for <strong>the</strong>ir contribution.<br />
O<strong>the</strong>r references:<br />
http://www.dpi.nsw.gov.au/biosecurity/animal/info-vets/Theileria<br />
James MP, Saunders BW, Guy LA, Brookbanks EO, Charleston WAG, Uilenberg G (1984).<br />
Theileria orientalis, a blood parasite of cattle. First report in New Zeal<strong>and</strong>. New Zeal<strong>and</strong><br />
Veterinary Journal. 32, 154-156.<br />
James MP (1984). Theileria orientalis in Northl<strong>and</strong> cattle. Surveillance 11(3), 18-19.<br />
Kamau J, de Vos AJ, Playford M, Salim B, Kinyanjui P, Sugimoto C (2011). Emergence of<br />
new types of Theileria orientalis in Australian cattle <strong>and</strong> possible causes of <strong>the</strong>ileriosis<br />
outbreaks. Parasites <strong>and</strong> Vectors 22, 1-10<br />
Kawamoto S, Takahashi K, Onuma M, Kubota S, Nejo H, Kurosawa T, Sonoda M (1991).<br />
Rebound phenomenon of parasitemia in splenectomized calves primarily infected with<br />
Theileria sergenti. J Vet Med Sci. Feb;53(1):127-8.<br />
L’Hostis M, Seegers H (2002). Tick-borne parasitic diseases in cattle: Current knowledge<br />
<strong>and</strong> prospective risk analysis related to <strong>the</strong> ongoing evolution in French cattle farming<br />
systems. Veterinary Research 33, 599-611.<br />
McFadden AMJ, Rawdon TG, Meyer J, Makin J, Morley CM, Clough RR, Tham K, Mullner P,<br />
Geysen D (2011). An outbreak of haemolytic anaemia associated with infection of Theileria<br />
orientalis in naive cattle. New Zeal<strong>and</strong> Veterinary Journal, 59, 79-85.<br />
The World Organisation for Animal Health, technical disease cards:<br />
http://www.oie.int/fileadmin/Home/eng/Animal_Health_in_<strong>the</strong>_World/docs/pdf/THEILERIOSIS_FINAL.<br />
pdf<br />
Yagi Y, Ito N, Kunugiyama I (1991). Decrease in erythrocyte survival in Theileria sergentiinfected<br />
calves determined by non-radioactive chromium labelling method. J Vet Med Sci.<br />
Jun;53(3):391-4.