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Theileria orientalis ikeda

Theileria orientalis ikeda

Three papers will be presented at the 2014 New Zealand Veterinary Association (NZVA) Conference, being held at Claudelands, Hamilton, between Tuesday and Friday.

Prior to August 2012, report cases of Theileria orientalis reported in New Zealand were rare and sporadic. From 2012 to present day, Theileria orientalis ikeda has been a challenging disease for the government, primary industries, veterinarians, and farmers to manage. Theileria orientalis is a tick-borne protozoan parasite of cattle which can cause a range of clinical and subclinical disease in infected cattle herds. Transmission of disease to cattle is normally dependent on a tick intermediate host and the only tick vector present in New Zealand is the cattle tick, Haemaphysalis longicornis.

Confirmed ikeda cases (to February 2014) include 473 farms in the upper half of the North Island of New Zealand. The clinical prevalence within herd is approximately 1%, with a mortality rate of 0.3% (i.e. case mortality rate of about 25%). Reports of the disease have spread south from the historic centre of infections in Northland down into the Waikato, Taranaki and the King country.

Theileria orientalis is endemic in New Zealand and has been for at least 30 years. However, the ikeda strain had not previously been identified in New Zealand. At the end of 2012 an investigation into disease in beef cattle in Northland, by Ministry for Primary Industries (MPI) Animal Health Laboratory, identified Theileria orientalis ikeda as a potential emerging disease.

A working group was established with representatives from key stakeholders - NZVA, MPI, Beef + Lamb NZ, DairyNZ, Meat Industry Association, Fonterra, Veterinary Council of New Zealand, and Federated Farmers.

Documenting of the progression of the disease over the past two years has resulted in three papers being presented to the NZVA Annual Conference.

1. Theileriosis on beef farms in the Bay of Islands
Garth Riddle, BVSc , Bay of Island Vets
Tuesday 17 June, 7am (Sheep and Beef Cattle stream)

Theileria orientalis infection has gone from being seen as an incidental finding to a disease of cattle in its own right. Most of the attention has been on the effects of new infection on dairy farms, as this is where there have been the most cases and the most severe clinical disease and mortality.

The change has corresponded with a different serotype Theileria orientalis Ikeda being isolated. As with other strains of Theileria the main vector for transmission is the cattle tick Haemophysalis longicornis.

Garth Riddle documents the disease progression in beef animals and he shares some trial information on attempted prevention strategies so far.

Most startling is his findings that the disease is not directly related to tick numbers as there are many herds with ticks on calves that do not seem to have problems. He also notes that “we can no more keep animals tick free than we can keep them worm free.”

Riddle discusses four trials:
1. Tick control using Python Ear tags
2. Testing to see if repeat treatments of buparvaquone (BPQ) are necessary
3. Testing to see if treatment to prevent ticks prevents disease due to Theileria in imported animals
4. This was a repeat of trial two on a different property.

2. Theileria orientalis ikeda response
Katie Hickey, BVetMed MRCVS,Senior Adviser, Animal and Marine Response Team, Ministry for Primary Industries - Manatū Ahu Matua
Thursday 19 June, 12.30pm

This presentation outlines how Ministry for Primary Industries (MPI) Biosecurity Response System managed the emerging disease issue. The response aimed to reduce the potential impacts through knowledge transfer to veterinarians and farmers, as well as providing access to veterinary medicines to treat infected animals.

The response system involved assessing the risks and desired outcomes; it also recommended a number of outcomes:
• Effectively communicate information to stakeholders and animal producers to enable them to mitigate the impact of the disease associated with Theileria orientalis ikeda.
• Understand the epidemic and its impact through conducting surveillance projects and apply the outputs to response decision-making and disease management.
• Support cattle producers through conducting appropriate activities to increase understanding of the disease.
• Manage trade risks associated with the outbreak.
• Ensure effective communication, decision-making and implementation with the joint working group.

An example was the recommendation that access to Buparvauone (BPQ) be approved. This had several factors to consider before its approval for importation. These included the impact of Theileriaon animal welfare which was regarded as significant. Meanwhile, clinical and subclinical impacts on production were considered serious while the potential risk around residues in animal products was assessed as manageable through appropriate monitoring and verification processes.

This presentation will also discuss the current situation and provide details on where the disease is prevalent.

3. Effect of Theileria orientalis ikeda on reproductive performance of a dairy herd
Scott McDougall, Lachlan Pearson, Margaret Perry and Chris Compton - Cognosco, Anexa Animal Health, Morrinsville
Friday 20 June, 7am (Dairy Cattle stream)

This session looks at a study to assess the effects of Theileria on reproductive performance in a single commercial Waikato dairy herd. Scott McDougall says that while primary pathophysiology is associated with anaemia, clinical signs include resultant pale mucous membranes, jaundice, respiratory distress, and in a proportion of cases, death. Abortions may also occur.

However, he says, the effects of Theileria on reproductive performance have not been defined.

The study was of a farming operation that consisted of two spring calving dairy herds in the eastern Waikato with leased land on the west coast near Raglan and another block of land at Waihi. The home farm considered in this investigation consisted of approximately 450 lactating cows, while the other unit consisted of 300 lactating cows. The herd owner had purchased the second farm in June 2012 and had purchased 120 cows from Northland at about the same time. The majority of these cows were managed away from the farm involved in the current study.

The presentation details the study and shows a significant economic impact of Theileria. This is detailed by summing the losses associated with death, direct treatment costs and the losses associated with reduced reproductive performance. For this herd with 446 cows, the loss was greater than $19,000 or an average of >$40 per cow. This calculation does not include any estimates of ongoing loss of milk production associated with Theileria as no herd testing was undertaken in the herd to quantify the loss.

The study concludes that Theileria orientalis ikeda resulted in significant reproductive as well as morbidity and mortality effects on this dairy farm. However, the authors suggest further analysis is required to quantify the effects of this disease on milk production and to determine the cost benefit of control measures, such as use of accaricides under the New Zealand dairy grazing systems.

ENDS

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