Theileria equi case in NZ thoroughbred mare a “single, isolated case”

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Testing of dozens of horses has confirmed that the positive test for Theileria equi in a thoroughbred mare in New Zealand last month is a single, isolated case.

All 263 horses Cambridge Stud were tested by Ministry for Primary Industries (MPI) after an imported mare returned a positive test for Theileria equi, a protozoan that causes piroplasmosis.

The horse concerned was imported to New Zealand for breeding purposes in February 2019 and was found to be infected with Theileria equi as part of standard export certification before being shipped to Australia, and has not displayed any signs of illness while in New Zealand.

Ministry scientists worked with the Cambridge Stud to quarantine the mare and immediately test all adult horses who were either paddock mates of the infected mare or had grazed the same pasture. These 22 animals all tested negative for Theileria equi. Subsequent testing was carried out on 241 other horses at the stud to provide confidence that the operation is free of the organism, and that there has been no transmission of it within the farm.

Theileria equi is an organism that can cause the blood condition Piroplasmosis which causes anaemia and poor condition. It is primarily spread from horse to horse by ticks. It is not infectious directly between horses, and the ticks that are known to transmit the disease are not a species present in New Zealand.

The situation temporarily halted the export of some horses from New Zealand to Australia as Australian importing requirements include certification from the New Zealand government that the entire country is free of Theileria equi. Exports have now resumed under an interim arrangement and MPI continues to work with Australian authorities. Negotiations are also under way with other importing countries.

“At the time of its import to New Zealand, the horse met all our requirements including testing negative for Theileria equi within the required 21 days before its shipment. It had also undergone full quarantine in the UK before export and in New Zealand on arrival,” New Zealand Thoroughbred Breeders Association (NZTBA) president Justine Sclater said.

“Agreed trade conditions for a number of countries that import New Zealand horses require veterinary certification stating that New Zealand is completely free of the disease to accept horses from here. As statements of country freedom cannot currently be given, alternate measures now need to be agreed until such time New Zealand can regain this status hopefully in the not too distant future.”

MPI has been working closely with Australian authorities and has agreed on an interim testing regime for individual horses that has allowed exports to Australia and via Australia to resume. This testing will incur an additional cost to exports as the testing requires specialist expertise and therefore is subcontracted to an Australian laboratory.

Airfreight companies have now resumed flights but additional testing will be required.

“The NZTBA is relieved this is an isolated case but shows the importance of our border controls as an exporting country and that we must remain vigilant. We are fortunate that the co-operation and efforts of Cambridge Stud assisting MPI to complete the testing in such a prompt manner have meant we are hopeful in regaining our country freedom status in the near future,” Sclater said.

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