Horse in NZ tests positive for piroplasmosis, Australia halts imports

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Protozoa that cause piroplasmosis. Photo: Centers for Disease Control/ Steven Glenn (Public domain)

Horse exports from New Zealand to Australia have been suspended after an imported mare about to be shipped across the Tasman Sea tested positive for equine piroplasmosis.

The ban by Australia comes just a fortnight after the resumption of horse movements between the two countries following the Covid-19 lockdown.

Equine piroplasmosis is a protozoan blood infection spread by ticks.

It can be caused by either of two protozoa, Theileria equi or Babesia caballi.

Infected animals present with severe acute disease characterized by high fever, lethargy, poor appetite, swelling in the extremities, an enlarged spleen, destruction of red blood cells resulting in anaemia, a rapid heart rate, urine discoloration, and occasionally death.

Animals who recover from a primary infection remain recessive carriers, with fluctuating levels of the parasite. Infectious carriers are not always symptomatic.

The disease is widely distributed in Asia, Europe, Africa and South America. It causes economic loss and affects international horse movements.

The disease is not found in New Zealand horses.

The country’s Ministry for Primary Industries said the horse returned a suspected positive test result for Theileria equi. The animal, a mare, is being retested, with the results expected in a few days.

The horse was being tested for piroplasmosis as part of standard export certification requirements before shipment overseas.

It is understood she had been imported into New Zealand from the European Union early last year for breeding, and has shown no signs of ill health.

New Zealand’s import requirements include a negative test for piroplasmosis within 30 days of shipment. Before leaving the country of origin, horses must be quarantined and treated for ticks. They are inspected and quarantined on arrival in New Zealand.

Although New Zealand has ticks, they are not the species known to transmit the protozoa that causes the infection.

The disease is not directly infectious between horses, but in rare instances it can also be transmitted between animals through contaminated medical equipment, such as needles or other invasive items.

Biosecurity New Zealand is investigating the case.

Other horses on the same farm as the positive horse will also be tested.

Authorities are understood to be hopeful that Australia will lift its ban if its officials can be satisfied it is an isolated case. Australia would normally require New Zealand to be free of piroplasmosis for three years.

Australia is New Zealand’s largest export nation for thoroughbreds.

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