Piroplasmosis outbreak in the USA

23rd December 2009

In September we drew attention to a reported outbreak of Equine Piroplasmosis affecting a number of horses at an equine facility in County Meath Ireland. This month, it has been reported that more than 860 horses have been tested in the USA for the tick-borne disease as authorities work to eliminate an outbreak centred on Texas. The disease has been confirmed in 334 horses, according to the US Department of Agriculture's latest report to the World Organisation for Animal Health.

"To date," said spokesman Dr John Clifford, "even though Theileria equi positive horses have been identified in 12 states, all positive horses are directly epidemiologically linked to the index premises. All positive equine piroplasmosis horses identified so far in the investigation are either currently living on the index premises or previously lived on the index premises."

Dr Clifford said 289 positive horses are located on the index ranch in Texas, 22 are on other premises in Texas, one is in Alabama, two are in California, five are in Florida, one is in Georgia, five are in Louisiana, one is in Minnesota, two are in North Carolina, three are in New Jersey, one is in Tennessee, one is in Utah, and one is in Wisconsin.

He said all known positive horses remain under quarantine.

Dr Clifford said ticks which have been shown to be experimentally capable of transmitting the disease have been found on the Texas property. "Additional tick transmission studies are pending and the tick investigations are continuing," he said.

Babesia caballi and Theileria equi are protozoal organisms, which are naturally spread by ticks, or may also be spread through use of shared, contaminated veterinary needles or other instruments. Both organisms are capable of causing the disease piroplasmosis, which may cause life-threatening fever and anaemia in naive (never previously exposed and therefore non-immune) horses. There are currently no cases identified in the UK, Canada or Australia but there is widespread concern that the increasing international transport of horses and the specific tick vectors, perhaps aided by climate change, may be resulting in piroplasmosis becoming an important emerging disease in previously free areas.

For further information, including a video which is available on www.thehorse.com website, please refer to the links below and our client education page under 'Medical Conditions' .

Piroplasmosis outbreak in the USA

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