Thirty-two horses positive for equine piroplasmosis

October 23, 2009

Thirty-two quarter horses at a property in Kleberg, Texas, have tested positive for the tick-borne protozoal disease, equine piroplasmosis.

The property is under quarantine as officials from the United States Department of Agriculture and the Texas Animal Health Commission work to trace the source of the infection.

Equine piroplasmosis is caused by a parasite, Theileria equi, which can transmitted from horse to horse by certain kinds of ticks. It can also be transferred through needles.

Agriculture department veterinarian Dr John Clifford, in reporting the outbreak to the World Organisation for Animal Health this week, said a total of 32 cases had been confirmed at the property in Kleberg County.

Dr Clifford said a seven-year-old quarter horse was taken to a local veterinary hospital on October 2.

"A blood-borne pathogen was subsequently suspected and the horse was placed in isolation and initial diagnostic samples taken."

The positive test for equine piroplasmosis was returned on October 12.

The following day, a quarantine was imposed and 31 other horses linked to the first horse were tested. Ticks were also collected from five horses to be tested for the disease and to have the species identified, as only certain kinds of ticks are known to be able to carry the infective agent.

Those tests came back positive on Monday.

A further 96 horses have been tested and resulted are awaited, Dr Clifford said.

Meanwhile, Canadian authorities have closed the country's border to horses from Texas while the outbreak is resolved. Horses from any other US state must have additional certification that they have not been in Texas in the previous 21 days.

In June, equine piroplasmosis was detected in Missouri, with a related case found in Kansas. In 2008, the infection was detected in Florida - which was then the first occurrence of the disease in the US in 20 years. These cases have been resolved.

Equine piroplasmosis can affect horses, donkeys, mules or zebras and cause clinical signs common to many diseases, including poor appetite and weight loss. Deaths can occur.