Although EIA (equine infectious anemia, aka ”Swamp Fever”) is an established disease in Europe, with 10 cases documented in Germany this year, Ireland had been free of the illness until 2006. The first confirmed case was on June 14, in a mare from Troytown Stud in County Kildaire, but authorities suspect two horses that had died shortly before then may have been cases as well. As of mid October, the total is 24 cases, with 1,100 horses under quarantine.
The outbreak is believed to trace back to the use of plasma illegally imported from Italy. Animals infected with the plasma then served as virus sources for biting insects. The authorities believe they have all potentially infected and exposed animals under quarantine. Otherwise, movement of horses between England and Ireland continues freely and, as we go to press, there’s no requirement for a negative Coggins test for horses going from Ireland to England.
Although routine use of Coggins testing, with state and federal laws spelling out when a horse must be tested, has reduced the problem in this country, EIA remains a health risk for U.S. horses. Infected animals may either die of the acute infection or become carriers. Carriers may harbor the virus for many years before themselves going downhill with chronic loss of condition, weakness and anemia. Carriers also serve as a source of the virus for biting insects, with virus levels in their blood rising when they are having symptomatic episodes, or potentially with any stress.
The latest U.S. figures available are for 2004. There were 333 confirmed cases. Outbreaks are sporadic, but states in the south and along the Gulf of Mexico consistently have the most cases due to the high density and year-round presence of biting insects. Oklahoma with 98 had the most cases in 2004, Texas 92, followed by Louisiana with 27, Florida 19, Arkansas 18, Mississippi 15 and Colorado 14.