As of Oct. 8 more than 2,300 horses associated with the Kleberg County, Texas, piroplasmosis outbreak have been tested for the disease, and 409 have turned up positive--only one more since the previous report from the USDA to the World Organization for Animal Health on Aug. 25, 2010.
The first case associated with the Kleberg Country outbreak was diagnosed in late 2009. Other horses that tested positive either live or have lived in Kleberg County, Texas, or are considered "dangerous contacts" (e.g., temporarily boarded on or near the initial "index site" (i.e., the site where the first case was identified). Horses associated with the Kleberg County outbreak tested positive in such states as Alabama, Indiana, Louisiana, North Carolina, and Tennessee.
"Investigations of the initial index site under investigation in Texas point to a strong suspicion that much of the disease transmission there was tick-borne rather than via needle transmission," reported Jim Barrett, public affairs specialist for the Animal and Plant Health Inspection Service. "However, most of the time there is no way to know for sure exactly how a horse becomes positive for the disease."
Despite having been eradicated from the United States in 1988, several cases of piroplasmosis have been reported in the U.S. in addition to the Kleberg County outbreak.
"There are ongoing investigations monitoring piroplasmosis in other states as well as Texas," said Barrett.
As noted by Scott Weese, DVM, DVSc, Dipl. ACVIM, an associate professor at the University of Guelph's Ontario Veterinary College, on a Sept. 29, 2010, posting on EquIDblog.com, "an ongoing series of unrelated epidemics makes it clear that this disease is active in the country (U.S)."
Why is controlling piroplasmosis in the U.S. so important?
Barrett explains, "It's important to track the disease because it can be fatal for the horse and sometimes doesn't go away (chronic infection)."
Despite the large Kleberg County outbreak in Texas and the other smaller epidemics that have occurred since the disease was officially eradicated from the U.S. 22 years ago, officials still consider the U.S. "free" of piroplasmosis.
"We continue to treat this disease as a foreign animal disease and will continue surveillance of the disease, regulating movement of horses across state and national borders," said Barrett.
More information on piroplasmosis is available at APHIS.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.