The only countries free from EP are consistently reported to be the United States, Canada, Australia, Japan, England, Ireland
and Iceland, but the situation here in America may be slightly more complicated.
Historically, Walking Horses from Cuba are believed to have introduced EP into the Miami, Fla., area in 1959.
This "new" disease finally was confirmed in 1962, according to Dr. Ralph Knowles, retired Chief Staff Veterinarian at the
U.S. Department of Agriculture, who explains: "It spread through that region of Florida, resulting in the death of 20 percent
of affected animals."
A massive state-federal eradication program was begun in 1962 in South Florida. EP finally was removed as a threat to the
equine population in 1988 at a cost of nearly $12 million.
In August 2008, however, a diagnosis of EP was made in a horse from Manatee County, Fla. This "outbreak" eventually resulted
in almost 20 infected horses being identified on seven different premises. A statement from the Florida Department of Agriculture
and Consumer Services, Division of Animal Industry, noted that, "evidence uncovered during the investigation indicated that
transmission of the EP organism occurred due to management practices and not by natural transmission via ticks".
Still, it is the presence of the right types of ticks and the correct environment for development of the protozoan parasite
that keeps agricultural officials vigilant and drives policy decisions concerning piroplasmosis in horses in the Southeast.
It was estimated that the Georgia International Horse Park contained 1.3 million ticks per hectare during Olympic competition.
Because of this staggering number, seropositive horses were permitted to compete in dressage and show jumping in arenas, but
affected horses were not allowed out on the three-day course which contained significant vegetation.
Testing at the 2000 Sydney Olympics found, in contrast, no tick species implicated as vectors of EP on the competition site.
Seropositive horses were allowed to compete in all phases of Olympic Equestrian Competition at this event.
Low risk in Kentucky
Risk assessment for the 2010 games at the Kentucky Horse Park shows a vastly different situation from Atlanta. There is a
low prevalence of tick species capable of transmitting EP around the horse park, and the park itself consists of manicured
grounds with short field grass.
Farms and pastures around the park share this type of grounds management, which will vastly reduce the percentage of horses
being exposed to ticks. Computer models of the probability of one or more susceptible horses becoming positive for EP at the
2010 WEG Games in Kentucky put the chances at 0.00065, or seven horses in a million.
Additional measures being put into place in Lexington include continued tick surveillance (to determine number and species
of ticks), treatment of the environment and treatment of individual horses if necessary.
Currently, other than the Olympics or World games, few waivers are given to competition horses that test positively for piroplasmosis.
Developing research, however, soon may offer a treatment option that attempts to clear horses of their previously diagnosed
Researchers report that horses responding to new therapy show a clearance rate of 95 percent to 97 percent for B. equi and rates of 97 percent for B. caballi.
Not all horses will be candidates for this treatment, but substantial improvement is noted in some horses and clearing the
label of "piroplasmosis positive" from a nice jumper or dressage prospect can significantly increase the value, usefulness
and international travel plans for that equine athlete.
Marcella is an equine practitioner in Canton, Ga.