Geographic Distribution
The parasites that cause equine piroplasmosis are endemic in many tropical and
subtropical regions including parts of Africa, the Middle East, Asia, Central and
South America, the Caribbean and Europe. To a lesser extent, they may be found in
temperate areas. T. equi is thought to have a wider distribution than B. caballi.
Australia, New Zealand, Canada, Japan and some other countries are free of these
parasites. Equine piroplasmosis was eradicated from the United States by the 1980s,
and it is considered to be an exotic disease. However, false negatives can occur in the
complement fixation test, which was used for import testing in the U.S. until 2004/
2005, and there is a possibility that some horses might be inapparent carriers. Other
piroplasmosis-free countries that used this test could also have some carriers.