The number of piroplasmosis-positive horses imported from Europe varies considerably from one country to another, according to new findings by Swiss researchers.

With piroplasmosis steadily creeping across the globe in the 21st century, spreading out of its once traditional tropical/subtropical regions, these researchers have been looking into prevalence statistics to better understand how their once disease-free country now hosts the parasites responsible for piroplasmosis.

Since 1994, when its first case was discovered, Switzerland has jumped to an alarming piroplasmosis seroprevalence rate of 7.3%, according to Liv Sigg, DVM, PhD, researcher at the equine clinic in the department of clinical veterinary medicine at the University of Berne, and primary author of the study. With 85,000 horses living in Switzerland, this means more than 6,000 are probably infected with either Theileria equi (T. equi) or Babesia caballi (B. caballi), or both. T. equi and B. caballi are parasites that live in the blood and cause piroplasmosis. They are spread primarily by ticks, but can also be transmitted via contaminated needles, as seen recently in North Carolina.

By studying a representative sample of both native-bred and imported horses, Sigg and her colleagues found that horses imported from Spain and Portugal had the highest seropositive rates (36.4% and 50.0%, respectively). Those from France had the third highest rate at 17.4%, and at least half the native-bred horses that were seropositive had traveled to France in the past (staying in the country from one day to three years). Less than 5% of the native-bred population was seropositive, she said