Piroplasmosis: Searching for Answers in Europe

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.

German-imported horses had a very low seropositive rate of only 1.0%, and none of the horses imported from the Netherlands, Ireland, Belgium, or Denmark was seropositive, Sigg said.

The spread of piroplasmosis to non-tropical environments such as Europe and North America is probably related to increased equine transporting, a growing population of both ticks and their hosts (horses and other mammals), and global warming, according to Sigg. Her findings were recently published in Parasitology International and were presented during the Swiss Equine Research Day held April 30 in Avenches.

"Accurate diagnosis of equine piroplasma infection is essential for providing baseline information on the prevalence, incidence, and distribution in the affected equine population," said Sigg, "and is thus a prerequisite for elaborating appropriate and effective control measures."

Despite these findings, Liv said caution should be used in their interpretation because the number of horses from some individual countries was small. Full details of the results can be found in the journal article, "Seroprevalence of Babesia caballi and Theileria equi in the Swiss horse population."

About the Author

Christa Lesté-Lasserre, MA

Christa Lesté-Lasserre is a freelance writer based in France. A native of Dallas, Texas, Lesté-Lasserre grew up riding Quarter Horses, Appaloosas, and Shetland Ponies. She holds a master’s degree in English, specializing in creative writing, from the University of Mississippi in Oxford and earned a bachelor's in journalism and creative writing with a minor in sciences from Baylor University in Waco, Texas. She currently keeps her two Trakehners at home near Paris. Follow Lesté-Lasserre on Twitter @christalestelas.

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