True Prevalence and Seroprevalence of Piroplasmosis in Horses in Southwestern Europe

Simple Summary: Equine piroplasmosis (EP) is a parasitic tick-borne disease caused by Apicomplexa hemoprotozoans with a worldwide distribution. Due to global warming, tick expansion to previously EP-free countries, and higher international horse movements, the prevalence of this disease is increasing worldwide. This study evaluates EP prevalences by PCR and serology in Andalusia, the most southwestern European region and one of the main international horse exporters. Results showed regionality (with different EP prevalences between western and eastern provinces), seasonality, and age effects (old horses more likely to be seropositive), respectively. Although Andalusia is an EP endemic region, an increase in EP prevalences was not observed during the studied period.

Abstract: Equine piroplasmosis (EP) is an endemic parasitic disease in southern European countries, such as Spain. Andalusia, the most southwestern region of Europe, is the community with the highest number of registered horses and farms in Spain and one of the main international exporters of Andalusian (Spanish Purebred) horses worldwide. Considering the current expansion of this disease and the possible effect of climate change on its prevalence, studying the EP prevalence in this region is compelling. Molecular (PCR) and serological methods (cELISA and IFAT) were used to study the true and apparent prevalences during a period of three consecutive years, evaluating the effects of age, sex, season, year of testing, and province. Results showed different EP prevalences between western and eastern provinces, as well as among seasons. Moreover, a positive association was observed between age and T. equi seropositivity, without any effect of sex. Our findings demonstrate that Andalusia is an EP endemic region, but prevalences were lower compared to central and northern Spanish regions. Moreover, EP prevalence has not increased in Andalusia in recent years despite climate changes.