Epidemiological status of equine piroplasmosis in Menorca (Spain): serological, molecular survey and associated factors

Equine piroplasmosis (EP), caused by the apicomplexan parasites Theileria equi and Babesia caballi , is a tick-borne disease of major clinical and economic importance in equids worldwide. This study reports, for the first time, the presence of EP and associated variables in the Menorca Purebred Horse (PRMe), an endangered breed of high genetic, cultural, and socio-economic value, based on a sample of participating horses from Menorca (Spain). A cross-sectional study was conducted on 213 horses, combining serological (cELISA), molecular (multiplex quantitative real-time PCR (qPCR) and nested PCR (nPCR)), and entomological analyses. An overall apparent seroprevalence of 56.34% was recorded, with a true seroprevalence of 59.31% (95% CI: 52.00-66.40) for Theileria equi and 3.26% (95% CI: 1.56–6.61%) for Babesia caballi . The overall molecular apparent positivity was 42.72% (95% CI: 36.27–49.44), confirming a substantial proportion of assessed horses with chronic subclinical infection at the time of sampling. Theileria equi was the predominant parasite in both serological and molecular analyses. Multivariate analysis identified different host-related and husbandry-related variables as potential risk factors. Entomological analysis revealed that Hyalomma was the dominant tick genus (96.43%) in the evaluated animals, detecting DNA of Theileria or Babesia species in 12/112 tick samples (10.71%), and more specifically DNA of EP-agents in 10/112 samples. Under the conditions evaluated, nested PCR detected more positive samples than qPCR, and column-based extraction yielded more qPCR-positive results than automated extraction. These findings establish a baseline for the epidemiological monitoring of EP in Menorca and provide evidence to inform vector-control and health-management strategies for the Menorca equine population.