Comparison of Seroprevalence and Identification of Risk Factors for Theileria equi in Horses From Vector-Free and Infested Areas in Southern Brazil.
Authors: Pereira Marco Rocha, Trein Cristina Rodrigues, Webster Anelise, Dallagnol Bruno, Gonchoroski Greice Zorzato, Pellegrini Débora Payão, Doyle Rovaina, Klafke Guilherme, Reck José
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Theileria equi Risk in Southern Brazil Equine piroplasmosis, caused by the tick-borne protozoan *Theileria equi*, represents a significant disease risk in many regions, though its epidemiology varies considerably depending on tick vector presence. Researchers compared 356 horses across 48 farms in southern Brazil—contrasting an *Rhipicephalus microplus*-free zone (215 horses on 23 farms) with an adjacent tick-infested region (141 horses on 25 farms)—using serological testing and structured farm questionnaires to identify exposure risk factors. The disparity in infection rates was striking: only 6% of horses in the tick-free area tested seropositive for anti-*T. equi* antibodies compared with 70% in infested areas, demonstrating that *R. microplus* plays a critical role in disease transmission. Farms where ticks had been observed on horses showed a fourfold increased odds of seropositivity, whilst those with tick-infested cattle sharing pastures faced a threefold increased risk, highlighting both direct and indirect transmission pathways. For practitioners in regions with established tick control or eradication programmes, these findings underscore the value of maintaining vector-free status and suggest that targeted livestock management—particularly separation of cattle from horses or enhanced tick surveillance on shared grazing—could substantially reduce disease exposure even in endemic areas.
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Practical Takeaways
- •Implement rigorous tick control and monitoring programs on farms, as tick presence on horses or shared cattle increases infection risk 3-4 fold
- •Establish quarantine and testing protocols for horses entering tick-free zones to prevent introduction of T. equi, given the dramatic difference in seroprevalence between areas (6% vs 70%)
- •Consider geographic location and local tick burden when assessing disease risk and implementing herd health strategies for equine piroplasmosis prevention
Key Findings
- •Seroprevalence of T. equi was 6% in R. microplus-free zone compared to 70% in tick-infested zone
- •Observation of ticks on horses increased odds of T. equi seropositivity by 4-fold
- •Observation of ticks on cattle sharing paddocks with horses increased odds of T. equi seropositivity by 3-fold
- •R. microplus tick species plays a major epidemiological role in T. equi transmission in Southern Brazil