Seroprevalence of Tick-Borne Infections in Horses from Northern Italy

SIMPLE SUMMARY: Equine vector-borne diseases, which include equine granulocytic anaplasmosis (EGA) and equine piroplasmosis (EP), are caused by several pathogens transmitted to horses by ticks. Considering the spread of equine vector-borne diseases in Italy and worldwide, a study was planned to investigate the seroprevalence of Anaplasma phagocytophilum and the other two selected pathogens, Theileria equi and Babesia caballi, in northern Italy. Data obtained from the present study demonstrated a high seroprevalence for all the three surveyed tick-borne pathogens and emphasized the importance of establishing control programs with the adoption of certain practices, including tick control, correct horses management, serological screening, regular usage of long-lasting acaricides and proper treatment of positive and clinically infected animals. ABSTRACT: Tick-borne diseases in horses are considered an emergent problem worldwide; the geographical redistribution of ticks, due to climatic and ecological changes, and the movements of infected horses between different nations play important roles in the spread of tick-borne diseases affecting these hosts. In this study, a survey was planned to estimate the seroprevalence of the Gram-negative bacterium Anaplasma phagocytophilum and the piroplasmid protozoa Babesia caballi and Theileria equi in Italian horses, as well as to evaluate possible risk factors associated with seropositive cases. Serum samples from 261 horses reared in northern Italy were collected and analyzed by indirect immunofluorescence antibody test for the detection of A. phagocytophilum-, B. caballi- and T. equi-specific antibodies. The overall seroprevalence to at least one of the investigated pathogens was 51%; sixty-one horses were seropositive to A. phagocytophilum (23.4%), forty-nine to B. caballi and the same number to T. equi (18.8% each). Seropositivity for more than one of the investigated agents was detected in thirty-two horses and the most common co-infection was observed between B. caballi and T. equi (5.7%). A significant risk factor for all the three pathogens was the elevation above sea level; indeed, the risk of infection was higher with an increase and decrease in elevation for A. phagocytophilum and for B. caballi and T. equi, respectively. Tick control in horses is strongly recommended considering the high seroprevalence values of transmitted pathogens.