Prevalence and Factors Related to Leishmania infantum Infection in Healthy Horses (Equus caballus) from Eastern Spain

SIMPLE SUMMARY: Leishmaniosis is a zoonotic disease transmitted by sandflies. The main reservoir is the dog, although the number of species involved is increasing. Horses, due to their high level of contact with humans and ability to control the disease, could be a silent reservoir. However, data related to the prevalence of Leishmania spp. infection in horses are scarce, especially in Europe. In this study, the prevalence and factors related to L. infantum infection in apparently healthy horses have been studied. The results indicate that the equine prevalence is elevated, and the main factors related to infection were equine breed, morphotype, outdoor living, use, and season. Horses with a calm temperament and outdoor living conditions have a higher prevalence of infection, and the number of positive animals increases in spring, when the mean of temperature is higher. These results indicate that horses could be a silent reservoir of the parasite and that the increase in temperature due to climate change will probably increase the Leishmania spp. infections in all species, including humans, in the future. From a One Health perspective, to control this zoonosis it would be advisable to also incorporate measures in horses, such as the use of repellents. ABSTRACT: Leishmaniosis is a zoonosis caused by Leishmania spp., an intracellular protozoan parasite. This parasite is transmitted by sandflies, and the disease is endemic in the Mediterranean basin. In recent years, the number of species which could be a reservoir of the parasite is increased. One of the most relevant species is the horse, due to their contact with humans and ability to control the disease, thus being a possible silent reservoir. In this study, we have analyzed the prevalence and factors related to L. infantum infection in healthy horses in the Mediterranean region. Epidemiological data and serum samples were obtained from 167 apparently healthy horses, and the presence of L. infantum was evaluated via the ELISA method and real-time PCR. The results show 27.5% of prevalence and that the main factors related to infection are equine breed, morphotype, outdoor living, use, and season. In conclusion, the prevalence of L. infantum infection in apparently healthy horses from eastern Spain (Mediterranean basin) is elevated. To control this zoonosis, it would be advisable to carry out more studies on this and other species that could be silent reservoirs of the parasite, as well as carry out measures such as the use of repellents on a regular basis.