Seroprevalence of leishmaniosis in horses living in endemic area in Tuscany.

Leishmaniosis is an infectious disease caused by protozoa of the genus Leishmania. The host spectrum is broad and, to complete its cycle, the protozoan uses a vector host, the female sandfly (Diptera: Psychodidae) that spread the infection to vertebrates. Leishmaniosis is currently prevalent in countries with tropical or subtropical climate, including the Mediterranean basin, in which Leishmania infantum is the most common specie. In these regions the main sandfly vectors belong to the species Phlebotomus perniciosus, P. ariasi, P. Perfiliewi, P. neglectus and P. tobbi. Leishmaniosis is present mainly in dogs and humans, however, the parasite can be found in other animal species. The interest in leishmaniosis is increasing also in equine medicine in Europe. In the horse Leishmaniosis showed dermatological picture characterized by skin nodules, single or multiple, with a tendency to ulceration, especially localized in head, ears, scrotum, legs and neck and in most of the cases the infection is selflimiting.The purpose of this work was to carry out an epidemiological survey on the prevalence of positive antibody titers for Leishmania infantum in horses living in Tuscany were the disease in other species is endemic and no cases of equine leishmaniosis have never been observed. Materials and methods: Blood samples were obtained during June-November 2011 from 223 horses of different breed, sex or age and living in endemic areas for canine leishmaniosis in Tuscany. Inclusion criteria: 1) horses living for more than two years in endemic areas; 2) horses living 24 hours a day outside in paddocks; 3) horses living in direct contact with dogs affected by leishmaniosis. Blood samples were drawn from the jugular vein and collected in serum-tubes. Serum specimens were used to perform IFAT at the screening dilution 1/10. Positive and negative controls were prepared, in each slide, using reference sera. Sera that showed a clear apple-green fluorescence of promastigotes were considered positive and diluted to determine the final title. Results: 105/223 samples (87.5%) were negative and 28/223 (12.5%) positive. IFAT titers were 1/10 titer in 10/28 (35.5%) horses, 1/20 titer in 17/28 (61%) horses, and 1/40 titer in 1/10 (3.5%) horses. No animals presented skin abnormalities compatible with equine lesihmaniosis during the study-period. Moreover, anamnesis did not report any skin nodules or ulcers that resolved spontaneously in the past years, in any of the horses included in this study. Discussion Leishmania infantum is the infectious agent that causes leishmaniosis in several European countries. The disease predominantly affects men and dogs, however studies have demonstrated the presence of protozoa in other animal species. In fact, the parasite was found in cats, foxesand black rat which is considered by some authors a natural reservoir of this parasite. In equine specie, the seroprevalence obtained in the present study is similar to that reported in Spain (12.5 vs. 14.2%), but higher than the prevalence obtained in Greece (0.3%). In the dog the seroprevalence of leishmaniosis in Tuscany vary from 15.1 to 38.9%. It is surprisingly that in Tuscany no cases of equine leishmaniosis have been documented in the past and during all the study-period, although the seroprevalence is similar to the survey performed in Spain where equine leishmaniosis have been previously diagnosed, as well as in Portugual. Furthermore, several cases of equine leishmaniosis have been observed in central europe, where the disease in the dog is not so frequent as in Italy. These authors described autochthonous equine infections in geographically distant regions of Germany and Switzerland caused by an apparent novel Leishmania specie with molecular similarities to the closely related organism Leishmania sp. Siamensis. However Muller’s results can not explain the absence of clinical lesions reported in this study, becouse the vector is not species specific and the phlebotomine activity is longer during the year in Italy respect to Northern Europe. It is stated that horses living in endemic areas show humoral and cellular immune responses to L. infantum, indicating that exposure and development of an immune response to the parasite occur also in the absence of clinical manifestations. Thus, the immune response in horses probably is effective to control the disease.16,18 These considerations could be the reasons of the lack of clinical cases of equine leishmaniosis in Italy despite a similar seroprevalence to Spain and Portugal, where the disease has been observed.