Leishmaniasis due to Leishmania infantum: Integration of human, animal and environmental data through a One Health approach.

The aim of this study was to explore Leishmania infantum epidemiology through a One Health approach that promotes a better estimation of leishmaniasis burden and a deeper understanding of the spatial distribution of the key actors of the parasite life cycle (vectors, reservoirs and humans). We conducted a 14-year mixed retrospective and prospective study of leishmaniasis cases in an endemic area in southern Spain (Granada province), to estimate the human incidence and its association with the vector presence, cryptic leishmaniasis rates and canine leishmaniasis prevalence. We found an annual linear increase in the incidence that cannot be fully explained by active case surveillance and the improvement of PCR diagnostic techniques. 49.4% of cases were not reported to the surveillance system. Approximately half of the human cases correspond to the visceral form that occurred more frequently in men; cutaneous, mucosal and cryptic forms were also detected. Leishmaniasis is no longer a disease of young children, accounting for a quarter of immunocompetent patients and most infected people remained asymptomatic. Human and canine leishmaniasis, cryptic or symptomatic, are present in the whole province, where there is a medium/high risk of the presence of Phlebotomus perniciosus, the main vector. We found association between the incidence of human leishmaniasis and the presence of the vector, but not with the prevalence of canine leishmaniasis and cryptic human leishmaniasis. A potential hot spot was also found, where high leishmaniasis incidence may be associated to the involvement of host species other than dogs.