Use of Antigen Combinations to Address Complex <i>Leishmania</i>-Seropositivity Patterns in Dogs Living in Canine Leishmaniosis Endemic Regions of Portugal

Abstract

Canine leishmaniosis (CanL) is a vector-borne disease caused by <i>Leishmania infantum</i>. Infection in dogs can result in a disease with non-specific clinical signs or in a subclinical condition. Infection diagnosis is crucial to guide public health measures considering the zoonotic potential of <i>L. infantum</i>. Serological approaches to detect infection with a reduced antigen panel potentially limit the quality of the information obtained. To evaluate the impact of using distinct antigens in a serological survey, a cohort with 390 dogs from endemic regions in Portugal was subjected to a serological evaluation using ELISA and DAT. Using ELISA, six <i>Leishmania</i>-specific antigens in conjunction with a non-related antigen, <i>Escherichia coli</i> soluble antigens, were evaluated. The global seroprevalence was 10.5% for DAT and 15.4 to 23.1% for ELISA, depending on the antigen for the latter. Still, only 8.2% of the animals were seropositive to all <i>Leishmania</i>-specific antigens. Importantly, a further 31.0% presented antigen-dependent seropositivity. Considering this observation, a serological score system was proposed and validated to address the complex serology results. With this system, the overall dog seropositivity was 26.9%. This work highlights the limitations of single-antigen serological surveys and presents an approach that might contribute to the establishment of CanL-specific serological profiles.