Seroepidemiological survey of Leishmania infantum infection in dogs from northeastern Portugal

Northeastern Portugal is a region where canine leishmaniasis (CanL) is endemic. In this study, a sero-epidemiological survey was conducted in 654 dogs from that geographical area. Serum samples were evaluated by the direct agglutination test (DAT) and also by enzyme-linked immunosorbent assay (ELISA) using five different defined antigens. Seroprevalence of infection was 21.3% based on the assumption that seropositive animals were positive for at least three tests. A high degree of agreement was found between DAT and LAM-ELISA (89%; kappa value [κ] = 0.67). A statistically significant difference (p < 0.05) of seropositivity was found between adult (23.4%) and juvenile dogs (12.2%), apparently healthy (14.8%) and sick dogs (40.2%), vaccinated (19.7%) and non-vaccinated (41.2%) animals, seropositive (26.9%) and seronegative (18.0%) for Toxoplasma gondii, living in rural (18.5%) or urban (32.6%) areas, and between animals living exclusively outdoors (18.2%) and those living in a mixed habitat (27.5%). Risk factors for canine Leishmania infection, as defined by multiple logistic regression analysis, were of clinical status (odds ratio [OR] = 3.1) and Toxoplasma infection (OR = 1.5).