Serological and molecular positivity for Leishmania infantum in dogs referred to two veterinary hospitals in Barcelona, Spain

BACKGROUND: Leishmania infantum is endemic in the Mediterranean basin, with dogs serving as the primary domestic reservoir for human infection. Although the city of Barcelona has historically been considered a low-risk area, recent environmental and demographic changes may favor parasite transmission. This study aimed to estimate and compare the positivity to L. infantum using serological and molecular methods in dogs referred to a veterinary hospital in the city of Barcelona (urban) and to another located in its residential metropolitan area (peri- urban), and to assess potential associated risk factors. METHODS: A cross-sectional study was conducted from September 2022 to September 2023 at two veterinary referral hospitals in the urban (hospital A) and peri-urban (hospital B) areas of Barcelona. Blood and conjunctival swab samples were analyzed by quantitative ELISA and qPCR targeting L. infantum kinetoplast DNA. RESULTS: A total of 189 client-owned dogs were enrolled (77 from hospital A and 112 from hospital B). Of these, 93/189 (49.2%) were presented for an annual check-up and appeared healthy, while 96/189 (50.8%) were sick. Leishmania infantum infection-defined as positivity by ELISA and/or qPCR-was detected in 10.6% (20/189) dogs, exclusively among sick patients (20/96;20.8%). None of the healthy dogs tested positive. Both serological and molecular tests yielded a 6.3% (12/189) positivity. All qPCR-positive dogs belonged to hospital B, resulting in a higher positivity rate among dogs referred to the peri-urban hospital (15.2%) than among those referred to the urban hospital (3.9%). Significant associations were identified between positivity and both clinical status (P < 0.001) and hospital location (P = 0.013), but not with the other variables evaluated. CONCLUSION: The findings confirm active L. infantum transmission among dogs in Barcelona, with higher positivity among dogs referred to a hospital in the peri-urban area.