Canine Leishmaniosis in Liguria, Northwest Italy: A Nine-Year Retrospective Study in a Historically Endemic Area

Canine leishmaniosis (CanL), caused by Leishmania infantum, is an endemic zoonotic disease in the Mediterranean basin, with changing epidemiological patterns. This study aimed to evaluate seroprevalence, assess temporal and seasonal trends, compare owned and shelter dogs, and identify dog-level and environmental factors associated with L. infantum exposure in Liguria, a historically endemic area of northwest Italy. A retrospective observational study was conducted using diagnostic data from dogs tested for L. infantum in Liguria between 2016 and 2024. Serological results were obtained using an indirect immunofluorescence antibody test (IFAT; cut-off ≥ 1:160). The dataset comprised 75,702 dog-year observations (an observation from the same dog in a different year was considered separately) from 36,679 dogs. Descriptive statistics were used to summarise the study population and factors associated with seropositivity were investigated using generalised estimating equation models with a binomial distribution and logit link function, including demographic and environmental variables. Overall, 10.1% (n = 3693) of dogs tested positive at least once. Inter-annual variability and an increased prevalence during summer and autumn were observed. Shelter dogs had higher odds of seropositivity. Exposure risk increased progressively with age and was slightly higher in males, while minor differences were observed between pure-bred and cross-bred dogs. Environmental factors were also associated with seropositivity, showing a higher prevalence in rural areas and a marked spatial gradient from west to east. This study updates the epidemiology of L. infantum, highlighting a non-negligible risk for both dogs and humans and the need for targeted surveillance and control strategies.