Canine leishmaniasis seroprevalence in asymptomatic dogs: results from an epidemiological study in endemic Mediterranean countries

Introduction Canine leishmaniosis (CanL), caused by Leishmania infantum , is a major zoonotic disease in Mediterranean countries, where dogs act as the primary reservoir for transmission by phlebotomine sand flies. A significant proportion of infected dogs remain in an asymptomatic subclinical (AS) state and may contribute to maintaining the parasite’s transmission cycle. Identifying these AS dogs is essential for disease surveillance and for implementing effective preventive strategies. Methods From January to April 2024, the non-transmission period for sand flies, 548 clinically healthy dogs were enrolled in France, Greece, Italy, and Spain during routine veterinary visits. Dogs underwent clinical examination and rapid immunochromatographic testing for anti- Leishmania antibodies. Demographic and clinical variables were recorded, and statistical analyses were performed to explore associations between test positivity and factors including age, sex, body weight, sample matrix, and country of residence Results Overall seroprevalence was 7.3%, with marked variation among countries: France (2.9%), Spain (3.2%), Italy (8.8%), and Greece (19%). Univariable analysis showed no significant association between rapid test positivity and age, sex, or body weight. In contrast, country and sample material (plasma vs serum) were significantly associated with test results. In the multivariable model, only the country remained a significant predictor. A relevant proportion of seropositive asymptomatic dogs was detected among owned healthy dogs in endemic European regions, highlighting their potential epidemiological role in sustaining L. infantum transmission. Discussion These findings underscore the crucial role of veterinarians in promoting regular screening of clinically healthy dogs, increasing owner awareness of CanL, and encouraging the use of effective repellent-based parasiticides to reduce the risk of parasite transmission.