Asymptomatic Leishmania infantum infection in dogs and dog owners in an endemic area in southeast France.

The prevalence of asymptomatic leishmaniasis in dogs and their owners in the main endemic areas of France has not been studied to date. The objective of this study was to quantify asymptomatic Leishmania infantum infection in southeast France in healthy people and their dogs using molecular and serological screening techniques. We examined the presence of parasitic DNA using specific PCR targeting kinetoplast DNA (kDNA) and specific antibodies by serology (ELISA for dogs and Western blot for humans) among immunocompetent residents and their dogs in the Alpes-Maritimes. Results from 343 humans and 607 dogs were included. 46.9% (n = 161/343) of humans and 18.3% (n = 111/607) of dogs were PCR positive; 40.2% of humans (n = 138/343) and 9.9% of dogs (n = 60/607) were serology positive. Altogether, 66.2% of humans (n = 227) and 25.7% of dogs (n = 156) had positive serologies and/or positive PCR test results. Short-haired dogs were more frequently infected (71.8%, n = 112) than long-haired dogs (12.2%, n = 19) (p = 0.043). Dogs seemed to be more susceptible to asymptomatic infection according to their breed types (higher infection rates in scenthounds, gun dogs and herding dogs) (p = 0.04). The highest proportion of dogs and human asymptomatic infections was found in the Vence Region, corresponding to 28.2% (n = 20/71) of dogs and 70.5% (n = 31/44) of humans (4.5/100,000 people). In conclusion, the percentage of infections in asymptomatic humans is higher than in asymptomatic dogs in the studied endemic area. It is questionable whether asymptomatic infection in humans constitutes a risk factor for dogs.