A multidimensional epidemiological study of 905 canine leptospirosis cases, metropolitan France, 2020-2024

Despite availability of multivalent vaccines, leptospirosis remains a major concern in dogs, yet its epidemiology and associated risk factors are still poorly defined. Integrating molecular, serological, clinico-pathological, hemato-biochemical, spatio-temporal, and demographic data on 905 cases across metropolitan France, this study characterises the contemporary epidemiology of dog leptospirosis. From 2020 to 2024, 4,839 dogs with suspected infection were tested by qPCR, with genotyping of qPCR-positive (lfb1 gene) samples, and microscopic agglutination tests (MAT) were performed on serum samples. Overall, 18.7% of suspected dogs were qPCR-positive (median age = 3 years). Annual incidence peaked in 2024 with an estimated 2.72 cases per 100,000 dog-years at risk. Spatio-temporal patterns showed strong seasonality (July-October) and southern hotspots. Seven species-group (SGs) were evidenced, dominated by Leptospira interrogans SG5 (47.3%), associated with serogroup Australis, and L. interrogans SG1 (45.6%, serogroup Icterohaemorrhagiae). Clinically, most cases presented with a core syndrome, though L. interrogans SG1 was strongly associated with icterus. Urine qPCR outperformed blood qPCR test, especially during the acute phase. Vaccination significantly reduced risk of icterus but not mortality. These findings confirm that leptospirosis persists in dogs despite vaccination and remains a clinical challenge, underscoring the need for prevention strategies tailored to circulating serogroups, particularly in young dogs.

Antech Diagnostics
Complexity Science Hub Vienna CSH - Verein zur Förderung wissenschaftlicher Forschung im Bereich komplexer Systeme
Institut Pasteur