Serological and Molecular Epidemiology of Leptospirosis and the Role of Dogs as Sentinel for Human Infection in Nigeria

Abstract

Objective: Prospective cross-sectional study of dogs in Nigeria to study leptospirosis, inferred to be endemic in all regions of the country by researchers. Aim is to generate empirical updated evidence of leptospiral infection and delineate serovars involved. Methods: Study determined the sero-prevalence and infection rate in 342 dogs of various demographics using sero-assays, culture isolation and novel qPCR. In-house designed primers targeting conserved regions were used to amplify genes in quantitative Real-Time PCR (qRT-PCR) assays for leptospiral detection to serogroups. Molecular analysis of the leptospiral 16S rRNA and LipL 32 genes, reported earlier as novel diagnostic targets, were used for identification of pathogenic Leptospira species. Primers targeting the O-antigen ( rfb ) region of the Leptospira lipopolysaccharide (LPS) were used for differentiating serovars based on comparative melting temperature (Tm) analysis of PCR product against reference serogroups. Results: Overall serological and bacteriological prevalence of 56(16.4%) and 40(11.7%) respectively was recorded. German shepherds were the most highly represented group, with a sero-prevalence of 17(22.4%). Vaccination, ages and season(s) were the strongest determinants of infection and the presence of circulating antibodies to leptospires after seroconversion. Unvaccinated animals, stray dogs as well as symptomatic dogs presented statistically significant (P<0.05) higher risk of infection: OR 25.531(6.108, 106.712; 95% CI). Discussion: The evidence suggests 1 of every 10 dogs is infected and could be symptomatic for the disease or a carrier of leptospires in the studied region in Nigeria. Given the proximity of dogs to humans, quantifying the burdens of leptospirosis in dogs is a priority from a public health perspective. Funding Information: The Vinetz Laboratory and the Fulbright Grant #15150575 jointly funded this work. Declaration of Interests: None to declare. Ethics Approval Statement: Animal Approval was obtained from Usmanu Danfodiyo University with number 2014/RO-11.