Molecular surveillance of Leptospira infection in domestic dogs in Soledad, Northern Colombia.

Abstract

Canine leptospirosis is a public health concern due to its zoonotic potential, as infected dogs may act as asymptomatic carriers and shed Leptospira without showing clinical manifestations. The epidemiological boundaries of leptospirosis become blurred in areas where environmental and socio-economic conditions favor pathogen persistence and transmission. A preliminary epidemiological survey was conducted to detect Leptospira DNA in dogs in Soledad municipality, characterized by poverty, unplanned urban growth, limited sanitation services, and recurrent flooding, to estimate infection frequency and assess their potential role as Leptospira carriers. A descriptive, cross-sectional study was performed in dogs. DNA was extracted from blood and urine samples and analyzed by PCR targeting the 16S rRNA (rrs) and lipL32 genes. Sequences generated were compared through BLASTn. Only the rrs sequences underwent phylogenetic analysis. A total of 154 dogs were enrolled. Sixteen breeds were represented, with mixed-breed predominating (43.50%; 67/154). Overall, infection rate was 9.1% (14/154). Based on rrs and lipL32 sequence identity, and rrs phylogeny, all positive samples were associated with pathogenic Leptospira, most closely related to Leptospira interrogans. Of these, 7.14% (11/154) showed renal shedding, compatible with chronic carriage, while 1.95% (3/154) tested positive in blood, suggesting recent infection. Our findings underscore the need to consider dogs as potential chronic carriers and support the integration of preventive measures into public health programs to reduce transmission risk in the municipality and northern Colombia.