Canine Leptospirosis in Flood-Affected Areas of Southern Brazil: Molecular Assessment and Public Health Implications.

Background: Southern Brazil faced massive rains and floods in May 2024, which led to social, infrastructural, and One Health issues affecting over 478 municipalities and 2.3 million people. Exposure to floodwater increased the risk of bacterial infections, including leptospirosis. Despite the zoonotic nature of leptospiral infections, only human leptospirosis is subject to mandatory reporting, while canine cases are less closely monitored. Considering the extent of this climatic event, many emergency shelters were created for rescued dogs, highlighting the need to monitor infectious diseases to mitigate the spread of hazardous pathogens.

Methods: We performed a molecular assessment of canine leptospirosis in Porto Alegre and its metropolitan region. A total of 246 dogs rescued from the flooded areas underwent molecular diagnosis targeting lipL32. In addition, positive samples were identified by sequencing of the partial secY gene.

Results: A total of 9 (4%) dogs were positive for Leptospira spp. Molecular and phylogenetic analyses of secY from the positive samples determined that the circulating strains belonged to L. interrogans (n = 8)-Icterohaemorrhagiae and Pomona as the suggested serogroups-and L. kirschneri (n = 1).

Conclusions: Our findings point out the challenges in diagnosing and controlling leptospirosis during severe climatic events and reinforce the need for preventive sanitary measures to mitigate the dissemination of Leptospira spp., including the adoption of a mandatory notification system for canine leptospirosis.