Serological Evaluation for Leptospirosis on Samples Received by the Connecticut Veterinary Medical Diagnostic Laboratory (CVMDL)

Leptospirosis is a globally distributed zoonotic disease caused by pathogenic species of Leptospira, motile spirochetes capable of infecting humans and animals. Transmission typically occurs through contact with water or soil contaminated by the urine of reservoirs or infected animals. Although leptospirosis is considered a neglected tropical disease, its geographic range is expanding due to climate change and urbanization. Surveillance remains limited in many regions, especially in the United States. This study aimed to assess the seroprevalence and serovar diversity of Leptospira exposure in a variety of domestic and wild animals submitted to the Connecticut Veterinary Medical Diagnostic Laboratory (CVMDL). A total of 144 serum samples were tested using the microscopic agglutination test (MAT), targeting 32 Leptospiraserovars. Samples were divided into four groups: two domestic animal groups consisting of livestock and companion animals, and two wildlife groups composed of wolves and bobcats. Serological reactivity patterns were visualized using heatmaps, and diversity was further assessed using the Shannon Diversity Index. Results showed that domestic animals exhibited broad serovar reactivity, likely influenced by vaccination. Wild animal groups showed narrower reactivity patterns, consistent with natural exposure to circulating environmental strains. The highest serovar diversity was observed in bobcats from Hartford County, Connecticut, with the most observed serovar being Leptospira licerasiae. These findings support the continued use of MAT within a One Health surveillance framework and highlight the importance of wildlife monitoring in understanding regional Leptospira circulation. Expanded surveillance efforts are warranted to define environmental reservoirs, risk of spillover, and guide public health interventions.