Leptospira Seroprevalence in Companion Animals in Tennessee

Leptospirosis is a re-emerging zoonotic disease in humans and animals. The bacteria Leptospira spp. causing this disease is maintained in the kidneys of animals such as rodents and cattle as well as in the environment. Animals harboring Leptospira spp. in the kidneys frequently shed the bacteria in their urine, contaminating the environment. Contact with contaminated soil and water may result in infection. Animals and humans may develop serious life threatening disease from Leptospira infection. Approximately 1 million new human cases and over 50,000 deaths are reported worldwide. Numerous animal species including rodents, cattle, and dogs may serve as reservoir hosts and can act as carriers for the infection. Our objective was to determine the Leptospira seroprevalence in dogs, horses, and cats in Tennessee.

In this study, we collected convenient serum samples from dogs (n = 376), horses (n = 88), and cats (n = 169) submitted to The University of Tennessee College of Veterinary Medicine clinical pathology diagnostic laboratory. We tested the serum for Leptospira using the Microscopic Agglutination Test (MAT) against 12 Leptospira serovars. Seroprevalence was recorded as 29.41% (110/376) in dogs, 47.73% (42/88) in horses, and 12.35% (21/169) in cats. The seroprevalence in our study was higher in dogs and cats than previously reported in the Cumberland region. The highest seroprevalence was observed for serovar Autumnalis (82/110; 74.55%) in dogs, Bratislava (40/42; 95.24%) in horses, and Bratislava (9/21; 42.86%) in cats. We found a significant cross-reactivity between multiple Leptospira serovars tested, specifically among serovars Autumnalis, Canicola, Copenhageni, Grippotyphosa, Mankarso and Pomona. We also found that vaccinated dogs had a significantly higher seroprevalence (45.92%) compared to unvaccinated dogs (16.28%; p < 0.001). A significant difference in seroprevalence was observed in vaccinated and unvaccinated dogs to all of the serovars included in the canine vaccine; Canicola, Grippotyphosa, Icterohaemorrhagiae, and Pomona (p < 0.001).

This study provides critical knowledge on Leptospira seroprevalence in companion animals allowing for a wider picture of the impact of the disease in this state.