Leptospira Infections on the Rise: Shocking Seroprevalence Findings in Dogs, Cats, and Horses in Tennessee

Leptospirosis, a bacterial infection caused by Leptospira species, is a growing concern for pets and livestock. A recent study out of Tennessee has revealed eye-opening seroprevalence rates for Leptospira in dogs, cats, and horses, offering new insights into the widespread nature of this zoonotic disease. This research, conducted by Kellie A. McCreight and her team, used the microscopic agglutination test (MAT) to measure the presence of antibodies against 12 Leptospira serovars in these animals, providing important data for veterinary professionals and pet owners alike.

Study Overview

The study aimed to estimate the seroprevalence of Leptospira in Tennessee’s dogs, cats, and horses. The team tested a total of 632 animals: 374 dogs, 170 cats, and 88 horses, to understand the prevalence of Leptospira antibodies across different species.

Key Findings

1. Leptospira Seroprevalence in Dogs, Cats, and Horses

   • Dogs: 29.4% of dogs tested positive for Leptospira antibodies, with the highest prevalence observed for serovar Autumnalis (74.6%).

   • Cats: 12.4% of cats tested positive, with serovar Bratislava being the most common (42.9%).

   • Horses: Horses had the highest overall seroprevalence, with 47.7% testing positive. The most common serovar in horses was also Bratislava (95.2%).

2. Vaccination Impact in Dogs
   A significant difference in seroprevalence was observed between vaccinated and unvaccinated dogs. Vaccinated dogs showed a much higher seroprevalence (46%) compared to unvaccinated dogs (16%) for the four Leptospira serovars commonly included in canine vaccines, such as Autumnalis and Bratislava. This highlights the importance of vaccination in preventing Leptospira infections and underscores the need for veterinarians to assess vaccination history when interpreting test results.

3. Cross-Reactivity Among Serovars
   One of the study’s notable findings was the significant cross-reactivity between multiple Leptospira serovars. This was particularly true for dogs, where serovar Autumnalis showed the highest cross-reactivity. This finding is crucial for accurate diagnosis and interpretation of serology results, especially when considering the possibility of false positives or overestimating seroprevalence.

4. Diagnostic Laboratory Data
   The study also reviewed diagnostic laboratory submissions from 2021-2023. Of 252 canine serum samples tested, 40% were positive for Leptospira, with Autumnalis being the most frequently detected serovar. Additionally, Leptospira real-time PCR testing revealed that 10.7% of urine samples and 5.8% of blood samples were positive, further highlighting the prevalence of Leptospira in the region.

Clinical Implications

These findings have significant clinical implications for veterinarians. The high seroprevalence rates in both vaccinated and unvaccinated dogs, along with the marked cross-reactivity between serovars, suggest that Leptospira infection may be more widespread than previously thought. Veterinarians should carefully consider vaccination status and the possibility of cross-reactivity when interpreting MAT results, particularly in regions with high Leptospira exposure like Tennessee.

For pet owners, this research emphasizes the importance of keeping up with Leptospira vaccinations to reduce the risk of infection. Understanding the role of vaccination in seroprevalence is crucial for managing the health of dogs, cats, and horses in areas where Leptospira is endemic.

Conclusion

Leptospirosis remains a significant public and veterinary health concern, with seroprevalence data from Tennessee revealing widespread exposure in dogs, cats, and horses. This study serves as a valuable reminder of the importance of vaccination and accurate diagnostics in preventing and managing this zoonotic disease. As Leptospira continues to be a threat in both urban and rural areas, staying informed about seroprevalence and taking proactive health measures are essential steps in safeguarding the health of pets and livestock.

Read full study here: https://journals.sagepub.com/doi/10.1177/10406387241299880