Introduction

Leptospirosis is a global zoonotic disease occurring frequently in tropical developing countries. Infection occurs through contact with the bacterium, Leptospira, from infected animals or with contaminated surfaces of urine from animals shedding the organism. Renal failure and death are common with leptospirosis. In Trinidad and Tobago, data from previous serological studies have shown that serovar Copenhageni is the predominant agent responsible for canine leptospirosis, and not the serovars found in the commercial canine vaccine.

Objective

To determine the onset and duration of immunity induced by the vaccine in vaccinated dogs.

Method

Two vaccination-challenge experiments involving 23 puppies were performed using a vaccine prepared from formalin-killed cultures of L. interrogans serovar Copenhageni. A cell suspension of 1 x 10⁹ organisms (8 mL) was administered after primary and secondary vaccination. Each dog was observed for clinical signs of leptospirosis for five weeks, while intermittent sampling was done for serological and cytokine analyses. At the end of the five weeks, samples were collected for histological analysis.

Results

All the control dogs showed signs of leptospirosis, including vomiting, dehydration and jaundice, hence illustrating severe illness unlike the vaccinated dogs. This was supported by the high antibody titers detected using the microscopic agglutination testing (MAT), which remained for a longer duration after the second vaccination was done.

Conclusion

The vaccine was successful in producing short-term immunity to clinical leptospirosis, which can be used by veterinarians to prevent disease in dogs and zoonotic transmission of leptospirosis.