Leptospira Vaccination Information

This bacterial spirochete is the most important non-core vaccine due to its zoonotic potential. It has a worldwide distribution and there are geographical variations in the prevalence of different serovars. The severity of clinical disease can vary according to the infective serovar in addition to other factors. Exposure to contaminated sites is related to the dog’s roaming tendencies and the wildlife population density. Dogs at high risk are hunting dogs, working dogs, dogs with exposure to wildlife, rodent pests or livestock, show animals and dogs with access to ponds or slow-moving streams. Middle-aged dogs (4 to 7 years of age) and sexually intact male dogs have the greatest risk of infection. However, ANY dog may contract this disease, even small breed apartment dwellers.

Why is Leptospirosis not a core vaccine?

The issue is with the vaccine efficacy. A high percentage of dogs vaccinated do not develop protective levels of antibodies to ensure immunity or if they do it tends to be short lived.
Serological titers have been performed and demonstrate that a decline in the serum antibody titers occurs 16 weeks post-vaccination. This does not indicate that the animal would not be able to mount an effective immune response if exposed as the serum titer does not take into account the cell mediated response or the anamnestic response.
The vaccines are also serovar specific. Therefore, if the animal does mount an antibody response to the vaccination it would only be protected against the serovars contained in the vaccine. If the dog encounters a serovar that was not in the vaccine, the dog is not protected. The vaccines maybe effective at preventing the systemic invasion of the Leptospira, however, they do not prevent the infection of the proximal renal tubules with the organism, nor do they prevent shedding of this organism into the urine. Therefore, asymptomatic dogs can shed and contaminate the environment. Thus the public health threat from the organism being shed into the environment still persists. The final consideration in the efficacy of this vaccine is the number and severity of adverse reactions that occur upon administration. It is apparent, both experimentally and anecdotally, that the Leptospira component of the vaccine has been associated with multiple types of immune mediated hypersensitivities and moderate to severe vaccine reactions.
Therefore, the risk to benefit ratio of administering this vaccine must be considered for each individual dog. If the vaccine is to be administered it makes sense to vaccinate against the serovars that the dog is likely to encounter.

Suggested Guidelines for Leptospirosis:

Dogs being vaccinated against Leptospirosis should be at least 12 weeks of age or older. A booster vaccination should be administered 3-4 weeks later, and annually thereafter.