Leptospirosis vaccination – what you need to know
Veterinarians weigh a number of factors when vaccination planning for their patients, including assessing risk of exposure to a pathogen. Some vaccinations, such as rabies, are pretty straightforward (even legally required). Others are less so, especially when considering disease risks can evolve and change over time for any given pathogen, including the bacteria that causes leptospirosis.
Leptospirosis was recognized more than 100 years ago and was relatively rare for many years. Since 1983, leptospirosis in dogs is on the rise, and worldwide there is a resurgence in both people and dogs. Vaccines are available, but it can be confusing to know which vaccine is best for your dog and whether these vaccines are safe.
Leptospirosis is caused by bacterial spirochetes. Subspecies of Leptospira interrogans penetrate the skin and spread throughout the entire body, reproducing in the liver, kidneys, central nervous system, eyes and reproductive system. Fever and bacterial infection of the blood can develop. These signs typically clear as the dog produces antibodies. Leptospirosis can result in multi-organ failure depending on the age and immune status of the host as well as the virulence of the invading organism. Leptospira spirochetes also can remain in the kidneys and lead to chronic infections. Younger animals are at the highest risk for severe complications.
There are many different strains of leptospires, which varies from one geographical region to another. These subtypes are referred to as serovars. Not all serovars cause disease, and vaccination against one serovar doesn’t necessarily protect a dog from infection by another serovar. Current vaccine guidelines suggest a four-way vaccine (directed against the four most common disease-causing serovars) be administered to at-risk dogs.
In the Golden Retriever Lifetime Study, at baseline, we found that approximately half of enrolled dogs were vaccinated against leptospirosis. The vaccine is not recommended for puppies under 12 weeks of age. After 12 weeks, two doses of vaccine given two to four weeks apart are required for initial vaccination. Current guidelines suggest dogs receive an annual booster. Recommendations for vaccination can depend on where a dog lives, and their risk of exposure.
Veterinarians and dog owners have voiced concerns about the safety of leptospirosis vaccine. A study published in 2005 suggested that small-breed dogs and young dogs (under 6 months of age) were at higher risk for vaccine-adverse events. A new study from 2015 supports these observations. However, the new study found a very low incidence of adverse reactions overall (roughly 8.5/10,000 dogs), leading the authors to conclude that in areas where leptospirosis is a threat, owners should consider the health benefits versus risks of vaccination. Each study participant needs to consult with their veterinarian about the relative disease risk for their dog.
The Morris Animal Foundation Golden Retriever Lifetime Study gives veterinary scientists a rare opportunity to monitor a large group of genetically similar dogs spread across a geographically diverse country. The study lets us look at patterns of infectious disease, such as leptospirosis, in a way rarely available to most researchers, and might answer many lingering questions about infectious diseases that threaten our dogs, including the efficacy of preventive vaccinations.