Next up in our canine vaccination series – leptospirosis (lepto for short). This vaccine falls under the “situational” category, meaning that some dogs should receive it while others should not. The determination is based on a risk-benefit analysis that looks at the dog’s lifestyle and health history.

First, a bit of background on the disease. It is caused by infection with bacteria from the genus Leptospira. Dogs typically develop lepto after having contact with the urine of an infected animal or when they wade/swim in bodies of water contaminated with lepto from such urine. The bacteria enter the dog’s bloodstream through small wounds in the skin, through extremely wet skin, or through mucous membranes. Lepto can also be transmitted via bite wounds, through sexual contact, across the placenta, or if a dog eats infected tissues. Once in the body, the bacteria travel through the blood vessels (damaging them as they go) and typically take up residence in the kidneys and sometimes the liver. Other organs (e.g., the brain and eye) can also be affected, although this is relatively uncommon. Lepto bacteria secrete toxins and incite a lot of inflammation, which can result in severe tissue and organ damage often resulting in acute kidney and/or liver failure and sometimes death. Timely treatment with appropriate antibiotics and supportive care can save many but not all dogs diagnosed with leptospirosis.

Lepto is obviously a very serious disease for a dog who picks up the infection from the environment, but it is of additional concern because it is also highly contagious to other animals (including people) that have contact with that infected dog. Therefore, an effective canine vaccine could play a role in protecting both animal and human health.

At this point you may be wondering, why don’t we just go ahead and vaccinate every dog against lepto? Well, the disease is more prevalent in some parts of the country than in others (check out Figure 5 in this article), and some dogs have very little risk of coming in contact with urine or urine contaminated water no matter where they live (think “handbag” Chihuahuas).

Also, lepto vaccines are far from perfect. There are over 200 serovars (variations) of Leptospira interrogans, the species that most often infects dogs. Some lepto vaccines only contain two serovars; these should never be used. The best vaccines available contain the four serovars that most commonly produce disease in dogs, but the immunity these vaccines confer is not complete or long-lasting, sometimes even waning before the typical revaccination interval of one year. Therefore, vaccinated dogs are at a lower but still not negligible risk of contracting the disease. (As a historical aside, lepto vaccines used to be responsible for more than their fair share of adverse vaccine reactions, but with improved manufacturing techniques the newer products are much safer.)

The best way to determine whether or not your dog could benefit from a lepto vaccine is to sit down and talk with a local veterinarian about your dog’s lifestyle and the incidence of the disease in your area and anyplace your dog may travel.

Dr. Jennifer Coates

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