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Ask a Vet: Do Lepto Vaccines Cause Bad Reactions in Dogs?

Yes, they can, and I have decided NOT to vaccinate my dog against leptospirosis -- though I have in the past.

Dr. Eric Barchas  |  Dec 22nd 2015


Superstition is part of the human experience. And, in fact, it appears to be a nearly universal part of existence for birds and mammals. In 1948, B. F. Skinner published a paper titled “Superstition in the Pigeon.” The paper outlined an experiment in which Skinner and his colleagues chronically starved a group of pigeons (researchers before the late 20th century were not exactly known for their kindness) and then dropped food into captive pigeons’ cages at regular intervals.

The pigeons apparently believed, superstitiously, that their behavior was triggering the feeding, and they responded by adopting ridiculous behaviors. Here is how Skinner describes it:

One bird was conditioned to turn counter-clockwise about the cage, making two or three turns between reinforcements. Another repeatedly thrust its head into one of the upper corners of the cage. A third developed a ‘tossing’ response, as if placing its head beneath an invisible bar and lifting it repeatedly.

The pigeons fell for an age-old fallacy: They confused correlation with causation.

Several decades after the pigeons made their errors, Jenny McCarthy made the same mistake. She fell for the hoax that vaccines cause autism.

Human vaccines have been controversial since the beginning. Some people feel that vaccines are unnatural. Others worry about autism. Still others fret that vaccines are un-Islamic (polio is resurgent in Nigeria for exactly this reason).

Veterinary medicine has its share of anti-vaccination activists as well. I have met dog owners who believe that vaccines are the cause of all manner of canine ills. My personal favorites are the people who believe vaccination is a money-making conspiracy between drug companies and veterinarians. (Pshaw! Vets make far more money from treating parvovirus than we do from vaccinating against it.)

But there is another group of dog owners. This group is not superstitious and does not contain conspiracy theorists. It is composed of thoughtful, reasonable people who understand that vaccination is one of the greatest advances in the history of medicine. They understand that vaccination is one of the most effective and cost effective ways to reduce human and animal suffering. But they wonder, reasonably, whether dogs are being over-vaccinated. They furthermore have noted, correctly, that vaccination — like everything in life — carries risks and benefits.

Adverse reactions to vaccination are possible. My dreaded once-per-decade tetanus vaccine renders me bedridden for two days. And dogs also may experience negative effects from vaccines.

Some documented canine adverse vaccine reactions include facial swelling, hives, poor appetite, vomiting, diarrhea, pain at the injection site, and lethargy. Life threatening anaphylactic reactions are very rare but not unheard of. It is my opinion that vaccines do not cause autoimmune disease in dogs. However, I do believe that vaccines may trigger flareups of problems in dogs who already have autoimmune disease.

Any thoughtful dog owner will want to strike a balance between the benefits of vaccines and the risks, albeit slight, that vaccines pose to their pet. Among the questions that such owners confront is that of which vaccines to administer.

One of the most controversial vaccines for dogs protects against leptospirosis. The so-called lepto vaccine has a reputation among both veterinarians and dog owners for causing a disproportionate number of adverse vaccine reactions.

Leptospirosis is a bacterial disease of dogs, wildlife, and humans. It most frequently is spread by urine. Dogs most commonly are infected by drinking or swimming in water in which wild animals have urinated.

Infected dogs may suffer liver failure and kidney failure. The condition has the potential to be fatal. And it gets worse. Dogs with leptospirosis may spread the disease to their owners through their urine.

Therefore, two concerns must be simultaneously addressed by dog owners. Lepto is dangerous to both dogs and owners, but the vaccine has a reputation for causing adverse reactions. What is the best way forward?

Enter Peng Ju Yao, DVM, MPVM et al. The group published a paper in the November 15, 2015 issue of the Journal of the American Veterinary Medical Association. The paper outlines the group’s efforts to tease out the true risk of reactions to lepto vaccines.

The data show that dogs in the study who received a lepto vaccine were significantly more likely to suffer an adverse reaction than those who did not. In fact, the rate of adverse reactions was approximately twice as high among dogs who received lepto vaccines. However, the overall rate of reactions was low in both groups. In fact, the authors drew the following conclusions from the study.

The overall [incidence rate] for owner-reported post-vaccination [adverse events] was low. Results suggested vaccination against Leptospira (an organism that can cause fatal disease) is safe in the majority of cases, slightly increasing the risk of owner-reported [adverse events] but not associated with a significant increase in [allergic and anaphylactic] reactions, compared with other vaccinations administered.

When deciding whether to vaccinate your dog against Lepto, you must decide whether you are more concerned about the risk of a vaccine reaction or about the risk of your dog — and potentially you — contracting the disease. And you must own that risk. Your vet should be able to offer guidance based on your location and your dog’s age and lifestyle.

I am a dog owner who has grappled with such a decision. My pal Buster loves to hike in wooded areas where leptospirosis exists. Furthermore, leptospirosis has been reported in our hometown of San Francisco. However, Buster suffered significant pain and lethargy the last time I vaccinated him against lepto.

I made a decision not to vaccinate him again. His last lepto vaccine was six years ago. I acknowledge that my decision may put him, and me, at risk, and I own that risk.

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