
When I was a child, I don’t remember there being anti-vaxers. I do remember the early equivalent of robo-calls, when the John Birch Society barraged our town with their anti-fluoridation campaign. Although I am sure there were people back then who were suspicious of vaccinations, the predominant mood was fear of diseases like polio. Everyone knew someone who had been affected by polio. Every parent was afraid for their children. Then, when I was 6 years old, a nurse came to our school, and we all went to the gym where, one by one, she gave us a mysterious, magical (and painless) sugar cube topped with a drop of mysterious, magical liquid. The oral polio vaccine had arrived. There was a sense of wonder, relief, and amazement. Science was conquering a truly horrible disease.
So I grew up firmly believing in the power of vaccinations. I still believe. But as more and more vaccines for more and more diseases were developed, even those of us who are strong proponents of vaccination had some concerns about whether we were “over-vaccinating.” In the veterinary world, this has been addressed with “vaccination guidelines” put out by various professional organizations. These guidelines suggest which vaccines to consider “core vaccines,” meaning they should be given to every patient, and which vaccines are not. Non-core vaccines are usually given on a case-by-case basis, taking into consideration individual lifestyle, risk, and other medical factors.
This is similar to human medicine. For example, I am vaccinated against rabies. You probably are not. That’s because I spend my life sticking my hands in the mouths of lots of animals, including sick ones. My increased risk of being exposed to rabies warrants my vaccination. “Herd immunity” is also an important concept. Mass vaccination against viruses like COVID-19 in people, canine distemper in dogs, and feline leukemia in cats dramatically reduces the incidence of such diseases in the population as a whole. So deciding what vaccines to give to what patients is all about risk versus benefit.
Which brings me to today’s topic. Leptospirosis — a serious disease caused by various strains of the Leptospira bacterium, which can infect dogs, livestock, people, rats, and some other wildlife. It is spread primarily via exposure to water or soil contaminated by the urine of infected critters. Signs in dogs range from mild to life-threatening, depending on the strain involved, and may include vomiting, diarrhea, lethargy, jaundice, excessive drinking and urination, and abdominal and muscle pain. Liver and kidney failure can ensue. Although it’s treatable with antibiotics, 50 percent or more of infected dogs may die, and those that survive often have chronic kidney and/or liver disease.
When I was in veterinary school, we were taught that the canine population at risk for leptospirosis infection was primarily large dogs in wet environments, such as hunting dogs or farm dogs exposed to water contaminated by the urine of wildlife and livestock. We had leptospirosis vaccines for dogs, but in the early days of their development, there were problems. There are many strains of leptospirosis, called “serovars.” Different vaccines addressed different strains. If a dog was vaccinated for one serovar but then got infected with a different serovar, the vaccine did not provide any protection. In addition, serious vaccine reactions were not uncommon.
At first, I dutifully vaccinated all my canine patients for leptospirosis. But I also saw way too many dogs have severe reactions to those early vaccines. After 20 years of this, one day I thought, “I have never seen a single endemic case of leptospirosis in an Island dog.” An endemic disease is one that is consistently present in a particular region. The only cases of leptospirosis I had ever treated all contracted the infection somewhere else. I decided then that since the first rule of medicine is “do no harm,” for most of my patients, the risk with the leptospirosis vaccines then available outweighed the benefit. I opted to stop giving them to most Island dogs.
But times have changed. In recent years, leptospirosis is increasingly being diagnosed in other populations of dogs. Small dogs. Urban dogs. These pups are being exposed through environments such as dog parks, boarding kennels, or simply living in places like cities, with high densities of rats. And vaccines have changed. The current lepto vaccines are significantly safer and more effective than the versions of my youth. Bad reactions are no more common than with any other standard canine vaccines. Some sources anecdotally report that small breeds are more likely to have adverse side effects, but there is no definitive evidence to support this.
So if there is a safe and effective vaccine for leptospirosis, we should give it to Floofy, right? Well, yes and no. Recent guidelines from the American Animal Hospital Association now advise veterinarians to consider leptospirosis a core vaccine for all dogs. I admit that I am an old dog, slow to learn new tricks, but have to acknowledge that even here in paradise, things have changed. I have still never seen a case of endemic leptospirosis here, but the incidence of the disease is increasing nationwide. Our population is traveling more, with their dogs — traveling to other places that do have endemic leptospirosis.
The protocol is an initial series of two injections, followed by an annual booster. Like COVID vaccines in people, leptospirosis vaccines do not always prevent infection, but they will reduce the severity of the illness. Another point in favor of vaccinating Floofy is that leptospirosis is a zoonotic disease. That means people can get it. Though most human cases in the U.S. can be traced back to activities involving exposure to contaminated water or infected rodents, transmission from an infected family dog to a person is unlikely, but not impossible. Many veterinarians have always routinely vaccinated for leptospirosis, so Floofy may already be protected. But if your doc has been like me (considering it a “non-core” vaccine), it may be time to revisit that decision with your veterinarian.