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Wednesday, April 17, 2024


We are frequently asked why we vaccinate, or immunize pets against certain diseases as many of these pathogens have become rare in our area. It is true that distemper virus is not common in our city, but this is due to veterinarians and clients being diligent about vaccinating against distemper. Vaccines provide immunity today, prevent outbreaks tomorrow, and can quell a current epidemic of a disease. Let’s explore how they work and why they are so important to canine and feline heath.

In 1955 Dr. Jonas Salk announced that his laboratory had successfully formulated a vaccine against polio, a debilitating and feared disease of people, especially children. With a concerted vaccination campaign, the vaccine was eventually eliminated from the United States, and nearly the world. We went from having a feared illness to making it nearly extinct. But we still vaccinate children against polio. Why?

The Centers for Disease Control and Prevention compares vaccination and disease control to bailing out a boat with a slow leak. Initially there is a large amount of water in the boat, but with constant bailing (vaccination) the water will be reduced to a very small amount. But there is still a leak. Unless the leak is completely stopped (i.e. the organism is declared extinct), the boat will slowly refill. Therefore it is necessary to always be bailing, or in this case, vaccinating.

Vaccines prepare the body to fight a disease without exposing it to the symptoms of the disease. Most vaccines work by priming the body’s immune system to recognize and destroy a specific dangerous organism. The body sees the vaccine and makes antibodies, specific proteins, which via a number of different pathways, destroy the invading pathogen. The vaccines cannot cause an infection, but the body’s cells now know how to produce antibodies to the infection and can do so quickly.

It is also important that many pets be vaccinated. Certain people or pets cannot receive vaccines, such as those that are elderly, too young, or have immune system problems. They rely on herd immunity – that everyone surrounding them has the vaccine so that they are unlikely to come in contact with the disease. This works well for diseases that are passed within a species, such as distemper and parvovirus in dogs, but does not work well for leptospirosis, which can come from the environment.

Parvovirus used to be a plague of dogs here in the northeast. Today it still occurs, but is rare in our area, with most cases originating from outside the District. The rarity is due to the parvovirus vaccine being given to dogs in a series as puppies and then every three years as adults. If we stopped giving the vaccine it, in theory, could take only one infected dog to cause an epidemic in the city. The risk is that real. This is the importance of immunizing as many pets as possible.

Leptospirosis and Lyme disease are two organisms which do not benefit as strong from herd health. Lepto is spread via the urine of infected mammals, with rats and raccoons being the most important vectors here in the District. Lyme comes from ticks, which are carried by many different mammals, including mice. It is not possible to eliminate lepto and Lyme from wildlife populations, therefore each dog needs to be protected from these organisms.

Vaccination is a discussion that should be had with your veterinarian. Many diseases are now much less common due to vaccines, but this does not mean that one should not vaccinate. A classic example occurred in Japan with whooping cough in children. Vaccination nearly eliminated the disease, so parents elected to not give the vaccine. The number of vaccinated children significantly dropped, and then there was an outbreak, with tens of thousands infected and forty-one deaths–all from a preventable illness.

All medicines and vaccines have some element of risk, albeit very low for dog and cat vaccines. There are articles and postings on social media and websites decrying the dangers of vaccines, but provide scant evidence of problems. In an age where vaccines for parvovirus, distemper virus, rabies, leptospirosis, and feline leukemia are so effective, it is easy for there to be vaccine skeptics. They do not have the history of what happened before these vaccines. In order to not slip backwards to where preventable illnesses maim or kill our pets, we must remain vigilant in responsible vaccination. Talk to your vet.


Dan Teich, DVM is Medical Director at District Veterinary Hospitals.

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