10 Most Contagious Dog Diseases

by Elizabeth Xu

As a dog owner who likely thinks of your dog as a member of your family, you never want them to get ill. After all, our pets can’t exactly tell us what’s wrong. Like humans, dogs can get plenty of diseases—especially from other dogs.

Medicine is always advancing, for both human and animals. And while that means that many of these diseases aren’t as prevalent as they once were, you should still be aware of any disease your dog may be exposed to, whether at the dog park, daycare kennel, or elsewhere.

This article was verified and edited for accuracy by Dr. Katie Grzyb, DVM

Parvovirus is one of the first things puppies get vaccinated for—and with good reason. Puppies with parvo can get severe diarrhea, vomiting, and regurgitation, which can lead to dehydration and death, said Dr. Colin Parrish, professor at the Baker Institute for Animal Health at Cornell University.

“Vaccination for parvovirus is highly effective,” he says. “Basically we recommend that everyone get parvovirus vaccines for their puppies. You’d be sort of insane not to vaccinate your puppy against parvovirus.”

The virus is spread orally, through fecal/oral transmission, Parrish said. If a dog becomes infected, it’s important to keep them hydrated and make sure they’re getting nutrients.

The American Society for the Prevention of Cruelty to Animals (ASPCA) notes that parvo is highly contagious and suggests a thorough cleaning of toys, food and water bowls, and other surfaces with a bleach and water solution if a dog with parvo has been in contact with them.

Distemper is deadly and used to be seen much more decades ago, before it became the first big vaccine for dogs, Jones said. The disease is spread by bodily secretions and causes three issues: gastrointestinal upset, upper respiratory issues, and then it affects the neurologic system, after which dogs could have seizures and die, he said.

Luckily the vaccine is safe and effective, and Jones says he doesn’t see distemper very often these days. “For the most part we’ve done a good job of controlling a very devastating disease.”

Leptospirosis is often spread through wildlife, so veterinarians used to think of it as a more rural disease, Jones said. That’s not the case anymore, though it’s hard to tell where exactly a dog might get it since the disease is transmitted through urine, he said.

When dog diseases can affect humans, they’re extra worrisome for society, Jones said, noting that it can cause liver and kidney failure in both humans and animals. In fact, it could even lead to infected humans needing a kidney transplant, he said.

The American Veterinary Medical Association (AMVA) says that the signs of leptospirosis vary from dog to dog, but could include fever, vomiting, thirst, jaundice, and either frequent urination or lack of urination. It also notes that, if treated early, dogs can recover. However, Dr. Richard Baumgartner of Atlantic Veterinary Hospital in New Jersey notes that recovery could take months, and some dogs might never fully recover.

Like canine influenza, coronavirus is spread from dog to dog through coughing and sneezing, according to the AMVA. Jones said it can be hard to diagnose.

“[People say] corona is a virus looking for a vaccine, meaning there’s a lot of corona out there but it may not clinically do very much,” he said, adding that it can cause vomiting and diarrhea, but some veterinarians have stopped vaccinating for it in an effort to reduce the number of vaccines a dog receives overall.

Dogs of any age can be affected by CHV, but the highest mortality rate is in puppies, says Dr. Gerlinde Van de Walle, professor at the Baker Institute for Animal Health at Cornell University. Older dogs might have a mild fever or respiratory problems, but otherwise CHV might be unnoticed in them unless they have compromised health for other reasons, she says. However, it’s important to note that this virus can establish latency, thus dogs can have it for life, she says.

Though treatment is available, veterinarians have mixed opinions on whether it should be used because puppies with CHV so commonly die, Van de Walle says. While there’s a CHV vaccine in the United Kingdom, it’s not available in the United States. However, there are a few things you can do to protect puppies from CHV.

“What you for sure should do is try to prevent infection of puppies by keeping newborn puppies warm,” Van de Walle says, noting that puppies have poor temperature regulation and CHV thrives in lower temperatures. “That's why these puppies are so susceptible for infection and that's why it's leads to such a devastating outcome.”

Named for the pattern the disease makes and not because it’s an actual worm, ringworm is a fungus that affects a dog’s skin. While it is contagious, isn’t necessarily seen in many dogs these days.

“Most of the time a healthy dog isn’t going to get ringworm,” Baumgartner said, noting that it’s more often seen in puppies and older dogs who already have other health issues. Jones said it’s most often seen in shelter settings.

Rabies is well-known, but Jones said that the vaccination’s been so good that people let their guard down about this deadly disease.

“I think because the vaccine has been so good, a lot of humans aren’t as worried about rabies,” he said.  “What they don’t realize is that rabies is 100 percent fatal in people. We really, really have to be careful about that and make sure we’re keeping the animals up-to-date for rabies.”

The ASPCA says the disease spreads through a bite from an animal with the disease, and dogs who are in contact with wild animals are at highest risk. They also note that if a dog bites someone and there’s no proof that the dog has been vaccinated against rabies, a period of quarantine or even euthanasia could occur.

In most states, there is a legal requirement that all owners get their dogs vaccinated for rabies. The duration of the vaccine required varies from state to state.

Not only will the vaccine keep your dog safe, it will protect you as well, Jones said. “The rabies vaccine is really to protect people. We’re vaccinating the dogs and cats as a buffer between wildlife and people.”

While this disease is spread through saliva and other body secretions, it can cause liver inflammation and even be deadly, Jones said most dogs are vaccinated for it these days and thus it’s not seen very often. It’s part of the core vaccines given to puppies as the immunity they received from their mother wears off, he noted.

“Their most susceptible time is when they’re a puppy,” Jones said. “Just like kids, their immune system is not fully developed.”

As the name suggests, kennel cough is most likely to occur in a setting with many dogs, such as a kennel or at a dog groomer.

However, it is important to note that since this virus is spread via aerosol route, it is common for kennel cough to affect dogs in cities where there is a lot of dog-to-dog interaction while walking down the streets. It is also frequently passed around at dog parks and through shared water bowls.

“Kennel cough is kind of an interesting thing because it’s really a constellation of about 10-20 different bacteria and viruses that can cause coughing; it sounds like croup in kids,” Jones said, adding that bordetella is the disease that’s the most common and most often vaccinated for.

When dogs visit a boarding facility, it’s often stressful for them, Jones said. That means their immune system is down and more susceptible to diseases like kennel cough. Overall, Jones said that many contagious diseases can be taken care of through vaccinations.  “A lot of it is educating our owners based on exposure of what their pet does and what diseases we’re worried about and how often we’re vaccinating for them,” he said.

Your veterinarian can advise you on what vaccinations would be good for your dog, depending on your location and your dog’s risk factors.

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