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Will My Dog Catch a Disease or Fleas at the Vet’s Office?

A reader's dog sat next to a sick pup with fleas at the vet's office. Is her dog at risk?

Dr. Eric Barchas  |  Mar 8th 2016


I recently received a letter from Donna. In the letter, she raises a few interesting points.

I would like to know if my dog will be OK. She was at the vet and had a good checkup, but before the appointment this lady came in and placed her dog right beside my dog, then proceeded to tell me her dog was sick. I immediately moved my dog away from hers. A little later, she proceeded to tell me that her dog had fleas. I looked, and on the top of its head there was black stuff. I hope that I did not contact any fleas on my coat or my dog got any flea dirt from this dog. Will my dog get sick or could any flea eggs have gotten on her?

From the letter I can parse two main questions that Donna is asking. First, could her dog have contracted a contagious disease from the other dog? And second, could fleas have spread from the thoughtless neighbor’s dog to Donna’s dog?

Donna, when it comes to transmissible diseases, there is bad news and good news.

The bad news is that dogs, like most species, are capable of contracting and spreading very serious, and often deadly, diseases. Diseases such as parvoviral enteritis (also known simply as parvo) and distemper are highly contagious and may be fatal when contracted.

Here is the good news: Any dog who has received her complete puppy series of basic vaccines, and has received at least one booster as an adult, is likely to be immune to parvo and distemper for life. Also, especially in the case of parvo (which is much more common than distemper in the U.S.), adult dogs are substantially less susceptible than puppies. In fact, I have never treated a case of parvo in a dog who was over 2 years old.

Dog getting vaccinated by Shutterstock.

Dog getting vaccinated by Shutterstock.

Of course, parvo and distemper are far from the only diseases that can spread from dog to dog. A large number of bacteria and viruses can cause a syndrome known as canine infectious respiratory disease, or CIRD. CIRD is a new moniker for what used to be called infectious tracheobronchitis. The syndrome is known colloquially as kennel cough. Most of the pathogens that cause CIRD do not cause serious illness, although a few, such as canine influenza virus, have potential to be dangerous.

There are other transmissible diseases that can cause vomiting or diarrhea (or both) in dogs, just as in humans. Human norovirus recently has been in the news for sickening people who have eaten at a certain restaurant chain. In dogs, a bug called circovirus is believed to be a transmissible cause of severe vomiting and bloody diarrhea (known as hemorrhagic gastroenteritis).

Donna, did your neighbor in the waiting room mention what symptoms her dog had? Was the dog coughing in the waiting room? Did the dog have other respiratory symptoms, such as sneezing or nasal discharge? Did the dog vomit or have diarrhea in the waiting room?

If the other dog did not have respiratory or gastrointestinal symptoms, it is not likely that anything spread to your girl. Most (although I confess not all) veterinary offices have protocols to prevent disease transmission. For instance, at my hospital, dogs with respiratory symptoms and puppies with diarrhea or vomiting (which have a high risk of being infected with parvo) are not brought into contact with any other patients. We have special areas of the hospital for patients with known or suspected infectious diseases, and we have specific cleaning protocols for removing pathogens from the environment. I would hope that your vet’s office utilizes similar protocols.

What’s more, most sick dogs do not have something transmissible. The overwhelming majority of sick dogs that I treat (and since I’m an emergency vet, I treat a lot of sick dogs since the well ones have no reason to see me) suffer from either organic disease processes such as organ failure and cancer, or from gastrointestinal distress caused by dietary indiscretion (self-inflicted food poisoning), or from exposure to toxins. None of these types of problems poses any significant risk of contagion.

And even if your neighbor’s dog did have something contagious, odds are still good that your girl didn’t catch it. Most contagious diseases are relatively opportunistic. They are most likely to affect weak dogs with compromised immune systems. Your girl got a clean bill of health at her checkup, so there probably isn’t much to worry about.

Puppy biting at fleas by Shutterstock.

Puppy biting at fleas by Shutterstock.

Donna, you mentioned that the other dog had a flea infestation. You should be aware that fleas can carry diseases that can sicken dogs, so they may have been playing a role in the other dog’s illness. However, to contract such diseases your dog must become infested with fleas.

Which brings us to the matter of flea contagion. How likely is it that Donna’s dog contracted fleas from her neighbor’s pet? Not likely.

First, flea dirt and flea eggs cannot spread from one dog to another. Only adult fleas can move from host to host. And, in most cases, they do not bother to do that. A flea already living on a dog has a good gig; why would it take the chance of leaving its host, giving up on a sure thing for something else that might not work out?

In fact, most dogs become infested with fleas not through contact with other infested animals, but instead by coming in contact with an area where flea eggs have matured to pupae. The fleas that infest them are newly hatched and looking for a host for the first time.

Areas where flea pupae are common include yards, where fleas are spread by wildlife, and in homes, where they may be spread by rodents or other pets with active, egg-laying flea infestations living in or visiting the home. They are not common in vet’s offices, where tile or linoleum floors are regularly cleansed, providing an environment that is poorly suited to flea development.

In short, Donna, I consider it unlikely that you need to be worried for your dog’s well-being as a result of your neighbor’s poor manners. Watch your dog for any unusual symptoms, and use a good flea preventative (all dogs need good flea preventatives). Seek veterinary attention if something comes up. I’ll bet something will not come up.

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