Before 2003, respiratory illnesses in dogs were thought to be pretty straightforward.

We had “kennel cough,” which was caused by bacteria known as Bordetella, with a virus or two sometimes complicating the picture. Since then additional research and the occurrence of some new actors on the scene have markedly complicated the picture for pet owners and veterinarians alike.

Let’s start by clarifying the difference between a bacterial and a viral infection. This is important because what they are and how they differ is related to what we can do to protect our pets from them. A bacterium is a single-celled organism – a complete, independent life form.

We live with billions of bacteria. Some help us digest our food while others can cause life-threatening skin infections. Viruses are even smaller than bacteria and require a living host to survive and multiply. When a virus invades it takes over some of the cells and redirects them to produce more of the virus.

One important difference between bacteria and viruses is that antibiotic drugs can usually kill bacteria, but they are not effective against viruses. Another important difference is that we have been very often successful in making vaccines that can protect us from viral infections. Making a vaccine against bacterial infections is typically not as easy or as effective.

So let’s look at the main respiratory infections we are now seeing in dogs with recommendations for you to consider to protect your dog.

Kennel Cough

The most well-known respiratory condition in dogs, kennel cough is caused by the bacteria Bordetella bronchiseptica. It is very common in shelters and other areas where dogs congregate (dog shows, kennels, and dog parks). It is characterized by a hacking, retching cough that develops about six days after exposure.

It is an upper respiratory infection that affects the trachea, but severe cases can develop into a bronchopneumonia. Most cases are self-limiting and do not always require antibiotic therapy. Vaccination is highly recommended to protect your dog, and most kennels require it to board your dog.

There are two types of vaccines commonly available – an intranasal variety and an injectable form. Recent data supports the injectable variety for longer term immunity.

The common kennel cough caused by Bordetella can be complicated by several viruses (parainfluenza, adenovirus, etc.). In these cases, a simple case of kennel cough can become more severe and require much more aggressive therapy by your veterinarian.

Canine Influenza

Canine Influenza Virus (CIV) was first identified in racing greyhounds in Florida in 2004. It has since been labeled as H3N8, and it affects dogs in much the same way that flu viruses affect people — causing a runny nose, cough and fever. And also like people, most dogs are able shake off the virus with rest and time.

But in some dogs, with no real relation to age or health status, the flu may progress to pneumonia. To date, despite a lot of sensational press, there have been a limited number of cases across a number of communities.

There are two vaccines available, and protection is expected after receiving two doses at least two weeks apart followed by annual boosters.

One concern, though, is that, like human influenza viruses, the canine virus can mutate fairly quickly making any single vaccine potentially less effective. Veterinary disease experts recommend vaccinating dogs that travel regularly to places where dogs congregate, such as shows and racetracks, as well as dogs in areas with a documented outbreak. State Veterinarian, Dr. Leonard Eldridge says there have not been any confirmed cases of canine influenza to date here in Washington.

“Kennel cough” has now become a very complex issue of multiple pathogens with the possibility of co-infections becoming more common. The relatively short history of the H3N8 virus makes it that much more challenging for veterinarians to sort out the facts, since researchers are still learning how the virus behaves.

This is further complicated by the fact that in veterinary medicine there is no equivalent of the Centers for Disease Control to help coordinate research, so much of the information comes from vaccine manufacturers.

The best advice I can recommend is to keep your dogs vaccinated against Bordetella, and ask your veterinarian for the latest information about H3N8 to see if it is becoming an issue here or someplace you plan to travel to.

Dr. J.M. Kiel is the U.S. Army veterinarian currently supporting NAS Whidbey Island and Naval Station Everett. Please send questions or comments to Dr. Kiel at joseph.kiel@navy.mil.