Despite guidelines that recommend vaccinating dogs every three years, many veterinarians continue to push annual vaccinations, a CBC Marketplace investigation reveals.

And when dogs get annual jabs, pet owners may be getting gouged.

“It’s inappropriate and [veterinarians] need to get with the current policies and guidelines,” said Dr. Jean Dodds, a California-based veterinarian and researcher, who is an expert in dog vaccination protocols and an outspoken critic of over-vaccination.

Some veterinarians told Marketplace staff who documented vet visits on hidden camera that they recommend yearly vaccines as a way of making sure that pet owners schedule wellness exams.

Other vets either were not familiar with or did not trust research that says annual shots are unnecessary.

Research in this area is “black and white,” Dr. Dodds said in an interview with Marketplace co-host Erica Johnson for the show’s season premiere, “Barking Mad,” which airs Friday at 8pm.

“There’s plenty of documented evidence that shows that vaccines last much longer than we used to believe, and from now on, vaccines should be given less frequently to those animals that are properly immunized when they were younger.”

Hidden camera investigation

There are about 14.5 million dogs and cats in Canada, according to research published in the Canadian Veterinary Journal in 2009, and 50 per cent of cats and 78 per cent of dogs saw a veterinarian in the past year.

Money may be a factor: Pet care spending in Canada increased 90 per cent between 1997 and 2009, according to Statistics Canada.

In its investigation, Marketplace took Marshall, a healthy three-year-old English bulldog, to 10 veterinarians. During the exams, Marshall was prescribed treatments and procedures that experts say are not needed, including unnecessary testing and a weight loss program.

The Marketplace investigation uncovered five ways in which veterinary bills may be inflated, from vaccines to the price of pet medications.

Despite being up to date on all vaccinations, six out of 10 veterinarians Marketplace visited recommended that Marshall be given at least one vaccine during the exam.

Most veterinarians -- and veterinary medical groups -- agree that all dogs should receive “core” vaccines, which immunize against illnesses that are contagious, widespread or very serious, including rabies, distemper, adenovirus and parvovirus.

Guidelines released in 2011 by the American Animal Hospital Association (AAHA) recommend that dogs receive core vaccines every three years, though some jurisdictions may require that the rabies vaccination be given more frequently.

The guidelines are based on “professional, scientific, and clinical evidence, as well as published and unpublished documentation,” and note that protection from the shots often lasts much longer than three years. Published research has demonstrated that the protection offered by core vaccines can last seven to nine years.

The Canadian Veterinary Medical Association (CVMA) maintains that the research on vaccines is still controversial, and that the vaccination schedule should be determined on an individual basis.

“The decision on how often to vaccinate and what to vaccinate for is a direct conversation between the client and the veterinarian based on the individual animal and the circumstances that that animal lives in,” said Dr. Jim Berry, president of the CVMA, who notes that the guidelines do allow veterinarians to determine their own vaccination schedule based on the pet, resources and other factors.

Over-vaccination increases cost, risk

But other experts maintain that annual vaccinations are unnecessary.

“[Core] vaccines provide long-term immunity,” said Dr. Ron Schultz, who teaches veterinary medicine at the University of Wisconsin and helped develop the AAHA guidelines.

Dr. Schultz said that giving dogs core vaccines every year is “like vaccinating a human for measles every seven to 10 years for the rest of their lives.”

In addition to the financial cost -- vaccines can cost about $40, in addition to the cost of the exam -- over-vaccinating dogs is not without risk.

“There is always the risk of adverse reactions, albeit small,” said Dr. Schultz.

Annual wellness visits are important in keeping dogs healthy, said Dr. Schultz, but veterinarians shouldn’t be using vaccinations as a premise to book the annual exam.

“It’s very difficult for me; I love my profession,” said Dr. Dodds. “Are we going to harm [pets] by giving them something they don’t need?”

For more on the Marketplace investigation of veterinary bills, watch the season premiere “Barking Mad” on Friday, October 4 at 8pm (8:30 in Newfoundland).

Join the investigation by sending in your veterinary bill and a photo of your pet as Marketplace maps basic services coast to coast.