Amid an Ontario parvovirus outbreak, here's what a Canadian veterinarian say dog owners should know

CTV News

07-07-2025

Tonya Dixon's puppy Sassy prepares to receive deworming medication at a free dog vaccine clinic to combat a canine Parvovirus outbreak on Monday, Feb. 3, 2025, in the Tenderloin in San Francisco. (AP Photo/Emily Steinberger)
Recent outbreaks of canine parvovirus (CPV) in Ontario led to spikes in online searches for information on the dog disease.
Asked about the outbreak earlier this summer in London and about the prominence of CPV in Canada, an expert says it's a fairly common and persistent disease.
Tracy Fisher, a veterinarian from Regina and the president-elect of the Canadian Veterinary Medical Association, told CTVNews.ca that the frequency of cases varies every year.
How do dogs get parvo?
CPV, or parvo, is a disease that first appeared in dogs in 1978, according to Veterinary Centers of America (VCA)'s Canadian division.
'The virus that causes this disease is similar to feline panleukopenia (feline distemper); the two diseases are almost identical,' the website for VCA Canada, a network of animal hospitals, says. 'However, that has never been scientifically proven.'
The primary source of infection is through the ingestion of the feces of already-infected dogs, according to VCA Canada.
It can also be easily transmitted through contact with the hair or feet of infected dogs or with objects contaminated by the infected feces.
The virus first enters the tonsils or lymph nodes of the animals, where it invades lymphocytes – a type of white blood cells –which later carry the virus through the body to places like the bone marrow and the lining of the intestines, VCA Canada said.
This disease is particularly problematic in animal shelters due to the high number of unvaccinated dogs being kept together.
Parvo symptoms
The main signs of CPV are severe vomiting and diarrhea that often come with a powerful stench, and contain mucus and blood. Infected dogs can suffer from loss of appetite, fever and depression, according to VCA Canada.
It is most common in unvaccinated dogs who are less than one year of age, they said.
It is generally not fatal, but there is a much higher fatality rate for some breeds, including the rottweiler, doberman pinscher, Labrador retriever, American Staffordshire terrier and Arctic sled breeds, according to animal hospital group.
Fisher said severity and survival also depend on the age of the dogs who are infected.
'Very young puppies almost never survive. If they are not given any supportive care, their survival rates can be as low as 20 to 30 per cent,' she said.
Parvo treatment
Unfortunately, there is no treatment for the disease available in Canada, Fisher said.
But if they are hospitalized and given the right kind of supportive care, the survival rate can be upwards of 80 per cent, she explained.
'The traditional treatment is just supportive care, very intense supportive care,' Fisher said. 'So, we would have that animal hospitalized on intravenous fluids, controlling the nausea, controlling their blood sugar levels, antibiotics to prevent secondary infection. It's quite intensive.'
A new treatment has been conditionally approved in the U.S. for CPV. It could potentially be used to treat the disease in puppies and dogs that have been exposed to the disease, according to veterinary publication website dvm360.com.
It is not available or approved yet in Canada, Fisher said, but she called the U.S. approval a promising sign.
'It's a monoclonal antibody. That means is that we're providing these animals with antibodies directly for the parvovirus,' Fisher explained. 'We're really excited about the promise of this, because parvo is such a miserable disease.'
But the vaccines have gotten better and more effective with time, which has helped keep the problem under control, she added.
How common is parvo in Canada?
Fisher said she treats approximately two or three cases a year at her practice in Regina. Outbreaks are usually localized to certain area, she said.
In late June, a London housing community faced a CPV outbreak that prompted local veterinarians to launch an on-site mobile clinic, offering testing and vaccinations for the residents' dogs at a lower cost.
In December, an outbreak in Windsor led to the death of 14 dogs, CTV News reported.
And a Winnipeg dog rescue organization warned owners last fall about a possible outbreak in parts of Manitoba.
Fisher's advice to pet owners is that the most effective treatment for CPV is prevention. Get your dogs vaccinated on time, especially puppies, she said.
With files from CTV News London's Reta Ismail and CTV News Windsor's Robert Lothian, and CTV News Winnipeg's Jon Hendricks