A new strain of the highly contagious canine parvovirus has been discovered in Australia for the first time. The new form of the common virus, known as Canine Parvovirus-2c, did not always show up on in-clinic diagnostic tests and has been found in vaccinated dogs.
Parvovirus strains 2a and 2b have existed in Australia for decades, but 2c first emerged in Italy in 2000. Researchers at the University of Adelaide have now confirmed cases in South Australia and Victoria, and suspect that more exist in Queensland and the Northern Territory.
What is parvovirus?
Parvovirus infection (known as parvo) is a viral illness that causes vomiting, bloody diarrhoea and weight loss in dogs. In puppies aged between six weeks and six months it can be fatal, although early vaccination has been effective at reducing death rates.
Over the last two years vets around Australia noticed dogs presenting classic parvo symptoms, but returning negative in-clinic tests. Some of these cases were sent to the Companion Animal Health Centre at the University of Adelaide, where a team lead by Dr Farhid Hemmatzadeh and Dr Lucy Woolford began investigating.
Their report, published recently in the journal Viral Immunology, found a 99% genetic match for 2c in three Australian cases: an 8-week-old puppy, an 11-month-old female Saint Bernard and a 9-month-old male Siberian husky.
Dr Farhid said his team has confirmed a dozen cases of 2c around Australia, although there were many more suspicious cases reported.
“In most of the cases the disease occurred in already vaccinated dogs. The vaccines are excellent, but for this particular strain they produce [only] partial immunity,” he said.
Dr Farhid nevertheless emphasised that the vaccine is still the best way to protect your pet from parvovirus.
Protecting your dog
Associate Professor Richard Squires, who leads the veterinary clinical sciences team at James Cook University, told The Conversation it’s not surprising that this strain of parvovirus has shown up in Australia. Parvovirus, he said, survives by being extremely tough:
“It can hang around the environment for many months [and only] requires a relatively small amount of viral particles to infect a puppy,” he said.
According to Professor Michael Ward, chair of Veterinary Public Health and Food Safety at the University of Sydney, the virus could have entered Australia on someone’s hands, clothes, or dog equipment.
They both agree that the single most important thing pet owners can do is vaccinate puppies, who are most at risk.
Professor Squires is involved in developing the guidelines for the World Small Animal Veterinary Association, and said improperly administered vaccines were often responsible for parvo outbreaks.
“The authors [of the study] tell us that the affected adults in their study were vaccinated according to manufacturers’ instructions. That is not necessarily (in fact, in Australia, not usually) the same as vaccination according to WSAVA or American Animal Hospital Association vaccination guidelines,” he said.
“These guidelines were published more recently and recommend the last puppy shot at 16 weeks or later.”
Professor Squires explained that the antibodies very young puppies receive through their mother’s milk will interfere with the vaccination if it’s given earlier than 16 weeks.
This transition period – where a puppy goes from being naturally protected to no protection at all – is the most dangerous time. According to Professor Ward, we don’t know exactly when this occurs.
Owners should keep young puppies away from hot spots with lots of dogs, like parks and puppy schools, and avoid sharing equipment. Crucially, it can take seven to ten days before the vaccine becomes effective, and Professor Ward said he has seen cases of puppies becoming infected during that critical window.
“People get their puppies vaccinated, and they think it’s protected right then. They can then be exposed to the virus,” he said.
While the University of Adelaide study has proved that 2c now exists across Australia, the researchers have no idea how widespread it might be. Further research, they argue, is needed to find the extent of its spread.