The B.C. SPCA has issued a warning to dog owners in the Vancouver area after six puppies were diagnosed with a rare, potentially fatal virus downtown.

The dogs all caught parvovirus, or parvo, over the last six weeks. Four have already died, and it's believed none of them had been vaccinated against the illness.

Parvo is a highly contagious viral disease that attacks dogs' gastrointestinal system. It can also damage the heart.

The B.C. SPCA issued a statement Thursday urging owners to check their pet's history out of concern that the infected dogs may have exposed others in the community.

Owners who think their pet is showing symptoms of parvo should see their vet.

"It causes vomiting, diarrhea, dehydration and then eventually bacteria can just go into the bloodstream and cause sepsis," said Emilia Gordon, senior manager of animal health for the B.C. SPCA. "That's usually how they die."

Part of standard puppy vaccinations

The virus is spread through an infected dog's feces and can live in an environment for several months or longer. It's resistant to many disinfectants.

Puppies less than five months old and unvaccinated adult dogs are highly vulnerable, though the disease is preventable with a vaccine. Treatment is an option if the virus is caught early.

"If an infected dog visits a park and then another dog goes to the same park. they could certainly get it. But also if they just have a bit of poop on their side and they track it down the hallway ... even licking a piece of grass that has it," said Gordon. "That's why it's so important for all dogs to be protected with vaccination."

Parvovirus spreads through contact with an infected dog's feces. The virus can live in an environment for several months or longer. (Evan Mitsui/CBC)

The vaccine for parvo is part of the core group of shots dogs usually receive as puppies. Those vaccines typically start at six to eight weeks with follow-up boosters at four-week intervals until the animal is 16 to 20 weeks old. Another booster comes at one year old.

Adult dogs that did not have a full set of parvo vaccinations as a puppy should receive at least one shot.