Vets are warning about an outbreak of the deadly parvovirus that has infected hundreds of dogs.

WA Veterinary Emergency and Speciality clinic vet Katrin Swindells said the virus was spreading because of a surge in puppies being born and dogs being re-homed over Christmas.

Dr Swindells says owners need to be vigilant and ensure their dogs are vaccinated.

“The vaccine for parvo is highly effective,” she said.

“When you get this sort of situation, it means there’s just not enough dogs that are vaccinated. The virus can last six months easily in the environment — sometimes a year.

“It needs the majority of dogs protected to stop excreting it.”

Outbreaks have been reported in Armadale, Gosnells, Kelmscott and Huntingdale.

Parvovirus attacks the gastrointestinal tract and cardiovascular system of dogs and causes excessive diarrhoea and vomiting.

It can kill a dog in 24 hours.

Dr Swindells said even with treatment, many dogs died from parvovirus.

“One of my vets had to euthanase 11 dogs the other day,” she said. “Without any treatment, up to 91 per cent of dogs with parvo will die. With treatment, 50-90 per cent will survive.”

Humans can spread the disease if they come into contact with highly contagious parvovirus particles.

“We can spread it through our shoes or our car tyres,” Dr Swindells said. “Even when you no longer see the diarrhoea, the virus can still be there.”

She said many dog owners mistakenly believed their dogs were vaccinated.

“If you have a rescue dog and you did not get it with a vaccine certificate, assume it is not vaccinated and vaccinate it,” she said.

“It’s such a devastating disease.”

Dr Swindells said if someone had a dog that died from parvovirus at home, they should not get a new puppy for at least a year and should not let other dogs into their yard.