Vet Services Wairarapa have been handling cases of parvovirius in dogs since mid-January in Wairarapa, a trend for this time of year, according to vet Stuart Bruere.
Parvo virus is a severe viral infection in dogs that causes depression and a sudden onset of vomiting and bloody diarrhoea.
In most cases, untreated dogs will die.
"We've seen eight positive cases since January," he said.
Mr Bruere said if owners are bringing in dogs to their vet, it is better to call the clinic first, and leave the dogs in the car first rather than walk them into the clinic.
"There's a quick test we can do, we can walk out to the car with the testing kit, test them in the vehicle, and take that into the clinic. We can get an answer in 10 minutes."
Keeping the dog in the car prevents the chance of contagion to any dogs waiting at the clinic.
"If an animal tests positive, we can take them into the side of the clinic, so there's no cross-contamination."
He said they are dealing with severe dehydration, so dogs are put on fluids as soon as possible.
"It's like a very nasty gastroenteritis, it can be very painful.
"Usually in 24 hours, it can turn around. In most cases, they make it through."
Mr Bruere said avoiding cross-contamination was a design aspect they considered when they built their Lincoln Rd, Masterton clinic last year.
The New Zealand Veterinary Association says all puppies from six weeks of age should be vaccinated against parvorvirius and other canine diseases.