Canine Parvovirus

- a potentially fatal disease in dogs

by Shane Jackson M.A., Vet M.B., MRCVS



After reading  in ‘LATEST NEWS’ the Dogs Trust’s warning to the general public against the purchase of ‘battery farmed’ puppies and the risk of these puppies contracting parvovirus, I thought this might be the moment to discuss the problem more fully.  This disease is not necessarily confined to farmed puppies and occasionally there are small outbreaks of this infection when all dogs may be at risk.

Canine parvovirus is a relatively new disease and when it was first seen in 1978 all dogs, both young and old, were susceptible.  It killed a large number of dogs, either from heart failure (mainly the very young) or from severe bloody gastroenteritis, which we now regard as the typical form.  As some immunity developed in dogs and, more importantly, they were vaccinated, bitches passed on their immunity to their pups thus protecting them at the time when their hearts were likely to be damaged.  This form of the disease is now less commonly seen and cases of parvovirus usually present as the intestinal form.

Any age of dog can be affected by the virus, and as is usual with such infections, the severity of the disease will depend on the severity of the challenge (how much virus the animal is exposed to), whether the dog is already weak or ill, and its age.  The very young and the very old are usually more susceptible.  How severe the clinical signs are varies from hardly any symptoms at all to death within 24 hours, but we will commonly see a very depressed dog which is vomiting.  If the profuse bloody diarrhoea has not already started, this will be seen in the next phase.  Death occurs from dehydration; there are vast fluid losses with canine parvovirus.

When young puppies from unvaccinated mothers are infected, the virus attacks the heart; either it will cause such a weak heart that the puppies die early and suddenly, such as when they are excited, or will it will cause heart disease resulting in death within the first year of life. 

Treatment of the condition is not very successful if there is a major heart disease, but in the intestinal form, there is a better response.  Replacement of lost fluids is essential if the dog is to have any chance of recovery.  Since large quantities of fluids are required, and since the dog will be vomiting, the patient should be admitted to the veterinary surgery so that fluids can be given intravenously.  We usually give antibiotics as well to support the treatment.  Such dogs are liable to be further weakened by opportunistic bacteria which would normally be shrugged off.  The recovery period in severely affected dogs can be quite long.  The patient may need several days on intravenous drips before it can take fluids orally without vomiting, and then it may be several days after that before it can take food.  Even when eating and fit enough to be discharged from the surgery, the dog’s motions may be soft and pasty.

Obviously, the best course of action is prevention rather than cure.  Modern vaccines are very good and parvovirus protection is included as standard in the routine puppy vaccination schedule.  However, it is important that all dogs are revaccinated routinely since immunity starts to wane relatively quickly.  Your own vet will advise you when a booster is due.  It is particularly important that bitches which are intended for breeding are vaccinated so that her offspring are given every protection.