Tuesday 20 August 2019

Parvovirus is still a threat to unvaccinated dogs

Dogs with Parvovirus often die, despite intensive treatment
Dogs with Parvovirus often die, despite intensive treatment

By Pete Wedderburn - Animal Doctor

Parvovirus is one of the most serious and lethal viral infections of dogs. Epidemics of the disease have rarely been seen in recent years due to widespread vaccination of dogs, but there are concerns that there may now be an increased risk of this happening again. Many pet owners have become complacent about vaccination, and when less than 70% of a local population of dogs are unprotected against a viral disease, a new epidemic is a real threat.

Last week, amongst the callers to my radio vet spot on Newstalk's Pat Kenny Show, one lady contacted me describing how all eight of her dogs had been struck down by a serious gastro-intestinal illness. One dog had died, two had to spend several days in intensive care at the vets, and the other five had recovered after simple treatment. Initial tests for Parvovirus had come back as negative. Could it still be Parvovirus, and what should she do?

It's impossible for a radio vet to comment on detail on such incidents: the best advice is always to liaise closely with your own vet, who is aware of all of the important details around the situation.

But there are some broad facts about Parvovirus that are worth sharing. First, if a dog tests as negative initially, it does not definitely mean that Parvovirus has been definitively ruled out as the cause of an illness. The most commonly used tests for Parvovirus have "high specificity but low sensitivity": this means that when Parvovirus is identified, it's almost 100% sure that Parvovirus is the cause of the illness, but when the test comes back as negative, it still hasn't been completely ruled out.

In this case, there were other possible causes, including so-called "compost toxicity", when dogs eat rotting vegetation that can include poisonous compounds. The lady's dogs often went for walks together in woodland, and there was a chance that they could have all rummaged around in the undergrowth, eating substances that created severe gastrointestinal irritation.

But the truth was that a mini-outbreak of Parvovirus remained a possibility, and that's a worry for pet owners all over Ireland.

I heard recently about a veterinary colleague based in Australia who is currently dealing with a local epidemic of Parvovirus: the first after many years of freedom from the disease. The situation there is similar to Ireland, with many animals who have lapsed vaccinations. In her case, Parvovirus has definitely been confirmed through tests. In her small town, there have been over twenty dogs affected, and most of them (nearly 80%) have died despite the best efforts of the vets to save them. A wide range of ages of dogs have fallen ill, from pups of just eleven weeks of age through to an elderly dog of thirteen, with many of all ages in between these extremes. The one factor in common with every affected dog was that they had not been vaccinated for at least 18 months.

My Australian colleague has been using social media to keep everyone informed about the outbreak, with online maps used by all the vets in the town to show where the disease has happened. The map resembles the fall-out maps after a nuclear accident: you can see how the virus has spread from street to street, gradually crossing the town. All of the local residents now know about the epidemic, and their dogs have been fully vaccinated. The one bit of good news is that vaccination is highly effective, and this Australian epidemic is already settling down.

Canine Parvovirus was first discovered in the 1960's when it was identified as the cause of mild diarrhoea in dogs. In the 1970's the virus mutated into a new genetic variant which caused the life threatening bloody gastroenteritis that is still the hallmark of the illness. The virus is passed on by dogs licking areas that have been contaminated with dog faeces from infected dogs. The secret of the virus's success is that it is incredibly infectious: one teaspoonful of dog faeces contains fifty million infective doses of Parvovirus, and the virus remains active for up to a year in a contaminated area. Cleaning and disinfection needs to be done thoroughly, using special chemical agents proven to be effective against the virus. Even then, unvaccinated dogs should be kept away for at least a year.

When dogs get Parvovirus, intensive treatment is needed, including intravenous fluids, antibiotics, pain relief and other medications. The sadness is that even when everything possible is done, most dogs still die, and they suffer for up to a week before it finally becomes obvious that they are not going to make it. Veterinary staff find Parvovirus one of he most devastating illnesses to deal with.

The good news is that it's easy to protect dogs against Parvovirus: all puppies need a full course of vaccinations. Repeat booster vaccinations should be given one year later, then typically at 3-year intervals throughout the dog's life, in combination with other vaccinations. The precise vaccine requirements vary , depending on the vaccine brand used, and the local disease situation, so owners should always consult with their own vets to find out the safest answer for their own pets. Whatever you do, make sure that your pets are protected.

Wexford People

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