Parvoviruses in Pets

Some of the most common infectious diseases in our pets are caused by a family of viruses called Parvoviruses. These nasty little germs have a particular fondness for rapidly dividing cells, and are an important cause of disease, and (sadly) death in our pets. In this blog, we’re going to look especially at Canine Parvovirus (CPV) and Feline Parvovirus (FPV), how they spread, the diseases they cause, and how we can protect our pets from them.

Parvo dog.jpg

When talking about these conditions, it’s important to remember that CPV (in dogs) and FPV (in cats) are very closely related - in fact, CPV is thought to have arisen naturally from a mutated version of the feline version of the virus within the last hundred years. As a result, the effects they have tend to be very similar as well.

There have been reports in Europe of unvaccinated cats in shelters and petshops that shed canine parvovirus with some succumbing to the disease. We are currently collecting samples to help with research into this phenomenon via the University of Sydney. Hopefully next year we will have some results, which will give us even more knowledge of the disease process here.
 

Why are they such common diseases?

The answer is twofold; firstly, there is an extensive “reservoir” population in which the virus can spread. For CPV, that population includes unvaccinated dogs, and wild animals - especially the Arabian Red Fox, which is well established in urban areas across the Emirates. FPV is specific to felines (especially feral and unvaccinated cats), but sandcats and wildcats can also carry and can transmit the virus. As a result, there’s always a certain amount of both of these viruses in circulation, and even if every pet cat and dog was vaccinated, the virus would not become extinct.

However, to make matters worse, these viruses can survive for a very long time in the environment, weeks or months - even in the UAE, especially if away from direct sunlight, as the virus can easily survive temperatures up to 50C - while indoors it may last much longer. As a result, the virus particles are easily transferred between animals and between houses (on the sole of a shoe, for example).

As a result, we have to assume that every cat and dog is potentially at risk of infection.

 

What is a parvovirus?

Parvoviruses are a family of small and fairly simple viruses. The virus particle is about 20-25nm across (so 2000 times thinner than a human hair!), and is comprised of a series of proteins that it uses to “lock-onto” and invade a dog or cat body cell. Inside these proteins is a length of DNA, which the virus injects into the victim cell. Once inside, this DNA overrides the cell’s own genes, and hijacks the cell’s biological systems to make more viruses. This results in the cell exploding, releasing thousands upon thousands of fresh virus particles, ready to attack other cells. However, the viruses aren’t indiscriminate killers - they really prefer rapidly dividing cells such as gut cells and bone marrow.

 

What diseases do they cause?

The original version of the disease was the cat form, FPV. This causes a disease known as Feline Paneleukopenia, or Feline Infectious Enteritis. In this disease, the damage to the gut and bone marrow causes fever, lethargy, and loss of appetite; this soon progresses to severe vomiting and often diarrhoea. In older cats, symptoms are milder and death is uncommon, but kittens may die of dehydration. Even if a cat survives the initial infection, their immune systems may be severely damaged by the virus destroying their bone marrow, and death can occur as a result of secondary infection; however, this is relatively uncommon except in kittens under six months or so.

Infection in dogs is generally more severe. Although the symptoms of canine parvo are similar, bloody diarrhoea is more common, and in the UAE (because of the import of immune-compromised young pets), the mortality rate is usually 50 - 70%.

 

Can it be treated?

There is no specific treatment, as antibiotics do not work against viruses and there are no antiviral drugs for parvoviruses. The mainstay of treatment is supportive care (intravenous fluid drips to prevent dehydration, anti-vomiting medication, antibiotics to prevent secondary infection); however, the use of artificial interferon medications does seem to reduce the mortality rate by “supercharging” the animal’s immune system to fight the virus.

 

How can we prevent disease?

The best solution is vaccination - there are very effective vaccines for dogs (against CPV) and cats (against FPV), which last up to 3 years once the primary course is completed. Of course, the biggest risk is to unvaccinated animals, and young puppies and kittens who have not yet completed their primary course.

 

Does cat parvo affect dogs?

No - wild-type FPV can ONLY infect cats. The original CPV-2 virus, likewise, can only infect dogs. However, there are now strains of CPV that can infect cats too - CPV-2a (which rarely causes disease) and more worryingly, CPV-2b and -2c, which seem to be capable of causing Feline Panleukopenia as well as Canine Parvo. According to some studies, as many as 80% of cats in some countries have been infected with Canine Parvovirus, and up to 5% of Panleukopenia cases are caused by the canine virus. The only good news is that, so far, the CPV viruses seem less dangerous to cats - but we don’t know how effective the cat vaccines are at preventing infection.

We have recently had a cat in the clinic with Panleukopenia, and the initial lab results suggest that these multi-infectious strains of CPV have indeed reached the UAE. [1] 

As a result, we are strongly advising that all dogs be vaccinated, not only to protect them and other dogs, but to protect cats as well!

 

If you have a query about parvoviruses, or think your dog or cat may be infected, call us immediately.

 

If you want to know more…

There are great articles from the MSD Vet Manual website on Canine Parvo here and Feline Panleukopenia here. There’s also a review of the new strains of parvovirus from the American Society of Microbiology here and the journal Emerging Infectious Diseases here.

Use this sentence if the lab results come back positive, otherwise, delete!

Posted on October 24, 2017 and filed under Blog.