The veterinarian looks at a sad 10 week old Rottweiler puppy lying on her exam table. His head is down, his breathing is rapid and his gums are pale. The worried owner describes the pups rapid decline from a ball of energy eating everything put in front of him to a puppy that wants nothing to do with his dinner and will not fetch even his favorite toy. This behavior was so unusual for the puppy that his owner brought him in immediately to be examined. The puppy had only had a couple of soft stools and no vomiting but the doctor gently said "I think we need to test him for Parvo".
Parvo. Parvo? This word can strike fear into the heart of a dog owner or bring puzzled thoughts of "why is everyone so worried?" and "how does this happen?"

Parvo is an intestinal virus that affects all canids (domestic dogs, coyotes etc). The type of virus, a parvovirus, affects rapidly growing cells such as those in the intestinal lining. When a dog is infected by a large amount of virus the clinical signs we see are gastrointestinal such as vomiting and diarrhea.

One of the most difficult things about parvo is that it is highly contagious. Ingestion of infected feces by an unvaccinated dog or puppy can cause clinical disease. This is called fecal-oral transmission. It takes 5-7 days for a puppy that has been exposed to parvovirus to get sick. Parvovirus is a labile virus which means that it is not easily killed and lives in the soil through cold and draught conditions. The best disinfectant for this virus is household bleach.

Parvovirus was first identified as a cause for hemorrhagic gastroenteritis (bloody diarrhea) in the late 1970s and at that time was very deadly. There was no vaccine for it and infected dogs developed severe signs that were many times fatal. As viruses do, parvo has mutated over the years into causing less severe gastrointestinal disease although there are still strains that are deadly. Smaller (less than 10 pounds), younger (less than 3 months) puppies have a harder time recovering from a parvo infection simply because they have so few reserves to begin with and their immune systems are weak or too immature to fight off the virus.

The good news is that there is an extremely effective vaccine for parvovirus that should be given to all puppies in a series of 3 to 4 shots. Puppies are not fully protected until they have had their last vaccine and are older than 4 months of age so even a young puppy that has had only one or two shots can still become sick. Any young pups or unvaccinated dogs should not visit communal dog areas (parks, dog park) because the risk of coming in contact with parvovirus is high in those places. Even active, healthy adult dogs can shed parvovirus in their feces.

We have seen several cases of parvo here already this spring. The disease is more prevalent in the spring and summer because of warmer temperatures and more active animals. Two cases we saw were in older 4 month old puppies that had only had their first vaccine at 8 weeks old. This means they were not well protected and exposure to parvovirus caused clinical signs. Incidentally they live in the same neighborhood but have different owners and did not play together. One pup was a pit bull and the other a lab mix, both very susceptible breeds due to their weak immune systems. They presented to the clinic about a week apart with very similar signs of vomiting and not eating. They were also lethargic which was most concerning to their owners as both were normally very active pups. Neither pup had bloody diarrhea which occurs when there is enough virus in the intestinal tract to make the cells die and slough off. It is a good sign for prognosis when the puppy does not already have blood in its stool.

When seeing a depressed or vomiting puppy with a limited vaccine history, most vets think immediately of either a foreign body in the intestines or an infectious disease. There is a very fast test we run in the clinic on a small sample of feces that can tell us in 10 minutes if the puppy is infected with parvovirus. If the test is positive, we put these pups in our isolation ward to keep all the other hospitalized patients safe. Technicians and doctors going in and out of isolation must dip their shoes and wash their hands in a bleach solution to prevent spreading the virus. The only treatment for parvo is what we call supportive care. The goal of this treatment is preventing dehydration and infection. An intravenous catheter is put into their front leg for fluids and antibiotics and medications are given to stop vomiting. The puppy may need treatment for several days before the virus runs its course and the patient is able to eat and drink without vomiting. One of the best sounds is a puppy barking from our isolation room; it means that a Parvo Patient is ready to go home!

Both the pit bull and lab pup recovered quickly from their parvo infections. The pit pup stayed in our hospital 3 days and the lab only 2 days before they were eating well and off of fluids. Their owners were ecstatic to take them home so soon since it is hard to predict how each pup will respond to treatment.

A puppy that has recovered from parvo will never get this disease again and has a lifelong immunity. In fact, the immune response to parvo is so strong that serum or blood from a dog that has had parvo contains so many virus fighting antibodies that it can be used as a treatment for a sick dog. Vaccination is still important for these pups since there are vaccines for other diseases in the combination parvo shot. Parvo vaccine also helps reduce the amount of virus that is shed in the feces of a dog. A puppy that has had parvo can shed large numbers of virus for up to 6 months after recovery so owners of these pups need to be aware that they can still be contagious to others.