Canine parvovirus (CPV) disease is currently the most common infectious disorder of dogs in the United States.

'Parvo' is a highly contagious disease characterized by diarrhea that is often bloody. Also uncontrolled vomitting.  Prior to 1980, most canine parvovirus that caused disease was Type 2 (CPV-2). After 1980, CPV-2 was replaced by CPV-2a became more common and in 1986, another variation called CPV-2b appeared. In the past few years, a new strain, CPV-2c has been detected. Today, CPV-2b has largely replaced the previous strains as the most common parvovirus causing disease in the dog. There is currently some discussion that there may be other strains that are beginning to emerge and have yet to be formally identified. Current vaccinations have helped to control the spread of this disease but despite being vaccinated, some dogs still contract and die from parvo. There is much that we do not know about the virus or the best way to control the disease, but we are learning new information daily. Misinformation about the disease, its spread, and vaccination is widespread. We hope that with a better understanding of the disease, pet owners will be able to make good health decisions for their dogs that will help prevent and reduce the spread of this disease.

How is parvovirus spread? Parvovirus is spread through contact with feces containing the virus. The virus is known to survive on inanimate objects - such as clothing, food pans, and cage floors- for 5 months and longer in the right conditions. That also means the seat where the last vet patient sat with their sick puppy.  Insects and rodents may also serve as vectors playing an important role in the transmission of the disease. This means any fecal material or vomit needs to be removed with a detergent before the bleach solution is used. The bleach solution should be used on bedding, dishes, kennel floors and other impervious materials that may be contaminated.

The normal incubation period (time from exposure to the virus to the time when signs of disease appear) is from 7-14 days. Active excretion of the virus in the feces can begin the third day after exposure, often before clinical signs appear, and may last for one to two weeks after the onset of the disease.

What are the symptoms of parvovirus infection?

There is a broad range in the severity of symptoms shown by dogs that are infected with parvovirus. Many adult dogs exposed to the virus show very few, if any, symptoms. The majority of cases of disease are seen in dogs less than 6 months of age with the most severe cases seen in puppies younger than 12 weeks of age. There are also significant differences in response to parvovirus infections and vaccines among different breeds of dogs, with Rottweilers, Doberman Pinschers, and Labrador Retrievers being more susceptible than other breeds. The most common form of the disease is the intestinal form known as A, less common form of the disease causes myocarditis (inflammation of the heart).

How is parvovirus infection diagnosed? Not all cases of bloody diarrhea with or without vomiting are caused by parvovirus and many sick puppies are misdiagnosed as having 'parvo.' The only way to know if a dog has parvovirus is through a positive diagnostic test. In addition to the more time consuming and expensive traditional testing of the blood for parvo virus. 

How is parvovirus disease treated? The treatment of parvovirus is fairly straightforward and directed at supportive therapy. Replacing fluids lost through vomiting and diarrhea is probably the single most important treatment.

Undertaking the treatment of affected dogs and puppies without professional veterinary care is very difficult. Even with the best available care, the mortality of severely infected animals is very high. Without the correct amount of properly balanced intravenous fluids, the chance of recovery in a severely stricken animal is very small.

All parvoviruses are extremely stable and are resistant to adverse environmental influences such as low pH and high heat. Exposure to ultraviolet light and sodium hypochlorite (a 1:32 dilution of household bleach - ½ cup bleach to 1 gallon of water) can inactivate parvovirus. The bleach solution can be impaired by organic matter and needs to have adequate exposure time and proper concentrations to work effectively.

Immunity and vaccination If a puppy recovers from parvovirus infection, he is immune to reinfection for probably at least twenty months and possibly for life. In addition, after recovery the virus is not shed in the feces. There are many commercially prepared vaccines. 

The primary cause of failure of canine parvovirus vaccines is an interfering level of maternal antibody against the canine parvovirus. Maternal antibodies are the antibodies present in the mother's milk during the first 24 hours after the puppy's birth. In one study of a cross section of different puppies the age at which they were able to respond to a vaccine and develop protection covered a wide period of time. At six weeks of age, 25% of the puppies could be immunized. At 9 weeks of age, 40% of the puppies were able to respond to the vaccine. The number increased to 60% by 16 weeks, and by 18 weeks of age, 95% of the puppies could be immunized.

When we examine all of the information about maternal derived antibodies, windows of susceptibility, breed susceptibilities, the possibility of unidentified strains, and the effectiveness of different vaccines, we begin to see why there are so many different vaccination protocols and why some vaccinated animals still develop the disease.

Vaccination protocols have been developed that will help protect the widest range of dogs. In using these protocols, we understand we will be vaccinating some dogs that are not capable of responding and we will be revaccinating some dogs that have already responded and developed a high titer. But without doing an individual test on each puppy, it is impossible to determine where the puppy is in its immune status. We also realize due to the window of susceptibility, some litters will contract parvovirus despite being vaccinated. By using quality vaccines and an aggressive vaccination protocol, we can make this window of susceptibility as small as possible. The generally recommended protocol is to vaccinate puppies against parvovirus beginning at 6-8 weeks of age, and revaccinating every 3 weeks until the puppy is 12-20 weeks of age.

Conclusion In summary, parvovirus is a very common problem that is a huge killer of puppies. Due to its ability to be transmitted through hands, clothes, and most likely rodents and insects, it is very important to make every effort to avoid being exposed to the disease. 

Modified live vaccines are safe and effective, but despite the best vaccination protocol, all puppies will have a window of susceptibility of at least several days where they will be at risk. In addition, the newer CPV-2c strain presents new challenges since it is less detectable in laboratory tests and current vaccines may not be as effective in providing protection against it. Prompt treatment by a veterinarian will increase survivability in infected puppies and working with your veterinarian on a vaccination program that is best for your puppy is important.

References and Further Reading Lamm, CG; Rezabek, G.B. Parvovirus infection in domestic companion animals. In Kapil, S; Lamm, CG (eds.) Veterinary Clinics of North America Small Animal Practice: Emerging and Reemerging Viruses of Dogs and Cats. W.B. Saunders Co, Philadelphia, PA; July 2008:837-850.Macintyre, D. Management of Severe Parvoviral Enteritis. Presented at the Western Veterinary Conference, Las Vegas, NV; February 2004.

 ** My personal note is... luckily Schnauzers are way down low on the list of suseptable breeds.  Though it is possible for schnauzers to contract parvo if not imunized properly as puppies, they are less likely to contract it than many other breeds.