Parvovirus

CANINE PARVOVIRUS

Parvoviruses are a large group; almost every mammal species (including humans) seems to have its own parvovirus. Fortunately, each virus is pretty specific about what animals it can infect (i.e. the pig parvovirus will not infect people, the canine parvovirus will not infect cats etc.) The canine parvovirus will affect most members of the dog family (wolves, coyotes, foxes etc.).

Parvoviruses are smaller than most viruses and consist of a protein coat (a "capsid") and a single strand of DNA inside. It is hard to believe that such a simply constructed organism could be so deadly; however, this virus has proved especially effective at infecting rapidly dividing host cells such as intestinal cells, bone marrow cells, cells of the lymph system, and fetal cells. Parvoviruses are not enveloped in fat the way many other viruses are. This makes parvoviruses especially hardy in the environment and difficult to disinfect away.

While the parvoviruses of other species have been well known for decades, the canine parvovirus is a relative newcomer. The original canine parvovirus, discovered in 1967 and called "CPV-1," did not represent much of a medical threat except to newborn puppies but by 1978, a new variant, "CPV-2" appeared in the U.S. This newer version seems to represent a mutation from the feline parvovirus. Because this virus is shed in gigantic numbers by infected animals and because this virus is especially hardy in the environment, worldwide distribution of the virus rapidly occurred. At this time, the virus is considered to be "ubiquitous," meaning that it is present in EVERY ENVIRONMENT unless regular disinfection is applied.

Attempting to shield a puppy from exposure is completely futile.

In 1978, no dog had any sort of immunity against this virus. There was no resistance and the epidemic that resulted was disastrous. To make matters worse, a second mutation creating CPV-2a had occurred by 1979, which seemed to be even more aggressive. Vaccine was at a premium and many veterinarians had to make do with feline distemper vaccine as it was the closest related vaccine available while the manufacturers struggled to supply the nation with true parvo vaccines.

Over thirty years have passed since then. The current form of the virus is called CPV-2b. Virtually all dogs can be considered to have been exposed to it at least to some extent which means that most adult dogs, even those inadequately vaccinated can be considered to have at least some immunity. It is also worth mentioning CPV-2c, discovered in the year 2000, which is able to infect cats. Cats vaccinated for distemper should be protected.

Parvoviral infection has become a disease almost exclusively of puppies and adolescent dogs.

Parvoviral infection must be considered as a possible diagnosis in any young dog with vomiting and/or diarrhea. With proper hospitalization, survival rates approach 80%. Still, there are many myths and misunderstandings about this virus, how it is spread, and how to prevent it.

Vaccination is the ONLY prevention.