Parvovirus is a very small DNA virus that lacks an outer envelope. It is one of the most highly resistant viruses known, easily surviving in the environment for as long as 5 months. The virus is resistant to the action of most common household detergents and disinfectants, but is susceptible to chlorine bleach.
The virus usually gains entry through the oral cavity, with the initial infection occurring primarily in the tonsils. Form there, the virus threads its way through the system reaching the bloodstream and disseminating throughout the body. In the intestinal tract, Parvovirus produces death of rapidly dividing crypt cells that are essential for maintaining the nutrient-absorptive lining of the small intestine. Loss of these cells, together with the accompanying inflammatory response, impairs the normal absorption of nutrients with resultant signs of diarrhea and fluid and weight loss. Within a week of infection, massive quantities of new virus particles are being generated in infected intestinal cells and released into the feces, contaminating the environment. By 2 weeks, the immune defenses normally succeed in suppressing the infection and virus shedding ceases. Rapid regeneration of affected tissues usually occurs in concert with suppression of virus replication.
Parvovirus infection is most severe in puppies 6 to 14 weeks of age. The mortality rate, even if the puppies receive veterinary care, approaches 20%. Although the disease tends to be milder in older animals, fatal infections are still possible.
Peracute (extremely rapid onset) Parvovirus exhibits abdominal pain (colic), depression, and lethargy, then proceed rapidly into shock and death before other clinical symptoms are evident. The acute (rapid-onset) form of the disease is far more common and the earliest signs are often fever, depression, and colic. These are rapidly followed in most cases by vomiting and diarrhea. In milder cases the stool is semisolid and there may be an increased frequency in defecation. In more severe cases, the stool becomes watery and has a characteristically fetid odor. The most severe cases exhibit bloody diarrhea (hemorrhagic enteritis). Shock caused by fluid and electrolyte loss in the diarrheic feces is a serious and life threatening complication.
Dogs that recover from Parvovirus are solidly immune against subsequent clinical disease.
Care is aimed at preventing dehydration and secondary bacterial infections. The primary objective is to stabilize the patient until the normal immune defenses can clear the infection and initiate recovery.
Vaccinate your dog!