Parvo Virus

Prior to 1977-78, parvovirus did not exist in the dog. The virus is a 
close relative of feline panleukopenia (feline distemper) and in fact, 
may have mutated from the cat and infected the dog in the late 1970¹s. 
The virus is extremely hardy and survives for long periods outside its 
host.  The virus will live in the environment up to 6 months and survives 
winter nicely under a blanket of snow where the temperature is usually 
around 25-28 degrees F. Extremely  cold temperatures prior to snow fall 
will kill the virus. Sodium hypochlorite (bleach) is the only effective 
disinfecting agent. 

The virus is transmitted by oral ingestion of viral contaminated feces. 
Upon ingestion by the new host it infects local lymph nodes, quickly 
multiplies and then via the blood moves to the small intestine where 
signs of the disease begin in approximately 5-6 days. The virus is 
extremely deleterious to the lining (mucosa) of the small intestine. The 
surface of the mucosa is stripped away upsetting crucial barriers and 
interfering with normal balance of digestive enzyme secretion and 
nutrient absorption. Additionaly, the normal bacterial flora of the small 
intestine which aid in digestion are now exposed to ulcerated mucosa,  
providing a direct route into the blood stream. Fluid loss from both 
vomiting and diarrhea is dramatic and dehydration ensues. The onslaught 
of bacteria and toxins into the blood will ultimately cause death. 
Precipitous drops in white blood cell (WBC) counts are common and relate 
directly to the prognosis and outcome of the infection. Ominous drops in 
white blood cells are attributed to overwhelming degradation of WBC¹s and 
the direct depressive viral effect on WBC production in the bone marrow. 


The incidence of the disease is highest in young dogs and tends to start 
some time after the puppy has lost its maternal protection passed on at 
birth with the first milk (colostrum). Any age can be infected but, most 
dogs are infected between the ages of 2-6 months  when maternal antibody 
decreases below a protective level in the puppy. Signs of the disease 
usually are mild to nonexistent. However, a full blown case of parvovirus 
untreated can easily be fatal. Certain breeds seem to be more sensitive 
to the disease; possibly related to their immune system. They include 
rottweilers, Doberman Pinschers, and possibly black Labrador retrievers.

Generally, a diagnosis is made on the signs of the disease and falling 
white blood cell counts. Good rapid diagnostic tests are also available 
at veterinary clinics. Additionally, the virus can be found in the feces 
by commercial labs using electron microscopy.

Treatment for the disease is primarily supportive although recently 
immunotherapy has become important. Historically, dogs were supported by 
aggressive intravenous fluid therapy to combat hydration and antibiotics 
given to reduce secondary bacterial infection. Food is withheld until 
vomiting has ceased. Many veterinarians employ antiemetics to lessen the 
signs and aid in the control of dehydration. Blood transfusions have been 
employed to increase the level of globulins, red blood cells and serum 
protein being lost via the bowel¹s bloody diarrhea. Most recently, 
antitoxins and antiparvo serum are showing results. With hospitalization 
and vigorous support most dogs will survive severe cases of parvo virus. 
Early detection and aggressive therapy are the key to success.

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