When presented with a “sick puppy,” most veterinarians conduct a thorough physical examination and take a complete history. The initial data base typically includes blood work and a urinalysis, the results of which can guide the attending veterinarian toward or away from a diagnosis of canine parvoviral (CPV) infection. Fecal floatation and microscopic examination of feces on a wet slide preparation can be used to identify the infective organisms, although the results of these tests are not reliable. Abdominal radiographs (X-rays) may be recommended to rule out other causes of gastrointestinal distress, such as intestinal blockage by a foreign body or other forms of intestinal obstruction.
Presently, the best way to diagnose CPV infection is to identify the viral antigens. This can be done by an ELISA test on a fecal sample, which is commercially available in almost any veterinary clinic. Test results may report false negatives during the early course of the disease, before the period of peak viral shedding. False negative results can also occur after approximately 10 to 14 days of infection, when viral shedding rapidly decreases. Dogs that have been recently vaccinated against CPV with a modified live vaccine can have false positive results ELISA results for parvoviral infection.
More advanced and more precise techniques to detect CPV infection include PCR (polymerase chain reaction) testing, electron microscopy, tissue culture and viral isolation. However, the financial considerations of many owners practically prohibit exhaustive diagnostic testing with these advanced techniques. Most owners opt to spend their resources on treating their sick puppy empirically, assuming that it has CPV infection, rather than pursuing advanced diagnostic techniques. This is probably a good approach in most cases, because without treatment the mortality rate for dogs with parvoviral infection is quite high.
Parvoviral infection is especially common in young dogs housed in close quarters with other dogs, such as in animal shelters, humane societies or the facilities of backyard breeders or puppy mills. Vaccination against CPV is almost always effective.