Canine parvovirus is commonly diagnosed by an evaluation of the animal's clinical signs accompanied by clinical laboratory tests. It must be remembered that not all cases of bloody diarrhea and vomiting are caused by parvovirus.
Common clinical laboratory tests include the ELISA, PCR (polymerase chain reaction) and complete blood count evaluation. Each test provides slightly different information, and sometimes more than one type of test may be combined for optimal diagnosis.
Viral antigen detection methods such as the IDEXX Snap test ELISA are generally quick and inexpensive, but may lack sensitivity as they are dependent on timing of sample collection. These are a good "first wave" test to have at the ready in every shelter.
A complete blood count or blood smear can be done in-house in many shelters, or sent out for a nominal fee. This can be done as a back-up to look for low white cell counts – a hallmark clinical sign of the disease. PCR can be used to detect nucleic acids. These assays are highly sensitive, specific and rapid, but can be difficult to interpret when vaccination is recent.
Finally necropsy and histopathology has value any time animals are dying.
Shelters should also be prepared to run bedside ELISA parvo tests, particularly when puppies experience small bowel diarrhea or diarrhea with concurrent systemic signs. The ELISA test is a useful screen for canine parvovirus as well as feline panleukopenia, both viruses which have significant population implication for shelters. This test utilizes a fecal swab to detect viral antigen, and can be run in 10 to 15 minutes. While no test is 100% sensitive or specific, positive results on a symptomatic animal are worth heeding. Negative results may occur even when animals are infected depending on timing of sampling, or excessive blood in stool, so an ill animal with negative test results may require further testing and care Results are most accurate with this test if it is administered the first few days after infection, or within five days after clinical signs appear. Immunologists disagree about the impact of vaccination on the tests. Some believe the vaccine antigen should not generate a positive result at all while others believe the weak positive is a true positive. However, a positive test accompanied by clinical signs, a low white blood cell count or history of exposure to parvovirus should be interpreted as positive regardless of vaccination.
Parvovirus can have a higher mortality rate in shelter puppies despite early or aggressive therapy because of concurrent debilitation, parasitism and stress. However, if appropriate treatment is provided, the prognosis for these puppies to recover can be excellent, comparable to that for any other puppy. There is no specific cure, so treatment consists of providing supportive care, which consists of antibiotics to fight off secondary bacterial infections, fluids to correct the dehydration, broad spectrum deworming and control of the vomiting and diarrhea.
It was previously believed that all food should be withheld until vomiting and diarrhea had stopped, but new treatment modalities suggest that early nutrition may actually hasten recovery in some cases. Puppies who survive for 3-4 days generally have a good chance of making a full recovery within a week, but it must be remembered that they will be shedding virus for up to 14 days post-infection.
Decisions to treat parvo in the shelter should be thought out carefully. Consideration should be given to the following:
Shelters are not hospitals and seldom have the resources to provide proper isolation and treatment
It takes several days of intensive care therapy to treat, with overnight monitoring and care often required
Suffficient recovery to reach adoptability may take 1-2 weeks or longer
The ability of the virus to persist in the environment long-term endangers the lives of both current and future residents
Recovered puppies should still be isolated for at least 10-14 days post recovery from clinical signs because they may still continue to shed virus
Note: If a strict isolation area managed by staff skilled in maintaining the integrity of an isolation protocol is not available, animals with parvovirus should be removed from the facility for treatment or euthanasia considered to curtail their suffering and minimize disease spread. According to the ASV guidelines for shelter standards, "Allowing animals with severe infectious disease to remain in the general population is unacceptable."