Diagnosing and Treating Parvovirus in the Shelter

Diagnosing Parvo

The most common clinical signs of canine parvovirus (CPV) are acute vomiting and diarrhea, often severe. The diarrhea may or may not be bloody. Affected dogs are typically lethargic and can quickly become dehydrated. 

Puppies under five months and dogs who have never been vaccinated are at greatest risk for infection.

CPV is diagnosed by evaluating the animal's clinical signs in conjunction with diagnostic tests. Not all cases of bloody diarrhea and vomiting are caused by CPV, so a definitive diagnosis should be sought to help guide treatment and management decisions in the shelter.

There are several tests that can be used to diagnose CPV, including the ELISA, PCR (polymerase chain reaction) and complete blood count (CBC) evaluation. Each test provides slightly different information, and sometimes more than one type of test may be combined for optimal diagnosis.

The fecal CPV ELISA antigen tests are the test of choice in the shelter environment. These tests, which utilize a fecal swab to detect CPV antigen, provide quick results (usually within 10-15 minutes) and can easily be performed by staff.

Positive results are a reliable indicator of infection when associated with consistent clinical signs. Negative results may occur even when the dog is infected if the level of virus in the sample is low -- this can be seen early in the course of disease and/or when clinical signs are mild.

The ELISA should be completed on any dog displaying clinical signs consistent with CPV infection but should not be used in healthy-appearing animals. Recent vaccination (within 7 days) with a modified-live virus parvovirus vaccine can occasionally result in false positive ELISA test results.

The PCR test can also be a reliable indicator of CPV infection when clinical signs are present; however, there is a delay in definitive diagnosis since the test cannot be performed in shelter. This test can also be affected by recent vaccination, making results difficult to interpret.

A CBC can be done in-house in many shelters or sent to an outside laboratory. This test can determine if the white cell count is low, a common finding in many CPV cases. The test is not a definitive diagnosis of CPV, but it can support a positive diagnosis if the initial diagnostic test was equivocal and can help assess the overall clinical picture of infected dogs.

Necropsy along with histopathology can provide a definitive diagnosis of CPV infection. These should be performed any time there is unexplained death in shelter dogs.

Treating Parvovirus in the Shelter

When appropriate treatment can be provided, the prognosis is generally good for CPV-infected dogs. There is no specific anti-viral treatment, so treatment consists of providing supportive care, including antibiotics to combat secondary bacterial infections, fluid therapy to correct the dehydration, pain control, broad-spectrum deworming, nutritional support, and control of vomiting and diarrhea.

Once clinical signs resolve in treated dogs an ELISA test can be utilized to determine if virus is still being shed. Once viral shedding has ended the dog should be bathed before being placed back into the shelter population.

The decision to treat in the shelter should be made while considering available resources and the ability to prevent transmission to the rest of the shelter population. If treatment in the shelter is not an option, shelters can consider in-patient treatment at a private veterinary clinic or out-patient treatment in a foster home setting.

If the shelter elects out-patient treatment, veterinary involvement is crucial for protocol development and guiding individual treatment decisions. In addition, caregivers must receive the appropriate training in biosecurity protocols, including the use of personal protective equipment and proper sanitation protocols.

Use the resource assessment tool to aid in making decisions about treatment plans.