Diagnosis of Canine Parvovirus
A puppy with a bloody diarrhea could have a parasite problem, a virus other than parvovirus, a stress colitis, an intestinal foreign body, or may simply have eaten something that disagreed with him. It is important to confirm the diagnosis of parvovirus before embarking on what could be the wrong treatment.
TESTS THAT ARE ESPECIALLY USEFUL
THE FECAL PARVO ELISA TEST
A false negative result is possible. The puppy could be infected but no longer shedding virus in its stool or only shedding virus intermittently. Alternatively, the virus particles may be so thoroughly coated with antibodies that they cannot react with the chemicals of the test. Any test will have some potential for false negatives as well as false positives but if the puppy's clinical presentation fits and the ELISA test is positive, treatment for parvo infection should be pursued.
THE DROP IN WHITE CELL COUNT
TESTS THAT ARE HARD TO INTERPRET AND RARELY USED
(BUT YOU MIGHT HEAR ABOUT THEM SO WE'LL EXPLAIN THEM)
PCR ("Polymerase Chain Reaction") testing is probably the newest method of testing for parvo. A fecal sample must be submitted to a reference laboratory for PCR testing; this is not the sort of test that can be done while you wait. The DNA of the parvovirus is recognized and amplified so as to be able to detect even small amounts of it. PCR testing is generally too sensitive to be clinically helpful yet canine parvovirus is commonly included on PCR panels that test for multiple intestinal virus organisms. The problem with PCR testing is that, because it amplifies DNA, very small amounts of virus can be detected which means that positive results will turn up on dogs that are vaccinated or who are passing insignificant amounts of virus. PCR testing is very helpful for many infections but often clouds the issue for parvovirus.
Titering is mostly used nowadays to determine if a dog has adequate protection against parvo, either through vaccination or prior exposure. In a shelter setting, a dog of unknown vaccination status can be tested to determine if he or she is considered protected from infection or not. In the pet setting, a dog can be tested to determine if a vaccine is needed or not. Certain antibody levels are associated with protection; however, because of other contributing branches of the immune system, an inadequate titer does not necessarily mean a dog is vulnerable.
Parvovirus lesions in the GI tract are of a classical appearance. There is no mistaking them under the microscope. Unfortunately, tissue samples of the GI tract are not readily available and most infected puppies are not good surgical candidates. Still, if a puppy has died and the cause is unclear, submitting samples of the GI tract can generally confirm or rule out a parvovirus diagnosis provided the tissue has not degenerated.
It is also important to realize that puppies with parvovirus infection may have
There will be complicating conditions that must be monitored. This means that other tests will be required during the management of the parvo patient. The above tests are simply those that can be used to confirm the parvovirus diagnosis.
Page last updated: 5/6/2022