Parvovirus—therapeutic options (Proceedings)
Canine Parvovirus (CPV) is a family of viruses that cause vomiting, hemorrhagic diarrhea, and leukopenia. The virus can infect dogs of any age but, because of effective client education and early, aggressive vaccination protocols, is commonly noted in dogs less than 1 year of age. There are currently 2 active variants of the virus in the United States - CPV-2b and CPV-2c – of which the latter is the most recent and most virulent to appear. CPV infection is acquired by the fecal-oral route. Initial viral replication occurs in extra-intestinal lymphoid tissues, where the virus is spread through the blood to other lymphoid tissues where the cycle is repeated, eventually resulting in intestinal epithelial infection. The virus then localizes to the crypt epithelium, bone marrow, and other lymphoid tissues, where it produces crypt epithelial cell necrosis, diarrhea, leukopenia, and lymphoid destruction and depletion.
Patients suspected of being infected with Parvovirus are commonly young dogs (age 6 weeks to 6 months) of any breed that are under-vaccinated. Presenting signs include vomiting, diarrhea that is commonly hemorrhagic, and anorexia. Initial triage examination findings commonly include hyperthermia or hypothermia, tachycardia, altered pulse quality, tachypnea, evidence of dehydration, abdominal discomfort, along with the vomiting and diarrhea.Initial biochemical abnormalities commonly found in patients suspected of being infected with canine Parvovirus include leukopenia/neutropenia, hypoalbuminemia due to enteric losses, azotemia due to dehydration, hypokalemia, and hypoglycemia. Due to decreased perfusion from dehydration, metabolic acidosis and increased serum lactate concentrations are noted on blood gas analysis. Due to enteric losses and a systemic inflammatory response, coagulopathy may be present.
In-hospital confirmation of canine parvovirus infection is achieved through the use of a SNAP test. These tests are easily performed and require a small sample of stool from the patient. These tests have been shown to detect the current CPV-2b and CPV-2c variants of the virus. Whether these tests show false positive results due to recent vaccine is a subject for debate. A recent study showed that these tests did not produce positive results as a result of vaccination with modified live Parvo vaccines, suggesting this test when positive indicated infection with wild type CPV-2.