Effect of sampling site on the diagnosis of canine parvovirus infection in dogs using polymerase chain reaction

Background: Accurate diagnosis is imperative in dogs with clinical signs of parvovirus infection (CPV-2). Objectives: To assess quantitative real-time PCR (qRT-PCR) for the diagnosis of CPV-2 infection, and determine the optimal sampling site. Secondarily, to compare qRT-PCR with a point-of-care PCR kit (PCRun), and to assess sensitivity of serology for CPV diagnosis. Animals: Sixty dogs with naturally acquired parvovirus infection, 44 unvaccinated puppies, of which 16 were followed after first and second vaccination, 15 adult dogs, of which 10 were followed also after a booster vaccine, and 9 dogs with distemper virus infection. Methods: Prospective study. Samples from the rectum, blood, and pharynx were obtained for PCR. Results: All dogs with a clinical diagnosis of parvovirus infection were positive by qRT-PCR in at least 1 sampling site (ie, rectum, blood, pharynx), and 50 (83%) of 60 were positive in all sites. qRT-PCR was negative in 67 (99%) of 68 healthy puppies (before-vaccination), puppies with distemper, and healthy adult dogs. Ten days after initial vaccination of puppies, 62% (fecal), 31% (blood), and 12% (pharyngeal) of samples were positive for CPV-2 on qRT-PCR. The proportion of positive pharyngeal samples decreased 20 days after vaccination and all sites were negative 12-28 days after second vaccination. Vaccinated adults were negative before and after booster vaccination. Conclusions and Clinical Importance: Molecular detection of CPV is sensitive, but specificity is hampered temporarily during the vaccination period. Blood, feces, and pharynx are suitable sampling sites. Fecal samples had the lowest sensitivity in sick dogs and highest positivity in puppies after vaccination.