THE USEFULNESS OF TWO MOLECULAR METHODS FOR THE DETECTION OF PERSISTENTLY INFECTED CATTLE WITH BOVINE VIRAL DIARRHEA VIRUS USING ORAL SWAB SAMPLES

Serum and oral swab samples were collected from a persistently infected cow and her calf in a two-month period to test usefulness of oral swab samples for the detection of bovine viral diarrhea virus. Nucleic acids of the virus were detected by two molecular methods: conventional gel-based RT-PCR and commercial real-time RT-PCR. The bovine viral diarrhea virus genome was detected in serum and oral swab samples on days 0, 7, 15, 22, 23, 29, 36, 37, 43, 44, 46, 51, 52, 53, and 57. The dry cotton swabs showed a reduction of diagnostic sensitivity after three days when samples were stored at room temperature (+ 21 °C), but storage of oral swab samples at + 4 °C or in a freezer (< – 15 °C) for at least 10 days had no negative impact on the detection of the virus. No reduction of diagnostic sensitivity was observed when oral swab samples were collected in tubes with a liquid virus transport medium. Oral swabs provide an easy, reliable and cost-effective sampling tool for identification of PI animals, together with RT-PCR methods. The oral swab sampling could be especially useful for screening newborn calves during testing and removing PI animals from bovine viral diarrhea virus-infected herds.