An experimental study of Bungowannah virus infection in weaner aged pigs

Bungowannah virus is a pestivirus identified from an outbreak of stillbirth and increased mortality in the first 3-4 weeks of life on a piggery in New South Wales, Australia in June 2003. The aims of this study were to determine if post-natal infection results in any clinical abnormalities and quantify the amount of Bungowannah virus RNA in blood, oropharyngeal, nasal and conjunctival excretions and faeces during the course of infection. Thirty pigs were infected intra-nasally with one of six different doses of Bungowannah virus or a control inoculum and clinical signs and rectal temperatures monitored. Sera, leukocytes and oropharyngeal, nasal, conjunctival, rectal and tissue swabs were tested for Bungowannah virus by qRT-PCR and sera for antibody by peroxidase linked assay and virus neutralisation test. The infectious dose by the intra-nasal route in weaner pigs was determined to be between 1.6 and 3.2 log10 TCID50. Few clinical signs could be attributed to infection. Viraemia and viral excretion in oropharyngeal secretions were detected from 3 days post-inoculation and seroconversion from 10 days post-inoculation. Viral shedding was greatest and most frequently detected in oropharyngeal, and to a lesser extent, nasal secretions, and generally detected in lower amounts and less frequently in conjunctival secretions and faeces.