The Mechanism Of Transmission Mechanism For Porcine Reproductive And Respiratory Syndrome Virus Aerosol

Porcine reproductive and respiratory syndrome (PRRS) is a seriousinfectious disease of swine which is caused by porcine reproductive andrespiratory syndrome virus (PRRSV). It is characterized by severereproductive failure in sows and respiratory distress in piglets and growingpigs.Since the first case reported in the United States in 1987, it has beenspread to most countries and it caused large economically lost. A highlypathogenic disease which is characterized by high-fever, high morbidity andmortality rate was outbreaked in the south of China in 2006, and then spreadquickly to most provinces. Most experts believed that PRRSV mutant was oneof the main pathogen.Piglets with negative anti-PRRSV antibody were bred in a positive andnegative pressure isolator. Aerosol samples were collected by AGI-30 (AllGlass Impinger-30) extractor, simultaneously nasal swabs, whole blood andserum sample were collected in different periods after challenged with PRRSVThe above-mentioned samples were detected by cell culture and RT-PCR. Theresults indicated that aerosols were isolated from the day 4 to the last day ofthe experiment. The aerosol concentration peaked at day 15past-innoculation(dpi). Airborne transmission did occur, as shown by clinlcalsymptoms, pathological change, tissue nucleic acid and seroconversion toPRRSV in aerosol exposed pigs. Also, the PRRSV could be isolated from theaerosol exposed pigs by nasal swabs. Direct-contact group and indirect-contactgroup were infected at the same time. It was proved that high virulent PRRSVnot only could form aerosols, but also very rapidly invade exposed pigs byaerosol.In order to study the regularity of shedding virus from infected SPFchickens and the formation of aerosol of H9N2 subtype AIV, SPF chickenswere bred in a positive and negative pressure isolator. Aerosol samples werecollected by AGI-30 (All Glass Impinger-30) extractor, and simultaneouslytrachea and cloaca samples were collected by tracheal swabs and cloacalswabs in different periods after challenged with viruses. The above-mentionedsamples were detected by HI, Dot-ELISA and RT-PCR methods. The resultsindicated that aerosols were isolated from the 4 days to the 43 days after inoculation. It was proved that H9N2 subtype AIV could copy themselves inrespiratory tract and cloaca, and then could formation of aerosols. AIV H9N2subtype could be isolated from cloacal and tracheal swabs 3 days afterinoculation and lasted for 45 days, viruses were detected from all infected SPFchickens on 7 days.The virus aerosol collection model was established under sterileconditions on the paper; H₉N₂ subtype AIV can formed virus aerosol; It wasproved that high virulent PRRSV not only could form aerosols, but also veryrapidly invade exposed pigs by aerosol.