Molecular Epidemilgy And Pathogenicity Of Swine Influenza Virus From Some Rigions Of China

1 Detection of swine influenza virus in clinical samples using RT-nested PCR assayUsing two pairs of primer based on conserved sequences of the NP gene of influenza A virus, a RT-nested PCR assay was developed to detect swine influenza virus in clinical samples. No cross reactions with three other swine pathogens of respiratory disease such as Porcine respiratory and reproductive syndrome virus, Porcine circovirus type 2 and M.suipneumoniae. As agarose electrophoresis detection, the RT-nested PCR was 100 times more sensitive compared to that of non-nested RT-PCR.35 clinical samples including 4 blood samples and 31 lung tissues from Southern China were tested by RT-nested PCR, and 28 (80%) out of 35 sample were positive. By propagated in 9-10-day-old SPF embryonated chicken eggs,23 stains of swine influenza virus were isolated from 28 positive samples. The result of RT-nested PCR was 82% in agreement with that of virus isolation, and the RT-nested PCR were more 18% sensitive than the virus isolation. No swine influenza virus was isolated from 7 negative samples. The results showed that the RT-nested PCR assay was rapid , specific and sensitive, and it was is advantageous to detect influenza virus in latent infections. The RT-nested PCR assay could facilitate influenza virus surveillance in pig population.2. Isolation and subtyping of swine influenza viruses from some regions in ChinaBetween December 2003 and October 2005, 106 clinical samples from 60 herds with respiratory disease, including 66 lung samples, 36 nasal swabs and 6 sera, were collected from eight diffirent regions in China. Through RT-nested PCR assay previously established, 67 sample (63%) were positive, which distributed in 32 pig herds. By propagated in 9-11-day-old SPF embryonated chicken eggs, 57 stains (85%) of swine influenza virus...