| Pseudorabies (PR) also called Aujeszky' disease is caused by pseudorabies virus (PRV), which can infect many animals. Its clinical symptoms are characterized in piglets by fever, dyspnea, nerval symptom, salivation, growth stopping, weight falling, and high mortality, in sows by breeding disorder such as abortion and dead fetus, in grown-up animals by light symptom. Now, PR prevailing in range of the world, was found in more than 20 provinces of China, and there was a trend of spreading and ascending. It also emerged in Guangdong Province, and influenced the development of pig industry, In order to realize the prevalence of PR in Guangdong, to prevent and control the disease, researches have been made on the following aspects in the thesis:1. Pathogeny investigation of pseudorabies in Guangdong Province200 samples were collected from pig farms of 20 areas in Guangdong Province and 148 samples were tested to be pseudorabies by PR-FA. 19 areas besides Meizhou was positive to PR. More cases were found in Jiangmem Guangzhou, Foshan, Dongguan areas than in other areas. Prevalence of PR reaching peak in 2000-2002 appeared a declining trend after 2003. Piglet age of attaching became older. The incidence rate was 10-50%, and the fatality rate was more then 50% in piglets.2. Seroprevalence research on pseudorabies in Guangdong ProvinceResearches on seroprevalence of pseudorabies in Guangdong were made from 1998 to 2004. In spatial distribution study, the seropositive rates of PR in Dongguan, Huizhou, Shenzhen, Yangjiang, Zhuhai were high which exceeded by 20%, and the highest was in Yangjiang(36.36%). The seropositive rates in Qingyuan and Shantou were low (<10%). The highest seroprevalence was 3.82 times as the lowest. Frenquency distribution study in pig farms showed: in 2003, the seropositive rates of 60.1% farms were less than 26% (median). The seropositive rates of 51.7% farms were less than 10%. The distributions of farms, which seropositive rates were 10% to 100%, were dispersive. In temporal distribution study PR seroprevalence rose as a whole and reached peak in 2003. There were potential rules that a peak value of PR seroprevalence may appear every 5 months. By ARIMA model forecast, seropositive rate in Jan 2005 may be 14.23% approaching the true value 15.06%. The spatial-temporal correspondence analysis showed: PR seroprevalence of the west (20.01%) was highest, followed by Pearl River delta (16.7%), the east (12.78%) and the north (11.5%). The high seroprevalence of PR for Pearl River delta appeared in 2002 and 2003,for the north in 2001, for the east in 2000, for the west in 1999. And two-dimension chart covered 83.3% original information.3. Investigation of pseudorabies molecular epidemiologyThe homologue of partial genes sequences between PRV isolates from China and from other areas was compared. It was found that the homologue of gene gC, gE, gD, gI, gL, PK and TK were high. The homologue of genes sequences between PRV isolates from feral swine and from swine and dog were relatively low. Phylogenetic trees of PRV genes gC, gD, gI, PK and TK were constituded. It was concluded that isolations from China formed a relatively independent branch approaching South Korea; the geographic difference on phyligenesis of partial genes might be existent.4. Risk factors for pseudorabies of pig herds in GuangdongStudy on risk factors for pseudorabies was made in 173 pig farms of Guangdong. Data of 27 items on herd characteristics, management, biosecunty, facility of farm and on random samples of blood serum and tissue were obtained from 110 PR positive farms and 63 PR negative farms. In case-control study, it were found that PR prevalence were associated with sub-farms, the distance to the nearest farms (<2.5 km), purchase of gilts, etc (P<0.05). By wilcoxon rank sum test, when the time of farm started became longer, when interval of production period became shorter, no showering and changing clothes before entering farm, when distance between work section and sale section, between segregation building and piggery...
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