Study On Epidemiological Investigation And Eradication Of Atrophic Rhinitis In Hubei Province

Atrophic rhinitis (AR), a severe pandemic respiratory infectious disease of swine, is caused by toxigenic Pasteurella multocida (T+Pm) alone or together with Bordetella bronchi septica I phase (Bb-I). According to the etiology and pathogenesis, the atrophic rhinitis can be classified into progressive atrophic rhinitis (PAR) and non-progressive atrophic rhinitis (NPAR). PAR's main pathogenic factor is T+Pm, which secretes a kind of Pasteurella multocida toxin (PMT). The toxin is encoded by the ToxA gene. This disease causes significant economic losses in the swine industry worldwide, as it results in serious atrophy of the turbinate bones, inefficient feed conversion and reducing growth rates of the swine. Besides, it leads to secondary infection of other respiratory pathogens. This study focused on the nested polymerase chain reaction(PCR) assay and indirect ELISA method as before and developed them as kits. The epidemiological investigation of etiology and serology of the atrophic rhinitis was carried out by using this kits in Hubei province. According to the survey, an eradication research of atrophic rhinitis was carried out on a pig farm. The more detailed information is as follows:1. Research on detecting method of etiology and serology of progressive atrophic rhinitisThe nested PCR for detection of toxigenic Pasteurella multocida from nasal swabs was optimized and developed it as a kit. The totle volume of the nested PCR and the concentration of the Taq DNA polymerase, primers and dNTPs were identified. The results of the tests demonstrate that the nested PCR is a specific, sensitive and reproducible technique. The lowest amount of bacteria required for positive result is 17 CFU. The coincidence dompliance is 100% compared this method with the nested PCR as before.The PET-28b-C2115/BL21 bacteria was constructed as before in our laboratory. The recombinant bacteria expression was induced with the low temperature and purified the recombinant protein. The purified protein was added into the 96-well flat-bottom plate to determine the optimal dilution of the antigen and the serum sample. The cut-off value was calculated. And the specificity, reproducibility and the expiration date of the enzyme-linked immunosorbent assay(ELISA) were studied. The results showed that the optimal dilution of the antigen and the serum sample was 1:800 and 1:40, respectively. The cut-off value was 0.385. The coefficient of variation(CV) of the specificity and reproducibility were below 10%. The expiration date of ELISA was 6 month. 2. Research on the epidemiological investigation of etiology and serology of atrophic rhinitis on large-scale pig farmsSerum samples and nasal swab samples from large-scale pig farms were detected for the epidemiological investigation of etiology and serology of atrophic rhinitis in Hubei province.The results showed that 18 positive samples of 1627 nasal swab samples from 8 large-scale pig farms were detected. The positive rate was 1.1%(18/1627). The positive samples were obtained from the 3 large-scale pig farms, and the positive rate of the pig farms was 37.5%(3/8).1101 positive of 2302 serum samples from 20 large-scale pig farms were detected. the positive rate was 47.8%(1101/2302). The positive samples were obtained from the 20 large-scale pig farms. The positive rate was among 8.3%～81.5% from 20 large-scale pig farms.3. Research on the eradication of atrophic rhinitis on large-scale pig farmsAccording to the results of epidemiological investigation, choose B pig farm to carry out the study of the atrophic rhinitis eradication. The nasal swab samples were collected from all the productive sows, boars, replacement gilt, and the nasal swab samples from 5-week-old piglets,8-week-old pigs,14-week-old pigs in this pig fram were collected 30, 20 and 20, respectively. These nasal swab samples were detected by the nested PCR. The pigs of positive samples were eliminated. Eradication measures were taken on this pig farm. Collect nasal swab samples separately three months and six months later. The results showed that 8 out of 895 nasal swab samples were positive. The positive rate was 0.9%(8/895). After the eradication measures, the detection results of the nasal swab samples showed that the positive rate was zero.