Epidemiological Investigation Of PRRS And Prevention In Hezhou City

Porcine reproductive and respiratory syndrome (PRRS) is an highly contagious infectious and immunosuppressive diseases caused by porcine reproductive and respiratory virus(PPRSV), which causes abortions in pregnant sows and respiratory disease in growing pigs. PPRS, classical swine fever (CSF) and Foot-and-mouth disease (FMD) are harmful pathogens, which causes tremendous economic impact in swine production worldwide.For the investigation of PRRS epidemic in Hezhou,53 samples were collected from 39 different pig farms whose main clinical features contains fever, cough, difficulty breathing, skin and ears cyanosis, high incidence, high fatality rate and so on between September 2006 to July 2007 in Hezhou, Guangxi province. Using reverse-transcription polymers chain reaction (RT-PCR) technique, PRRSV and other major pathogen were detected. The results showed that the positive ratio has highly reached to 56.60%(30/53), and PRRSV always mixed infection with other pathogens, PRRSV and PCV-2 double infection percentage is 39.62%(21/53), PRRSV and SIV double infection percentage is 32.07%(17/53), PRRSV?PCV-2 and SIV triple infection percentage is 30.19%(16/53).For the investigation of PRRS variant strains epidemic, so that know well the molecular genetic variation of epidemic strains of PRRSV in Hezhou. We analyzed Nsp2 gene of Variant strain by PCR amplification, cloning, sequencing and genetic variance analysis, successfully acquired 9 partial NSP2 of PRRSV mutant strains, and compaired with some representative PRRSV isolates. The result indicates: The genomic sequences of 9 acquired partial NSP2 had 94.7%-99.6% identity with each other, and the 9 acquired partial NSP2 deduced amino acid sequence was 73.5%-98.9% identical with each other. The 9 acquired partial NSP2 had 80.5%-99.4% identity with some other representative PRRSV isolates isolated in Chinese Mainland (Identical with JXAlwas particularly high,was 98.4%-99.4%).The deduced amino acid sequence was 55.5%-93.2% identical with some other representative PRRSV isolates isolated in Chinese Mainland. The 9 acquired partial NSP2 deduced amino acid sequence all have a "1+29" discontinuous deletion of 30 amino acids, which was as well as the typical PRRS variant strains.We analyzed ORF5 gene of Variant strain by PCR amplification, cloning, sequencing and genetic variance analysis, successfully acquired 10 ORF5 sequence of PRRSV mutant strains, and compaired with some representative PRRSV isolates. The result indicates:The genomic sequences of 10 acquired PRRSV ORF5 had 95.7%-99.8% identity with each other, the deduced amino acid sequence was 93.5%-99.0% identical with each other. The 10 acquired PRRSV ORF5 had 80.5%-99.4% identity with some other representative PRRSV isolates isolated in Chinese Mainland. The 13th and 151th amino acid of the 10 acquired PRRSV GP5 were all R, indicates that the 10 acquired PRRSV all have virulent strain feature. The 34th amino acid of the 10 acquired PRRSV GP5 all mutated from D to N, with was as well as the representative PRRSV isolates isolated in Chinese Mainland, such as CH-1a, HB-1, JXA1, etc. The 137th amino acid of the 10 acquired PRRSV GP5 were all S, indicating that the 10 acquired PRRSV were all evolved from Wild strain, but not Vaccine strains.The epidemiological investigation of PRRS in HeZhou shows that that the epidemic PRRSV in HeZhou are consist of Classical strains and variant strains in the meantime. According to the characteristics of localswine, Pig-breeding habits, feeding levels and region epidemic dynamic, comprehensive prevention and control measures in control of PRRS was developed by Hezhou veterinary bureau, such as technique training, epidemic situation inspection, immunization and so on. It has got a good prevention and control effect.