Epidemiological Survey And Comparative Pathology Study Of HP-PRRS In Inner Mongolia Region

Porcine reproductive and respiratory syndrome (PRRS),also known as"blue-eared pig disease", is an acute contagious viral infectious disease. The GP5 protein, encoded by ORF5 was most prone to mutation. PRRS is included on the OIE list of noticeable disease as a swine disease. In recent years, an variant atypical form PRRS affected over most pigs in China, this form of the PRRS virus was more virulent, high morbidity and mortality rates. PRRS is considered the most economically significant endemic infectious disease problem facing the China swine industry, which posed great concern to public health.Objective:The aims of this study were to study characteristics of HP-PRRS and explore its pathogenesis. We investigated some HP-PRRS in Inner Mongolia, with an emphasis on Information of the comparative pathology and genetic variation of main structural protei ns ORF5, ORF6, ORF7. This will, in turn, be exetremely valuable in the control of this disease.Material and methods:Firstly, we conduct surveillance the HP-PRRS pigs in recent years, through the epidemiology investigation, clinical observations and necroscopic examination. The most suitable samples and reliable data were collected for further study. Foll owing, ELISA, PCR/RT-PCR, Histological Examination, Immunohistochemical Study, Ge ne Cloning, and Sequencing Techniques were used in the study of HP-PRRSV. Finally, Conclusions were drawn through comparing and analyzing data.Results:It is believed that poor management, close to transport links and large lives stock traders can be a predisposing factor to initiate the HP-PRRS. The HP-PRRS incidentce rate of western region was significantly higher than Eastern region in Inner monoglia. A total of 754 swine serum samples from different regions were collected from pigs that were not vaccinated with a PRRS vaccine and tested for PRRS virus antibody using a commercial ELISA antibody detection kit, the results showed that PRRS virus antibodies is 69.13 % positive rate average and almost the same as 71% positive rate average in the immunize -d PRRS vaccines region. Study PRRS co-infection with various bacterial of 37 clinical samples that showed E.coli(5/37), Salmonella typhi (7/37), Salmo -lla choleraersuis(1/37), Mycoplasma hyopneumoniae(3/37), Swine Eperythozoonsis(1/37) Steptococcus suis(2/37). Clinical samples for PCR/RT-PCR testing. the results showed the 53.13% HP-PRRS positi vee, the 12.5% porcine reproductive and respiratory syndrome virus (PRRSV) positive, the 31.25 % classical swine fever virus (CSFV) positive, the 12.5% pseudorabies virus (PRV) positive, the 3.13% porcine parvovirus (PPV) positive, the 15.63% porcine circovirus type-2(PCV-2) positive. HP-PRRSV produces a multisystemic infection in pigs, main gross lesion are ususlly obser -ved in respiratory and lymphoid tissues, hemorrhage and congestion in the lung, like meat consolidation, fibrinous exudation in surface of the some lung. Microscopic examination reveals moderate to severe multifocal interstitial pneumonia characterised by alveolar sept -al infiltration by a mixed population of mononuclear cells, hypertrophy and hyperplasia of pneumocytes (cells lining the alveoli in the lungs),and marked mixed inflammatory and necrotic alveolar exudate. Lymph nodes show marked follicular hyperplasia, foci of follicu -lar necrosis, increased numbers of tingi le (stained) macrophages and karyorrhectic (frag -mented) nuclear debris within follicles. Eosinophilic inclusion bodies in astrocytes of the frontal cortex. Immunohistochemistry demonstrated that abundant PRRSV antigen was identified within the cytoplasm of pulmonary macrophages and pneumocytes and necrotic intra-alveolar debris. Sequenced for phylogenetic analysis showed the isolates in this study were of North American type, 90%~98% sequence identity to those of subgroup HP-PRRSV including isolates HE 1,HUB1, XA1 and so on. These results suggested that there are the same subgroups of HP-PRRSV isolates NM-1 and JXA1.Coclusions: Based on the results of this study, Swine disease occurred in Inner Mongloia were mainly caused by HP-PRRSV mixed by other pathogen. an atypical from of PRR S produces a multisystemic infection in all aged pigs, leading to multi-tissue bleeding, lea ding to multiple organ failure, highest mortality observed in nursery and growing pigs. Microscopic examination reveals moderate to severe multifocal interstitial peneumonia. Sequence analysis of the main structural protein indicated that determinants of PRRSV virulence are multigenic products of both nonstructural and structural genes, particularly the GP5 more likely related to PRRSV attenuation. Further research of this virus may lead to a more thorough understanding of PRRSV pathogenesis.