Research Of Co-Infection Of ALV-A And Proteus Mirabilis In SPF Chicken

Many pathogens can co-infect with ALV that makes the disease prevention and purification of chicken groups more complex, it has attracted people’s attention to the disease.Isolation and Identification of PM from chicken embryo yolk and To further understand the effcet of co-infection of PM and ALV-A in specific-pathogen-free chicken.1. The bacteria islated from dead chicken embryoes yolk samples, and identified by bacterial culture, Gram-staining microscopic examination and biological characteristics and16 S r RNA gene analysis.The results showed that the strins were identified as Proteus mirabilis. BLAST analysis showed that the gene shared more than 99% homology with the squences of Proteus mirabilis.2. In order to make a rapid and accurate detection of the antibody of Proteus mirabilis,thus providing effective prevention and control measures for the epidemic of chicken Proteus mirabilis disease. The purpose of this study was to develop agglutination antigen from the isolated and identified of Proteus mirabilis from the dead chicken embryo yolk was prepared through bacterial culture, inactivation, antigen concentration adjustment, sterility test and staining methods. The standard serum of Proteus mirabilis from chicken was developed by vaccinating the clean level rabbits with inactivation vaccine which Proteus mirabilis antigen mixed with freund’s adjuvant. In results, the inactivated antigen prepared by using formaldehyde was more sensitive than heating, and the optimal conditions for the concentration of formaldehyde and time to inactivate antigen were 0.5% and 24 h, antigen concentration reached to 8.05×109 CFU/mL dyeing with ammonium oxalate crystal violet.Preparation of Proteus mirabilis positive serum titer reached to 1: 512, which measured by Tube agglutination test.3. The immune suppression model of PM and ALV-A in chickens infected with SPF was established. 14 day old SPF chickens were randomly divided into 4 groups,ALV-A single infection group, PM single infection group, ALV-A and PM co infection group, blank control group,30 chickens in each group and isolation rearing. The chickens in each group were randomly selected and 3 at 1,2,3,4,5,6 weeks, and the related immune indexes were detected.The results showed that the infection group had some symptoms of clinical symptoms afterinfection in the first 2-3 weeks,ALV-A and PM co infection group（26.7%） was higher than that of ALV-A single infection group（20%）, and PM single infection group（16.7%）. The indexes of thymus, spleen, bursa and other immune organs of the infection group were lower than those of the control group and the degree of damage to the immune organs was increased by the co infection group. Infected chickens at 6 weeks of age, naked eye observation of internal organs without obvious enlargement or tumor nodules, however, it was observed in the liver, spleen, thymus, bursa and other organs showing lymphocyte like tumor cells and bleeding phenomenon by histopathology. Detection of T lymphocyte count in peripheral blood, Chicken Interleukin（IL-2） and interferon（IFN-γ） test results showed that CD⁸⁺、CD⁴⁺Tcell count, interleukin（IL-2） and interferon（IFN-γ） secretion of a single infection and co infection group were lower than the control group and the degree of immunosuppression was the most obvious in co-infection. The level of P27 antigen and ALV-A antibody in chicken fluctuated greatly, showing a certain negative correlation.The bacteria were identified as Proteus mirabilis and the prepared agglutination antigen of Proteus mirabilis could be used for clinical detection of both the pathogenic bacterium and antibodies after immunization. PM and ALV-A had synergistic effect, co infection with SPF chicken was more serious than single infection.