The Interference Of Coinfection Of Bordetella Avium With Reticuloendotheliosis Virus

Bordetella avium (B. avium) belongs to Bordetella species, which is known as an animalpathogeny causing severe tracheobronchitis in both wild and domesticated birds. In embryos,it mainly causes death and low hatchability; in chickens, it mainly causes acute death andrhinitis; in adult birds, it mainly causes ophthalmia. It is such a highly contagious, vertical andhorizontal propagation disease that has caused severe economic losses in allpoultry-producing regions. Immunosuppression is a state of temporary or permanentimmunity dysfunction and can make organism more sensitive to pathogens due to the damageof immune system. Reticuloendotheliosis virus (REV), a common immunosuppressive andoncogenic virus, was first isolated from turkey with viscus lymphoma in1958. Natural orexperimental infection of REV can cause a variety of non-neoplastic syndromes, such asrunting and anemia, as well as a chronic neoplastic disease of T or B lymphoid cells. Besides,REV has been considered as one of the most important vaccine contaminants.In production practice, more and more diseases showed multiple infections with variedpathogenies. In2010, our laboratory detected746embryos from three large chicken breedingfarms in China, and found that the rates of B. avium multiple infection with virus, such asReticuloendotheliosis Virus (REV5%), avian leukosis virus (ALV3%) were total23.56%.The coinfection of B.avium with immunosuppressive virus has brought about severeeconomic losses in poultry-producing industry.At present, there are no specific vaccines both for B.avium and REV, which leads to badprevention and treatment. Therefore, we used SPF embryos and chickens as our experimentalobjects to explore the interference of B.avium and REV to provid theoretical foundation forreasonable and effective prevention.Part One：Effects of Coinfection of REV and B. avium on Immune Systemin SPF embryosBordetella.avium (B.avium) and ReticuloendotheliosisVirus (REV) were used in thisstudy to infect SPF embryos and SPF chickens artificially. Chicken embryos mortality andhatchability were calculated. B.avium.The results showed that the dead time of embryos incoinfection of REV with B.avium was earlier than those in other groups, and with smaller embyos and many bleeding spots. The embryos hatchability was only27.85%under thecoinfection of B.avium and REV. Even after birth, the chicks were week. The embryo deathrate of B.avium was25.71%higher than that of REV. The dead time and pathologicalsymptoms of first infected with REV and then with B.avium were similar with B.avium only.Therefore, the damage of coinfection of B.avium with REV was huge. And the mechanism offirst infected with REV and then with B.avium needs to be developed in the future. It isstrongly recommended more attention be paid on coinfection in clinical diagnosis of virusesand bacteria in the poultry in the future.Part Two：The establishment of REV immunosuppressive modelMultiple infections of Bordetella avium (B. avium) with virus, especiallyimmunosuppressive virus, have become more and more severe in chickens in China. Theincreasing morbidity and mortality of its complications have amplified concerns about theimpact of B. avium on animal health. To evaluate the pathogenicity of B. avium underimmunosuppression status, we developed four types of Reticuloendotheliosis Virus (REV)infection models:1day-old chicks were infected with104TCID50and103TCID50REVrespectively;10day-old chicks were infected with104TCID50and103TCID50REVrespectively. Results showed that1-day with high dose of REV infection caused a more than30%of death rate, and the immune indexes in10-day with high or low dose of REV infectionwere not significant with the control group. After a comparison of body weight, relativeimmune organ index, Newcastle disease virus (NDV) antibody titers and lymphocyte ratio, wechose the early age with low dose infection as our immunosuppressive model.Part Three: Pathogenicity of Bordetella avium Under ImmunosuppressionInduced by Reticuloendotheliosis Virus inspecific-pathogen-free chickensTo investigate the pathogenicity of B. avium under this model, a study was completed inwhich chickens were inoculated with REV-only, B. avium–only, both agents (REV-B. avium)or first inoculated with REV and5d later with B.avium (REV/B. avium). Results revealed thatantibody titers to B. avium, concentrations of IFN-γ and SIgA were decreased in coinfectedchickens when campared to the B. avium–only chickens, but the changing trend was similarbetween REV/B. avium and B. avium–only group. Overall, REV did enhance the pathogenicity of B. avium. However, B. avium-only did not cause severe immune dysfunctionunless chicks were co-infected with REV. REV preceding infection with B. avium showedmild impairment, which needs further exploration.