Research Of Co-Infection Of ALV-B And Salmonella Typhimurium

Co-infection of ALV and other pathogens are common in China,causing great harm and economic loss.Previous studies have focused on the subgroup of ALV,ALV and some viruses.However,there are few reports of co-infection of ALV-B and bacterial diseases.In order to investigate the co-infection of ALV-B and Salmonella typhimurium,the following studies were conducted.The strain was isolated from cloacal swabs of infected chickens in a farm,then LD50,pathogenic and agglutination antigen of the strain were studied.120 healthy 1-day-old SPF chickens were randomly divided into four groups of A-D,and inoculated with the bacteria.Three SPF chickens were randomly selected for each group per week,and the following works were carried out.First,the chickens' bursa of Fabricius,thymus and spleen were collected.Then,These chickens were weighed.In addition,the immune organ index of these chickens were calculated.Last but not least,P27 antigen and the antibody of ALV-B,the INF-?,IL-2 of serum and the antibody of Salmonella typhimurium were detected.According to comparing the sequencing results of the strain with the reference strain at home and abroad,it was found that Typhimurium strain LT2.seq had the highest homology of99.7%,and identified as Salmonella typhimurium.It was found that the strain had the highest homology with Typhimurium strain LT2.seq of 99.7%,and identified as Salmonella typhimurium.The LD50 of the bacterium was 1.52×104CFU.Salmonella typhimurium positive sera was reacted with homemade Salmonella typhimurium agglutination antigen,however it did not show agglutination with the cross immunoassay reaction of Salmonella pullorum.The mortality rate of common infection group was 23.33%,it was higher than Salmonella typhimurium(13.3%),ALV-B group(16.67%).Both Single-infected group and co-infected group of chickens showed a certain degree of growth retardation phenomenon,and the weight of the co-infected group was significantly lower than that of the control group(p <0.05),which was significantly lower than that of the single-infected group.The spleen index of Salmonella typhimurium single-infected group was increased,but the spleen index of ALV-B single-infected group and co-infected group were decreased,and the co-infection group was significantly lower than the control group(p <0.05).The immune organ index of thymus and bursa of Fabricius group in each infection group were lower than the control group,and the co-infection group could aggravate the damage of immune organs.Both the single-infected group and the co-infection group,the disease was characterized by mental depression,anorexia and thin.The single-infected group of ALV-B and the co-infection groupshowed a slight enlargement of the liver after the dissection,and the organs of chickens did not find significant lesions by naked eye.There were found needle-shaped bleeding,hemorrhagic enteritis,liver enlargement and splenomegaly in the single-infected group of Salmonella typhimurium.There were also a series of phenomena such as inflammatory cell infiltration to form necrotic lesions in the spleen and liver,lymphocyte necrosis and degeneration of renal tubular epithelial cells.The levels of IL-2 and IFN-? in the single-infected and co-infected groups were significantly different from the control group(p<0.05),and the secretion of co-infected group was the lowest.The p27 detection of cloaca found that 4.34% of toxin was excluded from the ALV-B single-infected group in the second week,50% of toxin was excluded from the ALV-B single-infected group and 54.45% of toxin was excluded from the co-infected group in the fifth week.ALV-B antibody was not detected in the first 4 weeks,ALV-B inhibited the cellular immunity and humoral immunity of the body,Which led to the outbreak of the disease.As the 1-day-old SPF chickens infected with ALV-B is prone to immune tolerance,resulting in infected chickens continued to poison detoxification without producing antibodies.The results showed that the positive rate of the co-infected group was 45.45% in the first 5W,which showed that the co-infected was more harmful than the single-infected.In summary,a strain of Salmonella typhimurium was isolated and the antigen was prepared.A model of 1 day old SPF chickens infected with ALV-B and Salmonella typhimurium was established.The results showed that the co-infected of ALV-B and Salmonella typhimurium may have synergistic pathogenic effects.