| Avian leukosis virus(ALV),reticuloendothelial virus(REV)and chicken infectious anemia virus(CIAV)are three common immunosuppressive pathogens in poultry,all of which can be transmitted vertically through provenance.Mixed infection of multiple immunosuppressive viruses in chickens is very common,among which the co-infection of ALV-J and REV,ALV-J and CIAV has been reported,however,there is a lack of systematic study on the observation pathogenicity of co-infection between REV or CIAV and ALV-J vertical transmission,and the effect of co-infection with REV or CIAV on ALV-J eradication is also a matter of concern during this process.Therefore,experimental chicks models were established for co-infection of REV or CIAV with ALV-J through the chicken embryo inoculation in this study,respectively.The effects of co-infection of REV or CIAV with ALV-J vertical transmission on the pathogenicity and eradicaiton of ALV-J were analyzed by the rate of hatching,mortality,body weight,detection rate of ALV-P27 in meconium,and positive rate of viremia.In this study,three strains of ALV-J NX0101,REV LN1201 and CIAV LY08 were selected for amplification and quantification,the co-infection models of REV and ALV-J,CIAV and ALV-J were constructed after hatching inoculation through the yolk sac at 7-embryo-age,the effects of hatching and mortality rates from single infection group and coinfection group were observed and compared.The results showed that the hatching rates of the co-infection of ALV-J+REV group,co-infection of ALV-J+CIAV group were 68.57% and62.86%,respectively,which were lower than those in the single-infection group and the Mock group(85.71%).The survival curve showed that the mortality rate of co-infection both viruses and ALV-J was higher thanthe single-infection group and Mock group.The weight of chickens at different days of age was weighed and recorded,and the weights of the chickens from Mock group were 59.25 g at the age of 7 days,and chickens from the ALV-J,REV and CIAV groups was 50.83 g,49.67 g and 45.32 g,respectively,while the co-infection group of ALV-J and REV was 43.78 g,the co-infection group of ALV-J and CIAV was 44.27 g,the results indicating that co-infection increased the inhibition of growth.Plasma was collected from chickens at 1d,3 d,7 d and 14 d and inoculated into DF-1cells for ALV virus isolation,respectively.The results of ALV-p27 antigen detection showed that the positive rate of ALV-J group,ALV-J+REV group and ALV-J+CIAV group were 100%at each day of age,while the rate of Mock group was 0%.The samples of cloacal swabs were collected from chickens and tested for ALV-p27 antigen at 1 d,3 d,7 d and 14 d.The positive rates were 92.86%,90.90%,88.89% and 93.33% at all ages in the ALV-J group,91.30%,93.75%,90.90% and 100% in the ALV-J+REV group,respectively,and 91.67%,89.47%,90.90%,and 100% in the ALV-J+CIAV group.It indicates that the positive detection rate of ALV-J p27 in cloacal swabs was lower than plasma virus isolation.Three chickens from each group were necropsied at 1d,7d and 14 d,respectively,and the samples of spleen,thymus and bursa of Fabricius were collected for weighing and calculating the immune organ index.The analysis of the experimental results of the co-infection of REV and CIAV with ALV-J vertical transmission showed that the spleen organ index from the ALVJ+REV group was significantly lower than Mock and ALV-J groups at 7 d(p <0.05);the spleen organ index from the ALV-J+CIAV group was significantly lower than Mock group(p<0.001),significantly lower than CIAV group(p <0.05),and also signifiantly lower than ALV-J group at 7 d(p <0.01);the thymus organ index from the ALV-J+REV group was significantly lower than the REV and ALV-J single infection groups(p < 0.05),and had significantly lower than the Mock group(p < 0.01);the spleen organ index from the ALVJ+CIAV group was significantly lower than Mock group and ALV-J single infection groups(p<0.001),it had no significantly difference compared to the CIAV single infection group;the organ index of the bursa of Fabricius from the ALV-J+REV group was significantly lower than the REV single infection group(p < 0.05);the organ index of the bursa of Fabricius from the ALV-J+CIAV group was significantly lower than Mock group and ALV-J group(p<0.001),it had no significantly difference compared to the CIAV single infection group.The sample of plasma was collected at 1d,3d,7d,and 14 d,and the viral loads of spleen,thymus,and bursa of Fabricius of each group were measured.The results showed that the ALV-J viral loads developed of the three immune organs in the ALV-J+REV and ALVJ+CIAV groups were higher than in the ALV-J single infection group,and the REV viral loads of the ALV-J+REV group was higher than the REV group,and the CIAV viral loads in the ALV-J+CIAVgroup was higher than the CIAV group,and all the results showed that coinfection of REV and CIAV with ALV-J promoted the proliferation of ALV-J in immune organs,while ALV-J also promoted the proliferation of REV and CIAV in immune organs.In conclusion,both co-infection of vertical transmission of ALV-J and REV,ALV-J and CIAV caused a decrease in hatching rate,slow growth of diseased chickens,and increased mortality,inhibited the development of central immune organs,synergistically promoted replication between the two viruses,and increased the difficulty in ALV-J eradication.It is suggested that while ALV-J is being for eradication it is also necessary to strengthen the detection and elimination of avian immunosuppressive diseases such as REV and CIAV,and carry out multi-pathogen synergistic eradication to reduce the economic losses to the poultry industry. |
