Research Of Co-infection Of ALV-J And Salmonella Pullorum In Laying Hens

Subgroup J Avian Leukosis virus(ALV-J) mainly infect broiler and also have been foundin laying hens. The disease can cause tumors in laying hens, tumors’ forms are increasinglydiversified, including cell tumor, marrow cell tumor and hemangioma. Pullorum diseasecaused by salmonella pullorum(SP) that does a great harm to poultry farming for many years,the2-3weeks chicks mainly performance systemic serious infection and high mortality. Adultbirds clinical symptom is lighter, it can cause the loss of egg production, genital malformation,etc. Many pathogens can co-infect with ALV that makes the disease prevention andpurification of chicken groups more complex, it has attracted people’s attention to the disease.In the epidemiological investigation, we found that the high positive rate of ALV and the SPpositive rate is relatively high, the two pathogens are vertical transmission and both can causethe production performance and even death, they present a certain degree of correlation. Inorder to research the co-infection of ALV-J and SP may have synergy pathogenic effect, wemake the two pathogens back to the animal regression test.The experiment aimed to study interaction mechanism between ALV-J and SP. Firstly wedetected the ALV-J by ELISA kit and tested SP by plate agglutination. Choose the ALV-J andSP both positive layers for separation of virus and bacteria. Detected the body weight, theindex of immune organs, histopathology, haematological, part of the intestinal flora quantitychange, the viremia and antibody of ALV-J after inoculated the two pathogens.1. By infecting DF-1cells with epidemic materials and the PCR amplification fragmentwas924bp, that was consistent with the purpose fragment, we named it SD1306strain.Compared with the other14strains ALV-J gp85gene sequence,the homology was86.1%-96.5%, among them the homology of HPRS-103was as high as96.5%. Compared theseparated SP16SrRNA with standard strain, their homology was99%and its LD50was of4.4x107CFU.2. After the chicks inoculated the two pathogens, there was no obvious change in theincubation period; the co-infected group and the group infected ALV-J separately were significantly lower than that of control group (P<0.01) from the6th week, at the4th week theco-infected group and the separate infection group had significant difference (P<0.05), thedifference between the co-infected group and the group infected bacteria separately wassignificant (P<0.05) at the5th week, at the7th week the co-infected group average weightwas77.2%of the group infected ALV-J separately and was83.9%of the group infectedbacteria separately. The co-infected group thymus index were lower than those of the groupinfected with ALV-J separately, with the increase of age,that gap between them was more andmore big; the spleen index was always higher than that of the group infected with ALV-Jseparately, at the4th the two group spleen index fall down at the same time and after thenthey all on the rise. No evident nodular lesions and resembling tumors in any tissues wereseen at necropsy. Histopathological findings revealed large islands of leukomonocytes ormyelocytes in tissues containing tumors. The red eosinophilic granular could be seen in thecytoplasm and the normal tissue structure were destroyed by tumor cells. Hematologydetection indicated that the white blood cells and lymphocytes of co-infected group andthe group infected with ALV-J separately were decreasing from the4th week to the6th week,while the granulocyte of the two groups all continued to grow, the red blood cell count of theco-infected was down after rising while the group infected ALV-J separately continued to rise.The salmomella total number of the co-infected group in rectal feces was significantly higherthan that of the group infected ALV-J separately (P<0.05), its number of E.coli wassignificantly higher than that of the group infected with ALV-J separately(P<0.05),thedifference of the number of E.coli between the two groups were extremelysignificant(P<0.01). The P27positive rate of the co-infected group was69.23(9/13) at the5thweek. the group infected with ALV-J was38.46%(5/13). The two groups P27positive rateboth fall at6th week, the co-infected group positive rate was27.27%(3/11) and the groupinfected with ALV-J separately was18.18%(2/11). The positive rate of the two groups rised atthe7th week, the co-infected group positive rate was50%(5/10), the group infected withALV-J separately was30%(3/10). Correspondingly the positive rate of ALV-J antibody ofthe two groups continuted to decrease from the6th week to the7th week, the co-infectedgroup fell from54.55%(6/11) to30%(3/10) and the group infected with ALV-J separately fellfrom36.36%(4/11)to20%(2/10). This showed that P27antigen and antibody level fluctuated strongly in some time and there was a negative correlation between them. The co-infection ofALV-J and SP does have synergy pathogenic effect，the damage to the chicken is more seriousin the co-infection chicken compared with the chicken infected separately.