Continuous Observation And Research Of Tumors Mainly Induced By ALV-J For Three Groups Of Commercial Layer Chicken

Avian leukosis virus of layer chickens caused by ALV-J is characterized by hemangiomain recent years and now happens in some commercial hy-line layer chicken farms. And at thesame time, MDV and REV is also epidemic in chickens around China. All the reports aboutchicken tumors have been about one or several samples of the chickens till now and lack asystemic study. So, the objective of the study is to understand the occurrence anddevelopment of subgroup J avian leukosis in the commercial layer chickens as well as therelationship with the isolation of the virus and antibodies.Thirty-one chickens suspectable of ALV-J at the age of39to43weeks from3groups (A,B, C) were observed and compared continuously in clinical status, pathology, viremia anddevelopment of neutralizing antibodies.CEF cells are used to detect the possible tumor viruses in the blood of the chickens andIFA tests are conducted by the monoclonal antibodies.8,12and8chickens are ALV-J positiveand1,5and1chicken is MDV positive in A, B, C, three groups separately. And MDVsdetected in A and B group are all co-infection with ALV-J, which indicates that the highaliment rate and death rate has relationship with the co-infection. But the virus isolation rateshows that ALV-J plays the main role in the disease.Antibodies of ALV-J, ALV-A/B, REV are detected for4times.2,3and2chickens in A,B, C group show steady and high level antibodies for ALV-J;4,8,4chickens of the3groupshave instantaneous and low level antibodies of ALV-A/B;0,2,2chickens have steady andhigh level antibodies of REV; All of the tests show that the chickens in3groups have beeninfected by ALV-A/B/J, and chickens in B, C groups have been infected by REV.Gross and pathological lesions are detected after the death of the chickens. Hemangiomain the skin and tumors in livers, spleens, kidneys and bones are found by anatomy andpathological tests indicate that the tumor cells are most marrow cells which are the indicativeof avian leukosis by ALV-J. So the main reason of the tumors is ALV-J but not other viruses,but one chicken in B group shows the typical neural symptom of MD which shows that MDVhas working in the disease. Sequence analysis of the env gene and3’ter of ALV-Js in group B indicates that thehomologous rate is very low: the identity percent of amino acid sequence of gp85reaches aslow as88.3%; gp37reaches92.9%; the identity percent of nuclear sequence of3’ter reaches91.6%. All of the sequence analysis indicates that the ALV-Js in the chicken groups have highrate of variation which results in the large amount of quasispecies in one chicken group whichhave relatively high divergence.All the tests above indicate that the infection rate with ALV-J in these three groups wasvery high. Twenty-eight chickens wre infected with ALV-J or had persistent viremia, of which14were detected as immunotolerized persistent viremia without neutralizing antibodies.Indicative myelocytomatosis of ALV-J was found in chickens of these3groups, and could bedetected in almost all of the organs and tissues. Of these31chickens,13hadtumor/hemangioma in three or more organs and1chicken had in at least5organs. Results ofthis observation indicate that ALV-J is still epidemical in Chinese commercial layer chickens,and the virus is getting stronger during the epidemic.The existence of ALV-J as well as MDV and the antibodies of REV and ALV-A/Bindicates that the co-infection of ALV, MDV and REV is still inducing the tumors in layerchickens.