Abstract: An outbreak of productive diseases occurred in a commercial layer breeding company in Yuci, Shanxi Province during August 2009. Lymphocytoma presented in lung, liver, kidney, heart, etc. ELISA, PCR and IFA results indicated that the positive rate of serum antigen to ALVJ was 8/8 and the viremia rate was 7/8. The coinfection rate with REV was 2/8, and found no single REV infection. The pathogenic observation indicated that the most serious lymphocytoma presented in coinfected viremia chicken, but no myelocytomas were observed. Phylogenitic analysis showed that the homology was over 96.9% of three strains of ALVJ with the prototype HPRS103; The REV strain showed the highest homology with suvenv strain (93.8%). The case revealed that viremia state induced by ALVJ is necessary for lymphocytomas formation induced by REV, and it is the reason why lymphocytomas showed earlier than myelocytomas. So, it is critical to eliminate vertical transmission of ALVJ for prevention these diseases. The synergistic effect mechanism of ALVJ and REV need to be further study.

Key words: avian leukosis virus subgroup J, reticuloendotheliosis virus, coinfection, layer breeding chickens, viremia