Submitted to: Avian Diseases
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/15/1999
Publication Date: N/A
Citation: Interpretive Summary: Infection with a new subgroup of avian leukosis virus (ALV) termed ALV-J, previously not identified in flocks in the U.S., was diagnosed in several broiler and broiler breeder flocks experiencing a cancer-like disease known as myeloid leukosis. Using biological as well as molecular assays, we have isolated and identified several strains of ALV-J from samples submitted from affected flocks. Virological and serological surveys suggested that infection with ALV-J is widespread in affected meat-type chickens. Further, transmission experiments revealed that unlike other strains of ALV, contact transmission of ALV-J is highly efficient and therefore may interfere with current efforts to control this virus infection by eradication. Preliminary characterization studies have suggested that the U.S. isolates of ALV-J are related, but not identical to the strain originally isolated in 1991 from flocks in the United Kingdom. In order to develop more effective strategies for diagnosis and control of ALV-J, biological and molecular variations among strains of ALV-J are being studied.
Technical Abstract: During the last four years, several subgroup J-like avian leukosis viruses (ALV-J) were isolated from broiler breeder (BB) and commercial broiler flocks experiencing a relatively high incidence of myeloid leukosis (ML) at 4 weeks of age or older. In all cases, diagnosis of ML was based on the presence of typical gross and microscopic lesions in affected tissues. The eisolates were classified as ALV-J by:1) their ability to propagate in chicken embryo fibroblasts (CEF) that are resistant to subgroup A and E ALV (C/AE);and 2) positive reaction in a polymerase chain reaction (PCR) using primers specific for ALV-J. The prototype strain of these isolates, an isolate termed ADOL-Hc1 was obtained from an adult BB flock that had a history of ML. The AOL-Hc1 was isolated and propagated on C/AE CEF and was distinct antigenically from ALV of subgroups A, B, C, D and E, as determined by virus neutralization tests. Antibody to ADOL-Hc1 neutralized dstrain HPRS-103, the prototype of ALV-J isolated from meat-type chickens i the United Kingdom, but antibody to HPRS-103 did not neutralize strain ADOL-Hc1. Further, proviral DNA of strain ADOL-Hc1 and HPRS-103 tested positive in a PCR using primers specific for ALV-J. Virological and serological surveys revealed that the incidence of ALV-J induced viremia and antibody in several BB flocks from four different breeder varied from 11% to 87%, and from 30% to 87%, respectively. Further, the incidence of viremia in day-old chicks of three different hatches from a BB flock naturally infected with strain ADOL-Hc1 varied from 4% to 25%; in 2 of the 3 hatches, all contact-exposed chickens had evidence of viremia by 8 weeks of age. The data documents the isolation of ALV-J from meat-type chickens experiencing ML as young as 4 weeks of age.