Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 22, 2000
Publication Date: N/A
Interpretive Summary: Subgroup J avian leukosis (ALV-J) is an emerging economically important virus infection that can cause cancer-like disease and other production problems in meat-type chickens. Poultry companies that produce primary breeding stock are trying to remove this virus from their chickens because it is commonly transmitted through the egg to progeny. The main technique is to test hens and remove all those that are positive for virus. However, there is no agreement on what tests are best and when the tests should be performed. We showed that tests for infectious virus in blood gave good results when applied after about 12 weeks of age. Also, a combination of tests conducted at 18-22 weeks of age detected most hens that transmitted virus to their chicks; the patterns of infection were carefully described and classified into major groups. This information is essential to and should assist breeding companies in designing rational programs to eradicate this economically important virus infection.
Technical Abstract: Profiles of infection with avian leukosis virus subgroup J (ALV-J) and factors that predict virus transmission to progeny were studied. Virus was detected in 7% of chicks at hatch but spread rapidly. Over 40% of chicks developed persistent infections; others experienced transient infections. Five types of infection profiles were recognized. Of 80 hens that produced embryos, 21 produced at least one infected embryo and were identified as transmitters. All but one transmitter hen would have been detected by a combination of viremia, cloacal swab and albumen tests conducted between 18-26 weeks. However, virus was transmitted to embryos from hens that were not persistently viremic, or that rarely shed viral group specific antigen into the albumen of their eggs. Intermittent patterns of both antigen shedding and virus transmission to embryos were observed in some hens. These results validate current screening procedures to identify potential transmitter hens and provide some suggestions for improvement, but also show that identification of all transmitter hens by such procedures is unlikely.