title: Natural infection and transmission of a retrovirus closely related to myeloblastosis-associated virus type 1 in egg-type chickens.
abstract: Myeloblastosis-associated virus type 1 (MAV-1) is an exogenous avian retrovirus with oncogenic potential. MAV-1 was detected in young chicks hatching from eggs produced by an experimental genetic line of egg-type chickens. Transmissibility of MAV-1 had not been documented previously. This investigation was intended to partially characterize the virus involved and to study its transmissibility and oncogenicity in naturally and contact-infected chickens. Commercially produced white and brown layer pullets free of exogenous avian leukosis viruses were commingled at hatch with naturally MAV-1-infected chickens. The original MAV-1-infected chickens were discarded after approximately 8 wk, and the contact-exposed chickens were maintained in isolation for 36 wk. Young specific-pathogen-free (SPF) single comb white leghorn chickens were added to the group to study possible horizontal transmission of MAV-1 in young chickens. Upon weekly virus isolation attempts, MAV-1 was readily isolated from the contact-exposed white layers but not from the brown layers between 36 and 53 wk of age (18 wk in total). Three-week-old SPF chickens were readily infected with MAV-1 by contact as early as 1 wk postexposure. Throughout 22 hatches derived from the white and brown MAV-1-contact-exposed layers (between 36 and 53 wk of age), MAV-1 was frequently detected in the white layer progeny, whereas the virus was seldom isolated from the progeny produced by the brown layers during the same 18-wk period. MAV-1 induced a persistent infection in some of the SPF chickens that were exposed by contact at 3 wk of age. Gross tumors were not detected in any of the originally infected experimental chickens at 8 wk of age, in the contact-exposed brown or white layers at the termination of the study at 53 wks of age, or in the contact-exposed SPF chickens at the end of the study at 12 wk of age. Exogenous avian leukosis-related viruses may still be detected in egg-type chickens, emphasizing the importance of thorough screening before incorporation of experimental genetic material into commercial genetic lines of egg-type chickens.
authors.affiliation: Department of Population Health, Poultry Diagnostic and Research Center, The University of Georgia, 953 College Station Road, Athens, GA 30602-4875, USA. gzavala@uga.edu
authors.forename: Guillermo
authors.initials: G
authors.lastname: Zavala
authors.forename: Sunny
authors.initials: S
authors.lastname: Cheng
authors.forename: Taylor
authors.initials: T
authors.lastname: Barbosa
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D001353:Avian Leukosis / Q000473:pathology / Q000635:transmission*; D009189:Avian Myeloblastosis Virus / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D002645:Chickens; D004279:DNA, Viral / Q000235:genetics; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D008297:Male; D010047:Ovalbumin / Q000276:immunology; D010802:Phylogeny; D011201:Poultry Diseases / Q000473:pathology / Q000635:transmission*; D017422:Sequence Analysis, DNA; D013047:Specific Pathogen-Free Organisms; D014766:Viremia / Q000097:blood
chemical_list: D000914:Antibodies, Viral; D004279:DNA, Viral; D010047:Ovalbumin