Submitted to: Avian Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 13, 2001
Publication Date: N/A
Interpretive Summary: Myeloid leukosis (MD), a virus-induced cancer-like disease of chickens, is considered as a major disease problem in commercial poultry. Eradication programs have reduced the incidence of the disease, but very little is known about the mechanisms of virus transmission. The objective of this research was to study factors that influence the transmission of the virus from bird to bird. We have determined that transmission requires close physical contact between chickens and can be prevented by handling and rearing of chickens in small groups. This important information about horizontal transmission of avian leukosis virus will help scientists in academia and industry develop better methods for virus eradication and eventually lead to better control of the disease.
Technical Abstract: Transmission of avian leukosis virus, subgroup J, from donor chickens inoculated as embryos to simulate congenital infection to uninfected hatchmates was studied in two strains of commercial broiler breeder chickens. Transmission frequently occurred when chicks were hatched or reared in direct physical contact with infected donors, or were exposed in the hatchery by cloacal swab transfer, needle transfer during subcutaneous inoculation, or ingestion of infected meconium. However, transmission was reduced or prevented by wire partitions in the hatcher and rearing of small groups in cubicles. In a simulated field test, broiler breeder chickens subjected to a program of multiple interventions based on hatching, handling and rearing chicks in small groups through 4 weeks of age remained free of ALV-J infection through 32 weeks. A control group with a similar initial infection rate and hatched and reared as a single group transmitted virus to 5.7% of its progeny and about 5% of the hens developed tumors. Thus, the small group hatching and rearing practices employed in these studies allowed for the accurate identification and removal of groups containing chickens infected prior to hatching and prevented horizontal transmission of ALV-J between uninfected and infected groups for at least 4 weeks.