Identification and characterization of hens transmitting avian leukosis virus (ALV) to their embryos by ELISAs for detecting infectious ALV, ALV antigens and antibodies to ALV.

A total of 72 White Leghorn grandparent hens was examined by ELISA for avian leukosis virus (ALV), ALV antigens and anti-ALV antibodies to identify and characterize the hens transmitting ALV to their embryos (transmitters) by using fertilized eggs. These hens were divided into 3 groups as no antibody and non-viremic (NANV) (49 hens), antibody-positive and non-viremic (APNV) (21 hens) and no antibody and viremic (NAV) (2 hens) by testing the sera for the presence of ALV and anti-ALV antibody. Egg albumen and embryos were tested for the presence of ALV and ALV antigens. As a result, no ALV was detected in both albumen and embryos in the NANV group. On the other hand, all albumen samples collected repeatedly from 3 hens of the APNV group and 2 hens of the NAV group contained infectious ALV, although the infectivity differed with the individual. Also, these 5 hens produced infected embryos at varying frequencies. However, on AP hen which shed neither ALV nor ALV antigens into the albumen produced an infected embryo at a lower rate. These results indicate that testing for infectious ALV in albumen from a newly laid egg per hen is effective to identify the transmitters to some extent. When virus titers in each of 8 tissue samples from the 6 transmitting hens were determined, the highest virus titers were found in washing from the ampulla of the oviducts in most of the shedders, suggesting that embryo infection is closely correlated with ALV produced at the oviduct, but not with ALV transferred from the other parts of the body.