Detection of lymphoid leukosis virus infected chickens by testing for group-specific antigen or virus in feather pulp.

Exogenous lymphoid leukosis virus (LLV) and group-specific antigen (gsa) were detected in feather pulp and other specimens from naturally or experimentally infected chickens by phenotypic mixing or complement fixation tests, respectively. Electron microscopic studies on the calamus of plucked feathers revealed numerous C-type virus particles in intercellular spaces of the epidermis and pulp. LLV and gsa were detected in feather pulp from approximately 90% of 47 newly-hatched chicks that were shown to be congenitally infected. Chicks that were inoculated at 1-day-old or reared as contact controls were positive for gsa in feather pulp at 44 days, whereas at 111 days only the inoculated chicks were positive. Isolated controls were consistently negative. Titres of gsa </= 1 : 32 in feather pulp were found in adult chickens of three strains that tested negative for infection with LLV. In these chickens gsa was presumed to be associated with an endogenous virus infection. In chickens that were positive for exogenous LLV in feather pulp the gsa titres were usually >/= 1 : 64. It was concluded that gsa could be detected in the feather pulp of most chickens actively infected with LLV and that titres would generally be higher in exogenous than in endogenous infections.