Endogenous leukosis viral antigen in eggs from meat‐type chickens on an avian leukosis virus eradication programme

Abstract

SUMMARYIn an effort to eliminate exogenous avian leukosis virus (ALV) from a susceptible population, albumen of one egg per hen from each of four generations was tested by ELISA for groupspecific antigen (gsa) of leukosis/sarcoma viruses. From 1510 to 2099 hens were tested in each generation. Hens were not used as breeders if optical density readings for gsa were 0.4 or greater. Despite this procedure, there was no appeciable change in the occurrence of gsa in eggs from one generation to the next and in the sire population the percentage of hens with levels of 0.4 or greater was 7.1 and 8.7 in the first and fourth generations tested, respectively. There were no consistent differences in antigen levels in any of the eight strains that comprised the two populations.For the most part, antigen detected in eggs resulted from expression of endogenous viral genes since there was a low incidence of exogenous infection. Six of 234 hens of the second generation tested from the sire population were positive for ALV in serum and three of 161 were positive for antibody to subgroup A virus; no antibody to subgroup B was detected. Five of the six hens that tested positive for ALV were from the same strain and had been reared together. With one exception these hens would have been eliminated as breeders based on tests for antigen in eggs. In the fourth generation tested, no virus or subgroup A antibody was found in serum from approximately 250 hens from the two populations.

Detection of exogenous and endogenous avian leukosis virus in commercial chicken eggs using reverse transcription and polymerase chain reaction assay

“…In additional case studies of Smith (1987) and Ignatovic (1988), shedding of endogenous ALV did not occur in studies involving chicks that were experimentally infected with endogenous ALV. However, infection and shedding of endogenous ALV was found to occur commonly in meat-type chickens, but not in egglaying chickens (Ignatovic, 1986;Spencer & Chambers, 1992). In contrast, we found endogenous ALV in egg-laying chickens from two different commercial chicken stocks.…”

“…We expected the RT-PCR to detect subgroup A ALV because the prevalence of subgroup A ALV infections in chickens is higher than subgroup B ALV, while infections of subgroup C ALV and subgroup D ALV in chickens have only been reported in Finland (Sandelin & Estola, 1973;Calnek et al, 1991). However, subgroup E avian leukosis virus was not expected in commercial chicken eggs because infections of endogenous ALV usually do not result in detectable levels of GSA in egg albumen of egg-laying stocks (Spencer & Chambers, 1992). In this investigation, nucleotide sequence analysis performed on randomly selected RT-PCR products of albumen from eggs obtained from two different sources, White Leghorn chickens and retail stores, showed four of six samples were positive for endogenous ALV, while two of six samples were positive for exogenous ALV.…”

“…Based on previous studies, ELISA absorbance values of egg albumen infected with exogenous ALV are usually 0.5 or greater, while infections of endogenous ALV do not have detectable levels of GSA in egg albumen (Spencer & Chambers, 1992). The four samples positive by RT-PCR for endogenous ALV had ELISA absorbance values of 0.15, 0.18, 0.52 and 0.54, while the two samples positive for exogenous ALV had absorbance values of 0.97 and 2.99.…”

Relationship between egg size and subgroup J avian leukosis virus in eggs from broiler breeders

“…However, gs antigen in albumen can also result from expression of endogenous viral (ev) genes, and high levels of the antigen have been found in eggs from meat-type chickens that were negative for exogenous virus (Ignjatovic, 1986;Spencer & Chambers, 1992). Sabour et al (1992) reported that meat chickens carry more of these ev genes than do egg-type stocks.…”

Genetic analysis of Rous sarcoma virus (subgroup A) induced tumourigenesis and performance of synthetic broiler stocks in relation to group-specific antigen shedding

“…Again, it was observed that second-generation samples of SML and SDL had higher OD values than ® rst generation samples, indicating the presence of exogenous virus shedding. It has been established that testing for the gs antigen shedding can bene® t an ALV-eradication programme, as most chickens that were viraemic with exogenous ALV had high levels of gs antigen shedding in eggs (Spencer & Chamber, 1992).…”