Hatchery-related contact transmission and short- term small-group-rearing as related to lymphoid-leukosis-virus-eradication programs.

Pathogen-free chickens highly susceptible to lymphoid leukosis virus (LLV) were used to study the role of hatchery-related contact transmission of LLV. In one experiment, the efficiency of short-term small-group-rearing in conventional-type rearing units to prevent contact transmission of LLV from infected to uninfected groups was evaluated. Results obtained from these experiments suggest that LLV is not transmitted by congenitally infected chicks to uninfected hatchmates in the hatcher. However, LLV can be transmitted by congenitally infected chicks to uninfected hatchmates during standard manual vent sexing. Rate of contact transmission was lower in chickens reared on wire-mesh floors than in chickens reared on solid floors. Short-term procedures in which chicks were reared in colony cages and brooder batteries effectively reduced the transmission of LLV by infected groups of hatching chicks to uninfected groups. All these procedures should facilitate the rearing of small groups of chicks with little risk of infection for a period sufficient to conduct virus assays, an essential step in LLV eradication.