Novel insights into identification of shedders and transmitters of avian leukosis virus

Avian leukosis virus (ALV) infection is one of the most common infections in domestic poultry. Even though loss due to mortality is only 1%-2%, it causes drastic decline in production because of subclinical infections. Exogenous ALV infected birds follow a complex pattern of transmission. Transmission is strongly related to immune status of the birds against ALV. Based on the ability to transmit ALV, infected birds can be classified to either shedders or transmitters. The knowledge on shedders and transmitters of exogenous ALV will facilitate in implementing an effective strategy to eliminate ALV. Identification of these shedders and transmitters is of absolute necessity at breeding stock to achieve ALV free status. Presently group-specific antigen used based ELISA cannot differentiate endogenous and exogenous ALV infections. Advances in molecular diagnosis make better differentiation of various subgroups and few tests like loop mediated isothermal amplification, can be used as pen-side tests. Besides this identification of infection, selection of genetically resistant strains of birds to ALV also holds a key role in elimination of ALV. Thus, combination of different strategies in the breeding programs may facilitate eradication of ALV infection. Here in this review, we have discussed about biology of ALV shedders and transmitters, with reference to eradication programs.