Avian infectious laryngotracheitis: virus-host interactions in relation to prospects for eradication.

This review examines the virology, immunology and molecular biology of infectious laryngotracheitis virus (ILTV) and its interactions with the chicken, in the context of assessing the feasibility of eradication. Establishment of the latent phase during infection of the host, its central role in biological survival of ILTV and the host-viral events that are associated with reactivation of infection, are considered. In counterpoint there are several features of the biology of ILTV in its natural mode of infection which can be exploited in eradicating this pathogen from intensive poultry production sites. These include the high degree of host-specificity of ILTV, dependence on contact for spread, the short-lived infectivity outside the chicken and the stability of the genome and lack of significant antigenic variation. Further, ILTV cannot replicate productively in its main target organ, the trachea, in the face of local specific cell-mediated immunity. Genetically-engineered vaccines that are capable of generating immunity, but without the ILTV latent infections induced by conventional modified-live ILT vaccine strains, are now well into development. This paper postulates that, used in conjunction with specific site quarantine and hygiene measures, such vaccines can provide the technological tools required to eradicate ILTV from production sites, and then regionally, in developed poultry industries from around the year 2000.