Control strategies for Marek's disease: a perspective for the future.

Marek's disease virus is an evolving pathogen, acquiring virulence in response to increasingly effective vaccines. Although vaccine efficacy is generally good, industry has placed a high priority on more effective products. The search for better vaccines has been conducted mainly in the arena of molecular biology, and has been thus far disappointing. Various conditions prevail that currently limit the potential to develop suitable long-term solutions. A new paradigm based on reduction of early exposure, multiple levels of host resistance, and improved cooperation among stakeholders is proposed for consideration.