Poultry holds the title of the most widely consumed meat globally. However, this staple food faces a serious threat in the form of Marek’s disease—a highly contagious illness with mortality rates ranging from 10% to 50% in unvaccinated chickens, and up to 90% in certain breeds.
As the world’s second-largest chicken exporter, behind Brazil, the U.S. poultry industry is a powerhouse. In 2022 alone, the sector supported over 1.5 million jobs, $95 billion in wages, and contributed $417 billion to the economy, according to the National Chicken Council. Yet, Marek’s disease exacts a significant toll, with global economic losses surpassing $2 billion annually due to condemned meat, reduced egg production, and vaccination expenses.
To combat this, poultry producers rely heavily on vaccines. However, researchers at the Agricultural Research Service (ARS) are charting a new course—using insights into host genetics and epigenetics to develop long-term solutions for disease resistance. “A deeper understanding of these mechanisms could lead to more effective vaccines and better disease management,” says Dr. Huanmin Zhang, an animal geneticist with the ARS Endemic Poultry Viral Diseases Research Unit in Athens, Georgia.
What is Marek’s Disease?
Marek’s disease is caused by a strain of the herpes virus that induces tumors and a variety of debilitating symptoms in chickens, including paralysis, weight loss, and vision impairment. The disease spreads through direct bird-to-bird contact or indirectly via contaminated materials like feather dander. Importantly, it poses no threat to humans.
Advancing Resistance Through Genetics
Dr. Zhang and his team are focusing on the genetic and epigenetic factors that influence resistance to Marek’s disease. Their aim is to uncover how these factors interact with the virus and vaccination processes, paving the way for targeted breeding strategies and enhanced vaccine efficacy.
A major breakthrough from this research is the creation of a “pangenome” for domestic chickens. Developed in collaboration with Washington University School of Medicine, the pangenome represents the complete set of genes across all chicken breeds descending from a common ancestor. This resource allows scientists to pinpoint genetic differences among breeds and identify traits that could bolster disease resistance.
“The pangenome enables us to better understand the impact of genetic variations and facilitates breeding programs aimed at enhancing resistance to Marek’s disease,” explains Dr. Zhang.
A Global Effort for Disease Control
Containing and mitigating Marek’s disease will require collaboration among researchers worldwide and continued advances in biotechnology. Dr. Zhang notes that progress in understanding and managing the disease has accelerated over the past two decades, outpacing gains made in the previous 50 years.
Through genetic insights and innovative approaches, scientists are striving to protect poultry populations, ensure food security, and minimize economic losses—a vital effort for an industry that feeds millions and supports livelihoods around the globe.
