Penn State and USDA uncover genomic clues to combat emerging Marek’s disease virus strains

Researchers have identified genetic regions linked to increased virulence in Marek’s disease virus, paving the way for more resilient poultry vaccines to tackle evolving threats.

Researchers at Penn State and the US Department of Agriculture have identified 10 genomic regions in the Marek’s disease virus that appear to be linked to rising virulence, offering a possible route towards more resilient poultry vaccines.

The work, published in Science Advances on 29 July, analysed the full genomes of 65 virus strains collected between 1962 and 2016 from a USDA repository. The strains covered four pathotypes, ranging from milder forms to variants capable of overcoming vaccine protection. The researchers found almost 800 single-letter DNA differences, alongside several insertions and deletions, before mapping how the strains were related.

Their phylogenetic analysis suggested that the most virulent strains share a common ancestor, narrowing the search for the changes that may have allowed the virus to evade immunisation. A genome-wide association study then linked 10 variants with virulence, including a tandem repeat, where a DNA segment is duplicated.

According to Penn State, the findings build on more than a decade of work examining how vaccination, transmission and evolution interact on poultry farms. Moriah L. Szpara said the aim is to help design “next-generation vaccines” that could better block immune escape, while Andrew Read said the study underlines the value of long-term, collaborative research.

The current vaccines reduce disease rather than fully prevent infection, and the researchers said more durable protection remains a priority as hypervirulent strains continue to emerge.

Reference: Genome-wide analyses of an avian herpesvirus identify 10 loci associated with tumorigenicity and vaccine escape; Alejandro Ortigas-Vasquez et al. Science Advances 29 Jul 2026, Vol 12, Issue 31
DOI: 10.1126/sciadv.aee9024

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