What gene-editing approaches are scientists using to develop avian influenza-resistant chickens, and what are the implications for poultry nutrition and flock management?

The gene-editing approach: targeting ANP32A with CRISPR/Cas9

Researchers at the Roslin Institute, Imperial College London, and the Pirbright Institute are using CRISPR/Cas9 technology to edit the ANP32A gene in chickens. This gene is responsible for producing a protein that the influenza virus relies on during replication inside host cells. By making small, targeted changes to that gene, the research team aimed to cut off one of the virus's key entry routes.

The work was led by Professor Mike McGrew, a professor of avian reproductive technologies at the Roslin Institute, whose team has spent more than two decades applying developmental biology and reproductive technologies to practical poultry challenges.

What the trials showed

In experiments published in Nature Communications, gene-edited chickens were exposed to the low-pathogenicity H9N2-UDL strain. At the standard challenge dose, nine of ten edited birds remained uninfected, and there was no onward transmission to other chickens. When the viral dose was increased one-thousandfold, five of ten edited birds became infected — but even then, viral loads in those birds were lower than in unedited controls.

As McGrew put it: "We used gene editing to alter a small section of bird DNA and this was able to restrict, although not completely block, the flu virus from infecting chickens." The result is a chicken that is significantly less susceptible to infection, but not completely resistant.

The viral escape problem — and the three-gene solution

A key challenge identified in the research is viral adaptation. In birds infected after very high doses, the virus mutated to exploit two related proteins — ANP32B and ANP32E — to continue replicating. This means that editing ANP32A alone is insufficient for complete resistance.

Follow-up cell experiments showed that simultaneously editing all three genes can block viral replication entirely. However, the research team stresses that multiple simultaneous gene modifications must be evaluated carefully for potential effects on bird development, weight gain, reproduction, and susceptibility to other diseases before moving to commercial application.

Surrogate host technology and breed conservation

Beyond disease resistance, the Roslin Institute's gene-editing work uses surrogate host technology — a method originally developed to conserve genetics of rare poultry breeds. This same platform could accelerate the dissemination of disease-resistant traits across commercial poultry populations once the science matures, offering a faster route to widespread adoption than conventional breeding.

Implications for poultry nutrition and flock management

For feed producers and flock managers, the practical implications today are limited but worth monitoring:

• No immediate change to nutrition programmes: Gene-edited birds are not commercially available. Any multiple-gene edits must first be assessed for effects on growth, feed conversion, and reproductive performance before commercial use is considered.
• Biosecurity remains the priority: Vaccination, biosecurity, and surveillance remain the industry's primary defences. U.S. federal policy under USDA APHIS continues to rely on stamping-out as the core HPAI response, with vaccination a supplementary option. Heightened biosecurity is particularly important during fall waterfowl migration, when HPAI case counts typically rise.
• Parallel vaccine research continues: Alongside gene editing, Binghamton University is leading a $2.5 million USDA-funded project to develop a yeast-based, feedable avian flu vaccine that could be easier to manufacture, store, and transport than existing options — directly relevant to feed and nutrition operations. Avian flu outbreaks at U.S. poultry farms led to more than $1.5 billion in losses over the last two years and drove egg prices to all-time highs in 2025.
• What the sources do not settle: The evidence does not establish a timeline for regulatory approval of gene-edited chickens in any market, nor does it address how traits would be maintained across commercial breeding programmes. The effect of triple-gene editing on feed intake, FCR, or immune response to other pathogens is also not yet published in the evidence available.

Critical perspectives

Animal welfare organisation Compassion in World Farming has raised a concern that gene editing does not address the root conditions that enable HPAI spread, arguing that industry restructuring — including reducing flock size and density — should be part of any policy response. This is a separate question from the science of gene editing itself, but it is relevant to producers considering long-term flock management strategy.