SDSU researchers develop vaccine for destructive poultry virus

Researchers in South Dakota State University's Animal Disease Research and Diagnostic Laboratory have developed both live and killed vaccine candidates for avian metapneumovirus subtype B — a respiratory virus that has severely hampered U.S. poultry production.

In early 2024, a team of researchers in South Dakota State University's Animal Disease Research and Diagnostic Laboratory was the first to identify a fast-spreading respiratory viral outbreak affecting turkeys and chickens in major poultry-producing regions of the U.S.

Limited or restricted outbreaks of avian metapneumovirus (aMPV) subtype C had occurred previously, but this was the first time subtypes A and B — the two most pathogenic strains of the virus — had been identified in the U.S.

Led by assistant professors Sunil Mor and Tamer Sharafeldin, the team quickly developed assay tests to identify and confirm the virus in flocks. They also immediately began work to develop a vaccine — the primary control method for viral outbreaks in livestock.

Roughly two years after the initial identification, the research team has developed both "live" and "killed" vaccine candidates for aMPV subtype B. Future experimental tests and field trials will confirm the efficacy of the vaccines on subtype A. 

"Emerging subtypes A and B are causing huge economic losses to the poultry industry," Mor said. "We are expediting our efforts to provide the first vaccine based on a U.S. field strain that will provide better protection to birds hence will be helpful in sustainability of U.S. poultry production."

Vaccines are categorized into two classes: "live" and "killed." Killed, or inactivated, vaccines consist of the virus' pathogens that have been grown and then killed to destroy its disease-producing capacity. Killed vaccines must be injected, are not suitable for all types of poultry, and are less effective than live vaccines.

Live vaccines use a weakened form of the virus that stimulates an immune response without causing further disease. Live vaccines are needed to protect entire flocks, which for a standard operation is between 12,000 and 22,000 birds, as they can be applied on a large scale.

The team developed three live vaccine candidates representing low-, medium- and high-passage attenuation. The candidates were tested in chickens to evaluate safety and efficacy. The medium-passage candidate demonstrated the best protection (safety and efficacy) for poultry and included complete viral clearance. 

"Developing vaccines is not going to be the only objective," Sharafeldin said. "Continued monitoring of new variants due to vaccine pressure will ensure the preparedness for any future outbreak due to emerging variants. This experience achieved over the past two years is exclusively owned by the SDSU poultry research team. We have expanded our collaborations and network sharing experience with other academic parties to benefit U.S. poultry."

Both live and killed vaccines also demonstrated significant safety and efficacy in commercial turkeys. These vaccines will provide better protection to both chickens and turkeys, Mor noted.

With the completion of this vaccine development research project — funded by the U.S. Poultry and Egg Association and USPoultry Foundation — the candidates will move to preclinical evaluation and field testing.

The newly developed live attenuated and inactivated vaccines represent a promising, effective control strategy against aMPV subtype B in chickens and turkeys, the U.S. Poultry and Egg Association said in a press release.

This vaccine will be crucial for poultry producers in states like Minnesota and Iowa, where aMPV has caused widespread economic damage. According to the Minnesota Turkey Growers Association, producers lost an estimated 2.2 million turkeys to aMPV in 2024, amounting to around $112 million in economic damages. This was compounded by losses already inflicted from other outbreaks, including avian influenza.

"SDSU's role as a land-grant university is to focus scientific expertise on developing solutions to real problems affecting our communities and economy," said Daniel Scholl, SDSU's vice president for research and economic development. "This vaccine development in the face of a devastating viral outbreak in poultry is an excellent example of our university's commitment to solving problems for producers."

The results of this work demonstrate strong potential for practical, field-ready tools to help control aMPV in poultry. Overall, the work supports the development of U.S.-based vaccines to reduce future disease impacts and economic losses in the poultry industry.