AVIAN INFLUENZA VACCINATION IN NORTH AMERICA: STRATEGIES AND DIFFICULTIES

Authors: Suarez, David; Lee, Chang; Swayne, David

Submitted to: Developments in Biologicals
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/2005
Publication Date: 1/31/2006
Citation: Suarez, D.L., Lee, C.W., Swayne, D.E. 2006. Avian influenza vaccination in North America: strategies and difficulties. Developments in Biologicals. 124: 117-124.

Interpretive Summary: Avian influenza virus can cause a serious disease in chickens and turkeys that can result in severe economic losses to the poultry industry. Vaccination is one potential way to control an influenza outbreak, but historically has been seldom used. Currently vaccination is being considered more often because it can be used to not only control disease symptoms, but also to help eradicate the virus from a region or populations of birds. However, most types of vaccination still cause problems with disease protection because it is hard to differentiate infected from vaccinated animal (DIVA). However, recently several DIVA strategies have been proposed that can allow this differentiation. However, these techniques still need to be proven to be effective in the field and our trading partners must accept their accuracy for these techniques to have an impact. This review article describes the different vaccination strategies that have been used in the U.S. and highlights some of new technologies that may have an impact in the future.

Technical Abstract: Vaccination with high quality efficacious vaccines that are properly delivered can contribute to the control of avian influenza (AI) outbreaks when used as part of a comprehensive control program that includes quarantines, animal movement controls, increased biosecurity, enhanced surveillance, and education. In North America both whole virus killed adjuvanted vaccines and fowlpox recombinant vaccines have been used to aid in the control of AI. The fowlpox recombinant vaccine is licensed in several countries including the United States (U.S.), but it has only been used in the field in Mexico and some Central American countries. The U.S., however, has considerable experience with the use of killed vaccines, primarily in turkeys. In the state of Minnesota in the 80’s and early 90’s, outbreaks of AI in range-reared turkeys were common, and vaccines were used successfully as part of a controlled marketing program. More recently, several large layer flocks in Connecticut were vaccinated as an alternative to immediate depopulation after an H7N2 low pathogenic AI outbreak. The vaccinated flocks were intensively monitored for virus shed using sentinel birds, dead bird testing, and eventually some serologic surveillance using a neuraminidase DIVA (differentiation of infected from vaccinated animal) approach. With these successes, vaccination is being considered as a valuable tool in comprehensive AI control strategies. Consideration for matching the vaccine to the field strain should also be considered to provide optimal protection including reduced shedding of virus. Antigenic drift of AI viruses after extended vaccination programs has been observed in chickens, similar to what has been observed with human influenza viruses. Therefore, periodic evaluation of the vaccine to the field strain is necessary to maintain good protection from clinical disease and virus shedding.