Advocacy in action
Influenza surveillance in US swine

As I write this article, the US poultry industry finds itself fighting one of the largest foreign-animal disease introductions in US history, highly pathogenic avian influenza. I thought this would be a good opportunity to review influenza surveillance efforts in the swine industry.

In an effort to provide additional information on influenza circulation in the national swine herd, producers and veterinarians collaborated with government animal health officials, the Centers for Disease Control and Prevention (CDC), veterinary diagnosticians, and influenza researchers to implement the United States Department of Agriculture’s (USDA’s) Swine Influenza Virus Surveillance Program in 2010.

The objectives of this surveillance program are to 1) monitor genetic evolution of endemic influenza in swine to better understand endemic and emerging influenza virus ecology; 2) make available influenza isolates for research and establish an objective database for genetic analysis of these isolates and related information; and 3) select proper isolates for developing relevant diagnostic reagents and updating diagnostic assays and vaccine seedstock products. The influenza A virus (IAV-S) swine surveillance efforts are targeted towards these three swine populations:

  • Case-compatible sick-pig submissions to veterinary diagnostic laboratories;
  • Swine exhibiting influenza-like illness at first points of concentration or commingling events such as markets and fairs; and
  • Swine populations that are epidemiologically linked to confirmed human cases involving IAV-S.

Producers and veterinarians have been highly supportive of the anonymous program, recognizing the potential value of the information collected. Submissions have nearly tripled since the start of the program. The ability of the surveillance program to meet its objectives, however, has been mixed, in my opinion.

On the positive side, the swine industry has a much better understanding of the existence, emergence, and evolution of influenza viruses in the swine population. We are better able to answer questions regarding the presence and diversity of influenza viral strains in the US swine herd. In addition, many more virus isolates are now available for study by animal and human health researchers. Finally, the surveillance program has made available multiple isolates for possible inclusion in vaccines, diagnostic assays, and reagents.

On the negative side, USDA has not done a very good job making results of the program available to interested stakeholders on a consistent basis. To USDA’s credit, however, they have recognized this need, and the Center for Epidemiology and Animal Health has engaged AASV, National Pork Board, and National Pork Producers Council to design a comprehensive aggregate report for distribution to stakeholders on a regular basis. In addition, the industry has not done a good job providing diagnostic samples from all swine-producing areas of the US. For this reason, the results of the surveillance program may not be representative of the US swine herd as a whole. There are significant epidemiological gaps in the data regarding the distribution of those strains. The feedback I have received from CDC and USDA has been that the program is valuable, although it doesn’t necessarily provide the granularity of data they would perhaps like to see. Lastly, it is unclear to me to what degree vaccine manufacturers, researchers, and animal and human health officials actually utilize the information. At least, however, the data are now available for them to use if so inclined.

Having said all that, I think the influenza surveillance program has been a success overall. The program is an excellent model for the way comprehensive and integrated swine surveillance might work. It is providing valuable information for producers, researchers, animal and human health officials, and veterinarians. The future of the program is in jeopardy, however.

The program was implemented, and has been maintained, through a one-time allocation of funds from CDC to USDA. Those funds will be exhausted by early to mid-2017. Additional funds have not been allocated by USDA to support the project beyond that date. We are urging USDA and CDC to provide the necessary funding to continue to support this program. We would also encourage producers and veterinarians to support the surveillance effort by continuing to submit samples and to ensure participation from herds in all regions of the United States.

Harry Snelson, DVM Director of Communications