If foot and mouth disease (FMD) ever emerges in the United States, vaccination probably would play a role in our control strategy. The nature of the disease, however, makes vaccination a complex issue. Speaking at last week’s Beef Industry Summer Conference, veterinarian John Zack, with USDA/APHIS Veterinary Services outlined how vaccination would fit in various outbreak scenarios.
Historically, vaccination has been viewed as a secondary strategy, primarily because the FMD-protective antibodies in vaccinated animals mimic those resulting from exposure. However, attitudes regarding vaccination as an early intervention strategy are changing. Other elements of a control strategy include biosecurity and “stamping out,” or destruction of animals in an affected area.
Zack says APHIS has set three primary FMD response goals:
- Detect, control and contain FMD in animals as quickly as possible.
- Eradicate FMD using strategies that seek to stabilize animal agriculture, the food supply, the economy and protect public health.
- Provide science- and risk-based approaches and systems to facilitate continuity of business for non-infected animals and non-contaminated animal products.
If it becomes apparent that stamping out will not achieve control, containment and eradication of FMD, alternative strategies will be considered. Zack outlined several strategies that could come into play, depending in part on the size of the outbreak and the virulence of the virus.
- Stamping out – This could be used exclusively if the outbreak is contained within a relatively small area where culling of animals could eliminate the virus and prevent its spread.
- Stamping out with vaccination to kill – In an area with high concentrations of livestock, the logistics of killing and disposing of large numbers of animals in a short time would be daunting. This strategy would involve vaccinating animals in an affected area and surrounding buffer zones to prevent spread of the virus until those animals could be properly depopulated and disposed of.
- Stamping out with vaccination to slaughter – This strategy would involve stamping out on the infected premises, with vaccination used within the surrounding control area and vaccinated animals sent to slaughter.
- Stamping out with vaccination to live – This would involve stamping out of clinically affected and in-contact susceptible animals and vaccination of at-risk animals outside the control area. Vaccinated animals intended for breeding, slaughter or other purposes live out their useful lives.
- Vaccination to live with no stamping out – This could be used in protection vaccination zones outside control areas.
Upon news of an outbreak, the Secretary of Agriculture would activate the North American FMD vaccine bank, operated in cooperation with Canada and Mexico. The challenge would then be to produce adequate doses of the appropriate vaccine based on the serotype of the outbreak, maintain a cold chain and distribute doses to veterinarians in the field. In addition to the North American Vaccine Bank, U.S. officials likely would need to purchase vaccine doses on the international market. Supplies of vaccine might struggle to meet demand, especially if an outbreak were to occur in an area with high livestock density.
For more information, visit USDA’s National Center for Animal Health Emergency Management website.