Tuesday, April 28, 2009

Swine Flu And The Future Of Free-Range Pork

The current swine flu virus has fragments of human flu virus, pig flu virus, and bird flu virus. That mixing of traits may have contributed to this virus' ease of transmission (from pig), and suspected high virulence (from bird).

The pork industry recognizes the risks of a hybrid flu virus. I found this Fact Sheet from the National Pork Board, from 2004, that advises the following:1
"Reducing interspecies transmission of influenza viruses: It is in the best interest of both human public health and animal health that transmission of influenza viruses from pigs to people, from people to pigs, from birds to pigs and from pigs to birds be minimized."
They itemized ways to reduce transmission between pigs and people, which focused on vaccination, hygiene, and sick-leave policy ("The farm owner should ... encourage [employees] to remain away from work when they are suffering from acute respiratory infections. People typically shed influenza viruses for 3-7 days.")

They also itemized ways to reduce transmission between pigs and birds:
"The global reservoir of influenza viruses in waterfowl, the examples of infection of pigs with waterfowl-origin influenza viruses, the risks for reassortment of avian viruses with swine and/or human influenza viruses in pigs, and the risk for transmission of influenza viruses from pigs to domestic turkeys all indicate that contact between pigs and both wild and domestic fowl should be minimized.

The following factors are potentially useful to reduce transmission of influenza viruses between birds and pigs:
  • Bird-proofing - All doorways, windows and air-flow vents in swine housing units should be adequately sealed or screened to prevent entrance of birds. Although small birds such as sparrows, swallows, finches, wrens etc. are not thought to be important in the overall ecology of influenza viruses, they may carry influenza viruses from waterfowl feces into barns on their bodies.
  • Water treatment - Do not use untreated surface water (because of waterfowl fecal contamination with influenza viruses) as either drinking water or water for cleaning in swine facilities. Likewise, it may be prudent to attempt to minimize waterfowl use of farm lagoons.
  • Separation of pig and bird production - Do not raise pigs and domestic fowl on the same premises.
  • Feed security - Keep pig feed in closed containers to prevent contamination with feces from over-flying waterfowl.
  • Worker biosecurity - Provide boots for workers that are worn only within the pig housing units, thus eliminating the chance to carry bird feces into housing units from outdoors.
These recommendations clearly cannot apply to production units in which pigs are raised outdoors. Outdoor housing places pigs at increased risk for infection with avian influenza viruses."
This swine flu outbreak doesn't bode well for the future of free-range pork.
1 INFLUENZA: Pigs, People and Public Health, National Pork Board, January 2004