Swine CAFOs & Novel H1N1 Flu: Separating Facts from Fears

Abstract

With cases documented in more than 170 countries, the global swine flu pandemic that erupted in spring 2009 remains a serious public health problem. Caused by a strain of H1N1 influenza virus, which is normally found in pigs, the flu now known as novel H1N1 has so far been less severe than regular seasonal flu in terms of deaths and hospitalizations. Yet given its remarkable capacity for human-to-human transmission and a widespread lack of immunity among potentially exposed people, it’s likely the number of cases will rise during the flu season later this fall and winter, according to many public health experts. Given that possibility, enormous resources are being mobilized to address novel H1N1, with an emphasis on vaccine development, education, and efforts to its limit its movements among human communities. Yet one potential source of the original outbreak—factory swine farming in concentrated animal feeding operations (CAFOs)—has received comparatively little attention by public health officials. CAFOs house animals by the thousands in crowded indoor facilities. But the same economy-of-scale efficiencies that allow CAFOs to produce affordable meat for so many consumers also facilitate the mutation of viral pathogens into novel strains that can be passed on to farm workers and veterinarians, according to Gregory Gray, director of the Center for Emerging Infectious Diseases at the University of Iowa College of Public Health. “When respiratory viruses get into these confinement facilities, they have continual opportunity to replicate, mutate, reassort, and recombine into novel strains,” Gray explains. “The best surrogates we can find in the human population are prisons, military bases, ships, or schools. But respiratory viruses can run quickly through these [human] populations and then burn out, whereas in CAFOs—which often have continual introductions of [unexposed] animals—there’s a much greater potential for the viruses to spread and become endemic.” Gray says workers exposed routinely to livestock can pass these zoonotic infections—which transmit readily among humans and animals—on to the wider public. However, public health agencies that monitor risks from zoonotic infections routinely overlook CAFO workers, according to Ellen Silbergeld, a professor at the Johns Hopkins Bloomberg School of Public Health. And animal disease sampling data collected by the food animal industry typically are not shared publicly, according to Gray, although such data could reveal how novel pathogens evolve in CAFOs and how they might move among animals, workers, and the broader community. Experts believe that without these data, society has a diminished capacity to detect and respond to new zoonotic threats before they become more widespread.