Farm Feelings and Farm Evidence
When It Comes to Factory Farming, Policies Require Transparent Reasoning
There is complete consensus that pathogens will move very rapidly through the large populations of closely confined animals typical of industrial hog and poultry production. There is also a hypothesis that large populations of genetically similar animals being kept indoors and fed identical diets provide an environment conducive to vectoring new pathogens. This interesting and important hypothesis is exceedingly difficult to corroborate or refute given the current state of knowledge. The mere possibility suggests that so-called “factory farms” are a bad idea on precautionary grounds alone.
But there is an alternative hypothesis that is at least as well supported. It is that pathogens are likely to arise and jump species boundaries in environments where there is a lot of genetic and species diversity, where species have intimate contact with one another, and where climate and available nutrients support rapid turnover of microbial populations. This is the hypothesis that was popularized a few years ago in Richard Preston’s book The Hot Zone.
This hypothesis would suggest that we do well to isolate herds of domestic animals from wild relatives. This strategy is particularly relevant for controlling the spread of avian disease, since wild birds can travel long distances in a relatively short span of time. The alternative hypothesis also implies that we should also limit the amount of contact that animals have with human handlers. Both criteria make current methods in industrial livestock production appear sound. But which hypothesis is true?
Who knows? Possibly both. There is enough complexity in veterinary pathology to support active research along both lines, and there is no logical incompatibility posed by multiple mechanisms for the incubation of viral or microbial pathogens.
But the policy implications are incompatible. One points to more extensive livestock production systems in open air, while the other points toward intensive systems with greater environmental control. This is not an issue that is likely to be decided on scientific grounds alone. The way that people feel about these alternative livestock systems is as important as the scientific evidence on the incubation and spread of zoonotic disease.
There are many excellent reasons for thinking about reforms in animal production that have nothing to do contagion. Getting the science right sometimes means striking a balance between disingenuous skepticism and over-interpretation of weakly supported scientific results. We need not be shy about expressing our ethical predilections in the realm of caring for animals but we should be cautious in presuming that those predilections are supported by science.
Paul B. Thompson is the W.K. Kellogg Chair in Agricultural, Food and Community Ethics at Michigan State University.
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