The Transmission of Diseases from Livestock: Then and Now

By Josh Loeffler

The signs at the Philadelphia International Airport are bold and make a clear point. The bright, yellow billboards all but shout: "Keep Foot and Mouth Disease out of America." Soon after seeing these signs upon entrance to the airport, travelers are greeted by customs agents who check documentation and bags to insure that the traveler has not been prone to the disease on his journeys. Any traveler exhibiting the warning signs of an individual who carries the disease is quickly swept away- removed from the general populace in order to prevent possible spreading of the disease.

The above precautions may seem extreme. Then again, the precautions may appear normal in a world that has quickly strengthened airport security in response to recent terrorist activities. Neither of these reactions to the security checks would be fully accurate. The security checks preventing free entrance by individuals who have come into contact with animals or areas that house animals abroad are an innovation designed to prevent the most common method for spreading disease. These precautions have been implemented in order to prevent the spread of diseases infecting livestock.

Throughout the course of history, diseases have been the greatest killers of humans. In fact, the winners of most wars were simply the ones who proved less susceptible to the germs carried by the enemy (Diamond, p. 197). Diamond correctly points out, then, that diseases have been the largest shaper of history. For instance, what would the world look like now if the Native Americans had carried germs that were far more potent than the Spanish conquistadors? (p. 197)

The diseases that have been the great molders of the human experience are very often and quite easily traced back to animals, specifically livestock. Food production was seen relatively early in history of civilization as a better means for providing for a great number of people than the hunter-gatherer model that was once the primary model of existence. The success of food production in maintenance of human life leads to a society which has become dependant on farming, ranching, and other ways of life that produce foods from animals. The increased number of individuals able to be supported by a society supported by agriculture serves as an important factor in the spreading of disease. The most common method for spread of disease is direct transmittance from the animals to the humans. There are numerous diseases that afflict humans whose origins scientists now trace back to livestock. The spreading of the diseases is often due to the proximity to the livestock. Living close to the blood, excrement, and breath of the livestock allows for high rates of disease transmittance (Diamond, p. 207).

While it is true that there is a greater probability of disease transmittance from this lifestyle, the human population has flourished due to food production and livestock maintenance. Increased numbers of people leads to greater interaction, and a higher probability of transmitting the disease from person to person. The feces of the livestock and humans can surround the farmers, as this excrement is often used to increase fertilization of agrarian fields. The food produced by such animals can also attract disease-infected rodents (Diamond, p. 205).

Analysis of disease transmittance and evolution of diseases transmitted from animals to human reveals four stages of disease development in humans from an animal origin. First are those diseases transferred from pets, which are rare and even more rarely transmitted between humans. Second are those diseases that are transmitted directly from animals to humans and create epidemics that eventually disappear. Third are diseases that are transmitted by animals to humans that still pose a threat to humanity (ie. AIDS). Fourth are diseases that began with animals and have now become exclusive to humans. These diseases represent evolution, as microbes that infected humans and originated from animals transformed to become exclusively human syndromes (Diamond, pp.207-209).

The last three types of diseases are the type of transmittance and evolution that have the United States so worried about the spread of Foot and Mouth disease. All species with cloven feet, or hooves, are susceptible to Foot and Mouth disease. The disease is transmitted through feces, breath, and proximity to sores or legions are methods through which the disease is transferred between livestock. The disease results in lameness or salivation ( In short, the livestock becomes unfit to use in any manner.

While the spread of Foot and Mouth disease to humans is undocumented, and the origins of no disease in humans has been traced back to Foot and Mouth, there is still inherent danger. The disease wipes out livestock, (usually slaughtered to prevent further infection) making it much more difficult to support large civilizations. Rampant spread of this disease could result in the eventual complete change of diet. Also, the disease could evolve and later effect humans. As shown above, history reveals that diseases originating with animals can evolve to infect humans, or could later reveal effects on humanity. It is very possible, that without prevention or regulation, Foot and Mouth disease could evolve or reveal effects on humans over the course of time.

The explosion of travel, especially intercontinental travel has made the transmittance of Foot and Mouth disease a much greater possibility. This is especially true regarding Americans, who travel the world more than any other people. As Diamond points out, with an abundance of international travel, America is becoming a melting pot for disease (p. 206). As immigration continues, and individuals continue to travel to countries that contain foot and mouth, the possibility for transmittance of the disease increases.

It is because of this high level of travel and high chance for transmittance, that dire measures are taken at the airports. Customs agents must check to see if travelers visited farmlands, contacted livestock, or are carrying animals. If so, safety precautions must be taken to insure that the spread of disease is made nearly impossible. For instance, if an individual visited a farm, the shoes of that person are inspected and sterilized if found to be carrying manure ( While the safety measures at the airport may seem extreme, they are simply a way to prevent the spread of disease. In order to allow for travel, and prevent the spread of epidemics that have proved to be a plague on humanity throughout history, the precautions must continue. Society changes slightly to prevent the spread of disease. It does so in order to prevent disease from changing society vastly in the future.

Works Cited

Diamond, Jared, "Ch. 11: Lethal gift of livestock," in "Guns, Germs, and Steel" W.W. Norton & Co, 1997, ISBN 0-393-03891-2, pp. 195-214