In Eating meat: evolution, patterns, and consequences, Vaclav Smil offers some thoughts on the risk of massive antibiotic use in animals. Carnivores might want to think twice before reading.
A health impact of an entirely different kind arises from the massive use of antibiotics in all forms of animal husbandry. The Union of Concerned Scientists estimates that more than 11,000 t of antibiotics, eight times as much as used in treating humans, are now fed every year to US domestic animals for nontherapeutic reasons in order to prevent outbreaks of infectious diseases in crowded conditions (UCS 2001). Pigs and poultry each receive about 40 percent of the total and cattle get the rest. What is most worrisome about these practices is that several antimicrobials that are important as human medicines, including tetracycline, penicillin, and erythromycin, are used extensively for these prophylactic treatments. These massive dispensations promote bacterial resistance to essential antibiotics.
The most widely debated recent example is food poisoning (gastroenteritis) caused by the bacterium Campylobacter jejuni that acquired resistance to fluoroquinolones (ciprofloxacin and related compounds) when these were used to treat chickens for bacterial infections (FDA 2001). Every year an estimated 8,000–10,000 people in the United States contract fluoroquinoneresistant Campylobacter by eating chicken. The spread of vancomycin-resistant enterococci in humans is a development of particular concern among hospitalized patients (Ferber 2002). Thus it has been argued that we should not wait for incontrovertible evidence of harm before acting to preserve the usefulness of many antibiotics in human medicine (Lipsitch, Singer, and Levin 2002).
Finally, a relatively widespread acute medical problem is caused by enterovirulent Escherichia coli serotype O157:H7 that causes gastroenteritis and, particularly in children under age five years and in the elderly, a hemolytic uremic syndrome that destroys red blood cells and can lead to kidney failure. Most of this illness, estimated to reach 73,000 cases of infection and about 60 deaths in the United States every year, has been associated with eating undercooked, contaminated ground beef (FDA 2001; CDC 2002). Meat usually becomes contaminated during slaughter by bacteria living in cattle intestines, and the pathogens can then be thoroughly mixed into beef as it is ground. Given the widespread distribution of ground beef from large production facilities, infections from a single batch of contaminated meat can occur in many locations simultaneously.
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