Banning Prophylactic Antibiotic Use in Farm Animals: The Controversy Continues

 The subject of prophylactic antibiotic use in farm animals is one in which there are supported and learned arguments on both sides, for and against the practice among factory farm, non-organic producers. The discussion has reached an increased pitch in the United States of late due to proposed legislation that threatens to ban the use of non-therapeutic antibiotics in farm animals such has been done in the European Union and Canada. This article will present arguments from both sides, the reasons for the proposed ban and the arguments for the continued practice, for a more comprehensive look at this important public health issue.

In March, 2009, the late Senator Edward Kennedy (D-MA) and Senator Olympia Snowe (R-ME) introduced to the Senate the Preservation of Antibiotics for Medical Treatment Act (PAMTA), H.R. 1549/S 619 that would eliminate the use of non-therapeutic, medically important antibiotic drugs in livestock production. The bill was introduced to Congress by Representative Louise McIntosh Slaughter, and has been sponsored by 118 House Democrats as of July, 2010.

H.R. 1549/S 619 is considered to be important due to the increasing risks of antibiotic resistant bacteria to human health. FDA approval of the use of prophylactic, or preventative, use of antibiotics would be withdrawn without a reasonable certainty that its use will not contribute to antibiotic resistance with subsequent harm to human health. It does not restrict the therapeutic use of any antibiotics for the treatment of sick animals under veterinary supervision and it is limited in scope to classes of drugs used in human treatments of disease that include penicillin, sulfonamides, and tetracyclines. Non-therapeutic use is defined as the administration of antibiotics in the absence of disease for the purposes of weight gain, growth promotion, feed efficiency, or routine disease prevention.

On June 28, 2010, the FDA issued a guidance draft to farmers to voluntarily cease the use of non-therapeutic antibiotic use for poultry, cattle, hogs, and other livestock. FDA principal deputy commissioner, Joshua M. Sharfstein cited this call for voluntary compliance as a first step to address this “urgent public health issue,” further stating that new regulations, legally within the scope of the FDA, would be issued should the industry not respond voluntarily.

FDA attempts to limit agricultural non-therapeutic antibiotic use since 1977 have been met with successful opposition from farm lobby and drug industry efforts. This latest attempt at voluntary compliance has been criticized by both farming interests and public health groups. Industry representatives that include the National Cattlemen’s Beef Association and the National Pork Council state the need for additional evidence demonstrating that current antibiotic uses in livestock production are contributing to antibiotic resistance issues in humans. Public health and environmental groups argue that the voluntary guidance to industry doesn’t go far enough.

Antibiotics are the “miracle drugs” of modern medicine that are taken for granted by most in this age due their ready availability and ability to cure many of the diseases that were once fatal. The widespread, indiscriminate use of these drugs, however, has resulted in bacterial strains that have evolved resistance to them, creating a global “public health problem of potentially crisis proportions,” according to a 1995 study by the American Medical Association.

The mechanism for the creation of antibiotic resistant bacteria is well understood. Simply put, a person or animal infected with a pathogen is treated with an antimicrobial agent. Most of the bacteria are destroyed, allowing the person or animal to survive. Some of the bacteria also survive, immune to that particular drug, allowing them to reproduce offspring that are likewise immune, or resistant to successful treatment with that particular antibiotic.

When that strain of bacteria infects others, the patients will not respond successfully to treatment with the antibiotic that was previously used, since that strain is now immune to the effects. A different antibiotic is chosen for a successful outcome. It kills most of the bacteria, leaving behind bacteria that become resistant to that antibiotic, producing a strain of bacteria that is now resistant to both of the antibiotics. In time, bacterial strains develop that are resistant to treatment from many known antibiotics, such as currently seen in tuberculosis (TB) in which strains that are resistant to as many as nine antibiotics are being observed.

Many antibiotic resistant bacterial strains dangerous to humans are created in hospital environments and from the overprescribing of antibiotics to humans, often for viral infections such as colds or flu for which antibiotics are ineffective. There is also supported alarm for the practice of the routine overuse of antibiotics in livestock and fish, used for purposes other than treating disease, which may account for some 70 percent of all antibiotic use in the United States. Since the drug data collected by the FDA comes only from manufacturers and not from users, the exact quantity used in agricultural applications is not known, so it is not available for study.

Low doses of antimicrobial agents are added routinely to feed and water of healthy livestock to enhance feed efficiency, promote faster and increased growth, and to prevent infectious diseases. Scientific experiments have demonstrated that chronic exposure to low doses of broad-spectrum antibiotics quickly leads to resistant bacterial strains in the host animals treated. Moreover, these strains spread to others of their species in the environment as well as humans working on the farms. When antibiotic supplementation is stopped, there is a demonstrable decrease in resistance among the populations.