It may be eight times that in humans.
The Union of Concerned Scientists (UCS), a nonprofit alliance of citizen and scientist advocates for environmental issues, estimates that, in the United States, 25 million lbs. of antibiotics are given to livestock annually for "nontherapeutic" purposes (disease prevention and the promotion of growth)-an amount equal to 70% of antibiotic production in the United States. In comparison, three million lbs. are used annually to treat human disease, according to UCS estimates.
Livestock are routinely given antibiotics, often mixed in feed or water. This practice can breed strains of antibiotic-resistant bacteria that can infect people and is also believed to reduce the effectiveness of the human antibiotic arsenal.
The UCS's figures are in sharp contrast to those from the Animal Health Institute, a trade group representing veterinary drug makers, that estimated human antibiotic use to be 10 times that calculated by the UCS. The group also gauged annual antibiotic use in animals for both therapeutic and nontherapeutic purposes at 17.8 million lbs.
Calling this figure an underestimation, the UCS based its calculations on publicly available information including herd sizes and known amounts of antibiotics mixed into feed during particular growth periods. They determined that antibiotic use totaled 24.6 million lbs., which far exceeds the 16.1 million lbs. used for nontherapeutic purposes in the mid-1980s. The UCS estimated that, when therapeutic usage is included, 84% of U.S. antibiotic supplies go to livestock.
The UCS recommends that the FDA require that antibiotic makers selling to the livestock industry provide annual reports on the quantity of antibiotics sold, including indications, dosages, and treatment periods. This information is necessary to track patterns of bacterial drug resistance and to recommend guidelines for addressing the problem.
The UCS report, Hogging It: Estimates of Antimicrobial Abuse in Livestock, is available at http://www.ucsusa.org.
Chlamydia and Cervical Cancer
Is prior infection a contributing factor?
Human papillomavirus (HPV) has been firmly established as a cause of cervical cancer. But because many patients with HPV clear the infection without medical intervention and few develop carcinomas, researchers have long suspected that there are cofactors in the development of cervical cancer. Investigators in Finland have now demonstrated that previous infection with Chlamydia tracho-matis may be such a cofactor. They found an independent association between cervical squamous cell carcinoma and the presence of serum antibodies to several C. trachomatis serotypes. Cervical malignancy may ultimately be recognized as a complication of Chlamydia infection.
Anttila T, et al. JAMA 2001;285(1):47-51; Zenilman JM. JAMA 2001;285(1):81-2.