KANSAS CITY (Dow Jones)–Disease resistance to antibiotics among humans and animals continues to rise, despite declines in their use as a feed-ration additive to prevent illness and to promote growth in livestock and poultry, according to scientists and livestock industry members.
In addition, worldwide use of antibiotics to treat sick animals has increased in the last seven years, but total use remains below mid-1990s peaks, according to statistics for Europe by the Danish government.
The U.S. situation – declines in feed use to promote general herd or flock health and as a growth promoter – corresponds to an increase in therapeutic use to treat a higher numbers of sick animals or birds.
It “is precisely what is taking place in Europe,” said Ron Phillips, vice president of legislative and public affairs for the Animal Health Institute, citing figures from the Danish government’s program for surveillance of European antimicrobial resistance, called DANMAP.
Michael Hansen, senior scientist at the Consumers Union, which publishes Consumer Reports, pointed to the same report and said total antibiotic use in the European Union peaked in 1994. By the end of 1999, antibiotic use as a growth promoter was banned in the E.U., although the industry had begun to take
it out of the rations before then, he said.
The DANMAP report for 2005, the most recent statistics available, says, “antimicrobial consumption in food animals is still low compared to the total consumption before the cessation of growth promoter use.” A chart in the report also says antimicrobial use in animals leveled in 2004 and 2005.
At the same time, the use of antibiotics in humans has held about steady from 1997 through 2005, the DANMAP report showed.
The U.S. Food and Drug Administration approves antibiotics used in animals for disease treatment, disease control and prevention, which are considered by the FDA and the American Veterinary Medical Association to be therapeutic, and for growth promotion, Phillips said.
The FDA’s Web site said disease-causing microbes that have become resistant to drug therapy are an increasing public health problem, and the CDC says on its Web site that doctors and consumers should reduce their use and demand for antibiotics.
The FDA also says about 70% of infection-causing bacteria are resistant to at least one of the drugs most commonly used to treat infections. The FDA site does not say where these bacteria acquired their resistance, but says use of antibiotics in animal feed can cause microbes to become resistant to drugs used
to treat human illness.
The FDA adds that some research has shown that antibiotics are given by doctors to their patients more often than recommended by federal guidelines and other health care organizations.
In the U.S., subtherapeutic antibiotic use, or below the level required to cure a sick animal, in livestock and poultry feed has declined in the last three years, Phillips said. But he had no figures on the breakdown between livestock and poultry.
Subtherapeutic use among U.S. producers is falling out of favor slowly, because studies have made a connection between feed use and a growing incidence of antibiotic-resistant bacteria among humans, sources said. Antibiotics are being removed from animal feeds because consumers want them removed, and U.S. Department of Agriculture guidelines require the move in order for the meats to be labeled as organic.
In addition, in July 2005, the FDA removed its approval for Baytril, made by Bayer Corp. (BAY) for feed use because of its similarity to human antibiotics and concerns about resistant diseases. Baytril was used in poultry feed.
However, a western Kansas veterinarian with a large cattle feedlot practice said many of his clients continue to use low-dose antibiotics as growth promoters because they work and because there are no comparable human drugs in use. In essence, it wouldn’t matter if the animal’s bacteria developed resistance to these drugs, because the bacteria still would be susceptible to human drugs, he said.
Hansen took issue with that, saying the close proximity of genes giving a bacterium its resistance to one antibiotic can cause cross resistance. An Iowa veterinarian also said there is talk among hog producers of cutting back on antibiotics in feed, but “it’s a necessary part of production.” They are fed not only as a growth promoter but to prevent pneumonia and scours, or diarrhea, he said.
As if to underscore this need, the FDA recently approved another antibiotic for feed use in hogs, although it is to be done by “veterinary directive” only, the Iowa veterinarian said.
The new antibiotic’s use is restricted, the Iowa veterinarian said, because there is a human equivalent. This caused “some wringing of hands and gnashing of teeth” before it was approved, he said.
“Relative to antibiotic feeding, the biggest issues in the cattle industry are whether or not cattle feeders will be allowed to continue to feed tylosin phosphate (to prevent liver abscesses) and/or monesin (to prevent coccidiosis, an intestinal disease in cattle),” said Gary Smith, Colorado State University
professor of meat sciences, in an e-mailed response to questions.
In 2005, the last year of official records, total U.S. production for use in animals rose 12.3%, to 24.4 million pounds, according to data provided to the AHI by the research-based companies that produce animal medicines, Phillips said. This compares with 21.7 million in 2004.
The percentage of overall production used to maintain the health of animals and enhance growth dropped to 4.5% from 5.4% the previous year, Phillips said.
The ideal rule-of-thumb, according to Hansen, is to keep livestock away from antibiotics unless they are needed, and then to treat as few as possible with an effective dose.
-
-By Lester Aldrich; Dow Jones Newswires
