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Denmark’s ban on low-level antibiotic use for farm animals was supposed to improve the effectiveness of human drugs and lead to a healthier human population, but after a decade of data collection, the question remains whether that goal is achievable.
The findings within the Danish human health care sector are being closely monitored in the U.S. as pressure mounts to similarly limit antibiotic use in farm animals here.
Margaret Mellon of the Union of Concerned Scientists is among those who believe the removal of low-level antibiotics will help prevent the emergence of "superbugs" in people.
"When continually exposed to antibiotics, bacteria develop resistance to the drugs. Adding antibiotics to animal feed in CAFOs (concentrated animal feeding operations) turns these massive, overcrowded facilities into prime breeding grounds for antibiotic-resistant bacteria, which can move to humans through food, air and water. Then, when people get sick from these resistant bacteria, antibiotics are less effective," Mellon said in a statement issued last year in support of legislative efforts to withdraw antibiotics from use on the farm.
The Obama Administration also has indicated support for ending the non-therapeutic use of seven antibiotics for growth promotion and feed efficiency (Feedstuffs, July 13, 2009).
In July, Dr. Joshua Sharfstein, principal deputy commissioner of the Food & Drug Administration, said FDA now believes the judicious use of antibiotics requires that "all medications for prevention and control should be under the supervision of a veterinarian."
Still, the critical question at hand is whether Denmark has seen an actual improvement in the ability to control human disease and minimize antibiotic resistance.
This past September, House Agriculture Committee chairman Collin Peterson (D., Minn.) was part of a congressional delegation that traveled to Denmark to meet with government officials, industry representatives and Danish farmers.
Upon his return, Petersen issued a statement that said, "We didn't come back with a definitive answer on this complicated issue because we found no scientific evidence that reducing antibiotic use in agriculture has resulted in public health benefits in Denmark."
Even proponents of limiting antibiotic use concede that there is no evidence, to date, that enterococci of foodborne origin pose a direct threat as a human pathogen. The Danish experience has resulted in an increase in the number of human cases of salmonellosis and campylobacter, and that pattern can be seen across Europe despite continent-wide antibiotic bans.
With campylobacter, the evidence shows that there is little connection between the use of animal drugs and resistance in people. In fact, the bacteria's rate of resistance against the human antibiotic erythromycin has gone unchanged for a decade.
A four-fold leap in the rate of resistance in people against other antibiotics that are used only sparingly in Danish food animals has left some scientists suggesting that, perhaps, something besides animal use is to blame.
Most recently, a finger was pointed at disinfectants used in hospitals as possibly being associated with rises in bacterial resistance.
No success has been reported in Europe's efforts to eliminate Enterococcus faecium that are resistant to vancomycin, the animal form of the antibiotic, which Europe banned more than a decade ago. Over the past seven years, the incidence of vancomycin-resistant bacteria in hospital patients has fallen in only three countries while increasing significantly in six others and remaining unchanged in the rest.
The World Health Organization (WHO) has praised Denmark as being a "success" in restricting on-farm antibiotics, but in doing so, WHO has been careful to define that success by simply saying Denmark had "achieved a reduction in the reservoir of resistant microorganisms in food animals."
WHO said nothing about drug-resistant bacteria on the human side of the equation.
The level of drug resistance in strains of enterococci that are unique to animals did decline in those bacteria sampled from livestock as a result of the ban. Those findings are of little surprise to the U.S. livestock industry and scientists, who say it is normal to see a drop in resistance once the pressure from antibiotic use is removed.
From an animal welfare standpoint, some argue that the ban is a setback considering the higher incidence of sickness and mortality in some animals.
Danish officials acknowledged an increase in pig mortality and illness in the first few years following the ban on low-level antibiotic use. Health and productivity did eventually return to the Danish herds, which was attributed to better management at the farm level.
Overall, the ban prompted higher production costs for Danish pork producers. Those farmers who could afford its implementation survived the transition, but a number of small Danish farmers who raised pigs went out of business.
By 2015, it is projected that the number of Danish pork producers will be at about 5,000, down from 25,000 producers in 1995.
As the U.S. pursues efforts to counter political pressure against antibiotic use in farm animals, it must be remembered that disease and animal suffering are synonymous, said Dr. John Waddell, a veterinarian from Sutton, Neb.
Waddell said it can be argued that antibiotic use is hugely beneficial to public health.
"Since the Danish ban on antibiotics, the number of foodborne illness cases has risen. Even at best, per capita numbers have not decreased. Therefore, there's at least a 'reasonable certainty' that any public health benefit from reducing antibiotic use would be offset by eliminating production efficiencies that make protein more affordable and, thus, improve the overall quality of diets," he said.
There also is a growing body of evidence that points to the possibility that antibiotics may actually help keep consumers safe by preventing foodborne disease.
Risk assessment expert Dr. Tony Cox has mathematically modeled the human illness rates attributed to food poisoning -- both antibiotic resistance and susceptibility. He determined that for each day someone is sick because the use of antibiotics in chicken contributed to their treatment being less effective, 4,000 others are spared a day of illness because antibiotics reduce the risk of food poisoning.
At the farm level, a 2008 study at The Ohio State University found that 54% of hogs raised on antibiotic-free operations were infected with salmonella, compared to only 39% in conventional operations.
U.S. Department of Agriculture research conducted in 2002 found that cattle fed neomycin sulfate for 48 hours, held for the mandatory 24-hour pre-slaughter drug withdrawal and then shipped to market shed significantly fewer Escherichia coli O157:H7 than their pen mates that did not receive the antibiotic.
Waddell said as a veterinarian, his role -- along with his producer clients -- is to promote public health.
"Antibiotics are tools that help accomplish that mission," he said. | 
