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OVERUSE OF ANTIBIOTICS MAY BE LEADING TO RESISTANCE

by: Heather Smith Thomas

Use of antimicrobial drugs in food animals has become a controversial issue. There is growing concern among the public that overuse of antibiotics (in treating or preventing disease in both humans and animals) is possibly leading to resistant strains of pathogens that in the future may not be readily controlled by these drugs.

Marie Bulgin (Caine Veterinary Teaching Center, Caldwell, Idaho) says that no one not beef producers, nor veterinarians - advocates indiscriminate use of antibiotics. "We all know it's important for producers and veterinarians to be responsible in their use of antibiotics. This is essential for the future of our profession. But often we tend to look to antibiotics as a cover up for bad management. People would rather get out a syringe and needle than do what it takes to prevent the diseases in the first place (such as having the animals in a clean environment). I think there are a lot of improvements we can make; we need to look at what's causing the diseases we are treating, and look toward prevention rather than treatment," she says.

"That's a question of management. But no matter how good your management is, there will be times you need to use antibiotics. We do need to pay more attention to prevention programs, vaccination, ways to relieve stress, etc. If we do this, we won't have to rely on antibiotics so much; it won't be quite the issue it is now."

She feels that the medical doctors have been as much to blame for overuse of antibiotics as anyone. "If you go to a doctor with a cold, which is a viral infection and not affected by antibiotics, they give you antibiotics anyway because that's what people want. We do the same thing in veterinary medicine if the owner wants the animal treated. That's a real problem, due to pressure from patients and clients. The question of whether we are creating ‘resistances' in zoomatic organisms (that affect both species) out in the feedlot and pastures and passing this on to humans with veterinary use of drugs, however, is still a very up-in-the air question. I don't think there is any hard data to indicate that we (people from the medical profession) are creating a problem,” says Bulgin.

The low level antibiotics in feed is hardly an issue, since the drugs used in feed (rumensin, bovatec, neomycins, etc.) are not used in humans at all or rarely used. "Probably as long as these are not drugs used in humans, they will continue to be used. But the tetracyclines or others that are used in human medicine may eventually be taken away," she says.

"Even so, we could certainly do without the drugs in the feed, if we had to more than we could do without drugs for treating illness. If the feed additives become too expensive, people won't use them. We wouldn't get the feed efficiency or the greater weight gains (a factor in the economics of beef production), but when they start making certain drugs illegal for use in certain animals, this may lead to more losses from disease," she says.

There is no logic to some of these regulations. "For example, Chloromycetin (chloramphenicol) was made illegal to use in food animals, because supposedly any residues in meat might create problems in humans such as aplastic anemia. Yet they still allow this drug to be used in humans! I have a real problem with that. First of all, I don't think the low levels that you might possibly get in residues have ever been proven to be enough to cause aplastic anemia. And if those low levels COULD cause that problem, then what are they doing allowing it to still be used in humans?"

"They are also worried about the enrofloxacins (Baytril). This drug is illegal to use for anything but a respiratory problem in a beef animal in the feedlot. You cannot use it in dairy stock; you can go to jail for using it in dairy animals. There is an enrofloxacin cleared for use in poultry. If it is legal to use in one animal, what is the rational for making it illegal in another? Or, if you are going to make it illegal in one species, where is the rationale for allowing it in another?" she asks.

"My understanding is they are doing this because enrofloxacins (that group of drugs, the fluoroquinolones) are the only drugs today that are effective against salmonellosis, and they are trying to reserve those for this purpose. But my question is, are they more worried about getting salmonella from ice cream, hamburger or poultry? Their reasoning doesn't seem to hold water. Now they have just approved a new fluoroquinolone for use in respiratory disease in the feedlot. So if it is really true that they are saving this drug for use in humans against salmonellosis, why are they allowing it for veterinary use at all? None of those decisions are making good sense," she says.

Only about one percent of crops in the U.S. are "organically" grown, without use of pesticides, commercial fertilizers, etc. A small percent of food animals are also being raised "organically" without use of antibiotics, hormones, etc. This may work for some producers, but not others. "Most of the ones that are making it work are small producers whether they are growing organic apples or organic beef," says Bulgin.

Raising animals without the use of antibiotics is not always healthy, however. "In Oregon, one sheep raiser decided to go organic, because he could sell the carcasses for double what he would normally get. The only problem was, when he tried to do it, the animals he was taking in to have butchered were small, thin and scouring, because they had been severely affected by coccidiosis. Coccidia is a serious pathogen for sheep, and he wasn't raising them with any anti coccidia drugs. Those that survived were stunted, so this was not very economical. You might get twice as much for the meat, but the carcass only weighs half what it should! I don't think he stayed in business very long," she says.

"If growers don't have the use of antibiotics, it seems to me that the food produced would be less safe, in many instances." We are actually able to raise healthier animals, with proper use of antibiotics. We can keep them healthy, as they grow up. They are not stunted by coccidiosis or a low grade salmonellosis, or doing poorly when sent to market," she explains.

"In cases of disease problems, proper use of antibiotics helps keep animals healthier. Early intervention, when an animal first shows vague signs of illness, and immediate proper treatment, can greatly shorten the recuperation period. They bounce back faster, with a shorter course of treatment," she says.

"We may have to look at feeding them a little differently in the future, however. There is some work done that shows that the E. coli that causes problems in humans is more likely to be found in the manure of animals on high concentrate diets than in those being fed forage diets. More producers may go to grass fed beef, and in doing so may also have less problem with the diseases common to animals in confinement. I can see changes in meat production in the future, but not in the very near future. There is a trend, however, in that direction. It will become more and more expensive to raise or feed animals in confinement because there will be more rules and regulations on run off, fly control, odor control, etc. Regulations may eventually put the larger confinement operations out of business. There will be a lot of changes for agriculture, in general."

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