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Friday, August 10, 2012 - 12:26pm

Drug Resistant Pests and Parasites

Parasites that prey on livestock are now becoming drug resistant, according to experts. It’s the result of decades of frequently treating animals with anthelmintics, commonly called de-wormers.

Since farmers began using drugs to combat parasites 50 years ago, parasitic worms that live in animals’ digestive tracts have evolved through genetic mutations. That makes them immune to the drugs used to eliminate them. Livestock like sheep and goats that once grew faster and healthier on anti-parasitic drugs are now getting sick.

It’s putting some farmers out of business.

UGA Parasitologist Dr. Ray Kaplan says the parasitic worms have developed resistance, which gives then a selective survival advantage: "Following treatment with a dewormer, the susceptible worms are killed but the resistant worms survive. Thus until a new cycle of infection occurs only the resistant worms can reproduce. This results in the shedding of increasingly higher numbers of resitant worm eggs and larvae onto the pastures after every treatment. Over time, with frequent deworming, the resistant worms come to dominante the population, and the drugs cease to work. That’s where we are now, so many of our most important parasites are not affected by our most important drugs on many farms."

Rotating where herds graze can help, but some experts say farmers might be better off accepting low-level infections created by worms rather than using drugs to eliminate all infections.

A similar issue is putting Georgia crops in danger. There is an increase of insects resistant to classic pesticides.

Experts say a high rate of pesticide use over the years has created a generation of pest populations that are resistant to the poisons developed to eliminate them.

This is particularly damaging for Georgia’s specialty crops, like ornamentals, vegetables and fruit. They’re all high value crops but they’re produced on small acreages.

Dr. Dan Horton, a UGA Professor of Entomology says that limits the number of pesticides available for farmers to use to protect their crops:

“What are you going to do? Take a massive yield loss because you can’t control the pest? No, you’re going to grit your teeth and hope that by the time you develop a problem, that something else will be made legal for you to use.”

According to an Oregon State study, the development of a new pesticide takes on average $80 million dollars, while the typical time before a pest develops resistance is between ten and twenty five years.

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