Parasites are a big problem for sheep and goats. They can make animals sick and hurt farm productivity. One of the worst parasites is Haemonchus contortus. It's a tiny worm that lives in the stomach of sheep and goats. Farmers use drugs to kill these worms. But now, the worms are fighting back. They're becoming resistant to the drugs. This is a big deal because it makes it harder to keep the animals healthy.

One drug that farmers use is called eprinomectin. It's special because it's the only drug approved for dairy sheep with no withdrawal period. But some farms in southwestern France are having trouble with it. The drug isn't working as well as it should. Scientists wanted to find out why. They collected worm samples from six farms. Four of these farms had worms that were resistant to eprinomectin. The other two farms had worms that were still affected by the drug.

The scientists also had two lab-grown worm samples. These worms were known to be affected by eprinomectin. They tested all the worm samples with four different drugs: eprinomectin, ivermectin, moxidectin, and levamisole. They wanted to see how the worms reacted to these drugs. They used a special test to watch how the worms moved. This test can tell if the worms are resistant to the drugs.

The test showed that the worms from the four farms were indeed resistant to eprinomectin. The worms from the other two farms and the lab-grown worms were still affected by the drug. This means that the test can reliably tell if worms are resistant to eprinomectin. This is important because it can help farmers figure out if their worms are resistant to the drug. It can also help scientists develop better treatments for these parasites.

But there's still a lot we don't know. We don't know why the worms are becoming resistant to the drugs. We don't know if there are other drugs that can kill these worms. And we don't know how to stop the worms from becoming resistant to the drugs in the future. These are all questions that scientists are trying to answer. In the meantime, farmers need to be careful about how they use these drugs. They should only use them when necessary and follow the instructions carefully. This can help slow down the development of drug resistance.

DAIRY SHEEP

Sheep Parasites and the Drug Resistance Puzzle

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