Resistance in Worms: Why Some Drugs Don't Work

Meet Haemonchus contortus, a tiny worm that packs a big punch. It's one of the most troublesome parasites for sheep and goats, mostly because it's become resistant to many drugs. One group of drugs, called macrocyclic lactones (MLs), includes popular ones like ivermectin and moxidectin. Scientists still don't fully understand why some worms shrug off these drugs. They think it might be due to certain proteins and transport systems in the worms' bodies. Two teams of scientists compared a worm group that's easily killed by MLs to a tough, resistant group. They looked at specific genes that make proteins (cytochrome P450 enzymes) and others that help move substances in and out of cells (ATP-binding cassette transporters). These genes were more active in the resistant worms, even without the drugs around. This suggests that these genes might be helping the worms survive the drugs. It's like having a super-powered cleanup crew and security system. When drugs come in, these systems can either break them down or kick them out before they cause harm. But why are these systems so active in resistant worms even without drugs? That's one of the mysteries scientists are still trying to solve. Understanding how these worms become resistant could help farmers find better ways to protect their animals. It might also help scientists design new drugs that can outsmart these tough worms.