Parasite Resistance in Goats

Goats are funny animals. They can find the tiniest hole in the fence and show the entire herd how to get out - but they can't see the wide-open gate you're trying to get them to go through. They can pound on each other with their horns all day long - but get sick from eating the wrong kind of leaf. But perhaps one of the most stunning goat-paradoxes is how these comparatively large animals can get killed by a little worm that's smaller than the tip of a pin.

As the scientists refer to it, Haemonchus contortus, or the Barber Pole worm, is a parasite in goats and sheep that attaches to the walls of the stomach and sucks the nutrients from their blood. This lack of nutrition causes the animal to become anemic (which often leads to Bottle Jaw and eventual death).

Drug Resistant Parasites

So if you're like a lot of ranchers right now, you're thinking "AH - No big deal! I'll give them some wormer and they'll be good as new!" But here's the other side of that coin. Parasites, like the Haemonchus contortus, do not have static genetics. They are constantly changing and adapting to their environment. So, even though that wormer kills off most of the population, the one or two parasites that survive grow immune to the medicine. Then, as the population rebuilds from the survivors, a lot more worms have immunity to the drug.

People have been using modern Anthelmintics for over 50 years - and it's starting to show. According to Ray Kaplan, DVM, PhD, a professor at the University of Georgia, parasites that are common to cows, horses, sheep, and especially goats are becoming entirely immune to dewormers. There are already a lot of popular wormers on the market that, quite frankly, aren't worth much more than water for fighting parasites. This is why the agricultural market needs to start treating parasites differently.

Alternative Dewormers

Over the years, we've heard a lot of ideas for how to purge worms from a goat's system without drenching or injecting them with wormer. Some people absolutely swear by copple tablets, garlic, algae, and even tobacco. But none of these methods have really seemed to be as good advertised. Most of them have not performed well in scientific evaluations. Those that did, must be administered too regularly for commercial use (Although copper oxide wire particles did show promise for treating Barber Pole worms in goat kids). If you're interested in learning more about Alternative Deworming methods, check out this great article by the SCSRPC.

Another popular method for parasite management is pasture rotation. The idea behind pasture rotation is that, when parasite populations build up in one pasture (growing in the manure), the herd gets moved to the next 'clean' pen. Without hosts to feed on, the parasite populations in the first pasture die off. Using a system of three or four pens, this method can be quite effective - but it's a lot of work for commercial operations and it doesn't do anything to fix the problem. So here's what we're doing to combat worms - and I hope you will too!

Parasite Resistant Goats

In the same way that the parasites can grow resistant to dewormers, goats can grow resistant to parasites! But, just like the parasites, not all goats have the genetics for it. This is why culling is such a big deal! Whenever we see a goat that looks run-down or wormy, we immediately start thinking "Has that goat been wormy before? If so how recently?" Then we do a Famacha eye score to measure the parasite load of the animal. If they need to be wormed, we grab one of the few effective dewormers on the market and treat the animal. But if they have been wormy and run-down before (especially within the last two years), that animal has got a first-class ticket to the sale barn next time we go - whether or not she has nice babies, good conformation, or a pleasant personality.

By getting rid of the animals that are not parasite resistant, the genetics from the ones that are become more concentrated in the herd. As the years go by, the number of goats that need to be wormed/culled on the ranch plummets.

Most of our goats are wormed one to two times a year. If they need more than that on a regular basis, then we don't need them producing parasites for the other goats to pick up. Having goats that are completely parasite resistant is a pretty lofty goal - but it's one worth shooting for! If Dr. Kaplan is correct, traditional dewormers don't have many more years of effective use. Then ranchers are gonna have to make some tough decisions. I hope that parasite resistance in goats will become a more wide-spread goal before then. But if not, then maybe there will be enough savvy producers to supply the market with parasite resistant livestock.