A big part of my job is speaking at various meetings around the state. On average, I’ll have one or two speaking engagement per week. Parasites control is undoubtedly the most common topic that is requested. In this article, I will discuss the barber pole worm and methods to prevent it from negatively affecting your livestock.
If you own sheep or goats, you also have parasites. It is a fact! Eradication of internal parasites is not possible. The goal for farmers and ranchers is to keep the parasite load low enough that animal health is not compromised.
Before, we get too deep into parasite control strategies, it is important to know what parasite we are dealing with and how to recognize it’s a problem. The barber pole worm (H. Contortus) is the most damaging internal parasite to sheep and goats. It feeds on blood and causes anemia (low red blood cells), which leads to weight loss, depression, weakness, and could result in death. The most telling signs of this worm are bottle jaw (swelling under the jaw) and paleness of eyes and gums. The best method to properly diagnose the barber pole worm is to conduct a fecal egg count test. This test can be done by the farmer/rancher if they have the proper equipment or can be done by a veterinarian.
Often the barber pole worm is misdiagnosed. It does not typically cause diarrhea. Parasites that most often cause diarrhea are coccidia and the brown stomach worm. And the barber pole worm is not visible to the naked eye in the feces. Tapeworms are visible in the feces but they are not a major animal health concern.
To manage for the barber pole worm, it is important to understand its lifecycle. The majority of the time, the worm lives in the abomasum of the animal and feeds on blood. It then produces eggs that shed out of the animal in the feces. When temperatures are ideal (70 to 90 degrees Fahrenheit) the egg will rapidly hatch in the fecal pellet and develop into infective larva. It takes about a week for this to occur, depending on temperature. Rain or heavy dew is needed to help the larva move from the fecal pellet onto grass leaves. The cycle is completed when an animal eats the larva while grazing grass. As such, the barber pole worm is a major problem during periods of high rainfall in the spring and summer.
Larva can live on pasture for 3 to 6 months, depending on temperature. Once a sheep or goat consumes an infective larva, it takes 2 to 3 weeks before it develops into a blood-feeding, egg-producing worm. However, the parasite can remain in the animal without feeding on blood (hypobiosis) and wait until the animals defense system weakens to begin feeding on blood. This typically occurs after the animal gives birth.
The best defense against barber pole worm is the animal itself. Sheep and goats have the ability to defend themselves against the worm. Some animals are better at defending themselves than are others. Sheep tend to have a better defense system than goats. The animal’s immune system will build antibodies that will expel the worms or suppress them from feeding on blood. To defend themselves against the worms, they need a good quality diet to supply enough protein to build the antibodies. Lactating females are more susceptible to parasites because most often their bodily demands for protein exceed the dietary supply, which leaves them short on protein to produce antibodies to fight off parasites. In addition, young growing animals are susceptible because they too could have a deficiency in protein supply, plus it takes a couple weeks from the time a young animal is exposed to parasites until it is able to develop antibodies. Similar to how vaccinations work.
In some cases, parasites build up in the animals during periods of high rainfall; however, signs of parasitism are not seen because diet quality is high and the animal can fend off the parasites. But, when it stops raining, pasture quality drops, and temperatures heat up, and the animals will begin to show signs of parasitism.
Like all disease management, Prevention is the Best Medicine.
Body Condition: Maintaining the flock/herd in good body condition (not too fat or too thin) helps to keep the parasite load in the animals low, which in turn keeps parasite load on the pasture low. Low body condition females during lactation will have 2 to 3 times higher fecal egg counts than high body condition score females.
Pasture Management: The best method to breed for internal parasites is high stocking rate on continuously grazed pasture. Conversely, lower stocking rates and pasture rotation help to keep parasites in check. Ideally, rotate to new pastures weekly during parasite season (spring/summer) and don’t return to the same pasture for 6 months or longer; however this is often impractical for range operations. Nonetheless, monthly or quarterly pasture rotations will help to keep parasite load low.
Lambing/Kidding Season: Lambing sheep or kidding goats in the fall or winter helps to reduce risk of parasitism. This is due to fact that the barber pole worm does not efficiently complete its lifecycle outside the animal during cooler weather. If the animals carry a high load of parasite into the winter, they still can be affected by parasites. Especially, if the animals are short on feed in the pasture.
Multi-Species Grazing: The parasites that affect small ruminants (sheep, goats, and deer) are shared among each species. However, the parasites that affect small ruminants don’t have as large an impact on cattle and horses. Multiple species grazing within a pasture or in a pasture rotation helps to reduce the amount of parasites on the pasture.
Genetics: Sheep and goats can be resistant or resilient to parasitism. Resistance is when the animals keep parasites from feeding and shed lower amounts of eggs. Resilient is when animals don’t inhibit parasites but are able to cope with higher parasite load before animal health is compromised. Parasite resistance in sheep and goats is a highly heritable trait; whereas, parasite resilence is a lowly heritable trait. The breeds of sheep that are known for parasite resistance were developed in the tropical regions; most notably the St. Croix, Florida Native, and Barbado Blackbelly. These breeds have been used to develop composite breeds that carry these traits, such as the Katahdin and Royal White. Dorpers are known for being more resilient to parasites. Recently, breeders have used the National Sheep Improvement Program to develop estimated breeding values (EBVs) for parasite resistance. The Katahdin breed has used this technology more than any other breed. The top 10% of the Katahdin breed selected for parasite resistance have a 70% reduction in parasite load. To learn more, there will be an educational session and ram sale regarding this technology at the Texas Sheep and Goat Expo on August 18th/19th.
In summary, parasite control is a complicated segment of flock/herd health. I only scratched the surface of parasitology within small ruminants; and, I did not even get to proper use of drenches. In the coming months, I’ll write about the different dewormers available, strategic drenching, and natural dewormers. But always keep in mind that parasites should be managed using multiple control strategies applicable to your operation.
For more information or to provide feedback on this article, I can be reached at firstname.lastname@example.org or 325-653-4576.