Sheep, goats, & worms – Oh my!

By Emily Nogay, DVM

Skinny goat? Worms. Diarrhea? Worms. Pale eyelids? Worms. Gastrointestinal parasites often take the blame for any small ruminant that is looking ill. Many times, they are responsible; however, it is important to remember that parasites are a natural part of life, especially for animals that eat off the ground.

Although sheep and goats are susceptible to many types of gastrointestinal parasites, there is one that takes the cake – the barber pole worm or Haemonchus contortus. This worm lives inside the true stomach (abomasum) and attaches to the stomach lining to feed on the blood of the animal. This worm is common in all sheep and goats, and unfortunately, it is nearly impossible to eliminate. Large enough worm burdens can cause weight loss, diarrhea, anemia, localized edema (also known as “bottle jaw”), and subsequent death. Animals become infected when female worms pass eggs in the stomach, which are then deposited through manure onto pasture. Those eggs quickly become infective larvae, which are eaten when the ruminant grazes. Once ingested, the larvae later become adults in the true stomach to continue the cycle.

In the past, small ruminants were dewormed on a schedule to prevent disease and decreased production due to parasites. Unfortunately, over time, this practice created resistance of the worms to dewormers. This means that these nasty worms are very difficult to kill, causing many challenges for sheep and goat owners. Due to this widespread resistance, there have been many changes to how we deworm and prevent barber pole worm burden. It is incredibly important to adapt to these new changes, as there are currently no new deworming products being released. It is also important to understand that resistance patterns are complex, vary from farm to farm, and continue to evolve over time. It is vital to use stewardship when using any deworming product and to use a combination of methods for barber pole worm prevention, as just utilizing one or two methods usually is not enough.

First, it is important to understand that routine deworming in any sheep or goat is no longer recommended (including breeding, growing, and show animals). Deworming small ruminants is now always done on a selective basis. This process is known as saving the refugia. This method has been created to prevent the complete elimination of susceptible parasites. This allows worms that are still susceptible to dewormers to contribute to the next generation. If we continue to deworm animals regularly, that will quickly kill off those worms that are drug susceptible and leave only the resistant worms. Those resistant worms continue to reproduce, leading to large burdens of worms that are impossible to eliminate. Even routinely deworming a portion of your herd can lead to a heavy resistant worm population in the entire herd due to the life cycle of the worm. The goal is to keep drug-susceptible worms in the herd, which will reduce the number of drug-resistant worms. The more resistant worms within a herd, the less effective it is to treat animals with dewormer products.

This selective deworming process is done using the FAMACHA© scoring method. This process uses the color of the inner eyelid tissue to determine if the animal requires deworming. To obtain a FAMACHA score card and ensure you are performing the score correctly, complete the online or in-person certification, which can be found at wormx.info.

Most importantly, when choosing to deworm a sheep or goat, an oral product must be used. Injectable and pour-on products do not deliver enough of the active ingredients to the worms, making them ineffective. The use of these products will also allow for more resistance to arise, as the worms are introduced to a dewormer in a small amount. It is also very important to ensure the correct dose of the oral dewormer and to use the correct weight of the animal to prevent the perpetuation of more resistance. This is especially true in goats, as they require higher doses of dewormers due to their higher metabolism of these products. The American Consortium for Small Ruminant Parasite Control has created dewormer charts for each species, which include oral dewormers and their appropriate dose for that species.

It is also imperative that the dewormer being used is effective, which can only be determined through a fecal egg count reduction test. This test compares the number of eggs per gram of manure before deworming and 10-14 days after. To be effective, the dewormer must reduce the number of eggs by 90-95%. Whether a dewormer is effective depends on the worm population, which varies from farm to farm and can change over time. If no single product is effective on its own, then a combination deworming using more than one class of dewormer must be used to achieve that 90% reduction in egg count.

In addition to selective deworming, other practices must also be used for proper prevention of the barber pole worm. Rotational grazing is one practice that helps reduce the exposure of the animal to the infective larvae on pasture. This involves moving animals among pastures and returning them to a previously grazed area after waiting a certain amount of time, depending on land availability and forage quality.

Additional methods that can help decrease the burden of the barber pole worm are copper oxide wire particles and anti-parasitic plants. Copper boluses are designed to dissolve in the true stomach, where the copper wire particles are released and retained within the folds of the stomach, creating a hostile environment for the worms to live. These boluses must be used with caution, as they can cause the accumulation of copper over time, leading to copper toxicity, especially in sheep. Due to this possibility, it is recommended to only use copper oxide boluses on animals that require deworming (indicated by their FAMACHA© score).

Plants with high levels of condensed tannins have been shown to help decrease the barber pole worm burden in small ruminants. The plant with the most evidence of efficacy is the sericea lespedeza (Lespedeza cuneata L.) plant. Although other herbal dewormers have been proposed, only plants containing high levels of condensed tannins have been shown to be truly effective at decreasing worm burden.

Lastly, but certainly not least, Bioworma® or Livamol® with Bioworma are feed additives that contain a fungus that, once it is passed through the digestive system and deposited onto the pasture through the feces, it traps and feeds on the infective larvae of the barber pole worm. This helps to greatly reduce the number of infective larvae the animals are exposed to. When used appropriately, it can have reduction rates of 68-86% of larvae on pasture and is equally effective against resistant parasites! This product should be fed every day throughout the high-risk season (warmer months, >40°F); however, it has also been shown to have the same efficacy when fed every other day or 2 weeks per month. The Bioworma® product is made to be mixed directly with feed, while the Livamol® product is a protein supplement that has Bioworma® already mixed in and can be fed top-dressed on other feeds. The Livamol® product should be used with caution in males as the protein supplement can increase the risk of urinary stones.

Ultimately, proper barber pole worm management is crucial to ensure healthy and productive animals, as well as to prevent the development of resistance to current dewormers. It is imperative that dewormers are used judiciously on every animal and that a combination of practices is used for parasite management. It is important to discuss barber pole worm prevention and management with your veterinarian as each farm is different and requires individualized specifications. Additionally, consider other factors when discussing management practices, such as proper nutrition, multispecies grazing, genetic selection, dry lotting, and the periparturient egg rise. Managing the barber pole worm is challenging and constantly evolving. With animals that eat off the ground, gastrointestinal parasites are never going away, therefore we must learn to live with the ones we can kill rather than help create worms we cannot.