Managing parasite infections in small ruminants

Warm seasons are an excellent time for livestock to roam outdoors and munch on the wild vegetation, yet with grazing comes the risk of ingesting parasites.

Because small ruminants like sheep and goats are most at risk for parasites during grazing seasons, Dr. Isabelle Louge, a clinical assistant professor at the Texas A&M School of Veterinary Medicine & Biomedical Sciences, recommends owners familiarize themselves with parasite testing, treatment, and preventative measures ahead of the fall grazing season.

How to recognize and test for parasite infections

First, owners should be aware of one of the most common parasites that affects small ruminants who graze — haemonchus contortus.

“Also known as the barber pole worm, this parasite lodges itself in the walls of a ruminant’s stomach and drains their blood, leading to fatal issues like anemia and low protein,” Louge explained. “Animals that have heavy infections are often thin, pale, and possibly swollen under the jaw.”

The FAMACHA scoring system is a typical method to test for signs of haemonchus infections and to determine which sheep or goats require deworming, but individuals who are not veterinarians must be certified before receiving a FAMACHA card and using the test.

“The system compares the color of the mucous membranes in an animal’s eyelids to the FAMACHA card to determine how anemic the animal is likely to be,” Louge said. “The test is only accurate when an official FAMACHA card is used, and while it is not a perfect test, it can be an important way to screen animals that most need deworming and help owners monitor their flocks and herds for problems.”

Other parasites can affect sheep and goats as well; general symptoms include weight loss, poor hair coat condition, and itchiness. If owners suspect their herd or flock has a parasite infection, including a haemonchus infection, Louge encourages them to visit their veterinarian for more thorough testing.

“Since untreated parasites can lead to death, it is important to reach out to a veterinarian who can test your animals for parasites, confirm which parasites are the problem, and help you develop a plan to address them,” Louge said. “There are many techniques veterinarians will use to investigate parasite problems, but perhaps the most important test is the fecal egg count, which screens the manure of an animal for parasite eggs.”

Treating and preventing parasite infections

Once ruminants are confirmed to have parasites, owners should continue to work with their veterinarian to begin the treatment process. Louge pointed out, however, that medications used to treat parasites in small ruminants are becoming less effective over time because of their overuse.

“People are often tempted to treat an entire herd or flock of animals for parasites at once to reduce their worm burden but because it is impossible to get rid of all parasites, this leaves parasites that are the most resistant to the medications,” Louge explained. “The remaining parasites will reestablish the parasite population, which will now be even more resistant to the medications, launching farms into a spiral of worsening parasite problems with nothing that seems to work for treatment.”

One way to both treat parasite infections and slow the development of medication resistance is to only deworm the animals that need the treatment, making worm burdens manageable.

“To select which animals should be dewormed, owners should consider several factors: their body condition in terms of how thin or fat they are because thin animals are more likely to have a higher parasite burden; their age, since very young and very old animals are more susceptible to parasites; how pale they are using the FAMACHA system; and if they are pregnant or sick, which can make them more susceptible to parasites as well,” Louge said.

Veterinarians will also help owners slow medication resistance by determining which medication should be used based on what parasites are present and which dosage should be given, since sheep and goats differ substantially in how much they require, according to Louge.

Another way to protect small ruminants from parasites is by implementing prevention strategies.

“All flocks and herds need a parasite management plan, which should, ideally, include prevention strategies,” Louge said. “Examples include feeding animals in troughs and feeders that are designed to prevent manure from falling into them; ensuring there aren't too many animals on a piece of land, which can concentrate parasites and increase worm burdens; and using targeted, selective treatments for the animals that need them.”

Even though grazing may be a routine activity for your goats and sheep, you don’t want parasite infections to become a deadly issue in your flock or herd. By learning to recognize infection symptoms and consulting your veterinarian about treatment and prevention steps, you can help keep your small ruminants healthy as they graze.

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Pet Talk is a service of the School of Veterinary Medicine & Biomedical Sciences, Texas A&M University. Stories can be viewed on the web at vetmed.tamu.edu/news/pet-talk. Suggestions for future topics may be directed to vmbs-editor@tamu.edu.