Combating Internal Parasites

LU Research: Controlling Internal Parasites in Small Ruminants

THROUGHOUT OKLAHOMA AND AROUND THE WORLD, GOAT AND SHEEP PRODUCERS

FACE A SEVERE PROBLEM. YEAR IN AND YEAR OUT, GASTROINTESTINAL NEMATODES

— OR ROUNDWORMS — CAUSE SERIOUS HEALTH PROBLEMS FOR ANIMALS AND SIGNIFI

CANT ECONOMIC LOSSES FOR SMALL RUMINANT PRODUCERS.

The National Animal Health Monitoring System of the USDA Animal and Plant Health Inspection Service reported that in 2015 more than 86,700 goats died due to internal parasites — one in four of all deaths not caused by predators. Oklahoma ranked second nationally in nonpredator-caused goat and kid losses, with over 31,000 deaths resulting in financial losses of $4.8 million.

Among the major nematode parasites in goats and sheep, the blood feeder Haemonchus contortus, or barber pole worm, is the most pathogenic. This prolific blood-sucking roundworm is called the barber pole worm due to its appearance, with its white reproductive tract visibly wrapping around its blood-filled digestive tract. The parasite lives in the ruminant’s abomasum, or fourth stomach. In a single day, a worm can lay thousands of eggs, which embed in the animal’s feces and, once excreted, mature into infective larvae that contaminate pastures where herds graze and ingest the larvae. Unchecked, this cycle can lead to high levels of infestation. A single host animal can have thousands of these worms in its gastrointestinal tract, each one piercing the lining to consume blood. For the host animal, the outcomes are anemia, failure to thrive, and even death. For the farmer, the result is loss of productivity and income.

PROBLEMS WITH CHEMICAL DEWORMERS

To kill internal parasites, producers typically use chemical dewormers, technically called anthelmintics. But these chemical remedies face two of their own problems. On the one hand, roundworms have become resistant to the chemicals – in as little as three years in the case of one dewormer. On the other, markets have evolved, and increasing numbers of consumers demand organically grown foods. For small ruminant animals to qualify as organic, the methods used to control parasites must follow the regulations set out by the USDA’s National Organic Program.

Faced with this situation, a number of scientists are seeking to develop alternatives to chemical dewormers. Dr. Zaisen Wang of Langston University is one of them. He and visiting research scientist Dr. Jessica Quijada, in collaboration with AZ Nature Art LLC of San Diego, a biotech company engaged in natural product sourcing, collection, extraction, purification, and manufacturing, are exploring alternative approaches to controlling the barber pole worm in sheep and goats.

NEW WAYS TO CONTROL OLD PARASITES

Wang and Quijada are investigating a number of parasite control approaches

“Historically, these plants have been used for deworming … but we hope to improve their efficacy, and initial results from some plant compounds are positive.”

— DR. ZAISEN WANG

Drs. Jessica Quijada and Zaisen Wang check cultured infective larvae of the barber pole worm.

that can be described as indirect, that is, enhancing the animals’ resistance to the barber pole worm. First, they are studying how nutrition can enhance resistance. “Protein supplementation can enhance immunity in goats, for example, and we are conducting experiments on the efficacy of various protein types,” Wang said. The second focus of their research is on the host animal’s immune system. Small ruminants’ immune systems respond in various ways to parasite infection, and the immune systems of some breeds of goat and sheep are more parasite-resistant than others. The team is working to better understand the mechanisms of immunity, for example by identifying the immune cell types with the highest immunity to the barber pole worm, and to manipulate specific immune system pathways that best enhance the host’s protective resistance.

Another approach focuses on direct attacks on the actual parasites. Wang and Quijada are exploring and testing natural anthelmintics derived from plants, including several Chinese medicinal herbs, such as Rheum officinale, Cortex meliae, Melia azedarach, and Quisqualis indica, as well as garlic and ginger roots. “Historically, these plants have been used for deworming both people and livestock,” Wang said, “but we hope to improve their efficacy, and initial results from some plant compounds are positive. At the same time, we are also looking for new plants that will provide even stronger protection.”

With support from the USDA, Wang’s project is integrating the strengths of animal nutrition, herbal medicine, parasitology, immunology, and molecular technology with the aim of helping small ruminants and the producers who raise them.

For more information, please contact Dr. Zaisen Wang, wzaisen@langston.edu.