Related Articles
This is the first in a series of four articles concerning parasite control. These articles are excerpted from Texas A&M University Agricultural Extension Service pamphlets. They have been converted to HTML files from .pdf format for the convenience and education of our readers.
Management Tips for Internal Parasite Control
in Sheep and Goats [pamphlet L-5092 (4-98)]

Frank Craddock, Rick Machen, and Tom Craig

The primary control strategy for internal parasites in sheep and goats has been the use of anthelmintics. One result of the apparent overuse of anthelmintics has been the development of resistant strains of gastrointestinal nematodes. The following management tips can be used by producers to help control internal parasites and prevent resistance from occurring.

1. Treat during mid-winter (December, January, February) before partu-rition to destroy hypobiotic (dormant stage) larvae in the host. Use anthelmintics (ivermectin, fenbendazole, albendazole, and oxfendazole) that are effective against hypobiotic larvae. This will greatly reduce pasture contamination in the spring.

2. Use fecal egg counts to determine if treatment is needed. After treatment, 7 to 10 days, use fecal egg counts to determine if drug was effective. There should be a 95 percent reduction in fecal egg count in order to consider the drug effective. Treat animals when warranted. Treat every animal.

3. Always rotate to uncontaminated or clean pastures if possible. The use of cultivated land is recommended to break life cycle of parasite. The longer native pasture can be rested the better.

4. Do not underdose. Sort animals according to size and determine dose according to weight of heaviest animal in the group, not an average body weight. Regularly check that dosing equipment is functioning properly to insure proper dosage. A slight overdose on smaller animals is generally not harmful due to the large margin of safety of most wormers.

5. Wait a minimum of 48 hours after treatment before turning animals onto an uncontaminated pasture.

6. Rotate dewormers on an annual basis or when a resistance develops.

7. Regardless of time of year, routinely treat new animals that are introduced into the flock.

8. When using dewormers, always follow labeled directions. Regardless of product choice, oral dosing is the recommended route of administration. Anthelmintics approved for use in sheep and/or goats are limited to ivermectin, levamisole and thi-abendazole. Extra-label use of other dewormers can be utilized if prescribed by a veterinarian.

9. If possible, select livestock that show resistance to parasitism.

Table 1.
Anthelmintics available to U.S. sheep and goat producers.
Many are not approved for use in small ruminants.
Class of Compound
Active Ingredient
Trade Name
Efficacy against
Haemonchus contortus
Other gastrointestinal nematodes
Ivomec ®
Valbazen ®
Safe-Guard ®
Panacur ®
Telmin ®
Synanthic ®Benzelmin ®
Anthelcide ®
Tramisol ®
Levasol ®
*These products are approved for use in sheep and/or goats.

Educational programs of the Texas Agricultural Extension Service are open to all people without regard to race, color, sex, disability, religion, age, or national origin.

Issued in furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of Congress of May 8, 1914, as amended, and June 30, 1914, in cooperation with the United States Department of Agriculture. Edward A. Hiler, Interim Director, Texas Agricultural Extension Service, The Texas A&M University System.

The information given herein is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Cooperative Extension Service is implied.

Frank Craddock, Professor and Extension Sheep and Goat Specialist, San Angelo;
Rick Machen, Assistant Professor and Extension Livestock Specialist, Uvalde;
Tom Craig, Professor, Department of Veterinary Pathobiology, College Station;
The Texas A&M University System.
Original .pdf version produced by Agricultural Communications, The Texas A&M University System


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