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Comparison of anthelmintic control programs for sheep in Virginia
A M Zajac1, C D Thatcher, D Notter
1Departments of Pathobiology, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg 24061-0442.
Journal of the American Veterinary Medical Association
|August 1, 1992
Summary
Four anthelmintic programs for sheep parasites, including ivermectin and levamisole, failed to provide satisfactory control. Relying solely on these drugs may not be the most effective or economical strategy for sheep producers.
Area of Science:
- Veterinary Parasitology
- Sheep Production
- Anthelmintic Resistance
Background:
- Haemonchus contortus poses a significant parasitic threat to sheep in southwestern Virginia.
- Effective control strategies are crucial for sheep health and economic viability.
Purpose of the Study:
- To evaluate the efficacy of four different anthelmintic control programs for grazing lambs.
- To determine the most effective program for managing Haemonchus contortus infections.
Main Methods:
- Four treatment groups were established: monthly subcutaneous ivermectin (TR), intermittent subcutaneous ivermectin (SI), intermittent oral levamisole (SL), and extended intermittent subcutaneous ivermectin (TA).
- Efficacy was assessed through fecal egg counts and serum pepsinogen concentrations.
- Lamb weight gain was also monitored.
Main Results:
- None of the four anthelmintic programs achieved satisfactory parasite control based on fecal egg counts and serum pepsinogen levels.
- Lambs in the TR group (monthly ivermectin) showed significantly greater weight gain compared to SI and TA groups.
- Clinical haemonchosis was observed in the TA group, necessitating additional treatment.
Conclusions:
- Anthelmintic treatments alone may not be sufficient for effective and economical control of Haemonchus contortus in grazing lambs.
- Integrated parasite management strategies should be considered to improve sheep health and productivity.