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Proper Use of Anthelmintics in Veterinary Practice: Guidelines and Best Practices
Proper use of anthelmintics is essential for achieving effective parasite control while minimizing the development of anthelmintic resistance. Incorrect dosing, improper administration, and overreliance on a single class of dewormers can reduce treatment efficacy and accelerate the emergence of drug-resistant helminths. Therefore, evidence-based deworming practices are critical for maintaining animal health and preserving the long-term effectiveness of available anthelmintics.
Anthelmintics are still an important part of parasite control. However, they must be used properly to ensure treatment effectiveness and slow the rate at which worms develop drug resistance. The body weights of sheep and lambs must be known or accurately estimated to calculate the correct dosage of medication. Underdosing results in the survival of worms that are resistant to the anthelmintic used.
Oral medications should be administered over the tongue. If the medication is deposited into the mouth, it may stimulate closure of the esophageal groove and bypass the rumen.
If an anthelmintic is absorbed more slowly in the gastrointestinal tract, drug levels are prolonged, and the treatment may be more effective. Thus, fasting sheep for up to 24 hours may improve the efficacy of dewormers, especially when using benzimidazoles and ivermectin. However, access to water should not be restricted.
Anthelmintics should be used strategically, and rotation between anthelmintic classes should be based on parasite control programs, efficacy testing, and local resistance patterns.
To prevent the introduction of drug-resistant worms, newly purchased animals should be dewormed with drugs from at least two of the three major anthelmintic classes. Moxidectin should be favored over ivermectin because of its superior potency.
Levamisole should probably be the other choice, as widespread resistance is believed to exist to the benzimidazole class of dewormers. After deworming, the animal(s) should be released onto a contaminated pasture to help dilute any “super-resistant” worms that may remain in their system.
Alternative Dewormers
There is increasing interest in using natural products as complementary approaches to conventional chemical parasite control.
Copper oxide particles have been shown to reduce barber’s pole worm infections in sheep.
Copper oxide is available as a dietary supplement for cattle to alleviate copper deficiency and has also been used in sheep for the same purpose.
