My grandmother used to say, “The devil is in the details.” I could not always follow the meaning of the old cliché spoken in her warning tone, but the phrase often fits the angst I feel when challenged with devising a deworming protocol for a flock of sheep. There is not a “one size fits all” protocol, but at least we can talk about a “one size fits most” template. Let’s start by compiling a synopsis of the current situation.
- Species, breed, age and average weight of animals
- Pregnancy status
- Type of parasites historically diagnosed
- Previous treatment, dewormer class or name
- Current worm burden in the flock
- Current worm burden in the pastures
- Management system (housing, pasture and stored feedstuffs)
Collect as much of the above data as possible. Treat groups according to their worm burden and the season, keeping in mind their age, weight and pregnancy status. Select a deworming program that fits each group being sure to adamantly follow withdrawal periods. Fasting for 12 to 24 hours is recommended prior to oral dosing of dewormers to decrease gastrointestinal (GI) transit time. Slowing down the GI tract provides two benefits: increases both the time available for absorption and the time the parasite is bathed in the product. Consecutive day dosing can also be of benefit; it creates a serial build-up of product in the parasite that can help with some resistance issues. Follow the labeled directions closely as both under-dosing and over-dosing can have unwanted side effects.
The following list of deworming products is not meant to be assertive or exclusionary. Omissions are likely, but not purposeful. Note that many of these products are also being manufactured under generic labels.
Benzimidazole Class (white dewormers)
Kills adults and many encysted larval stages
Fairly active against Moniezia tape worm
Consider consecutive day dosing
*some resistance exists
Albendazole (Valbazen) DO NOT use in pregnant ewes during the 1st trimester
Fenbendazole (Panacur, SafeGuard)
Oxfendazole (Synanthic)
Imidazothiazoles and Tetrahydropyrimidines (yellow dewormers)
Paralyses the adult worms and some larval stages on the surface in GI tract
Effective against lungworms
Not effective against encysted larva
Weigh animals to avoid overdose (narrower margin of safety)
*low to moderate resistance
Levamisole (Levasol, Tramisol, Prohibit)
Morantel (Rumatel)
Macrocyclic lactones (avermectins and milbemycins)
Extended time of efficacy (slow release from fat)
Effective against both internal and external parasites (sucking lice)
*resistance varies
Doramectin (Dectomax)
Ivermectin (Ivomec, Privermectin)
Moxidectin (Cydectin)
It is important to note that most of the deworming protocols used in small ruminants are considered “extra-label” by the FDA. Extra-labeled drug use (ELDU) is allowed exclusively by the order of a veterinarian. Always engage in a formal discussion concerning deworming with your veterinarian as you develop or change your program. Two University of Georgia veterinarians, Dr. Ray Kaplan and Dr. Lisa Williamson devised a couple of thorough and useful charts of dewormer dosages in sheep and goats that can help you get started. This blog will quickly become old news, but your program should not. Stay current and updated with the latest information. The American Consortium for Small Ruminant Parasite Control (ACSRPC) has a comprehensive website to keep you and your veterinarian current on product efficacy, dosage, administration, withdrawal times and resistance information.
About the Author
Dr. Colleen Lewis is a 1996 graduate of Kansas State University, College of Veterinary Medicine. Her career has taken her to many places as a practice owner, consultant, embryologist, and mentor. She enjoys mixed animal practice, teaching, traveling, farming and high school sports with her husband, Andrew and their three boys.
