There is anecdotal information that amprolium is not effective in goats. In 2011, researchers from North Carolina State University conducted an on-farm study to evaluate the efficacy of two different doses of amprolium (Corid®) in goats heavily infected with pathogenic Eimeria species.
Forty Boer goat kids (3-5 months old) with naturally occurring coccidiosis were randomly divided into two groups and treated orally with amprolium doses of either 10 mg/kg daily for 5 days (n=20) or 50 mg/kg daily for 5 days (n=20). E. christenseni was the most frequently identified coccidia species in a pooled fecal sample (52%).
Oocyst per gram concentrations were significantly reduced on day 7 in the kids that received amprolium at 50 mg/kg, but not in the kids that received 10 mg/kg. The owner of the goats reported an improvement in clinical signs in the kids receiving the higher dose, whereas many of the lower-dose goats still had abnormal manure, rough hair coats, and reduced appetite.
Clinical signs improved in the low dose group only after they were re-treated with amprolium at the higher dose. No signs of polioencephalomalacia were observed in any of the goats. Amprolium was determined to be effective at reducing fecal shedding of Eimeria oocysts, when given for five days at a rate of 50 mg/kg.
Amprolium (Corid®) is not FDA-approved to treat coccidiosis in small ruminants. It requires extra-label drug use and a veterinarian-client-patient relationship (VCPR). Higher doses of amprolium have been associated with polioencephalomalacia.
Source: Short Communication, Veterinary Parasitology, 2011. Read abstract.