What is an effective treatment for clinical coccidiosis in cattle?

Amprolium is effective for treating clinical coccidiosis in cattle because it specifically targets the coccidia protozoa responsible for the disease. It works by inhibiting thiamine utilization in the parasites, which ultimately leads to their death. This mechanism is particularly effective against Eimeria species, which are the most common causative agents of coccidiosis in cattle.

Other options listed, while they may be used to treat various parasitic infections, do not have the specific activity needed to target the coccidia causing clinical coccidiosis. Levamisole, for example, is primarily effective against gastrointestinal nematodes and is not effective against coccidia. Ivermectin is a broad-spectrum antiparasitic that targets external parasites and some internal worms, but not coccidia. Praziquantel is used to treat certain types of cestodes (tapeworms) and does not affect coccidia either. Therefore, Amprolium remains the most appropriate choice for treating coccidiosis in cattle.