5-Deazariboflavin, its phosphate ester and non-toxic salts thereof and its novel bis(loweralkoxymethylene) derivatives have antiprotozoal and antiparasitic activity. They are particularly useful for controlling cecal and/or intestinal coccidiosis when administered in minor quantities to animals, in particular to poultry, usually in admixture with animal sustenance. The compounds are included in compositions useful for the prevention and treatment of coccidiosis in poultry.