The invention relates to the field of compositions useful for the prevention and treatment of coccidiosis in animals, methods of using such compositions and animal comestibles containing such compositions.
Coccidiosis is a disease caused by microscopic protozoal parasites called coccidia, belonging to the genus Eimeria. The infection in the host animals is initiated by ingestion, usually along with food, water, and/or fecal material, of Eimeria organisms in the sporulated oocyst stage. When the ingested oocysts enter the intestine, the infectious stage of the Eimeria soon develops from the oocysts and causes extensive damage to the inner walls of the intestine and the cecum or "intestinal pouch." Cecal coccidiosis in chickens, for example, is caused primarily by the organism E. tenella and results in the destruction of the cecal linings of the host.
A number of coccidiostatic agents are presently available for the prevention and/or treatment of coccidiosis. Still, many of these agents have certain shortcomings. Animals treated with some of the known coccidiostats sometimes show reduced feed efficiency and lower weight gains than normal. Moreover, the development of resistance to the more commonly used agents is becoming an increasingly significant problem; one which is becoming a limiting factor in successfully combating coccidiosis. Still other agents have very narrow safety and efficacy ranges with resulting toxicity risks for treated animals, as well as for other farm animals and man by virtue of incidental or accidental exposure or ingestion.
A napthoquinone antibiotic produced from Streptomyces roseofulvus, frenolicin B, has been shown to have some anticoccidial activity against E. tenella in chickens (Omura, et al., J. Antibiotics, Vol. 38, No. 10, pp. 1447-8 (1985)). Frenolicin B has recently been shown to be synergistic in combination with ionophoric anticoccidial antibiotics against which Eimeria field isolates had developed resistance due to the chronic usage of these agents to combat coccidiosis. See U.S. Pat. No. 4,839,382.