Coccidiosis of the Chicken

*'IT IS PROBABLE that coccidia cause greater economic loss among domesticated animals of the temperate zone than any other group of protozoa." Thus Becker ^ aptly indicated the importance of coccidiosis, the specific disease caused by these protozoan parasites. It may be added that the coccidia probably cause greater economic loss among chickens alone than among all other domesticated animals combined, despite the fact that coccidiosis occurs frequently in severe outbreaks among other domesticated fowl, cattle, and sheep and occasionally among goats, pigs and dogs. Because of the ¡preponderant significance of the disease in chickens, this article is confined to a description of the coccidia and coccidiosis of these birds. However, the ]ife histories of the parasites, the nature of the disease, and the principles of control are essentially similar for all domesticated and semidomesticated fowl, and the information given therefore applies in general also to coccidiosis of the duck, goose, guinea fowl, pheasant, pigeon, quail, and turkey, all of which harbor characteristic kinds or species of coccidia.