Coccidiosis—Coccidioidomycosis

Abstract

An error in terminology which recently occurred in this Journal again focuses attention on the confusion of coccidiosis and coccidioidomycosis. Coccidiosis refers to an infection by one of the animal parasites included under the Order Coccidia of the Class Sporozoa; coccidioidomycosis is an infection caused by the fungus Coccidioides immitis. Coccidia parasitize the epithelial cells of the intestines and livers of many hosts and are found in their feces. They are of considerable economic importance in poultry raising and other phases of animal industry. Coccidia commonly infect the intestines of chickens and other birds (Eimeria avium) , the livers of rabbits (Eimeria stiedae), the intestines of dogs and cats (Isospora bigemina), the intestines of cattle, guinea-pigs, mice, moles, and snakes. They have been claimed to infect the intestines and liver of man, but such infections as may occur in man are said to be very mild. Coccidioides is an etymological derivative of Coccidia. When Rixford and Gilchrist published their account of “Two Cases of Protozoan (Coccidioidal) Infection of the Skin and Other Organs” in 1896, they believed that the etiological agent was an animal parasite, a Sporozoon. They stated: “In order to emphasize the important analogies between our parasite and the coccidia, and at the same time indicate that we are not prepared at present to regard it as an unmistakable coccidium, we propose for it, in accordance with a suggestion of Dr. Stiles, the generic name Coccidioides, and we designate the species as Coccidioides immitis.” In 1900 Ophuls and Moffitt published the proof that the organism is a fungus and not an animal parasite. Five years later Ophuls stated: “As a name for the disease I should propose coccidioidal granuloma.” Unfortunately, no other valid name was proposed for the fungus so that now mycologists have generally accepted the designation Coccidioides, thereby insuring confusion with coccidia in perpetuity. Until Gifford and Dickson proved that so-called “San Joaquin” or “Valley Fever” was caused by C. immitis, coccidioidal granuloma was the only form of the infection which was recognized. When Dickson published his first paper on “Valley Fever” in 1937, he recognized the necessity of offering a name which would include those benign coccidioidal infections as well as the frequently fatal coccidioidal granuloma. His suggestion was “coccidioidomycosis.” While “coccidiosis” is a tempting abbreviation of this cumbersome word, it will be apparent from this historical review that it is entirely erroneous. We must all suffer for the errors of our fathers. One other error we should avoid is that of making coccidioidal granuloma synonymous with coccidioidomycosis.