150 INFECTIONS CAUSED BY MOLDS 



Taxonomy. In the method of endospomlation exhibited in the 

 parasitic growth phase of Coccidiodes immitis the resemblance to 

 the Zygomycetes is so great that it seems reasonable to identify the 

 mature Coccidioides cell as a sporangium and its endospores as spo- 

 rangiospores. Baker and his coworkers^ reported that small spo- 

 rangia are produced in culture by some strains, but this phenomenon 

 is not often observed. The hyphae which normally develop in culture 

 are richly septate, a condition which is rare among the Zygomycetes, 

 but in rate of growth and in the general aspect of cultures there is a 

 resemblance. It is true that the sporangium formed in tissue is not 

 associated with a mycelium and that there is no columella, but the 

 sporangia of many of the Zygomycetes (e.g., Mortierella and Syn- 

 cephalis) present so many anomalies that Coccidioides may well find 

 a place within the group. 



Geographical Distribution. Contrary to the earlier belief that the 

 disease was limited to the Chaco region of Argentina and to the San 

 Joaquin Valley of California, it is now recognized that it occurs 

 throughout the arid Southv/est in southern California, Arizona, and 

 New Mexico, and western Texas. The migration of infected persons 

 from these areas has not established recognized new endemic foci. 

 The cases which have been observed in other parts of the United 

 States, Italy, and elsewhere, are probably in persons who were in- 

 fected in the Southwest and developed the disease after an incubation 

 period, or who were infected from dusty fruit, packing material, or 

 similar sources originating in an endemic focus. 



Natural Habitat. Coccidioidomycosis is not transmitted from one 

 person directly to another. It is evident therefore that the fungus 

 grows in some habitat outside the human host. The primary lesions, 

 with few exceptions, are in the lungs and they follow inhalation of 

 spores of the fungus. Epidemiological evidence and study of case 

 histories indicate that the spores of the fungus are wind-blown. In- 

 fections follow exposure to dust storms and appear in agricultural 

 workers and others exposed to wind-blown soil. Most primary in- 

 fections occur in the summer and fall and few are seen during the 

 rainy season. It has been assumed, therefore, that the fungus grows 

 in soil during or following the rainy season and that spores mature 

 and are disseminated during the dry season. The fungus has, in fact, 

 been isolated directly from soil, first near Delano, California, at a 

 ranch house occupied by men who had coccidioidomycosis; second 

 in Panoche Valley, California, near a burrow from which a group of 

 university students (who subsequently developed coccidioidomy- 

 cosis) dug a rattlesnake; and third, from five soil samples taken from 



