Experimental Zygomycosis Due to Rhizopus spp. Infection by Various Routes in Guinea‐Pigs, Rats and Mice

Summary:  Streptozotocin‐diabetes was induced in Swiss mice and in Wistar rats. Hematological examination was performed before streptozotocin was administered, and for 5 weeks afterwards. Leukocytosis was present in all animals. Severe diabetes was found, and it persisted during the 13‐week follow‐up period. Serum glucose levels were controlled weekly. Nondiabetic animals infected by inhalation or by intranasal instillation with Rhizopus microsporus var. rhizopodiformis remained negative as well as diabetic animals infected by inhalation. In the intranasally instilled mice and rats, 33% and 67% respectively contracted severe zygomycosis. Non‐compromised guinea‐pigs and mice were infected intravenously or intraperitoneally with Rhizopus microsporus var. rhizopodiformis or Rh. oryzae. The guinea‐pig infected with small inocula was more sensitive than the mouse, and developed fatal zygomycosis with invasion of almost all organs and production of erythematous ulcerative skin eruptions. Fatal disease was also obtained in mice infected intravenously, but not intraperitoneally. Anatomopathology of the various organs and lesions revealed profuse invasion of various organs including brain, lungs, blood vessels, etc. Large coenocytic hyphae were present. In the lungs and the spleen of the guinea‐pig and in the pelvic cavity of the mouse, various forms of large vesicles and sporangium‐like elements were observed. The hyphae were in general distorted, broad, irregular and rarely septated. The infection of guinea‐pigs with Rhizopus spp. is proposed as a model for the study of the infection. It presents all aspects of zygomycosis that may occur in man and animals, especially in compromised or largely exposed individuals.