Experimental coccidioidomycosis in hamsters. Disease kinetics and death curve in relation to infective dose.

Abstract

A study of experimental coccidioidomycosis in hamsters (Mesocricetus auratus) is presented. Two experiments were conducted on 75 animals inoculated intracardially with the mycelial form of Coccidioides immitis. The first research (experiment I) studied the kinetics of experimental disease in 15 hamsters inoculated with 300 C. immitis arthroconidia. The parameters studied were: (a) presence of macroscopic lesions in the brain, lungs, liver, spleen and kidneys; (b) microscopic identification of spherules in wet mount preparations of these specimens; (c) samples from all organs cultured at 37 degrees C on Sabouraud glucose agar; (d) blood cultures drawn every 24 h during the first week and subsequently every 48 h and (e) histopathological studies of all organs. The second experiment (experiment II) determined the relationship between the inoculum size and death curve in six groups of 10 animals each, which had received doses of 10, 50, 100, 150, 200 and 300 arthroconidia, respectively. On day 14 post-inoculation, all the animals underwent skin tests and 1 ml of blood was obtained by cardiac puncture to detect antibodies. Disseminated disease with persistent fungaemia developed in all the studied animals. Coccidioides immitis was recovered from all organs, with the lungs being the first to present disease. Death occurred in all groups, regardless of the dose of arthroconidia and 83.3% died between day 22 and day 28 post-infection. The use of this model is proposed for the biological standardization of antigens, the study of prophylactic measures and the "in vivo" evaluation of new antifungal treatments.