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

A study of experimental coccidioidomycosis in hamsters (Mesocricetus auratu s) is presented. Two experiments were conducted on 75 animals inoculated in tracardially with the mycelial form of Coccidioides immitis. The first rese arch (experiment I) studied the kinetics of experimental disease in 15 hams ters inoculated with 300 C. immitis arthroconidia. The parameters studied w ere: (a) presence of macroscopic lesions in the brain, lungs, liver, spleen and kidneys; (b) microscopic identification of spherules in wet mount prep arations of these specimens; (c) samples from all organs cultured at 37 deg reesC on Sabouraud glucose agar; (d) blood cultures drawn every 24 h during the first week and subsequently every 48 h and (e) histopathological studi es of all organs. The second experiment (experiment II) determined the rela tionship between the inoculum size and death curve in six groups of 10 anim als each, which had received doses of 10, 50, 100, 150, 200 and 300 arthroc onidia, respectively. On day 14 post-inoculation, all the animals underwent skin tests and 1 mi of blood was obtained by cardiac puncture to detect an tibodies. Disseminated disease with persistent fungaemia developed in all t he studied animals. Coccidioides immitis was recovered from all organs, wit h the lungs being the first to present disease. Death occurred in all group s, regardless of the dose of arthroconidia and 83.3% died between day 22 an d day 28 post-infection. The use of this model is proposed for the biologic al standardization of antigens, the study of prophylactic measures and the "in vivo" evaluation of new antifungal treatments.