Virulence of fungal spores determined by tracheal inoculation of goats following inhalation of aerosolized sterile feedyard dust

Abstract

Objective - To compare the virulence of spores of 7 fungi by tracheal inoculation of goats following exposure of goats to an aerosol of sterilized feedyard dust. Animals - 54 weanling Boer-Spanish goats. Procedure - A prospective randomized controlled study was conducted. There were 7 fungal treatment groups, a tent control group, and a pen control group (n = 6 goats/group). Goats in the 7 treatment and tent control groups were exposed to autoclaved aerosolized feedyard dust for 4 hours in a specially constructed tent. Goats in the 7 treatment groups were then inoculated intratracheally with 30 mL of a fungal spore preparation, whereas tent control goats were intratracheally inoculated with 30 mL of physiologic saline (0.9% NaCl) solution. These treatments were repeated each week for 6 weeks. Results - Severity of pathologic changes differed significantly among the 7 fungal treatment groups as determined on the basis of gross atelectatic and consolidated lung lesions and histologic lesions of the lungs. Descending order for severity of lesions was Mucor ramosissimus, Trichoderma viride, Chaetomium globosum, Stachybotrys chartarum, Aspergillus fumigatus, Penicillium chrysogenum, and Monotospora lanuginosa. Trichoderma viride spores were the most invasive and were isolated from the bronchial lymph nodes and thoracic fluid of all 6 goats administered this organism. Spores were observed-histologically in lung tissues harvested 72 hours after inoculation from all treatment groups. Conclusions and clinical relevance - 4 of 7 fungal spore types induced significantly larger lung lesions, compared with those induced by the other 3 spore types or those evident in control goats.