Effects of inhaled fine dust on lung tissue changes and antibody response induced by spores of opportunistic fungi in goats

Authors: Purdy, Charles; LAYTON, ROBERT - TEXAS TECH UNIV; STRAUS, DAVID - TEXAS TECH UNIV; AYERS, JON - UNIV. OF NEBRASKA

Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2007
Publication Date: 4/1/2008
Citation: Purdy, C.W., Layton, R.C., Straus, D.C., Ayers, J.R. 2008. Effects of inhaled fine dust on lung tissue changes and antibody response induced by spores of opportunistic fungi in goats. American Journal of Veterinary Research. 69(4):501-511.

Interpretive Summary: Fungal immunity and pathology induced by Mucor ramosissimus and Trichoderma viride following inhalation of fine dust in non-immunosuppressed ruminants is unknown. Previous studies indicated that Mucor and Trichoderma commonly found in feedyard dust were more pathogenic to the respiratory system of goats than five other genera of fungi, also found in feedyard dust. Recently, aerosol researchers have shown that fine dust particles (2.5 µm or less in diameter) are toxic when inhaled deep into the lung tissue. We found that fine dust initially appeared to exacerbate Mucor and Trichoderma pathogenesis; however, this effect was minimized upon repeated fine dust and fungal exposures. Both fungal genera induced similar precipitating antibodies. Trichoderma induced agglutinating antibodies; however, none were induced by Mucor. White blood cells and rectal body temperatures were significantly increased in fungal treated groups compared to negative controls. Mucor induced firmer lung consolidated lesions compared to those induced by Trichoderma. Spores were found in lymph nodes associated with the lungs of those goats treated with Trichoderma. Goats exposed to dust and fungi had significantly more spores per gram of lung lesion than non-dust fungal treated goats, implying that fine dust decreased part of their natural immunity. These findings are important to the clinician to better understand the immunity and pathogenesis induced by two common molds in non-immunosuppressed ruminants.

Technical Abstract: The objective of this study was to compare the immunity and pathology induced by spores of Mucor ramosissimus and Trichoderma viride given by intratracheal inoculation of goats following exposure to sterile fine dust aerosol. Thirty-six weanling Boer-Spanish goats were used. A prospective randomized controlled study was conducted. There were 4 fungal treatment groups (two with dust and two without dust treatments), a tent-saline-dust control group, and a pen-control group. Five of the treatment groups were exposed to sterilized fine (mean < 7.72 ±0.69SD µm in diameter) feedyard dust for 4 hours in a specially constructed tent. Goats in 4 treatment groups were then inoculated intratracheally with 30 mL of a fungal spore preparation, whereas saline tent control goats were intratracheally inoculated with 30 mL of physiological saline (0.9% NaCl) solution, and the pen control goats were not inoculated or treated with dust. Mucor produced severe lung consolidation in all tracheally inoculated goats, and Trichoderma produced a softer lung consolidation in inoculated goats. Similar precipitating antibodies were induced among fungus treated groups. Goats exposed to dust and fungal preparations had significantly more conidia per gram of lung lesion than non-dust fungal treated goats. In non-immunosuppressed goats, both Mucor ramosissimus and Trichoderma viride spores induced lung fibrosis with formation of multiple granulomas with Langhan’s type multinucleated giant cells; however, Mucor produced a more severe and consistent reaction. Endotoxin in the fine dust induced inflammation and appeared at first to cause a more severe reaction clinically, but no differences were observed later after multiple dust and fungal treatments.