Pathogenesis of indoor fungal diseases*

Mold growth within homes and other buildings has been associated to varying degrees with human health problems. These problems vary from allergenic disease to toxicosis. Case definitions for mold exposure have not been adequately defined to allow for a pathognomonic diagnosis of mold-caused disease following indoor exposure. Some important factors that may contribute to the pathogenesis of indoor mold induced disease include beta (1,3)-D-glucans, outer cell wall fungal hydrophobins, 1,8-dihydroxynaphthalene melanin, fungal volatile organic compounds, mycotoxins, and stachylysin. The information in this contribution was presented as the ISHAM Presidential address as a means to clarify some of the confusing surrounding indoor mold-related health issues.

Stachybotrys, a mycotoxin-producing fungus of increasing toxicologic importance

BACKGROUND

Stachybotrys as a fungus has been implicated as a source of mycotoxins. While the toxicity of several well-known mycotoxins (aflatoxins) is well documented, recent studies on Stachybotrys have raised the question that mycotoxins produced by this fungus may be responsible for the health effects of occupants in water-damaged buildings.

METHODS

Published articles regarding Stachybotrys-related mycotoxins were reviewed with particular focus on human toxicity.

RESULTS

A critical review of papers, reports, and studies on Stachybotrys mycotoxins revealed only descriptive reports of suspected animal and human poisoning secondary to consumption of mold-contaminated food products. No studies of good toxicologic and epidemiologic designs answer whether airborne mycotoxins produced by Stachybotrys could produce specific human toxicity.

CONCLUSIONS

Current data on the toxicology of mycotoxins produced by Stachybotrys demonstrate that this group of mycotoxins is capable of producing immunosuppression and inflammatory insults to gastrointestinal and pulmonary systems. Case control study and case reports have suggested a possible association with environmental exposure to Stachybotrys mycotoxins, although a firm causal relationship has not been firmly established. Additional studies are needed to document that humans with sufficient exposure to these mycotoxins develop compatible clinical and pathologic pictures as demonstrated in animal models.

Differentiation of lesions caused by mycotoxin T-2 from autolytic morphologic change in CD-1 mice

Experiments with topically applied T-2 trichothecene mycotoxin were undertaken to determine whether lesions caused by this toxin could be differentiated from autolysis. Two pathologists, who had previously seen lesions caused by T-2 toxin, graded lesions without knowledge of treatment group and stated whether the animal had received the toxin or not. Both pathologists differentiated T-2 toxin-treated mice up to 6 h post-mortem. Failure to distinguish between treated and control mice resulted in false-negative diagnoses only. It was concluded that the diagnosis of trichothecene mycotoxicosis would probably be missed more than 6 h post-mortem.