In agriculture Fusarium is known to cause diseases of many economically important crop plants. Some species are known to colonize stored cereal grains not only causing losses but also producing mycotoxins such as trichothecenes, zearalenone, and fumonisins that are harmful to humans and animals(1, 3).

In the medical field, the species cause opportunistic infections of human eyes, skin or nails and may also cause systemic infections in individuals with weak immune system. The most important species as far as human infection is concerned are Fusarium solani, F. moniliforme (=Fusarium verticilloides), F. oxysporum and F. dimerum (1, 3). Fusarium solani is also allergenic and is occasionally found in indoor environments. It affects 4% of nasobronchial allergy patients (4).

Some of the infections attributed to some species of Fusarium are:

• Fusarium keratitis
• Onychomycosis (nail infection)
• Certain skin infections
• Fusarium osteomyelitis (bone and joint infections)
• Pneumonia

In the industrial environment, Fusarium species are known to contaminate industrial products such as pharmaceutical solutions or machine cooling fluids. Fusarium keratitis has been in the news as the cause of severe fungal eye infections through contamination of contact lens solution.

Sampling for Airborne Spores of Fusarium Species

Fusarium species do not grow well at low water activity levels and will usually colonize very damp or wet material, hence, presence of Fusarium in a building is an indication of a water problem. Fusarium may produce three types of spores: namely, macroconidia, microconidia, and chlamydospores (3).

The macro and microconidia are the most likely to become airborne, but since they are produced in wet form they do not easily become aerosolized unless the mould is completely dry. Indoor airborne spore counts for Fusarium are therefore rarely high. A few spores of this fungus indoors could be an indication of serious mould growth.

Airborne microconidia and chlamydospores are difficult to identify and for air samples analysed by direct microscopy, only the macroconidia of some species may be reported. It is therefore possible that Fusariumspores (especially the microconidia) are usually lumped together with other unidentified spores.

For viable samples it is important to note that desiccation affects viability of Fusarium spores and therefore a few colony forming units (CFUs) would also be an indication of a problem.

According to Health Canada, persistent presence of significant numbers of Fusarium species and other toxigenic moulds such as Stachybotrys chartarum, Aspergillus and Penicillium requires further investigation (2).

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References

1. Guarro, J., and J. Gene. 1992. Fusarium infections. Criteria for the identification of the responsible species. Mycoses 35:109-114
2. Health Canada (1995). Indoor Air Quality in Office Buildings: A Technical Guide. A Report of the Federal-Provincial Advisory Committee on Environmental and Occupational Health.
3. Nelson, P.E., Dignani, C.M., and Anaissie, E.J (1994). Taxonomy, Biology, and Clinical Aspects of Fusarium Species. Clinical Microbiology Reviews, 7(4): 479-504.
4. Verma J, Sridhara S, Singh BP, Pasha S, Gangal SV, Arora N. (2001). Fusarium solani major allergen peptide IV-1 binds IgE but does not release histamine. Clin. Exp Allergy, 31(6):920-927.