Tilletia tritici/Ustilago
Summary
Tilletia spp. (smuts) and Ustilago spp. (bunts) are common molds of the Class Ustilaginomycetes, mostly found in cereal crops and soil. They are well known plant pathogens which may have a role in the sensitization of allergic patients. The particles causing sensitization are spores found in the environment.
Smuts may be involved in the development of asthma and hypersensitivity pneumonitis. Cross reactivity with other molds within the Phylum Basidiomycota may occur.
Epidemiology
Worldwide distribution
There is a distinct lack of specific reports of allergic disease attributed to Tilletia spp. and Ustilago spp.; however, their involvement in developing symptoms of asthma was demonstrated in Australian studies. Smut species were also the cause of allergic disease in Japan and Northern America.
Risk factors
Some occupations (e.g. farmers) may be at higher risk of allergic respiratory conditions when exposed to smuts, given the prevalence of these species (Tilletia/Ustilago) as cereal pathogens.
Route Of Exposure
Main
Inhalation of spores.
Clinical Relevance
Asthma
In a study of 2,098 children who received treatment in hospital for asthma, it was shown that in the age group 14–18 there was a significant association between the presence of environmental Ustilago spores and hospitalization. People with asthma could show higher inflammation and lower lung function when exposed to Ustilago smuts.
Other diseases
Ustilago esculenta has been reported as a cause of hypersensitivity pneumonitis (HP) in a 40-year old patient with symptoms of cough, fever and dyspnea. In another study into the development of HP in farmers who experienced respiratory symptoms, 11.2% of positive results (SPTs or RAST assays) were associated with grain smuts extracts.
Diagnostics
Main methods
Burkard Volumetric Spore Trap.
Measures
The concentration of Ustilago spores detected daily was normally less than 1,000 per, though a peak of nearly 6,000 per was also recorded.
The presence of allergen-specific antibodies is usually determined by skin prick tests (SPTs) and serology for IgE. In a study investigating skin test reactions of allergic patients to lesser reported fungi, 56% showed a positive dermal reactivity to fungal extracts, including Ustilago maydis. In another study of U. maydis extracts in 200 patients with either asthma or allergic rhinitis, asthmatic patients were more likely to have immediate skin reactions on SPT, whereas the patients with rhinitis were more likely to have late phase sensitivity.
Prevention And Therapy
Allergen immunotherapy
Immunotherapy is currently not recommended for patients allergic to molds, due to complexities of the allergens and patient co-allergies.
Prevention strategies
Avoidance is difficult to achieve, due to the wide range of environments in which Tilletia spp. and Ustilago spp. can be found.
Cross-Reactivity
An extract of Ustilago maydis showed cross-reactivity with Cryptococcus neoformans, suggesting that some Basidiomycetes may share antigens.
References
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