SN4 SHORT NOTE 5M ★ High-yield

Describe the mycotoxins and fungal allergy with their importance and prevention.

Microbiology · 2nd Professional — Para-Clinical

Mycotoxins

Mycotoxins are toxic secondary metabolites produced by fungi growing on food and feed. The resulting illness is a mycotoxicosis — an intoxication, not an infection, so it is neither transmissible nor treatable with antifungals.

Mycotoxin	Fungus and source	Effect
Aflatoxin B1	Aspergillus flavus and A. Parasiticus growing on improperly dried and stored groundnuts, maize, cottonseed and spices — a major problem in humid Indian storage conditions	The most potent natural hepatocarcinogen known; a WHO Group 1 carcinogen. Causes hepatocellular carcinoma, with a striking synergy with hepatitis B (the combined risk far exceeding the sum). Acute high-dose exposure causes fatal hepatitis, as in the 1974 outbreak in Gujarat and Rajasthan. Also causes immunosuppression and growth stunting in children
Ochratoxin A	Aspergillus and Penicillium on cereals, coffee and dried fruit	Nephrotoxic and carcinogenic; implicated in Balkan endemic nephropathy
Ergot alkaloids	Claviceps purpurea on rye and bajra (pearl millet)	Ergotism — the gangrenous form ("St Anthony fire") from intense vasoconstriction, and the convulsive form. An outbreak occurred in Rajasthan from contaminated bajra
Trichothecenes (T-2 toxin)	Fusarium on cereals	Alimentary toxic aleukia with bone marrow suppression and haemorrhage; investigated as a biological weapon
Fumonisins	Fusarium on maize	Oesophageal carcinoma; neural tube defects; equine leukoencephalomalacia
Amatoxin	Mushroom poisoning — Amanita phalloides	Inhibits RNA polymerase II; fulminant hepatic failure after a deceptive latent period of 6 to 24 hours

CLINICAL PEARL

Aflatoxin and hepatitis B multiply each other rather than adding. Either alone raises the risk of hepatocellular carcinoma; together the risk is far greater than the sum, because aflatoxin causes a characteristic p53 mutation while chronic hepatitis drives the cell proliferation that fixes it. In parts of India where both are common, this interaction is a substantial and largely preventable cause of liver cancer — preventable by vaccination and by drying and storing grain properly.

Prevention of Mycotoxin Exposure

Adequate drying of grain and groundnuts before storage, and storage in dry, ventilated, pest-free conditions — fungal growth requires moisture, so this is the fundamental control
Sorting and discarding visibly mouldy, discoloured or shrivelled kernels
Regulatory limits and monitoring of aflatoxin in food and animal feed; India has statutory limits under food safety regulations
Hepatitis B vaccination, which removes the synergistic cofactor
Mycotoxins are heat-stable and survive cooking, roasting and processing, so contaminated food cannot be made safe by preparation — prevention must occur before and during storage

Fungal Allergy

Fungal spores are among the commonest aeroallergens — Aspergillus, Alternaria, Cladosporium and Penicillium are ubiquitous in air, and counts rise in damp weather and in poorly ventilated damp buildings
Allergic rhinitis and asthma — type I (IgE-mediated) hypersensitivity; Alternaria sensitisation is associated with severe and fatal asthma
Allergic bronchopulmonary aspergillosis (ABPA) — a combined type I and type III reaction in asthma and cystic fibrosis, with bronchiectasis; treated with corticosteroids, not with antifungals alone
Allergic fungal rhinosinusitis — nasal polyps with thick eosinophilic "allergic mucin" containing hyphae but no tissue invasion; treated by surgery and steroids. It is common in the hot humid parts of India and must be separated from invasive fungal sinusitis, in which steroids would be disastrous
Hypersensitivity pneumonitis (extrinsic allergic alveolitis) — a type III and IV reaction to inhaled organic dust: farmer lung (Aspergillus and thermophilic actinomycetes in mouldy hay), bagassosis (mouldy sugarcane bagasse, described in India), malt worker lung and bird fancier lung. Removal of exposure prevents irreversible fibrosis

Applied Aspects

Distinguish allergic from invasive fungal sinusitis before giving steroids; the clinical pictures overlap, the treatments are opposite, and the consequence of error is rapid invasive disease
Consider ABPA in asthma that is difficult to control, particularly with brown mucus plugs, fleeting infiltrates and eosinophilia; total IgE is the screening test
Take an occupational history in unexplained breathlessness — farming, sugarcane processing, grain handling and bird keeping each point to a specific hypersensitivity pneumonitis, and removal from exposure is the treatment
Aflatoxin exposure is largely preventable by post-harvest practice, which is an agricultural intervention with a direct oncological benefit
Damp housing is a genuine health issue, and remediation reduces both allergy and asthma exacerbations
Mycotoxicoses are not infections; antifungal drugs have no role, and management is removal of the source with supportive care

All questions in Mycology

Every Microbiology chapter →