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Human (including Animal) Diseases
Various fungi have proved to be pathogenic to man and animals by way of toxins (mycetism, mycotoxicosis) or by including allergic reactions (mycogenic allergies), or by progressive infections (mycoses).
(i) Mycetism (Mushroom Poisoning)
Some agarics (mushrooms) are poisonous to living being. The most severe type of mushroom poisoning is caused by species belonging to the genus Amanita. A mistake can result in very unpleasant gastrointestinal upset or even death.
Amanita phalloides (the death cup) is very poisonous and responsible for most of the mushroom poisoning deaths. A mixture of three toxins α-amanitine, -amanitine, β-amanitine and phalloidine ― is the cause of poisoning. Amanita muscaria (fly agaric) and A. pantherina (panther cap) are also poisonous.
Besides Amantia, some other poisonous mushrooms are Russula, Lactarius, Boletus, Entoloma etc. Symptoms of mushroom poisoning are - nausea, vomiting, abdominal pain and visual disturbances. The affected one finally falls into a coma and may succumb.
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(ii) Mycotoxicosis
Toxins produced by fungi are called mycotoxins. One of the most important mycotoxin is aflatoxin produced by some species of Aspergillus (especially A. flavus). Aflatoxins can be lethal to poultry. They may cause lever damage and are suspected to induce cancer in humans.
Claviceps purpurea produces ergot alkaloids which, if mixed with rye flour, may result in severe poisoning. Fingers, toes, whole arms, legs, sometimes eyes and noses become gangreneous, wither and fall off with no bleeding.
Some fungi like Stachybotrys atra, Pithomyces chartarurn and some Fusarium spp. produce mycotoxins which affect large animals like horses, sheep and cattle. They develop facial eczema and liver damage while feeding on contaminated grass.
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(iii) Mycoses
It is considered that around 1/5th of the global population (about 800 million) suffer or have suffered from mycoses. Mycoses can be considered of two types ― superficial mycoses and deep-seated mycoses.
Superficial mycoses are unpleasant but not lethal. Skins, hair and nails are infected. The fungi that cause superficial mycoses are called dermatophytes and the diseases they cause are called dermatophytoses.
Various species of genera Microsporon, Epidermophyton and Trichophyton are important dermatophytes. Malassezia furfur is the agent of Pityriasis versicolor (dandruff): Microsporum andouini is the agent for most cases of ring worm of scalp in children.
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Deep-seated mycoses are dangerous and may become fatal if not treated. Unfortunately, the diagnosis of mycoses is often difficult because there are no specific' mycoses symptoms'.
The isolation and idenitication of the pathogen is the only method to identity the disease.
About 15 deep seated mycoses are in knowledge e.g., Coccidioidomycosis, Blastomycosis, Candidiasis, Subcutaneous Phycomyosis, Sporotrichosis, Chromomycosis, Mucormycosis, Geotrichosis and Mycetoma. Details of some important ones are given below:
Aspergillosis. Caused by Aspergillus fumigatus which attacks ears, lungs etc. Pulmonary aspergillosis is diagnosed a5 T.B.
Blastomycosis. Popular as 'Gilchrist's disease'. In early stages it causes cough, chest pains and weakness following the formation of subcutaneous nodules, abscesses or lesions on face and arm. Blastomyces dermitidis is the causal organism.
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Candidiasis.
It is caused by Candida albicans, the mucous membrane of skin, lungs etc. are attaked. Ammons et al. (1977) have listed cutaneous candidiasis, oral candidiasis, pulmonary candidiasis, volvovaginal candidiasis and bronchocandidiasis as some of the infections.
Chromomycosis. A more or less localized and chronic infection of the skin and subcutaneous tissues by Cladosporium carrionii, Phialophora verrucosa, P. pedrosoi etc.
Coccidioidomycosis. Characterized by the lesions limited to the upper respiratory tract and lungs. In humans it is caused by Coccidioides immitis.
Cryptococcosis. The central nervous system is affected by this disease caused by Cryptococcus neoformans, it affects the vision and causes respiratory failure.
Histoplasmosis. This disease is caused by Emmonsiella capsulata. It is very widespread and serious in humans and is sometimes even fatal.
Geotrichosis. It is an oral pulmonary, bronchial or intestinal infection in humans caused by Geotrichum candidum.
However, warm blooded animals are also infected by fungi causing mycoses. Examples ― Cattle (Trichophyton verrucosum), and birds (Aspergillus fumigatus, Candida albicans).
(iv)Mycogenic allergies
Sometimes, air-borne spores and conidia of fungi attack the skin or mucous membranes of individuals causing dermatitis and asthma.
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