Fungi are simple parasitic life-forms that include yeasts, moulds, mushrooms, and toadstools. The fungi that are responsible for causing disease can be divided into two groups: filamentous fungi and yeasts. Filamentous fungi are made up of branching threads known as hyphae, which form a network called a mycelium. Mushrooms and toad-stools are the reproductive structures (known as fruiting bodies) of a filamentous fungus that has spread in dead matter of soil. Yeasts are single-celled organisms.

FUNGI AND DISEASE

The majority of fungi are either completely harmless or actually beneficial to human health. However, there are a number of fungi that can cause illness and disease.

The fruiting bodies of some fungi contain toxins that may cause poisoning if they are eaten (mushroom poisoning). Certain other fungi infect food crops and also produce toxins that may cause food poisoning. The best known of these fungi is a species that infects cereals and produces ergot, a toxin that constricts blood vessels. Another fungus that sometimes grows on peanuts and produces aflatoxin, a poison and carcinogen.

The inhaled spores of some fungi can cause allergic alveolitis, a persistent allergic reaction in the lungs. Farmer’s lung, which is caused by spores from mouldy hay, is an example of such a reaction. Fungal spores are sometimes responsible for various other allergic disorders, such as allergic rhinitis and asthma.

Some fungi are capable of invading the body and forming colonies in various parts of the body such as the lungs, the skin, or sometimes in a variety of tissues throughout the body, leading to conditions that range from mild irritation to severe, sometimes even fatal, widespread infection (fungal infections) and illness.

FUNGAL DISEASES

The skin, genitals, and nails are common sites of fungal infection. Examples include tinea (ringworm) and candidiasis (thrush). Fungi can rarely infect the lungs and other internal organs, causing a more serious disease. They may also cause allergic lung disease, such as farmer’s lung.

FUNGAL GROWTH

1. Many fungal colonies originate from spores that have been carried in the air and have settled at a suitable site for growth.
2. If nutrients are available and other conditions (such as temperature) are favourable, a spore starts to divide.
3. The cells of mani fungi divide to form a network consisting of branched chains of tubular filaments called hyphae.
4. Eventually a colony may start to form its own spores. These spores may be carried to new sites to set up new growths.

FUNGAL INFECTIONS

Fungal infections are a wide range of diseases that are caused by multiplication and spread of fungi. Fungal infections, which are also known as mycoses, range from mild and barely noticed to severe and sometimes even fatal. In addition to infections, fungi are also responsible for some allergic disorders, such as allergic alveolitis and asthma.

FUNGAL INFECTIONS CAUSES

Some fungi are harmlessly present all of the time in areas of the body such as the mouth, skin, intestines, and vagina. Usually, however, they are prevented from multiplying by competition from bacteria. Other fungi are kept from multiplying to a harmful degree by the body’s immune system.

Fungal infections are therefore more common in people who are taking antibiotic drugs (which destroy the bacterial competition) and in those whose immune systems are suppressed by immunosuppressant drugs, corticosteroid drugs, by a disorder such as AIDS, or by chemotherapy. Such serious fungal infections are described as opportunistic infections because they take advantage of the body’s lowered defences. Some fungal infections are more common in people with diabetes mellitus.

Fungi that cause infections thrive in warm, moist conditions, such as those that occur between the toes and in the genital area.

FUNGAL INFECTIONS TYPES

Fungal infections can be broadly classified into  three categories: superficial (affecting the skin, hair, nails, inside of the mouth, and genital organs); subcutaneous (beneath the skin); and deep (affecting internal organs).

The main superficial infections are tinea (including ringworm and athlete’s foot) and candidiasis (thrush), both of which are common. Tinea affects external areas of the body. Candidiasis is caused by the yeast Candida albicans and usually affects the genitals or the inside of the mouth.

Subcutaneous fungal infections are rare. The most common is sporotrichosis, which may follow contamination of a scratch. Most other conditions of this type, the most important of which is mycetoma, occur mainly in tropical countries.

Deep fungal infections are uncommon, but they can present a serious threat to people who have an immune deficiency disorder or those who are taking immunosuppressant drugs. Fungal infections of this sort include aspergillosis, histoplasmosis, cryptococcosis, and blastomycosis, all of which are caused by different species of fungi. The fungal spores enter the body through inhalation into the lungs. Candidiasis can also spread from its usual sites of infection to affect the oesophagus, the urinary tract, and other internal tissues.

FUNGAL INFECTIONS TREATMENT

Treatment of fungal infections is with antifungal drugs, either used topically on the infected area, or given by mouth or intravenously for generalized infections.

Source: A-Z Family medical encyclopedia by BMA

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