Facial eczema

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A sheep showing clinical symptoms of facial eczema.

Facial eczema, FE, is a disease that mainly affects ruminants such as cattle, sheep, deer, goats and South American camelids (alpaca, llamas). It is caused by the fungus Pithomyces chartarum that under favorable conditions can rapidly disseminate in pastures. The fungus requires warm humid weather with night time temperatures of over 13 °C (55 °F) for several days, and litter at the bottom of the sward.

Molecular formula of the sporidesmin mycotoxin.

Pithomyces chartarum occurs worldwide but is a problem predominantly where farm animals are intensively grazed, especially in New Zealand. The spores of the fungus release the mycotoxin sporidesmin in the gastrointestinal tract, causing a blockage in the bile ducts that leads to injury of the liver. Bile, chlorophyll and other waste products consequently build up in the bloodstream causing photo sensitivity of the skin especially that exposed to direct sunlight. This in turn causes severe skin irritation that the animal attempts to relieve by rubbing its head against available objects, resulting in peeling of the skin.

The large family of fungi that produce mycotoxins, of which sporidesmin is one, live mainly on ryegrasses and can cause significant problems in grazing animals. Sporidesmin can lower an animals immunity and affect total production in farm animals, and, when taken in larger quantities, can result in death.

The clinical symptoms of FE are distressing: restlessness, frequent urination, shaking, persistent rubbing of the head against objects (e.g. fences, trees etc.), drooping and reddened ears, swollen eyes, and avoidance of sunlight by seeking shade. Exposed areas of skin develop weeping dermatitis and scabs that can become infected and attractive to blow-fly causing myiasis.

Treatment[edit]

There has been anecdotal evidence provided by Elaine Ingham according to which susceptibility to facial eczema in cattle is related to nutrient deficiency of forage. The experiment, which Ingham conducted, showed that by improving soil biology the forage had better nutrient qualities and was associated with an elimination of the disease.[1]

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