Facial eczema is a mycotoxic disease that affects the liver of several animals, mainly sheep and cattle, but can also infect other ungulates. It is caused by ingesting sporidesmins released by the fungus ''

Pithomyces chartarum ''Pithomyces chartarum'' is a fungus predominantly found in subtropical countries and other localities with warmer climates. However, it occurs throughout the world including the United Kingdom, Europe and Netherlands. ''Pithomyces chartarum'' pr ...

''. Its visible symptoms are characterized by red skin that turns black and crusty before peeling off, as well as inflammation that can cause swelling of the udder, teats, ears and face. The disease is not always visible. Other symptoms include weight loss, weakness and death.

''P. chartarum''

It grows mostly in New Zealand but also occurs in Australia, France, South Africa, and South America. The fungus grows on dead plants, especially on perennial ryegrass near the ground (25mm height). It most commonly grows between January and May, as it requires warm, humid conditions, as well as moisture at ground level. Areas of spore growth can include urine patches and areas sheltered by hedges. The fungus grows in clusters and is normally invisible to human eye. It produces millions of spores with the toxic substance sporidesmin. Fresh spores are particularly toxic. Contaminated pasture loses its toxicity after 2 weeks.

Pathophysiology

The incubation period is 7-20 days after poison intake. Sporidesmin is hepatotoxic and leads to hepatogenous

photosensitization Photosensitizers produce a physicochemical change in a neighboring molecule by either donating an electron to the substrate or by abstracting a hydrogen atom from the substrate. At the end of this process, the photosensitizer eventually returns to ...

and phylloerythrin accumulation in the bloodstream. It damages the

bile ducts A bile duct is any of a number of long tube-like structures that carry bile, and is present in most vertebrates. Bile is required for the digestion of food and is secreted by the liver into passages that carry bile toward the hepatic duct. It ...

and then the liver. The worst case is liver necrosis. This causes – as a secondary effect – photosensitization, this means the inflammation of unpigmented areas and exposed skin (ears, teat, face) and photodynamic

dermatitis Dermatitis is inflammation of the skin, typically characterized by itchiness, redness and a rash. In cases of short duration, there may be small blisters, while in long-term cases the skin may become thickened. The area of skin involved can v ...

. Only 5% of affected animals show the respective clinical signs.

Symptoms

Sheep

Infected sheep experience sunburn at face, ears, teats and vulva. It is the primary symptom of the poisoning caused by sporidesmin. The sunburn is caused by the fact that the lower tissue is swollen. The skin gets crusty, dark and then peels,. making it susceptible to infection. Other symptoms include dullness, weakness, inappetence, and ill-thrift. An affection of the liver results in jaundice. In a worst-case, the sheep die.

Cattle

Infected cattle suffer from sunburn. Dark pigmented skin is often affected. Cattle produce less milk. Jaundice is possible and death after some months.

Treatment

Convalescence can take a long time, but some animals may not get healthy. External therapy is possible to treat the sunburn. Animals could be protected by the intake of

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...

. Zinc reacts with sporidesmin to create a metallic complex, so that the poison can be eliminated from the body.

Prevention and control

If animals are sunburned, they should be placed in the stable to protect them from sunlight. Infected cattle should no longer be used in milk production. Reduce flock density (0.45 hectare/ 15 cows or 100 sheep) GGT (enzyme) is released by the damaged liver over the course of this disease and can be tested to indicate disease severity.

References

{{Reflist Sheep and goat diseases