Facial eczema, also known as sporidesmin toxicosis and pithomycotoxicosis, is a disorder of grazing livestock caused by the fungus Pithomyces chartarum growing on dead plant material. It is frequently associated with perennial ryegrass pasture in New Zealand.

Clinical Findings:

Few signs are apparent until photosensitization and jaundice appear about 10–14 days after intake of the toxins. Animals frantically seek shade. Even short exposure to the sun rapidly produces the typical erythema and edema of photodermatitis in non-pigmented skin (particularly ears, eyelids, face, and lips). The animals suffer considerably, and deaths occur from one to several weeks after photodermatitis appears.

Lesions:

Histopathologic findings in the liver include degenerative changes in bile duct epithelium with both intrahepatic and extrahepatic bile ducts involved, biliary occlusion by inspissated bile and necrotic cells, hepatocellular vacuolation, particularly centrilobular hepatocytes. In a recovering liver, lesions can include the proliferation of bile ducts and periportal fibroplasia, with areas of atrophy and regeneration occurring in the liver. Characteristic liver and bile duct lesions are evident in all affected animals, whether photosensitized or not. In acute cases showing photodermatitis, livers are initially enlarged, icteric, and have a marked lobular pattern. Later, there is atrophy and marked fibrosis. The shape is distorted, and large nodules of regenerated tissue appear on the surface. In subclinical cases, livers often develop extensive areas in which the tissue is depressed and shrunken below the normal contour, which distorts and roughens the capsule. Generally, these areas are associated with fibrosis and thickening of corresponding bile ducts. The bladder mucosa commonly shows hemorrhagic or bile pigment-stained ulcerative erosions with circumscribed edema.

Diagnosis of Facial Eczema in Animals:

The clinical signs, together with characteristic liver lesions, are pathognomonic. In live animals, high hepatic enzyme activity may reflect extensive injury to the liver. Liver damage can be detected with serum chemistry changes of increased bilirubin concentration, cholesterol concentration, triacylglycerols concentration, bile acids concentration, gamma-glutamyl transaminase (GGT) activity, aspartate aminotransferase (AST) activity, glutamate dehydrogenase activity; a decrease in serum albumin concentration and increased prothrombin time can also be observed in affected animals. The diagnosis is usually based on clinical signs and the season, and a pasture spore count of Pithomyces chartarum can confirm whether the pasture is dangerous. A spore count of 100,000 or more per gram of grass is considered dangerous.

Treatment:

Supportive treatment: Treatment of the affected animals is supportive. Animals with photosensitization should be housed, provided with deep shade, and put out to graze only at night. Secondary bacterial infections should be treated as necessary. Benzimidazole fungicides on pastures: The application of benzimidazole fungicides to pastures considerably restricts the buildup of P.chartarum spores and reduces pasture toxicity.