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Seventeen sheep died, and many others showed signs of hepatogenous photosensitivity after being exposed to Microcystis aeruginosa at Lake Mokoan, Victoria, Australia. Two groups of sheep were observed, and their hepatic recovery was monitored by means of serum biochemical tests during the subsequent six months. During the first three weeks, their serum gamma-glutamyl transferase activity and bilirubin concentration declined rapidly to normal levels, and the signs of hepatogenous photosensitivity disappeared. Serum bile acid concentrations were above normal for almost three months. Thirty-four per cent of the sheep died during the observation period, and the serum biochemical tests provided no clear indication of the cause of these delayed mortalities. This study suggests that sublethal exposure to microcystins may cause prolonged morbidity and delayed mortality.

An epidemic of photosensitization was observed in a group of lambs on irrigated autumn pasture in western Oregon. Signs included crusting, necrosis, and sloughing of the skin over the nostrils, lips, and ears, and of the mucous membranes of the buccal regions. Microscopic examination of plant material from the pasture disclosed spores of Pithomyces chartarum. This fungus has been documented as a causal factor in photosensitization in sheep and cattle (facial eczema) in other parts of the world. An infective agent or other plant material that could have induced the clinical signs in the lambs was not evident. Weather and humidity conditions were ideal for fungal growth during the grazing period, and the fungus was detected in large numbers before and during the epidemic. Even though facial eczema has not been reported previously in northwestern United States, we feel the circumstances surrounding this epidemic warrant such a diagnosis.

Spores of Pithomyces chartarum (Berk. & Curt.) M.B. Ellis were only rarely seen on leaves of Narthecium ossifragum (L.) Hudson collected in summer from five areas in western Norway in which alveld, a photosensitization disease of lambs, is endemic. Cladosporium magnusianum (Jaap) M.B. Ellis was found on all 118 leaf samples collected in the summers of 1990 and 1991. The hypothesis that P. chartarum contributes to the aetiology of alveld could not be supported, but it is possible that C. magnusianum may have a role in the causation of the disease.