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Photosensitization associated with exposure to Pithomyces chartarum in lambs
D E Hansen1, R D McCoy, O R Hedstrom
1Veterinary Diagnostic Laboratory, College of Veterinary Medicine, Oregon State University, Corvallis 97331.
Summary
An outbreak of photosensitization in lambs was linked to the fungus Pithomyces chartarum. This diagnosis, commonly known as facial eczema, was made despite no prior reports in the northwestern United States.
Area of Science:
- Veterinary Dermatology
- Mycology
- Toxicology
Background:
- Photosensitization is a skin condition triggered by sunlight in animals.
- Facial eczema, caused by Pithomyces chartarum, is a known photosensitization disease in livestock globally.
- The northwestern United States had no prior reports of facial eczema.
Purpose of the Study:
- To investigate an epidemic of photosensitization in lambs in western Oregon.
- To identify the potential cause of observed skin lesions and mucosal damage in affected lambs.
Main Methods:
- Clinical observation of affected lambs.
- Microscopic examination of pasture plant material for fungal spores.
- Correlation of clinical signs with environmental conditions conducive to fungal growth.
Main Results:
- Lambs exhibited skin crusting, necrosis, and sloughing on the face and oral mucous membranes.
- Spores of Pithomyces chartarum were identified in pasture samples.
- Fungal growth conditions were optimal during the grazing period, with high spore counts detected.
Conclusions:
- The clinical signs and presence of Pithomyces chartarum strongly suggest facial eczema as the cause of the photosensitization epidemic.
- This diagnosis is considered valid despite the lack of previous reports in the region.
- Environmental conditions supported the fungal proliferation and subsequent disease outbreak.