PATHOMORPHOLOGICAL FINDINGS IN A CASE OF ONYCHOMYCOSIS OF A RACEHORSE

The hooves of a racehorse which were affected with white line disease and hoof wall disorders on both forelimbs were histopathologically inv estigated using thin ground section and standard paraffin section tech niques. On both hooves, large quantities of fungus were found to have invaded the white line tissues, especially in the terminal horn which were markedly damaged. The fungus was also present among the cellular debris in the fissures of horny tissues. The morphological characteris tics of the fungus were brown (its natural color), PAS-positive, mold- like shape with septa inside the tissues, and unicellular spores outsi de the tissues. These findings suggest that onychomycosis was a primar y and/or secondary cause of white line disease in this subject.