Cutaneous pythiosis in beef calves.

Six Brahman and Brahman-cross calves less than or equal to 9 months old were examined because of ulcerative swellings of the fetlocks (5 calves) or numerous focal ulcerated cutaneous lesions (1 calf). Biopsies revealed focal cutaneous granulomas around regular, thick-walled branching hyphae, 4 to 9 micron in diameter. In all cases, portions of the hyphae were surrounded by granular encrustations, which ultrastructurally were composed of amorphous material comparable to antigen-antibody complexes. The protist Pythium sp was isolated from 2 calves.