Disseminated Rhodococcus equi infection in two goats

Rhodococcus equi infection was diagnosed in two goats from the same herd. A t necropsy, numerous caseating granulomas were disseminated throughout the liver, lungs, abdominal lymph nodes, medulla of right humerus, and the righ t fifth rib of goat No. 1, and the liver of goat No. 2. Histopathologic exa mination confirmed the presence of multiple caseating granulomas in these o rgans. Numerous gram-positive and Giemsa-positive coccobacilli were identif ied within the cytoplasm of macrophages. Aerobic bacterial cultures of the liver and lung from both goats yielded a pure growth of R. equi. R. equi an tigens were immunohistochemically identified in caseating,granulomas from b oth goats. However, the 15- to 17-kd virulence antigens of R. equi were not detected, suggesting possible infection by an avirulent strain of this org anism.