Pathological and Immunohistochemical Analyses of Naturally Occurring Equine Glanders Using an Anti-BpaB Antibody.

Glanders is caused by the gram-negative bacteriumBurkholderia mallei. In this study, we investigated the histopathology and immunohistochemical localization ofB. malleiin natural cases of equine glanders. Four horses showing clinical signs of nasal discharge and multiple cutaneous nodules or papulae in the hindlimbs and abdomen were reported in Mongolia. They tested positive forB. malleiinfection on complement fixation, Rose Bengal agglutination, and mallein tests. Gross and histological lesions observed in these cases were similar to those previously reported in equine glanders. Immunohistochemistry using a monoclonal antibody toB. malleiBpaB showed localization of the bacterial antigen in the cytoplasm of neutrophils, macrophages, epithelioid cells, and multinucleated giant cells in the pyogranulomas and abscesses in target organs. Some alveolar type II cells and bronchiolar epithelial cells also contained the antigen. These results suggest that the anti-BpaB antibody is useful for identifyingB. mallei-infected cell types in naturally infected horses.