Bacillary angiomatosis in an immunosuppressed dog.

A dog being treated with immunosuppressive doses of prednisone and azathioprine for pancytopenia of unknown origin, developed, over a 2-week period, multiple erythematous nodular lesions in the skin including footpads. Skin samples revealed lesions identical to those of human bacillary angiomatosis (BA). The nodules were composed of multifocal proliferations of capillaries, each lined by protuberant endothelial cells. The capillary clusters were separated by an oedematous connective tissue, lightly infiltrated with degenerate inflammatory cells, including neutrophils and macrophages. Tissue sections stained with Warthin-Starry silver stain revealed large numbers of positively stained bacilli in the stromal tissue, most heavily concentrated around the proliferating capillaries. Lesions of vascular degeneration and inflammation were evident. Bartonella vinsonii subsp. berkhoffii genotype 1 was independently amplified and sequenced from the blood and the skin tissue. The pathognomonic nature of the histological lesions, demonstration of compatible silver-stained bacilli in the tissue, and identification of B. vinsonii subsp. berkhoffii in the blood and tissue indicates that this is most likely the aetiologic agent responsible for the lesions. Antibiotic therapy was successful in resolving the nodules. It would appear that B. vinsonii subsp berkhoffii, like Bartonella henselae and Bartonella quintana, has the rare ability to induce angioproliferative lesions, most likely in association with immunosuppression. The demonstration of lesions identical to those of human BA in this dog is further evidence that the full range of clinical manifestations of human Bartonella infection occurs also in canines.

Clinicopathologic findings associated with Lagenidium sp. infection in 6 dogs: initial description of an emerging oomycosis.

An oomycotic pathogen in the genus Lagenidium was isolated from tissues obtained from 6 dogs with progressive cutaneous disease. Initial clinical findings in 5 dogs included multifocal cutaneous lesions, subcutaneous lesions, or both associated with regional lymphadenopathy: the 6th dog initially was presented for evaluation of mandibular lymphadenopathy. Cutaneous lesions were ulcerated, exudative regions (often with necrosis and draining tracts) or multiple firm dermal or subcutaneous nodules. Two dogs subsequently developed hemoabdomen from great vessel rupture and died acutely. Four dogs were euthanized because of progression of subcutaneous lesions or lymphadenopathy. On postmortem examination, regional granulomatous lymphadenitis was found in all 6 dogs, great vessel invasion in 3 dogs, pulmonary lesions in 2 dogs. ureteral obstruction in 1 dog, mediastinal lymphadenitis in 1 dog, and hilar lymphadenitis with invasion of the distal esophagus and trachea in 1 dog. Histologically, lesions were similar to those associated with pythiosis and zygomycosis and were characterized by severe eosinophilic granulomatous inflammation (often with numerous large multinucleated giant cells) centered around broad (7-25 micro), infrequently septate hyphae. Immunoblot analysis of the serologic response of 4 dogs to a soluble mycelial extract of Lagenidium giganteum indicated that each dog's serum recognized at least 10 different antigens of L. giganteum. Culture of infected tissues yielded rapid growth of colorless to white submerged colonies. Microscopically, mature hyphae in culture were broad (25-40 micro), segmented, and occasionally branching and produced motile laterally biflagellate zoospores in water culture. This report is the 1st description of infection caused by an oomycete other than Pythium insidiosum in any mammalian species.