This report describes systemic yeast infection occurring in three captive Orinoco geese and two captive brown pelicans from the San Francisco Zoo during 1996 and 1999. Case 1 was a 2-year-old female captive-bred Orinoco goose (295001), and it had a history of recurrent lameness of 4 months’ duration. The bird was hospitalized during a 5-day period of lameness in September 1996. The goose received supportive care but died. Case 2 was a 2-year-old male Orinoco goose (295004) that had a history of recurrent lameness of 4 months’ duration. The bird had been hospitalized during a 7-day period of lameness in September 1996. The goose received supportive care but died. Cases 3 (298079/99-0010) and 4 (298045) were adult female brown pelicans that were found dead in a lake on the zoo grounds in January 1999. Case 5 was a male Orinoco goose (298064/1999-0086) that was found dead on the zoo grounds in 1999.
Histologically in all birds, intracytoplasmic organisms were detected in the endothelial cells or luminal macrophages of veins, venules and capillaries of the lung with associated mild to moderate perivascular lymphoid cuffs and interstitial lymphohistiocytic pneumonia. The organisms were also detected in endothelial cells of vessels in peripheral nerves of the leg in cases 1 and 2, and occasionally in low numbers in other tissues. The organisms in the endothelial cells were ovoid and approximately 1–3 µm in greatest dimension. The organisms stained positive with PAS and GMS, and they did not react with Brown and Brenn or Fite’s acid fast stains. Electron microscopy revealed that the organisms were 1.10x2.04 µm; they had a single central to slightly eccentric nucleus, trilaminar cell wall, thin outer capsule; and they replicated by budding from the apical or apico-lateral regions of the cell wall. The light microscopic, ultrastructural, and tinctorial properties of the organisms were features consistent with yeasts. Despite extensive culturing for fungal organisms from tissues of case 3, no significant fungal growth was obtained.
Disseminated yeast infection has been documented in birds, primarily those belonging to the order Anseriformes, particularly from northwest North America.1-3 The identity of these organisms is based on light and electron microscopic morphology and tinctorial properties. The etiologic agent or agents of this condition have not been named or further characterized, because culture attempts have been unsuccessful. The organisms typically infect endothelial cells and macrophages, and death is attributed to associated inflammation and vascular damage.
1. Randall, C.J. 1991. Intracellular yeast-like organisms causing disease in Muscovy ducks and other waterfowl. Poster presentation, American Association of Avian Pathologists; Seattle, WA.
2. Randall, C.J., S. Lees, P.A. Pepin, H.M. Ross. 1987. An unusual intracellular infection in ducks. Avian Pathol. 16:479.
3. Wobeser, G.A. Fungal diseases. 1997. In: Diseases of Wild Waterfowl, 2nd ed. Plenum Press. Pp. 101–102.