Disseminated unicellular green algal infection in two sheep in India

Unicellular green algae infected and disseminated in two adult Nellore brown rams in India. At necropsy multiple green lesions were observed in the lungs, liver and kidneys of both sheep. Histological examination revealed necrotizing granulomas that contained numerous spheroidal to elliptical organisms ranging from 5-20 micrometers in diameter. These organisms occurred in several reproductive stages: small (5-9 micrometers) single, undifferentiated cells; intermediate (9-15 micrometers) cells undergoing nuclear and cytoplasmic cleavage; and large, mature, endosporulating cells containing two to six or more endospores. In addition, occasional large (20-35 micrometers), round thick-walled forms were among the typical cells. The cytoplasm of the algal cells contained numerous, large, irregularly-shaped and densely packed granules of varying sizes, which were strongly stained by the Gridley fungus, periodic acid-Schiff, and Gomori methenamine silver procedures. Electron microscopic studies revealed chloroplasts in the cytoplasm of these organisms. The chloroplasts consisted of smoothly contoured electron-lucent or electron-dense granules, 0.5 to 3.0 micrometers in diameter, that were either surrounded by or contiguous to two or more tightly appressed membranes or multidisc bands. Some of the alternating membranes appeared to be spirally twisted or associated with several cytoplasmic granules in one plane of section. This is the first record of algal infections in India.