Scanning electron microscopy of Spironucleus (Hexamita) muris infection in mice.

An epizootic disease characterized by failure to gain weight, lethargy, enteropathy, and death developed in weanlings from a production colony of NIH/Nmri CV mice. Light microscopic and scanning electron microscopic examination of the intestine revealed large numbers of protozoan parasites identified as Spironucleus (Hexamita) muris. The extensive, entangled mass of organisms in the intestinal lumen enveloped the villi and continued deep within the crypts of Lieberkühn. Inflammation and significant intestinal lesions were not observed. The scanning electron microscopic appearance of the small intestine in spironucleosis gives credence to a pathogenesis of malabsorption with subsequent, severe malnutrition and death in weanling mice.