This species occurs in sewage. It is not a parasite of animals, but of the municipal digestive tract. It was found in the sewage disposal plant and sewer system of Moscow by Chalaya (1941, 1947), in sewage in Leningrad by Gnezdilov (1947), in sewage in Brazil by Amaral and Azzi Leal (1949), in sewage in London by Neal (1950, 1953), and in sewage in Quebec by Lachance (1959). Probably the same organism was found in sewage in California by Wright, Cram and Nolan (1942), altho they did not name it. Chalaya (1947) cultivated it from the water of 2 ponds and a river in Russia. Altho E. moshkovskii is not parasitic, the possibility of its accidental presence in fecal samples is of concern in diagnosis.
E. moshkovskii resembles E. histolytica morphologically. The trophozoites are active, 9 to 29 u (usually 11 to 13 u) in diameter. The nucleus has a small, central endosome and a peripheral layer of fine granules. The cysts are generally spherical, 7 to 17 u in diameter. They contain a very large glycogen vacuole at first which is eventually absorbed as the cysts age. The chromatoid bodies are large, rather elongate, and have rounded ends. The mature cysts have 4 nuclei. The cysts remain viable at 4° C up to 10 months if they are not allowed to dry out.
E. moshkovskii can be cultivated in the usual Entamoeba media. Its optimum temperature is about 24° C and it grows poorly at 37° C. The ability to grow at room temperature differentiates this species from E. histolytica.
Chalaya (1941) was unable to infect kittens with E. moshkovskii, and Neal (1953) could not infect rats, frog (Rana temporaria) tadpoles or salamander (Salamandra maculosa) larvae by feeding.
Fantham (1921) found this amoeba in the feces of 2 horses with signs of intestinal disturbance in South Africa. It is unusually large, fully extended trophozoites measuring 40 to 50 by 23 to 29 u and rounded ones 28 to 35 u in diameter. The nucleus is of the histolytica type, but is oval rather than round. Erythrocytes are ingested. The cysts are 15 to 24 u in diameter and contain 4 nuclei and chromatoid bars.
Fantham (1924) found this amoeba in the feces of a duck which had died of acute enteritis in South Africa. It resembles E. histolytica morphologically, and its trophozoites ingest erythrocytes. The cysts are spherical or subspherical, thin-walled, 13 to 14 u in diameter, and contain 1 to 4 nuclei and thin, needle-like chromatoid bodies.