This non-pathogenic species was described from the ceca of the chicken and turkey by Tyzzer (1920). By cecal inoculation of parasite-free baby chicks, Richardson (1934) found what appeared to be the same species in the ceca of the domestic duck, turkey and goose. E. gallinarum is common. McDowell (1953) found it in about 30% of a large number of chickens he examined in Pennsylvania.
E. gallinarum closely resembles E. coli. The trophozoites are 9 to 25 u in diameter, most measuring 16 to 18 u. The endoplasm is highly vacuolated and contains many food vacuoles. Altho Tyzzer (1920) said that E. gallinarum did not ingest bacteria, McDowell (1953) found that bacteria were its main food, altho it also ingested Trichomonas among other foods. The ectoplasm is clear or granular. The nucleus is 3 to 5 u in diameter, with an eccentric endosome and a row of granules around the outside. The mature cysts are 12 to 15 u in diameter and contain 8 nuclei.
Richardson (1934) transferred infection from chick to chick by association in the same cage. She found that the minimum oral infective dose of E. gallinarum for the chick was 240 cysts, and observed that the cysts remained viable in raw feces for 10 days and in feces diluted with water for at least 28 days.
Synonym: Amoeba bovis.
This non-pathogenic species occurs commonly in the rumen and feces of cattle thruout the world. Noble and Noble (1952) found it in the feces of all of 34 cattle from California, Pennsylvania, Korea and Japan. Mackinnon and Dibb (1938) found it in the feces of 4 gnus (Connochaetes taurinus) in the London zoo. It has been described most recently by Noble (1947) and Noble and Noble (1952). The trophozoites are 5 to 20 u in diameter. The cytoplasm is smoothly granular and filled with vacuoles of various sizes. The nucleus is large, with a large, central endosome made up of compact granules and a conspicuous row of chromatin granules of different sizes around its periphery. The cysts are 4 to 14 u in diameter and contain a single nucleus when mature. Their chromatoid bodies are irregular clumps of varying size and rods, splinters or granules. A large glycogen vacuole may or may not be present.
Noble and Noble (1952) found that the uninucleate entamoebae from the feces of cattle, goats, sheep and swine were morphologically indistinguishable. However, since their physiological characteristics have not been studied and cross infections have not been attempted, they considered it best not to assign them all to the same species. If future work should show that they are all the same, their correct name would be E. bovis.