THE AMOEBA 



143 



The cysts remain viable at 4" C up to 10 

 months if they are not allowed to dry out. 



E. nioshkovskii 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 spe- 

 cies 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. 



ENTAMOEBA EQUI 

 FANTHAM, 1921 



Fantham (1921) found this amoeba in 

 the feces of 2 horses with signs of intes- 

 tinal disturbance in South Africa. It is 

 unusually large, fully extended tropho- 

 zoites measuring 40 to 50 by 23 to 29)Lt 

 and rounded ones 28 to 35 /i in diameter. 

 The nucleus is of the histolytica type, but 

 is oval rather than round. Erythrocytes 

 are ingested. The cysts are 15 to 24 ju. in 

 diameter and contain 4 nuclei and chroma- 

 toid bars. 



ENTAMOEBA ANATIS 

 FANTHAM, 1924 



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 n in diameter, and con- 

 tain 1 to 4 nuclei and thin, needle-like 

 chromatoid bodies. 



ENTAMOEBA CO LI 

 (GRASSI, 1879) 

 CASAGRANDI AND 

 BARBAGALLO, 1895 



Synonyms : Am,oeba coli, Endamoeba 

 hominis. Council-mania lafleuri. 



This is the commonest species of 

 amoeba in man. According to Belding 



(1952), it was found in 28% in 19 surveys 

 of 17,733 persons thruout the world and 

 occurs in about 30% of the population of 

 the United States. It also occurs in the 

 gorilla, orangutan, chimpanzee, gibbon 

 and in various species of macaques and 

 other monkeys (Mackinnon and Dibb, 

 1938). Smith (1910) saw an amoeba sim- 

 ilar to E. coli in pigs, and Kessel (1928a) 

 found it in a Chinese pig. Kessel (1928a) 

 also infected pigs experimentally with E. 

 coli cysts from man, but the infections 

 lasted less than 6 weeks. 



Entamoeba coli occurs in the cecum 

 and colon. It can be cultivated on the 

 usual media. It is non- pathogenic, and 

 therefore must be differentiated from E. 

 histolytica. 



Its trophozoites are 15 to 50 /i (usually 

 20 to 30 jn) in diameter. The cytoplasm is 

 filled with bacteria and debris, and the 

 ectoplasm is thin. The organism moves 

 sluggishly. The nucleus has an eccentric 

 endosome larger than that of E. histo- 

 lytica, and a row of relatively coarse 

 chromatin granules around its periphery. 

 There may also be a few scattered chrom- 

 atin granules between the endosome and 

 the nuclear membrane. The cysts are 10 

 to 33 ju in diameter and have 8 nuclei when 

 mature. The cysts contain slender, splin- 

 ter-like chromatoid bodies with sharp, 

 fractured or square ends; these disappear 

 as the cysts age. The young cysts also 

 may contain a large, well-defined glycogen 

 globule; it usually disappears before the 

 cyst is mature. 



ENTAMOEBA WENYONI 

 GALLI-VALERIO, 1935 



Wenyon (1926) reported that he had 

 seen 8-nucleate amoeba cysts of the E. 

 coli type in the feces of goats. Galli- 

 Valerio (1935) described this form, naming 

 it Entamoeba wenyoni. The few tropho- 

 zoites which he saw measured 12 by 9j^i, 

 their protoplasm was fairly granular with 

 no distinction between ectoplasm and endo- 

 plasm, and they contained numerous bac- 

 teria. They moved very slowly with short, 

 rounded pseudopods. The cysts were spher- 

 ical, 6 to 9(i in diameter, and contained 8 

 nuclei. 



