THE AMOEBAE 



153 



an E. naua-\i]^e amoeba in 4 of 63 rats 

 which had been fed human feces but did 

 not know whether it had already been 

 present in the rats. 



Dobell (1933) transmitted E. nana 

 from Macaca sinica to a man (himself) 

 and from man to M. mulatto. Kessel 



(1928) infected M. irus with E. nana from 

 man. However, Simitch et al. (1959) were 

 unable to infect 4 young pigs with E. nana 

 from man and consequently named the pig 

 form E. siiis; they gave no details of their 

 experiments. 



Location: Cecum, colon. Hegner 



(1929) and Dobell (1933) found E. nana in 

 the vagina of macaques, where it was 

 most likely of fecal origin. 



Geographic Distribution : Worldwide. 



Prevalence : E. nana is common in 

 man. According to Belding (1952), it was 

 found in 20. 5% of 18, 333 persons in 20 

 surveys thruout the world and in about 

 14% of those examined in the United States. 

 Frye and Meleney (1932) found it in 5. 5% 

 of 127 pigs in Tennessee, Alicata (1932) 

 found it in 1 of 35 pigs in the U.S. , Kessel 

 (1928) found it in 14% of the pigs examined 

 by him in China, and Chang (1938) found 

 it in 15% of 209 pigs in China. Simitch 

 et al. (1959) found it in 8% of 1800 pigs 

 in Yugoslavia. 



Morphology : The trophozoites are 

 6 to 15 p. in diameter with an average of 

 10 ju. They move sluggishly by means 

 of a few blunt, thick pseudopods. The 

 endoplasm is granular, vacuolated and 

 contains bacteria and crystals. The nu- 

 cleus contains a large, irregular endo- 

 some composed of a number of chromatin 

 granules. Several achromatic fibrils run 

 from the endosome to the nuclear mem- 

 brane. There are ordinarily no peripheral 

 chromatin granules, but Stabler (1932) 

 noted that they are formed after fixation 

 in Schaudinn's fluid containing 20% acetic 

 acid. The cysts are oval, often irregular, 

 and thin-walled; they are usually 8 to 10 ^ 

 long but may range from 5 to 14 /i. The 

 mature cysts contain 4 nuclei, and they 



may contain ill-defined glycogen bodies. 

 They have no chi'omatoid bodies but may 

 have small granules resembling volutin 

 and occasionally a few filaments of uncer- 

 tain nature. 



Life Cycle : Reproduction is by binary 

 fission in the trophozoite stage. The 

 amoeba which leaves the cyst is multinu- 

 cleate, but it divides into uninucleate 

 amoebulae which grow into ordinary tropho- 

 zoites. 



Pathogenesis : E. nana is non-patho- 

 genic. 



Bionomics and Epidemiology : E. nana 

 is transmitted in the same way as other 

 enteric amoebae. Dobell (1933) found that 

 its cysts could live at least 2 weeks at 

 room temperature (15-24° C) and at least 

 3 weeks at 10° C, while all the trophozoites 

 died in 24 hours at both temperatures. 

 Frye and Meleney (1932) found E. nana 

 cysts in 1 out of 46 lots of flies which they 

 examined in Tennessee. 



Cultivation : This species can be cul- 

 tivated in the usual media. 



Treatment : Little is known about the 

 treatment of E. nana. Dobell (1933) and 

 others found that emetine has no effect on 

 it. 



Prevention and Control : The same 

 preventive measures recommended for 

 E. histolytica will also prevent E. nana 

 infections. 



ENDOLIMAX RATTI 

 CfflANG, 1925 



This species, which may be a synonym 

 of E. nana, occurs in the cecum and colon 

 of laboratory and wild rats. Andrews and 

 White (1936) found it in 1 out of 2515 wild 

 rats in Baltimore, and Baldassari (1935) 

 found it in 1 of 225 wild rats in Toulon, 

 France. Chiang (1925) did not describe it, 

 but merely stated that it was morphologi- 

 cally identical with E. nana. 



