136 



THE AMOEBAE 



histolytica (sensu stricto) which cannot be 

 induced to become pathogenic has not yet 

 been answered satisfactorily. Concomi- 

 tant bacteria, nutritional deficiencies and 

 other factors affect the pathogenicity of 

 the amoebae. Indeed, Phillips el al. 

 (1955) found it impossible to infect bac- 

 teria-free guinea pigs with E. histolytica 

 at all, altho normal guinea pigs or those 

 infected with Escherichia coli or Aero- 

 bacter aerogenes could be readily infected 

 and subsequently developed intestinal le- 

 sions. 



Some of the amoebae reported as E. 

 histolytica from domestic animals may 

 well have been actually E. hartnianni. but 

 unless they were specifically described as 

 having small cysts, it is impossible to 

 know which they were. 



The above discussion has to do pri- 

 marily with a matter of nomenclature. In 

 addition, another species morphologically 

 identical with E. histolytica has been 

 found in sewage. This is E. moshkovskii 

 It has not been found in fresh feces, but 

 nevertheless its existence must be taken 

 into consideration in diagnosis. It is not 

 infective for rats, kittens, guinea pigs or 

 frog or salamander larvae and its optimum 

 temperature is about 24° C, altho it will 

 grow poorly at 37° C. 



Before beginning a systematic account 

 of the species of Entamoeba, a word is in 

 order regarding the bovis group. All of 

 these look alike, with minor differences 

 which may not be of taxonomic significance. 

 Different names have been given to the 

 forms in different hosts, but no cross- 

 transmission studies have been attempted, 

 and it is quite likely that when they are, 

 some of these forms will be found to be 

 synonyms. In this case. Entamoeba bovis 

 will have precedence over the other names. 



The name Entamoeba polecki has 

 been used for members of the bovis group 

 from the pig and goat, but it is a nomeu 

 nudum. Prowazek's (1912) original des- 

 cription and figures of it are so poor that 

 it is impossible to know whether he was 

 dealing with a member of the genus Enta- 

 moeba at all. 



Noble and Noble (1952) and Hoare 

 (1959) have reviewed the amoebae of do- 

 mestic animals. 



ENTAMOEBA IIISTOL YTICA 

 SCHAUDINN, 1903 



Synonyms : Amoeba coli, Amoeba 

 dysenleriae, Entamoeba tetragena. Enta- 

 moeba dispar. Entamoeba venaticum. 



Disease : Amoebic dysentery. 



Hosts : Man, orang-utan, gorilla, 

 chimpanzee, gibbon, many species of 

 macaques, baboons, spider monkeys and 

 other monkeys, dog, cat, pig, rat, pos- 

 sibly cattle. The rat, mouse, guinea pig 

 and rabbit are often infected experimentally. 



Location : Large intestine, some- 

 times liver, occasionally lungs, and rarely 

 other organs including the brain, spleen, 

 etc. 



Geographic Distribution : Worldwide. 

 Maps of the world distribution of amoebic 

 dysentery and E. Jiistolytica, together 

 with climatological and other information, 

 were published by Piekarski and Westphal 

 (1952) and Westphal (1955). 



Prevalence : E. histolytica is most 

 important as a parasite of man. It also 

 occurs in monkeys and higher primates. 

 According to Belding (1952), it was found 

 in an average of 17.6% of 42,713 persons 

 (range, 0.8 to 50%) in 37 surveys thruout 

 the world from 1941 to 1948. In 10 surveys 

 of 10,867 persons in the United States from 

 1941 to 1948, it was found in an average of 

 13.6% (range, 0.8 to 38%). 



According to Benson, Fremming and 

 Young (1955), it has given considerable 

 trouble in their chimpanzee colony at the 

 Univ. of Texas. 



Sporadic cases of amoebic dysentery 

 have been reported in dogs; these animals 

 are generally considered to have acquired 

 their infections from human contacts. 

 Kartulis (1891, 1913) found £. histolytica 

 causing dysentery in 3 dogs in Egypt; in 



