140 



THE AMOEBAE 



among guests at two neighboring hotels 

 from which over 1000 cases with 58 deaths 

 were tracked down in 44 states and 3 Ca- 

 nadian provinces (Bundesen el al. , 1936). 

 Cross connections between the water and 

 sewage pipes, back siphonage from toilet 

 bowls into the water supply and leakage 

 from an overhead sewage pipe in the 

 kitchen were involved. 



Food handlers may play an important 

 role in transmission of amoebae, even tho 

 the cysts rarely survive more than 10 

 minutes on the hands, except under the 

 fingernails (Spector and Buky, 1934). 

 Thus, Schoenleber (1940, 1941) reported 

 that in a group of Americans living in a 

 Standard Oil Co. camp in Venezuela, the 

 prevalence of amoebic infection was re- 

 duced in 3 years from 25. 6% to 1. 9% and 

 the amoebic dysentery rate from 36.84 to 

 0.61 per 1000 per year by inspection and 

 treatment of food handlers. Winfield and 

 Chin (1939), in a comparison of the prev- 

 alence of amoebic infection with food hab- 

 its in different parts of China, concluded 

 that transmission by food handlers is 

 probably more important than by other 

 means in that country. E. histolytica is 

 much commoner in North China than in 

 South and Central China. This is corre- 

 lated with the serving and eating of cold 

 bread with the hands in North China as 

 contrasted to the handling of hot rice with 

 a serving spoon and chopsticks in South 

 and Central China. On the other hand, 

 Sapero and Johnson (1939, 1939a) found no 

 evidence that carriers were important in 

 the transmission of amoebae in a study of 

 919 persons in the U.S. Navy. The sani- 

 tary habits of American sailors probably 

 had something to do with this. 



Diagnosis : The laboratory diagnosis 

 of amoebiasis has been discussed in detail 

 by Brooke (1958). Live amoebae can be 

 found in wet smears made with physiolog- 

 ical salt solution. These smears may be 

 stained with Lugol's iodine solution diluted 

 1:5 to bring out the nuclei of the cysts and 

 stain glycogen. However, for accurate 

 identification and differentiation from 

 other species of amoebae, staining with 

 hematoxylin is essential. The smears are 

 generally fixed in Schaudinn's fluid and 

 stained with Heidenhain's iron hematoxylin. 



Sapero and Lawless's (1953) MIF (merthio- 

 late -iodine -formaldehyde) stain -preserva- 

 tion technic can also be used. 



For concentration of cysts, flotation 

 in zinc sulfate solution (Faust et al. , 1938) 

 can be used. The cysts are distorted be- 

 yond recognition, however, by the other 

 salt and sugar solutions in common use 

 for flotation of helminth eggs. For con- 

 centration by sedimentation, the FTE 

 (formalin- triton-ether) sedimentation 

 technic (Ritchie, Pan and Hunter, 1952, 

 1953) or MIFC (merthiolate- iodine-formal- 

 dehyde-concentration) technic (Blagg el al. , 

 1955) can be used. 



Cultivation can be helpful in diagnosis 

 of amoebiasis, but only if fresh specimens 

 are used and if the laboratory personnel 

 are expert. Cultivation is not recommended 

 for general use. 



E. histolytica cannot be differentiated 

 morphologically from E. haybiuDiiii, and 

 its differentiation from other intestinal 

 amoebae, and especially from E. coli, is 

 not an easy task. There is a surprising 

 amount of discrepancy even among those 

 who should be qualified. Thus, in an eval- 

 uation by the USPHS Communicable Dis- 

 ease Center of the diagnostic ability of 42 

 state health department laboratories 

 (Brooke and Hogan, 1952), an average of 

 4. 1 out of 18 £. histolytica infections was 

 missed among 98 stool samples sent to the 

 laboratories for examination, and an aver- 

 age of 4.4 false positive reports was made 

 among the 80 negative samples. Further- 

 more, in an analysis of responses by mem- 

 bers of the American Society of Tropical 

 Medicine to a questionnaire on the clinical 

 and laboratory diagnosis of amoebiasis, 

 Brooke et al. (1953) found a surprising 

 lack of agreement in statements concerned 

 with the identification of E. histolytica 

 cysts and trophozoites. 



Goldman (1959, 1960) was able to dif- 

 ferentiate between Entamoeba histolytica, 

 E. liart>}ianni, E. nioshkovskii and E. coli 

 by a fluorescence antibody technic. Three 

 originally invasive strains of E. histolytica 

 which he studied differed significantly 

 from a non-invasive strain. 



