E. histolytica: host resistance and susceptibility 



assumptions; but the pathogenesis of amoebiasis is open 

 to experimental study and not until properly conducted 

 experiments have been carried out can we state definitely 

 what actually occurs. We know even less about secondary 

 amoebiasis than we do about amoebic infection of the in- 

 testine, and any attempt to describe its pathogenesis at 

 present would be futile. 



7. resistance and susceptibility of the host 



The problems involved. Our knowledge of the resist- 

 ance and the susceptibility of the host to infection with 

 E. histolytica is fragmentary and scattered and mostly 

 based on experiments on animals. Some of the questions 

 involved are as follows : Do the members of the various 

 human races differ in resistance to infection and in 

 severity of the symptoms ? Does the age of the host have 

 an influence on susceptibility and the character of the 

 disease? Does an infection with E. histolytica or with 

 some other parasite increase the resistance of the host 

 to subsequent infection? What relation exists between 

 host resistance and the invasion of the tissues of the 

 intestinal wall? Does the character of the climate influ- 

 ence the resistance of the host or the aggressivity of 

 the parasite or both? What immunological reactions 

 have been obtained by experiments with E. histolytica^ 



Racial differences. The influence of race upon suscepti- 

 bility to amoebic infection is not very clear at present. 

 Fletcher and Jepps (1924) found that Tamils are much 

 more susceptible than Chinese to both E. histolytica and 

 E. coll. The Tamils gave 19.1 per cent and the Chinese 

 5.6 per cent of infection with E. histolytica, and 1 1.9 per 



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