HOST-PARASITE RELATIONS! INTESTINAL PROTOZOA 



in general the same as those discussed in Section II 

 above. It may be worth while, however, to repeat them 

 here. 



( 1 ) The viability of trophozoites and cysts outside of 



the body of the host 



(2) Methods of transmission 



(3) The factors involved in excystation 



(4) Excystation in the host 



(5) Localization within the host 



(6) Factors of the intestinal habitat in relation to 



trophozoites and cysts 



(7) Pathogenesis 



(8) Resistance and susceptibility of the host 



(9) Acquired immunity of the host 



(10) Resistance and infectivity of the parasite 



(11) Acquired resistance and aggressivity of the 



parasite 



(12) Host-parasite adjustments 



(13) Therapeutics 



(14) Host-parasite specificity 



(15) Prevention and control 



No special section in this chapter is devoted to the 

 practical aspects of host-parasite relations. These, how- 

 ever, are always kept in mind and any new data obtained 

 are always scrutinized for possible applications to pre- 

 vention and control. Investigations of host-parasite rela- 

 tions are of importance from the standpoint of personal 

 hygiene since they furnish the knowledge necessary to 

 protect the individual from protozoan infections. Of even 

 greater significance are the data oi use to workers in 



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