THERAPEUTICS 



lO. THERAPEUTICS 



Host-parasite relations may be profoundly modified 

 by treating the host. This may take the form of build- 

 ing up the resistance of the host (biological therapy) or 

 of destroying the parasite either directly or through the 

 host (chemical therapy). 



(i) Biological therapy. Constitutional, biological 

 therapy involves the usual procedures for maintaining 

 or increasing natural host resistance, such as rest, min- 

 imum movement, and the treatment of other infections 

 present. Often the host may be aided by a certain type 

 of nourishment. For example, a milk diet is prescribed 

 in cases of intestinal amoebiasis since milk produces a 

 small amount of putrefaction and is practically all ab- 

 sorbed before it reaches the large intestine where the 

 amoebic ulcers are located. 



Vaccines, antitoxins, etc., that increase the active re- 

 sistance of the host are not available for protozoan dis- 

 eases. There seem, however, to be no insurmountable 

 obstacles to their preparation and use. 



(2) Chemotherapy. Drugs may be used to aid the 

 host either as parasiticides by destroying the parasites 

 or as agents for building up host resistance. In many 

 cases it is difficult to determine which of these processes 

 is taking place. There seems to be no reason why, in the 

 case of intestinal infections, enemas containing drugs 

 toxic to protozoa should not be effective parasiticides. 

 Thus rectal irrigations with a solution of tannic acid or 

 of bihydrochloride of quinine have been recommended 

 in cases of amoebic dysentery, and rectal injections of 



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