560 Protozoa of the Digestive and Urogenital Tracts 



The factors responsible for development of severe amoebiasis have not 

 been determined. Although the appearance of precipitins and comple- 

 ment-fixing antibodies indicates an immunological response, the signifi- 

 cance of such factors in the host-parasite relationship is uncertain. 

 Differences in severity of amoebiasis may be correlated with differences 

 in diets (2, 55), but the relation of specific dietary deficiencies to the 

 development of severe amoebiasis remains to be established. The bacterial 

 flora of the colon may be a contributory factor occasionally, as indicated 

 by observations on experimentally infected rats (156) and kittens (33, 

 126). Such a bacteriostatic agent as penicillin has shown therapeutic 

 activity in infected rats and may also have a prophylactic effect when 

 administered before inoculation with E. histolytica (156). 



Chemotherapy 



Intestinal amoebiasis. Completely effective treatment involves 

 elimination of the infection. Therefore, the results can be determined 

 only by periodic laboratory examination of the patient for at least six 

 months, and preferably a year or more, after treatment. Even an ideal 

 drug would not maintain a perfect record in such tests because it is im- 

 possible to eliminate all chances of reinfection. Consequently, the best 

 that can be expected is a high percentage of "permanent" cures. 



During treatment and for a short time afterward, the diet of the patient 

 with a mild case should omit roughage and intestinal irritants. The 

 patient with an acute case is usually limited to liquid foods and is pref- 

 erably kept in bed during treatment. The choice of orally administered 

 drugs varies with the physician. The more commonly used types fall into 

 three groups, arsenicals, quinoline derivatives, and alkaloid derivatives 

 (1, 3, 40, 41). Some of the newer antibiotics form a promising fourth 

 group. 



The arsenicals include stovarsol (acetarsone, or acetylamino-hydroxy- 

 phenylarsonic acid) and carbarsone (4-carbaminophenylarsonic acid). 

 Carbarsone seems to be the best of various arsenicals (1), whereas stovar- 

 sol has been considered somewhat dangerous for routine clinical use (3). 



Several quinoline derivatives have given good results. Chiniofon (yat- 

 ren, quinoxyl, anayodin) is therapeutically satisfactory without producing 

 serious toxic effects (40, 41). Vioform (iodochlorhydroxyquinoline) seems 

 to be more active than chiniofon and produces only minor toxic effects 

 (3). Diodoquin (5,7-diiodo-8-hydroxyquinoline) is a more recently intro- 

 duced drug which seems to be quite effective. 



Widely used alkaloid derivatives include kurchi alkaloids and emetine 

 (the active agent of ipecacuanha). Kurchi alkaloids, from the bark of an 

 Indian tree, show no marked toxicity, but the amoebacidal activity is 

 somewhat less than that of other widely used drugs (3). Emetine-bismuth- 



