Dogs maintained on a fish diet were highly susceptible to infection with a human strain of Endamoeba histolytica, obtained from stock cultures or from an experimentally infected animal. Infected animals fed a strict fish diet developed and maintained acute or subacute infections for several months. The course of these infections was sufficiently uniform and mortality among infected animals was sufficiently low to permit chemotherapeutic studies. The infection was primarily an amebic colitis; extra-intestinal infections were not encountered.
Treatment of the infections with established antiamebic and antibacterial drugs revealed satisfactory correlation between the chemotherapeutic response of canine and human amebiasis. Emetine HCl, carbarsone, chiniofon, diiodo-oxyquinoline and amodiaquin exerted antiamebic action in dogs. Cures were obtained with carbarsone, chinifon and diiodo-oxyquinoline but not with emetine or amodiaquin. Chloroquin, sodium penicillin G, streptomycin, sulfadiazine and succinylsulfathiazole were ineffective under the conditions of this study.
The failure of the antibacterial agents—penicillin, streptomycin, sulfadiazine and succinylsulfathiazole—to affect the course of the infections indicated that amebae rather than bacteria are the primary etiologic agent in canine amebiasis.
Consideration of the relative merits of dogs, monkeys, kittens and rats for evaluating the activity of potential antiamebic drugs indicated that canine infections should be particularly useful in the search for new chemotherapeutic agents.