An historical review of the transmission of amebiasis indicates that little is known of the actual means of the transmission of the infection, and that the cysts of Endamoeba histolytica have not been recovered except within the body of man and reservoir hosts, under fingernails, in feces or associated with filth flies. The known continued high incidence of amebiasis in a children's home in New Orleans over a period of many years presented the opportunity of studying the mechanism of transmission of amebiasis in an institutional environment.
Two procedures were selected for the isolation of the organisms: (1) use of the Foerst centrifuge to recover organisms from liquid media, and (2) application of NIH swabs to detect contamination in relatively dry places of this institution. Experimental tests with the Foerst centrifuge indicated that the efficiency of the machine was above 70 per cent for the parasites tested. Concentrates of parasite organisms in this machine were obtained from dust samples, hands, toys, underwear and contents of the wading pool.
Endamoeba histolytica was isolated from six places: the hands and soiled underwear of the children, the bottom of the laundry chute, the damp sand in the play box, the pool contents, and the concrete floor of the pool after draining. Other parasites, including Endamoeba coli, Endolimax nana, Enterobius vermicularis, and undiagnosable amebic cysts, were found in these and other places. The tops of boxes, chairs, seats of toys, bed frames, laundered underwear, toys, book shelves, swings and slides, floors and stairways were all found contaminated with protozoan cysts and helminth eggs which had most probably originated from infections in the children.
The methods of transmission of amebiasis in this home suggest direct contact transfer aided by the general pollution of the environment. This conclusion has been reached as a logical inference. A description of the daily routine of the children has been presented, with an explanation of how these organisms might have reached the places from which they were isolated, and why they might serve as a source of infection for the children.
The epidemiologies of E. histolytica and Enterobius appear to parallel one another in this institution. The high incidence of these infections has continued in the home in spite of ordinary hygienic measures directed against them. On the other hand, the operation of this type of transmission has already been demonstrated for oxyuriasis. The habits of the children, living in close contact, and the employment of unskilled help who did not always realize the necessity of hygienic measures probably aided considerably in perpetuating the incidence of amebiasis in this institution.
Since the continued high incidence of amebiasis appeared to be due to direct contact transfer and general pollution of the environment, the home was cleaned throughout with live steam at the same time that mass chemotherapy directed against E. histolytica was carried out on the attendants and the children. The efficacy of steam sterilization as a supplementary means of eradicating the infection extrinsically was later tested by using NIH swabs in locations previously demonstrated as contaminated by the children. Four weeks after completion of the treatment the examination of one specimen from each of the children by means of the direct fecal film and zinc sulphate centrifugal floatation technic indicated that not a single stool specimen was positive.
These tests indicate that the use of live steam to sterilize the environment together with antiamebic mass chemotherapy constituted a simple and practical means of controlling amebiasis. It seems probable that, under similar environmental conditions elsewhere, this same technic might be applied with equal success.