amŒbic dysentery in chicago


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intestinal obstruction, a group of New York

investigators performed experiments on cats andare able to show that in these animals highintestinal obstruction is accompanied by a rise inthe blood potassium to levels that they regard aslethal. This is a definite advance in knowledgeand if the experimental findings are confirmed inother animals, and particularly in man, a real stepforward will have been made.One always hopes that new knowledge will lead

to an immediate advance in therapeutics. It mustbe admitted, however, that unless the administra-tion of the suprarenal extract " cortin " will dothe trick, the emergency physician or surgeon islikely to- find the lowering of serum potassiumalmost as difficult as the removal of hypotheticaltoxins.


LIKE pilgrims to the holy city of Benares, eightand a half million people visited the " Century ofProgress " exhibition in Chicago during the summerand autumn of 1933. They made epidemiologicalhistory, for at a cost of about a hundred lives

they proved that amoebic dysentery could occuras an extensive water-borne epidemic in a civilianpopulation. The report on this epidemic nowissued 2 is comprehensive and deserves the closeattention of epidemiologists and protozoologists.Briefly, the investigations of the board of healthand the division of water purification of the cityof Chicago and the U.S. Public Health Service

appear to have established the following facts.Two hotels, whose water-supply was partly in

common, were the source of the outbreak, and twomajor sanitary defects were found. In one hotelcross-connexions were discovered between a sewerand discharge pipes of condenser-water which,after being used for cooling, was distributed tothe hotel and to the upper floors of the secondhotel: in certain conditions of overloading of thesewers and heavy rain this water might becomepolluted by backwash up the pipes. Secondly, inthe same hotel, leakage round a rotting woodenplug in an overhead sewer could contaminate acooled drinking-water tank below.

In the previous eight years 232 cases of amoebicdysentery had been reported to the Chicago boardof health. Of these, 8’6 per cent. were subse-

quently traceable to the two hotels, and an investi-gation in 1926-27 had shown a carrier-rate ofabout 5 per cent. in their employees. Of the 1409cases reported during the 1933 epidemic, 1050were among guests or employees of these hotels,and during the epidemic itself the incidence ofcarriers among the employees rose to 37’8 and47’4 per cent., with a corresponding risk of pollu-tion of the water-supply. As was to be expectedfrom the nature of the disease there was a long

1 Scudder, J., Zwemer, R. L., and Truskowski, R. Theirreport appears on p. 74 of the first issue of a new monthlyjournal named Surgery edited by Alton Ochsner (New Orleans)and Owen H. Wangensteen (Minneapolis) and published by theC. V. Mosby Company, St. Louis, U.S.A. In this country thesubscription price of the journal is 42s. per annum, post free(single copies 4s.).

2 Epidemic Amebic Dysentery. The Chicago Outbreak of1933. National Institute of Health. Bulletin No. 166. U.S.Treasury Department. Washington. 1936. Pp. 187. 20 cents.

latent period-averaging over three months-between exposure to infection and notification ofthe illness to the Chicago health authorities. Theincubation period varied greatly, being most

commonly about a fortnight ; in a quarter of thecases it was 11 days or less ; in a quarter, 12-20 ;in a third quarter, 21-36 ; and in the remainder37-120. The delay in recognising the outbreakwas increased by the scattering of the visitorsto their homes and difficulties in diagnosing acomparatively rare condition. Not more than20 per cent. of cases were correctly diagnosedbefore it became generally known that a largeepidemic of amoebic dysentery had occurred, andthe absence of the characteristic diarrhoea and ofEntamaeba histolytica in many cases added to thedifficulties. An acute onset with fever and abdo-minal symptoms led to a diagnosis of appendicitisin 16 per cent. of the patients who afterwards died,and the fatality-rate in the 32 cases treated byappendicectomy was 40 per cent. The mostcommon erroneous diagnosis in the fatal cases wasmalignant disease, usually of the rectum. After acorrect diagnosis had been made, the results of

specific treatment were very satisfactory : indeedthe response to a therapeutic test is of great valuein establishing the diagnosis.3 The chief interestof the outbreak naturally lies in the epidemio-logical investigations, which were exhaustive. Acurious feature was the absence of the entericfever and diarrhoea usually associated with water-borne epidemics. The explanation suggested isthat the chlorine content of the Chicago water-supply suffices to prevent survival of bacteria,but not of cysts. In a later outbreak amongfiremen at the Chicago stockyards in 1934,4 inwhich the water consumed had escaped chlorina-tion, amcebiasis, enteric and gastro-intestinaldisorders were all noted. Control of the outbreakwas attempted by elimination of carriers of cystsfrom the food-handling staffs, but there was noevidence that these efforts were successful. How-ever the authors add a caveat " that the experiencein this respect is not to be regarded as an indicationeither of the value or lack of value of the procedureunder some other conditions."

By this unique epidemic a new hazard to civilpopulations has been revealed. The United Statesof America has led the way in personal hygieneand the careful protection of food and drink, butthe Chicago outbreak of amoebic dysentery showsthat in the end it is sanitation which counts, andthat, as has been consistently taught in this

country, an unpolluted water-supply must alwaysbe the first line of defence. Although there is lesslikelihood of any similar outbreak here, carriersare well known to exist,5 and one lesson to be learntis that especial sanitary vigilance is needed inconnexion with all water-borne diseases at times-

e.g., in London at the coming Coronation-whenaccommodation is strained and weak points in asanitary system are most likely to be revealed.

3 McCoy, G. W., and Hardy, A. V. (1937) J. Amer. med. Ass.2, 1357.

4 Hardy, A. V., and Spector, B. K. (1935) Publ. Hlth Rep.,Wash. Reprint No. 1676.

5 See Lancet, 1934, 1, 46.