theme 12 session 3 and 4 childhood helminth infections mc 2010_2.pdf

7/28/2019 Theme 12 Session 3 and 4 Childhood helminth infections MC 2010_2.pdf

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J. Parasitol., 85(3), 1999 p. 392-396? American Society of Parasitologists 1999

THIS WORMY WORLD*

Norman R. StollRockefeller Institute for Medical Research, Princeton, New Jersey

One cannot have experienced the war without having been impressedanew, and depressed, by the amount of parasitism in the world. Speak-ing helminthologically, it may be referred to as the grave host r6lewhich the lives of men play in the lives of worms. Or, think of it theother way about, for there is likewise the great parasitic role the livesof worms play in the lives of men. Back from the Pacific come a thou-sand-odd Americans with schistosomiasis, and a few times that manywith filariasis, and several multiples more with ancylostomiasis (sensustrictu). To homes widely dispersed throughout the land go these ex-service men, to live a lifetime in familiarity with the strangely soundingnames of their distantly-acquired helminthiases.

These observations suggest familiar concepts to the parasitologist.The One World of Wendell Wilkie that struck with the force of a newidea at the politicoeconomic level, is, of course, decades, and in somerespects centuries old, to the student of disease-producing agents. How-ever, each parasitologist is wont to live in his thinking in One Worldwith the species which particularly interests him. There have been,therefore,

onlya few

attemptsto

bringall

speciesof

majorhuman

concern into the short focus of a brief presentation. In the belief thatthere might flow from such renewed consideration certain emphasisuseful to world citizens and in our science, this attempt at such a suc-cinct statement has been made.

Just how much human helminthiasis is there in the world?The bare mention of the question will make those of you with noso-

geographical interests-or, better, helminthogeographical interests-warily scratch a mental ear and mull over a remark that ends "whereangels fear to tread." If so you are doing furtively what I did openlyand frequently in these last weeks, as the difficulties in the accomplish-ment of such a combined analysis and synthesis presented themselves.I need scarcely remind you of what some of those hurdles are: so manyparasitological surveys of but small numbers of people, frequently ofother design than to represent fair samples of an area, done by workersof varying aims and by techniques of even more variable efficiency inrelation to the task at hand. Worse, at first sight, from a true census

standpoint, is the fact that in order to gain a comprehensive perspective,examination results made at intervals over years have needed to becompressed as if made at a single recent point on the time scale, some-times without full knowledge of what complicating or ameliorative fac-tors had been interposed in the meantime.

One cannot change this state of affairs at the moment. Instead, onetakes the data as they are and does the best one can. One remembersthat whatever legitimate objection there may be to their projected useinheres also in all generalizations made in this field. The informationpresented this morning is from the same kind of data we all have had,of necessity, to employ in piecing out the impressions we currentlypossess, of the extensiveness of the problems to be discussed. In sub-stance, the net difference in the use made of them here by me, is thatI have restated such adjectival generalizations of the reference book as"rare," "common," "prevalent," into the best quantitative terms whichsearching of the records and epidemiological insight have permitted.

One needs to be reminded, of course, that even the statement of 2166

million human beings on the planet in 1940 includes estimates ratherthan uniformly precise census figures. White and Jacoby (1946) havenoted that the estimates for China, which run from 400 to 550 millions,represent a discrepancy, itself greater than the population of the UnitedStates. For my purposes I have relied primarily on data furnished orapproved by the Office of Population Research, Princeton University,including the recent League of Nations publication by Lorimer coveringthe U.S.S.R. The Statistical Yearbook of the League, which could equal-ly well have been employed, would have modified certain sub-totals,but it comes out with a like global total of 2170 million.

The censuses or estimates vary in date from 1920 to 1942, more than

* Address of the President, American Society of Parasitologists, De-cember 27, 1946, Boston.

half of them occurring in the 1935-1940 period. An approximately sim-

ilar statement as to dates applies to the helminthic infection figures,although publications into 1946 have been consulted.

Some of the details of the analysis can be visualized best by exam-ining the status of specific infections. Let's start with Trichinella spir-alis. Here is a parasite whose life history, one of the first worked outfor a helminth of man, has been known for nearly a century. It is aninfection about which, in this country, we have developed good epi-demiologic information in the last decade or so, an infection whichshould have special interest for a Boston audience, in view of Augus-tine's (1942) evaluation of it as the "most serious parasitic disease inNew England."

Trichinella is almost completely absent in man in a major portion ofthe world. East of Suez (more specifically Syria) all the way to SanFrancisco, as well as in Australia, in Africa, and generally throughoutthe torrid zone, it is substantially nonexistent as a human infection. Inthese regions live about 2/3 of the earth's inhabitants, but the few casesof record

suggestan infection rate there of the

order, say,of one hun-

dredth of one per cent in man.The classic zones of infection have been instead in central Europe,

and those parts of temperate America to which its emigrants and theireating habits for pig have gone. In Europe, the reports in the pre-waryears concerning man, as well as officially inspected pork, have sug-gested exceedingly low rates. The war years themselves, however, havefurnished outbreaks in nearly all European countries, and recurrent ep-isodes in German troops during the campaigns, especially in Poland andRussia. Results of surveys there on a comprehensive scale, by directmicroscopic examination supplemented by digestive techniques appliedto muscle obtained at human necropsies, are not yet available. Europe,including Russia, contains above 500 million people. If we assume thediaphragm infection rate throughout Europe to be as low now as oneper cent (and this is much higher than pre-war indices), that would meanabout 5 million cases.

In South America, recent rates reported from Chile, (Neghme, 1944)slightly exceed 10 per cent, and from Uruguay 3 per cent (Talice andFiandra, 1943), with the probability that the latter may reflect the situ-ation in Argentina. Mazzotti (1944) believes 12 per cent the likely figurefor Mexico City. These four areas of Middle and South America possessthen, by extrapolation, about one million cases. In Canada, accordingto the examinations of Cameron (1943), and Kuitenen-Ekbaum (1941),there is an apparently trifling infection rate of about 1 per cent, perhaps100,000 in all Canada-which is not so trifling but that clinical out-breaks occasionally develop. This low rate, and trichinosis outbreaksnonetheless occurring in Canada without the exigencies of famine, maybe taken as a pointer toward how low the index must become beforecomplete control of trichina is accomplished.

In the U.S.A. we have trichinosis in a bigger way. Thanks to thenearly 12,000 necropsy examinations in recent years, nearly half ofthem by the National Institute of Health workers, who combined mi-croscopic and digestive techniques, we have now what must be consid-ered a rather

good perspectiveof the situation

throughoutthis

country.It's over-all finding is about 1 in 6 Americans infected. On the basis ofthe 1940 census of 131 million people, there are then 21 million Amer-icans who have ingested Trichinella spiralis. Proportionately, in certainparts of the country it would be higher.

Trichinella incidence obtained at necropsies has the advantage ofbeing a figure which indicates total exposure, inasmuch as most infectedindividuals would appear to retain evidence of calcified larvae through-out life. It is further of interest, therefore, that the NIH data show 41/2per cent of positives with counts of 50 or more larvae per gram ofmuscle, infections of an order "capable of causing pronounced clinicalsymptoms." These individuals, if adults, would, I calculate, be carryingmuscle loads in excess of one million trichina larvae.

Hall and Collins (1937) emphasized that the United States "has thegreatest problem of trichinosis of any country in the world." The figures

392


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STOLL-THIS WORMYWORLD 393

adduced indicate that also it should be said: we have in this countrymore than 3 times as much trichinosis as is known in all the rest of theworld put together.

Because the problem is thus predominantly our own, one is temptedto digress and to muse a little about such a record, which, of course, isa preventable one, and maintained primarily through allowing hogs tobe fed uncooked garbage containing meat scraps harboring live Trich-inella. Those of you who travel the Pennsylvania R. R. into New York

become aware that we maintain in the Jersey meadows at Secaucus amalodorous demonstration for every traveller to observe how it is done.When we Americans manifest an unbecoming impatience at how sloth-ful other peoples are, in undertaking the necessary and obvious stepsto free themselves from this, that or the other endemic helminthiasis,let us pause a moment with ourselves. We can ruminate with profit onthe extraordinary slowness demonstrated by a supposedly widely edu-cated people, in failing to protect itself against trichinosis, when it cando so by the simple device of eating pork only when the trichinae in ithave been cooked, say, to the consistency of medium-boiled eggs. Sucha simple protective measure has been propagandized in this countrywidely for well-nigh a half-century. We can also ruminate on the ex-traordinary inertia of public officials, legislative and other, in their oddfailure to adequately control the feeding of uncooked trichinae in rawgarbage to hogs.

One is given to wonder, considering that our scientific analysis of thesubject is now competent, and the road to control thus clear, whether

we are dealing here not with a mercenary, but with a psychological,block against effective action. Perhaps "trichinosis" is a word of toolittle odium. Would Americans be equally comfortable in realizing thateach 6th among them is harboring garbage worms? And that one in 150persons dying from other causes takes to the grave a million or moregarbage worm larvae? What wasted "blind-alley" effort from the stand-point of Trichinella demography!

If time permitted considering the helminths of man, species by spe-cies, in relation to their incidence and the populations of individualcountries or other geographical units, it would be as illuminating anexperience to you, I think, as it has been to me. It is a sort of newperspective in helminthology, or at least a new emphasis-this view ofthe worms man lives with, not primarily in their taxonomic relations,nor in the accident of historical or local interest, but in terms of theover-all number of his fellows that are burdened with them. Omittingmany of the steps by which the factual statements are made, we comeout like this at the world level for some familiar forms:

Taenia saginata, the beef tapeworm, 39 million infections, most as-cribed to Africa and to the U.S.S.R., but Taenia solium, the pork tape-worm, less than 3 million, with nearly a half in Asia. Cysticercosismanifestly makes up only a small part of these. Further, one is surprisedto discover that the best estimate for hydatid infection, which, accordingto Barnett (1937), stimulates about a hundred titles a year in the liter-ature, appears to come to less than 100,000 cases, with South Americaleading. For Hymenolepis nana there are about 20 million currentlyindicated infections, 2/3 of them in Asia. This species seems rare inOceania. On Guam we did not encounter it or any other tapeworm innatives, although infections were found in 0.5 per cent of service men,which they had evidently brought to the area from homeside. Diphyl-lobothrium latum, the broad or fish tapeworm, shows about 3 millioncases each in the Baltic littoral, northern Russia, and U.S.S.R. in Asia,and a world total of 10 million. Thus, the cestodes altogether represent72 million infected individuals.

Of fish-transmitted trematodes, Clonorchis sinensis, the human liverfluke, confined to Asia, seems not to be in excess of 19 million infec-tions. The related Opisthorchis felineus, confined to fisher folk in EastPrussia, the Dneiper river basin, and northern Sverdlovsk in AsiaticU.S.S.R., has indications of one million.

Of the fishborne small intestinal flukes, Metagonimus and Hetero-phyes, I have been unable to find evidence of more than a few hundredthousand probable infections. A similar statement holds for Echinosto-ma and Gastrodiscoides.

The large intestinal fluke, Fasciolopsis buski, again a form confinedto Asia, totals 10 million infections, about a half of which are in theChekiang endemic center. The related form, Fasciola hepatica of theruminant liver passages, has been reported with increasing frequency inman and from all continents, but there is no indication that more than100,000 cases are involved. Dicrocoelium dendriticum, also normally

in ruminants, has been found (including confirmations at necropsy) es-pecially in the Stalingrad and Transcaucasus regions, where it occurs insufficient degree to indicate several hundred thousand cases.

Paragonimus westermani incidence has not been easy to define, butwith the aid of some relatively recent surveys it is possible to place thelimiting value of about 3 million cases of lung fluke infection in Asiaand a few thousand in West Africa.

The several trematode infections of man just mentioned account for

about 34 million infected individuals. The schistosomes represent morethan three times as many additional trematode infections, with S. ja-ponicum the most numerous. For the six major centers of S. japonicumendemicity in the Yangtze valley, an average incidence is given of about7 per cent microscopic positives, barring some heavily infected villages(Faust and Meleney, 1924). If for present purposes and to include non-egg-passing cases, one takes 20 per cent of the entire populations ofthe provinces in which such foci are described, adds to it 10 per centof the entire populations of such other Chinese provinces and Japaneseprefectures as are known to have foci, and includes for the Philippines30 per cent of the population of the islands of Leyte, Samar, Mindoro,and Mindinao-the total infected with S. japonicum represents 46 mil-lion people. The anomalous Dutch East Indies focus in the Celebes(Bonne and Sandground, 1940), presumably contains only a few thou-sand infections.

For S. haematobium, some regions as in East Africa suggest a 50 percent incidence, others grade down to 10 per cent as in North Africa,and for Egypt we have the estimate of Scott (1936, 1937a) of 6 millioninfected. The African areas free of infection are in general of low pop-ulation. To the millions carrying S. haematobium in Africa are to beadded only an approximate 200,000 in the Near East and a few thou-sands in Europe, for a world total of 39 million bilharzia-infected in-dividuals. A small outlying infective center on the southern end of Por-tugal (Bettencourt.and Borges, 1927) may have now a new and oppo-sitely placed focus in western India (Andreasen and Suri, 1945), bothat the moment inconsequential numerically.

S. mansoni is the most dispersed of the three schistosomes of man(if we include intercalatum with haematobium). Besides the equatorialzone in Africa, there is a band of infection from northern Nigeria west-ward. These with Scott's 3 million cases in Egypt total 23 million forAfrica. Whether establishment of our western hemisphere endemic areasis to be ascribed exclusively to the slave trade, seems to be a matter toquestion (Magalhaes and Dias, 1944). But foci on this side the Atlantic

appearto account for about a third of a million cases in the West Indies,

30,000 in Venezuela according to Scott, and nearly 6 million in thespreading infective zone in northeastern Brazil. All told this gives 29million persons infected with S. mansoni, and 114 million for the 3schistosome species combined.

In the absence of comprehensive surveys for parasites such as guineaworm and the filarids, a device of limiting values has been employed.The areas in India from which Dracunculus medinensis has been re-ported-which having small rainfall are in general the low hookwormzones in India-have about 110 million inhabitants. If as high as 25per cent is used for the guinea worm incidence, there are 271/2 millioninfections indicated. A similar tactic applied to Afghan, Iran, Arabia,and southwestern U.S.S.R. in Asia, yields slightly over 5 million morecases of "the fiery serpent." Similarly the African endemic areas wouldcontribute another 15 million infected, but the single focus on this con-tinent, in northern Bahia, Brazil, involves only a few thousand. Figuredby this method, which may be too generous, the world has 48 million

guinea worm cases.Onchocerca in Central America is localized on the Pacific slopes of

3 states in Guatemala, and 2 (not 3) departments of Mexico. (BothDampf (1942), and Bartter (1945) have taken occasion to insist that thedepartment of Guerrero is free from the disease.) These 5 political sub-divisions have a combined population of 2/3 million. In Africa, the zonefrom Sierra Leone eastward through the infected regions contains 57million inhabitants. If a third of all these are involved with the infection,the world total for Onchocerca would not exceed 20 million.

Mansonella ozzardi is confined to regions of Middle and SouthAmerica with a population of 21 million. If a third are infected thereare 7 million with Mansonella.

Acanthocheilonema perstans occupies the Onchocerca regions in Af-rica, supplemented by foci in North Africa; and in South America over-laps, in part, the Mansonella areas. It is also found in Dutch New Guin-


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394 THE JOURNAL F PARASITOLOGY, OL. 5, NO. 3, JUNE 1999

ea in the Pacific. These regions have a combined population of about81 million, and if a third are infected, there are 27 million Acantho-cheilonema cases.

Loa loa is strictly an African form of the west and west centralregions where dwell 39 million people. If a third of these have loaiasis,there are 13 million.

These four filarid forms, conveyed respectively by Simulium, by Cu-licoides, and by Chrysops, parasitize then 67 million people. Despitethe

simplifiedmethod of

approximatingthis

total,it

mayhave consid-

erable validity, although the estimate for Onchocerca is possibly toohigh, and that for Acanthocheilonema too low.

The same general method can be used for orientation of Wuchereria,although it cannot be applied so simply. In the following analysis W.bancrofti and W. malayi have not been distinguished. One, the other,or both, are at home in human beings and appropriate mosquitoes prettymuch throughout the tropical part of the world. Wuchereria is endemicin Oceania, with the notable exception of New Zealand, most of Aus-tralia, and some of the lesser islands; it is in the Dutch East Indies, withJava's 40 millions surprisingly free, however; it is in the Philippines,Formosa, and southern Japan; in the coastal area of Asia-broadly in-terpreted-from northern Kiangsu province in China clear around theeastern, southeastern, and southern fringe of the continent, almost toSuez; it is in the broad equatorial belt across Africa, together with Mad-agascar off the southeast coast, and North Africa; it is in South America,especially in an area around Belem, Brazil (Causey et al, 1945), and a

coastal belt from the Guianas to Colombia; and in the West Indies.How many in this broad tropical territory shall we define as having

filariasis? Only those who show microfilariae in the blood? If so themarines garrisoned near Samoan villages and later invalided home withtell-tale symptoms could not be said to have had this infection, for thenumber showing microfilaremia, even up to now, is of the order of muchless than one per cent. But if these service men were properly diagnosedas having filariasis after endemic residence measured in months, is therereasonable probability that anyone fails to receive infection who growsup from babyhood in a filariated area (Dickson, Huntington and Eic-hold, 1943; Franks, Chenoweth and Stoll, 1947)? The simplest assump-tion then would be to say that all the population in endemic regions isfilariated, and put the responsibility on any disputant to prove how manywere not. That would mean 758 million people, about 1/3 the populationof the globe.

Actually not all filarial foci are as hyperendemic as Samoa, with year-round mosquito breeding. In regions where the vector, through droughtor cold, gives the inhabitants an annual respite, it seems probable thatvariable proportions of the population escape. Determined country bycountry on this basis there are 157 million cases of wuchereriasis inAsia, 22 million in Africa, 9 million in Middle and South America, onemillion in Oceania, with a world total of 189 million, about half ofthem showing microfilaremia. Perhaps the over-all figure thus stated istoo low, but I do not believe it is too high.

Let us turn briefly to-shall I say-more homely findings? which inthe last decade or so have surprised even parasitologists, namely, thoseon enterobiasis. In the period following World War I, a number of work-ers in the Baltic countries and the U.S.S.R. explored various more directprocedures than fecal diagnosis for determining the presence of Ente-robius (Cram et al VI, 1937). For a time their results were somewhatunnoticed generally, but beginning with the reports of Headlee (1935)and Hall (1937b), the information accrued has been in some respectsstartling. Perhaps we were thinking what was true in Europe could not

happen here.You recall Stiles' generalization that with hookworms found in Texas,in Florida, and in Virginia, the triangle so defined demonstrated widedistribution of the disease in our Southern States. Now one may drawa polygon for Enterobius with vertices at Washington, D. C. (41 percent incidence, "considered as representing a fair cross section" of thewhite population, Cram XXVIII, 1943); Boston (boys 15, girls 23 percent, Weller and Sorenson, 1941); Toronto, Canada (adults 52, children60 per cent, Kuitenen-Ekbaum, 1943); South Dakota (39 per cent inschool children, Mauss, 1945); San Francisco (boys 29, girls 34 percent, Jacobs, 1942); New Orleans (30 per cent in removed vermiformappendices, Schenken and Moss, 1942). These data are not of institu-tionalized persons, where, even in the South, we have come to be ac-customed to much higher percentages than those noted (Evans andMoore, 1942; Sawitz et al, 1940).

The over-all results obtained during the last decade, by examiningfor Enterobius material taken directly from where the worms have been,suggest that there are factors, still not precisely defined, which are es-pecially favorable for pinworm dissemination in our modem way ofliving. This applies to families not only at low but at very high sociallevels, I assure you-and so could some of my friends; it applies torural as well as to urban life; it appears to apply more the farther northone goes; it applies particularly to institutionalized persons (Cram,

1941) both north and south, here and abroad, whether of the aged, thechildren, or the psychopathic; and up to now has been demonstrated toapply geographically to Europe (Young, 1942) both in and out of Russia(Schiiffner, 1944, says 100 per cent of the children of Amsterdam, areinfected), to the Argentine (Bacigalupo, 1941), to Mexico City (Maz-zotti and Quintanar, 1943), and to Manila (Chanco and Soriano, 1939),as well as to the United States and Canada.

It appears to apply in lessened degree the closer you approach thehumid tropics, as increasing evidence in Middle America (Mazzotti,1945; Sutliff and Echandi, 1946) and elsewhere attests. On Guam,where the natives were full of intestinal parasites, we found only oneper cent of the children positive by scotch tape (Stoll, Chenoweth andPeck, 1947), and except for Manila, it has not been reported in highincidence in the Pacific.

Only in Northern America and Europe, including U.S.S.R., can theover-all number of infected be extrapolated with confidence, and thetotals reach 18 and 87 million. This is about equivalent to the numberindicated in the balance of the world by the application of a cautiousbut reasonable increase in the incidence data from other types of survey.Altogether in the world this brings a tentative total of 209 million in-fected with pinworm.

Let us turn now to certain other nematodes that alone contribute overhalf of the helminthiases of man.

It is just over a hundred years since hookworms were first observedas human infections, and named A. duodenale. It is slightly less than ahalf hundred years since the endemicity and gravity of hookworm in-fection on this side of the Atlantic were recognized, and Stiles (1902)described N. americanus. The realization of the damage caused by theseforms eventually brought into play, first in this country and later inmany of the endemic areas of the world, the most formidable campaign-ing ever undertaken against human helminths. This considered and con-siderable attack did not eventuate in ridding hookworm completely frommuch territory. Except for certain mines, I have found only one specificreference to such a result-date 1941 (Spitzer), in re St. Martin of theNetherlands West Indies of a few thousand inhabitants.

It should be said immediately that the anti-hookworm goal did notfor long envision eradication. Instead it evolved, and campaigning ex-erted itself mostly in blunting the curse in areas which appeared to havethe greatest hookworm burdens. The making of permanent gains againstthis infection has come up against the changing of deep-seated, long-established customs that are not to be easily disestablished, and againstnutritional and economic problems not to be quickly resolved. As BaileyK. Ashford wrote (1934) near the end of his life: hookworm "parasitesplus poorly balanced food bring fatalities and serious grades of anemiawhich would not occur from parasites alone.... Only when the funda-mental thing is done will the disease as a disease disappear from PuertoRico. And that funda-mental thing is the provision of better food forPuerto Ricans.... It is, therefore, no longer a medical problem, but asociologic one of the very first water."

Nowhere in the world has grappling with the infection been so per-sistent (barring recessions) as in our own South, and Ceylon. I havefound no record of decreased incidence in Ceylon, but the resurveys inthis country made during the 1930s and summarized by Keller, Leathersand Densen (1940) point out a 2/3 decrease in incidence since 1910-14. About one-fourth of the remaining positives still show more than21/2 ggs per milligram, indicating worm burdens "sufficiently severe toproduce clinical symptoms."

If one studies the incidence data of 11 southern states at the earlierand later periods, in relation to white and negro rural populations of the1910 census and the 1935 census approximation, it would appear thatthe number of hookworm-infected Americans has decreased from about4/2 million to 13/ million in the interval. This would be a decrease of61 per cent in the number of infected individuals, to match the decreasein incidence of 68 per cent. What is equally of interest is that geograph-


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STOLL-THIS WORMYWORLD 395

ically the infected region of the 1930s is still co-extensive with that ofthe earlier period.

For the purposes of my present discussion, one of the results of theanti-hookworm campaigns, and the residual interest they engendered,has been the accruing of information on incidence throughout the world,not only concerning hookworm but associated intestinal helminths aswell. With no sizeable dents known to have been made in the incidenceof infection anywhere but here, it has been possible to employ data of

several years ago to supplement recently gathered facts, and thus helppiece out the picture of the number of infected persons. Without at thismoment presenting an analysis in detail, it summarizes as follows:

For hookworm. From one to a few million in Oceania, Europe, North-ern America, and the U.S.S.R.; up to 359 million in Asia, inclusive ofJapan, the Philippines, and Dutch East Indies. Of the Asiatic total, 205million are assigned to India, broadly speaking-a country whose hook-worm burden is increasing. The total for the world is put at 457 million,a numerical measure of the weight of mankind's worst helminthic path-ogen.

For Ascaris. In Northern America, 3 million; in Middle and SouthAmerica, 14 times as much; in Africa, nearly 60 million, in some areasthere, ascaris being said to cause more disability than any other hel-minth (you will remember that in our own South while incidence ofEnterobius and hookworm is less in negroes than in whites, the reverseis true of ascaris). For the world, 644 million ascaris infections-these,with hookworms, representing about half of man's helminthiases.

I have adopted Winfield's estimate, which is based both on his ownwork and that of the China Hookworm Commission, of 335 millioninfected Chinese. You may remember the graphic analysis from whichWinfield (I, 1937) concludes that the Chinese harbor 6 x 109 adultascarids; capable of producing 22 X 1016 eggs annually. Further, thatthis mass of adult ascarids is equivalent to the weight of 442,000 men.Winfield could have continued with a further interesting computation.If the daily egg-laying capacity of a well-fed pair of A. lumbricoides isput at 200,000, such fecundity is at the rate of about 5 grams of eggsper year. Winfield's average Chinese infections of 18 worms would thusyield over 1/10 of a pound, and his whole infected Chinese populationabout 18,000 tons of ascaris eggs annually. There is a huge nutritionalbeneficence bestowed upon ascaris by the human host in China alone.

For Trichuris. About a half million infections each in Oceania andin Northern America; roughly 25 to 35 million each in the U.S.S.R.,Africa, Europe, and Middle and South America; but 227 million in Asia.

The world total comes to 355 million trichuris-infected individuals.For Strongyloides we must accept any estimate based on present data

as inadequate. The usual surveys report very little, much less than isprobably present, and the high incidence figures in occasional specialreports have usually been on small numbers of individuals. Using avail-able data, only Africa with about 31/3 million, Middle and South Americawith 8/2 million, and Asia with 21 million contribute significantly to atentative world total of 35 million infections.

Of recent years another small-intestine-inhabiting nematode has ob-truded itself more and more in surveys for human helminths, namelyTrichostrongylus. Usually thought of as a parasite of ruminants, or per-haps better of herbivores, a half-dozen species have now been reportedfrom man. The data suggest about 3 million infections in Japan andKorea, and an additional 11/2 million in India, with a million more inthe U.S.S.R., mostly in Transcaucasus and the Ural region. The foci inAfrica appear to involve no more than a few thousand cases, but even

so the world total is 5/2 million.All told we have noted just over 2200 million helminthic infectionsassigned to just under 2200 million people on the planet. If you havegained the impression that it must be scientifically labelled a "tentative"statement, you may also have gained the impression that it was by nomeans lightly arrived at. Both impressions are correct.

The Chinese have a saying, "If you do not scale the mountain, youcannot view the plain." Once population totals of the helminthicallyinfected are available, certain generalizations immediately emerge.

First, a host view. Some people in the U.S.A. and Canada-NorthernAmerica in our classification-have a way of feeling that we are arelatively helminth-free people-it is the rest of the world that is reallyparasitized. Well, part of such a statement is partly true. Actually North-ern America shares with Oceania and Europe, exclusive of the U.S.S.R.,a status of about 1/3 as many helminthiases as people; for the U.S.S.R.

in both Europe and Asia this rises to 2/3 for Asia and Middle and SouthAmerica it is not far from 4/3; for Africa over 6/3.

Second, a worm view. The relative survival ability of different par-asitic groups is thrown into sharp relief in terms of the number ofparasitized human hosts. There are only 72 million cestode and 148million trematode infections in our totals, but over 2000 million nem-atode infections. This is doubtless a tribute to the variety and compar-ative biological efficiency of nematode life cycles. All cestodes reach

man by the host's own act, albeit at times not consciously; throughingestion by man of egg or larval forms; trematodes similarly reach himpassively, through ingestion of larval forms, but in addition activelythrough the parasites' own efforts, as witness schistosome cercariae. Itis, however, the nematodes that exhibit the most varied methods. Theyreach man by his own act of ingesting ova that have been recentlypassed, and ova that have had to ripen externally for days or weeks; byhis own act of ingesting larval forms in water, and larval forms in food.They also reach him not through his own act but on the initiative ofthe parasites themselves, infective larvae actively penetrating his bareskin in contact with moist soil, and actively penetrating his skin incontact with the mouthparts of blood-sucking insects which reached himby air-borne tactics. Each of five helminthic species, illustrating four ofthese nemic life-history styles, registers more human infections thaneither all the cestodiases or all the trematodiases. Only two in the clas-sification, namely Dracunculus and Trichinella, which come in by waterand food, show so few parasitisms as do the food-transported flatworm

species.Third, a sanative view (which might, less provocatively, be called a

sanitary view). If we bar hydatid and garbage worms from consideration(recall they represent only one per cent of the total), all these helmin-thiases depend solely, or mainly, on man as the definitive host, not onthe maintenance of reservoir hosts. In their ultimate cycle of man backto man, and cutting across the taxonomic fences, these helminthiasesfall into two great categories. One in sevent of the total helminthicinfections of man can he classified as due to his ineffective insulationfrom transfer hosts. The other 6/7 of man's helminthiases are due toineffective insulation from his own excretory products. The one-seventhreach him via cyclops, or they reach him via mosquitoes (sensu latu).The other six-sevenths reach him, immediately or eventually, by themethod of H. nana and Enterobius, or by the method of Ascaris andTrichuris, or by the method of T. saginata and Clonorchis, or by themethod of Ancylostoma and Necator, or by the method of the schisto-somes. In all of these 6 out of 7 cases what comes back to him or tohis fellows is, in fashion appropriate to each specific organism, some-thing biologically nursed along a return journey, that began the momenta relaxing sphincter permitted the passing of waste products from aninfected person. Somewhere along the line between the time when anegg was lost from that human host and the time the specifically appro-priate infective agent was ripe to return to him, somewhere along thatline a different brand of sanitation, broadly interpreted, would havebroken the biological chain and spared new human hosts.

My analysis has concerned itself with helminthic infections over-all,not alone those with the most serious worm burdens, for it is the wholepattern of infection of helminths in the world of man we are aiming tograsp. Tactically it may be required that we concentrate attack for ame-lioration and control on persons and communities most severely affect-ed. Strategically, at the world level, we need to know of the enemywherever he rears his head, in order that over-all planning omit nofavorable opportunity for neutralizing him. Helminthiases do not have

the journalistic value of great pandemics like flu or plague, althoughthey may have an as yet unrecognized relation to them; they do not,for the most part, present dramatic clinical cases, but to make up fortheir lack of drama, they are unremittingly corrosive. If you werearoused by the sufferings of, say, ten thousand service men with fila-riasis and schistosomiasis, what can your imagination do with ten thou-sand upon ten thousand natives in endemic areas-who have no ho-meside relatives to write letters to their congressmen?

The world population, according to informed prediction, may reach3300 million by the end of the century, an increase of 50 per cent(Notestein, 1945). The parasitoses, by extrapolation, may grow even

t This was given at Boston as "one in eight." My work sheets whichshowed 1 in 7 had been mis-read as 1:7.


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396 THE JOURNAL F PARASITOLOGY, OL. 5, NO. 3, JUNE 1999

more, for some of the areas marked for most population growth areamong those with higher helminthic indices.

Are there ways parasitologists can help reduce the prospect of havingthe world forge ahead to more than 3000 million human helminthiasesby the year 2000?

It seems to me there are possibilities.I. Certainly we can widely uphold, and strengthen the teaching of,

the nuclear principles that apply in our field. They obviously should beknown

by intelligentworld citizens, and we should make it

popularthat

they are. Certainly we should assist the firm establishment of compe-tently taught parasitology in medical schools, which the war has fos-tered.

There are some red entries in our own ledger of the war because suchknowledge was not more freely dispensed earlier. For instance, soonafter Pearl Harbor, training centers for marines were established in theSouth Pacific, including Samoa where American forces had been fordecades. Somewhere in the higher echelons there must have been amedical officer in a position of advice, or decision, as to how close tonative huts and villages it was prudent to barrack the men. Evidentlythat medical officer never heard of bancroftian filariasis being presentwhere men in uniform saw it with dismay, or else he did not know thatfilariasis is transmitted by mosquitoes. In the name of Manson, it is forus all to blush at that hiatus.

II. We can encourage by precept and example a shortening of theusual lag period there is in getting acceptable improvements in ideas

through to where they will do the most good, and be less tolerant whenthe lag seems unnecessarily long. I have two illustrations.The Health Section of the League of Nations recently published a

valuable "Handbook of Infectious Diseases" (1945 III 1, CH 1454),up-to-date enough to include "new chapters on the sulphonamides, pen-icillin, etc.," but with serious omissions concerning anti-helminth drugs.For instance, the recommended treatment for ascaris is merely santoninand chenopodium, and for hookworm thymol, chenopodium, or carbontetrachloride. This handbook had the admirable aim of noting "everyrecent addition to scientific knowledge concerning methods of combat-ing these diseases." Why, under a League imprint, should it miss beingup-to-date about such anthelmintics as tetrachlorethylene and hexylres-orcinol which have been valuable and accepted for more than a decadeand a half?

Or take the case of Guam. This little island of 200 square miles hasbeen in our hands since the Spanish-American war, administered by anaval governor continuously until December 1941, and re-establishedso since. As early as the published sanitary report for 1905 Surgeon R.P. Crandall, wrote, "Extraordinary prevalence of Ascaris lumbricoidesin nearly every individual member of the community has been forciblyrepresented as a veritable curse." The native population then was evi-dently about 10,000. By 1913 Surgeon C. P. Kindleberger was saying:"Practically every native adult, all native children over 2 years of age,and some as young as 6 months, are infected with one or more intestinalparasites." In 1914 the U. S. Naval Medical Bulletin reproduced, forPassed Asst. Surgeon E. O. J. Eytinge, a classic picture (which most ofyou have seen in textbooks) of a 3-year-old Guamanian child with fatalhookworm infection. In 1924, E. U. Reed, Lt.-Comdr., M.C., publishedthe results of nearly 2,000 fecal examinations made throughout the is-land. These showed that less than one per cent of the natives wereuninfected with hookworm, whipworm, or roundworm; other exami-nations showed that of navy and marine personnel and their families onthe island more than 6 months, 13 per cent of the adults and 76 percent of the children were

positivefor one or more of these three

para-sites, while those there less than 6 months were all negative. McKinley'sGeography of Disease (1935), quoting the Surgeon-General of theNavy, placed ascariasis and hookworm next only to leprosy and yaws,in public health importance on the island in 1933. Should it have causedsurprise, therefore, that 8 months after the American re-occupation, ofa fair sample of natives examined, as many as 9 in 10 were infectedwith hookworm and trichuris, and 6 in 10 with ascaris, with egg countsin all three infections among the world's highest? During the period 26January-9 August 1945, Zimmerman (1946) performed 50 post-mortemexaminations of Guamanian children 4 years of age and under, andfound "in 21 instances the primary cause of death was hookworm dis-ease with its attendant complications."

The friendly and gracious inhabitants of this little island, whose Cha-morro chromosomes have strong admixtures from European and Amer-

ican sources, through natural causes have no malaria, no filariasis, nofluke or cestode infections, and only a little enterobiasis. It is true theharshness of the helminthic assault in early 1945 with hookworm, tri-churis, and ascaris must have been accentuated because of the inevitabledislocation that occurs in the lives of native peoples in battle areas. Itis true that over the years conscientious and devoted medical officershad been stirred to alleviate the parasitisms by instigating sanitation andprescribing anthelmintic treatment. Then why such a result on an islandabout 1/3 the size of an

averageMassachusetts

county,and where most

of its 24,000 natives live in less than half its area? It seems to me theanswer is obvious-enough was not done, and what was done was notdone well enough. Thousands of anthelmintic treatments have been ad-ministered, case by case in hospital and dispensary. But treatment ofindividual cases was promptly nullified by a parasite-infested environ-ment. Here was an instance, if ever, where the treatment approach tocontrol would profit only if of the whole community. The success Lam-bert was having only a little way off, as Pacific distances go, seems notto have filtered through to Guam. So in place of a model Americantropical colony there comes to light instead an ancylostomized, trichur-ized, and ascarized community of long standing.

There are fortunately signs that postwar this gloomy picture will bebrightened. If they materialize Americans homeside will be glad to hearthat their friendly Guamanian wards, who aspire to American citizen-ship, have been assisted to gain a desirable Pacific freedom-freedomfrom worms. Perhaps the neighboring Saipanese could be included.

Why, at long last, should we not look forward to a demonstration ofsome perfection in the deworming of Guam-24,000 persons on anisland of 200 square miles?

III. Besides the possibilities mentioned, of encouraging wider dissem-ination of the central ideas in our field, and their application, there isanother side of the problem which is a challenge specifically to us. Thequestion is legitimately raised whether the tools furnished for attackingthe helminthiases of man are not in need of sharpening. Against theintestinal helminths we think of them as education, sanitation, and treat-ment. Stiles (1932) wisely observed in an article on hookworm disease,that among important factors in public health advancement of the Southwere "the automobile filling stations with the practical demonstrationin public health connected with their comfort rooms." Perhaps he wassaying obliquely what is all too true. Logically necessary as is the pitlatrine to combat soil pollution, the esthetic affront it gives to thosewho are supposed to use it, vitiates its virtues and drives adults as wellas children back to the out-of-doors where the air is free. That is true

even in this latitude, and the closer to the tropics the truer it is. Nowonder latrine construction and use is hard to establish there. Yeager'sbored hole substitute is praiseworthy, but makes slow advances. Whatwe need is to find a "convenience of civilization," an excusado, asattractive in its way as is the filling station comfort room.

In another direction, methods of soil sterilization, in which progressis being made against plant parasitic nematodes, could be profitablyexploited to determine whether they might not protect man against theconsequences of his using unconfined defecation sites. Have we tooeasily shrugged off improvements here, continuing to make and rec-ommend Model T ideas, when the demand is for less bumpy riding?

New chemo-therapeutic preparations are desirable, to encourage morewidely the breaking of parasitic life cycles within man himself. Againsthookworm our best present bet is tetrachlorethylene, against ascaris inchildren hexylresorcinol, against pinworm gentian violet. But all theseleave something to be desired, and against trichuris and other forms weare in worse case. What we need are worm treatments as effective andwell-tolerated as phenothiazine in sheep; and from the greatness of theneed, we ought to have a hundred workers seeking them, instead of ahandful in desultory effort. For our familiar intestinal fauna, as well asparenteral forms, one of the goals could well be something of lessdrastic action in individual dose, but potent cumulatively, and thus ap-plicable to population groups, as are vitamins in bread, iodine in salt,and fluorides in water.

And here, deliberately on a note of unfinished business, I prefer tointerrupt consideration of the problem of human helminthiases at theworld level. We need to leave it in a mood of work still to be done.

In March, with the Society becoming of age, my distinguished pre-decessor told you of the making of a parasitologist. If by chance he hadended with the line, "Bring me men to match my mountains," it wouldhave been allowed me to say: "Here are some of the mountains."

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