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Natural abatement of schistosomiasis Mansoni in St. Kitts, British West Indies
NATURAL ABATE,. {EN OF S(, HIS'[()SOM 1ASIS M ANSONI IN ST. K! -iS, BRYrisH WEST INDIES By F R E D E R I C K F. F E R G U S O N , . ~ : ~ . : ~ . s~,s., PH.D,~a CHARLES S, R I C H . ? , ~ R D S , ~',.s., M.S.. I'~:f,O.,= STANLEY T. S E B A S T I A N , ~.s., '~ IVAN C. B U C H A N A N , t',.s..*
THE natural decline and probable completc disappcarancc of mansonian schistosomiasis..in transmissible foml from the Island o f S t . K~t~,., "s B.W.t., is an unique instance in the history o f t b e epidemi.ology of this disease. It is a.,;sumed to have been .imported in African slaves during the 17th and 18th centuries to this and other Caribbean Islands (Faust. 193_~, 1 ergu.t ~ et al., 195.8; Hoffman, 1939). Locally termed [:dbarz,a , it became established in several wa.tcrshcd communities in a coastal strip extending west of Basseterre to the Wingfield River, and in the Cayon River area. on the north-east const. During 1920, S. B. Jones, government medical otficer of St. Kitts. became {nte.rcs~cd in the problem and followed, it with perspicacit.v for about t2 years (J,:nes, 192z: 1923; 1932). During that period, several "guts", o; creeks, had permanent annuai flows and others had residual mountait~, pools, atl of which had man), planorbid snails, then classified as Phmorbis antiguensis Reeve. Positive snails were rarely collected. Chronic cases with enlarged livers and spleens were common, and in the public healti~ clinic the~ were I25 gross cases under tartar .emetic treatment during 1932. The insular infection prevMence was estimated at. about 2570 of tbe island population_ of 22,415. Since shnptc faecal smear techniques reveal only about 10 ~'//oof the total positives deicetable by a variety of sedimentati~a and ccntrifugation methods, probably at least half of the rural population was infected. Two factors strengthen this vi~v: (1) streamside residents were not only subject to man-made seh,stosome pollution, but also. t o t h a t from upstream cercariae originating fiom the monkey-tomonkey parasitic cycle in the mountains; and (.2), unlike other s~m~lar .~ar~bbean islands, couatry people of St. Kitts do not live sca.ttercd at random over the hillsides but are congregated i n t o a village cuI.tt~re from which, in this.lnstance, the potential for infection was ever presem. ,
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i Contribution of the Ministry of Health, the Ministry oi"Comm~niaafions and Works, Government .of St. Kitts, B.WA., ~ and the l~iology Section.. T~hnie.al lDevclo,pmem.Lab~ra~ tories, Technology Branch, .Comr~mnicz~blc Disease Comte, Bureau of Stme~S~mcic~ t~abli¢ Health Service, U:S,.t~partment of HcMth, EducaIion.and Welfl~re,"Sava~n~I~.,:Georgia, •-"PuMic HeMth Sclcntist~, Pu.erto Rico Field Station, Pub~#cHealth.Ser~ce,.San Juan, Puerto Rico. 3 Public Health Engineer, Water Scrvi~s Depa~rn.ent~ B~s~err¢~ S{, KRts, CTdef Inspector, Ministry of Heahh, Basseterr¢, St. Ki2tS.
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}'k t~l 1~-" H ~ A I ' ~ H
"~ol
~XXtv
NO. 7
Since !932. ~.hc incidence has dropped as based on number of clinical
c~.,cs seen Ncgatixc I]ndi~'~gs er~ scl~istosome eggs during a sludy of ascariasis i~: 194(, ,:it Oh! Road \iIia~zc scl',ool conslilulcd the first ex idcnce thai transmission had ceased f l~uehanar~, 1959). TSe gradual disappearance of clinical cases darling ti~e pas'., decade is doc~:mentcd in bo~h public health arid privale medical records (McLean, t959i. The last Iwo known acute cases in St. Ki{~ fi'om lhe West I':mm ~staIc ~ere |rested by McLean, who reported that heavy infectio~ls in ~wo ~ecnagc boys (one of whom lives in Jamaica; the other in Canada) resMed both Faadin and anlhiomaline treatment, and still persisl strongiy in them t0 years later~ Thcre is no addiIional infom~alion on infection among feral monkeys, reported bu~ once (Cameron. 1929). That these monkeys are still capable of caroim,z infec~km with egg passage is midenced by recent posilive results obtained by cxposing specimens to cmvariae of Puerto Rican &'histosoma ,;w~soni (Ritchic, 1959). At preseta~,, these West African green monkeys (Cereopithecus sabaeus) populate thickly the central forested mountains, invading lower farm areas as energetic scaverlgers during dry seasons. There they are commonty seet~ on roads. There is no p~&~ent response of the public to a small head bounty placed upon them for reason of crop conservation. FIELD SURVEYS Traditionally, non-chlorinated water has been used on the two large plantations on St. Kitts and in Basseterre. During 1957, only 50.4 inches of rain fell, similar trends being reported for 1958. During March-April, 1957, only 1 inch of rain fell on ~hree of the subject watersheds--West Farm, Cayon~ and Wing,field. The average annual rainthtl for the past 42 years was 58.9 inches (Kelsick, 1955). Sleep slopes, high-gradient stream beds, and limited cut-over attuvium eoml~ine to dissipate this precipitation, Which is above average for most of the lesser Antilles islands. Three snail surveys made during March and November, 1958, and April, 1959, revealed Austratorbis glabratus (Say)? There are six "permanent" streams on the small island (68 square miles): Winglield River, East River, Stone Fort River, Phillips Gut, West Farm Gut, and Cayon River; and, of these, only the Wing'fieid River now flows continuously to the sea from its source. This condition has persisled for approximately the ]asi 15 years. No hydrologic surveys have been made ol~ St. Kitts and lopographic data are not detinitiye (Burdon, 1920} bu~ reveal ~t *oial of 28 named "guts" which have water temporarily as a Laboratory lasts executed during 1958-9 revealed that tile St. Kitts planorbid was in fac~ A. ,¢labragtts,the ~rineipal imermediate host of schistosomiasis in the Western Hemisphere. Sueces'sful crosses were made with an albino strain from Venezuela. Laboratory cx~lonisationof ',his planorbid was affected and studies of morphology, growth rates, and egg laying yielded resatls within the intra-specifie variations of Puerto Riean ,4. glabralu& The St, Kitts planorbid accepted Puerto Riean S. mansorff infection efficiently,
. , g a r - ~ , , .... ptardations, the " "" ' .. .,~ ° o ! [-::ast River anti Wingfield R.ive~ .~c;wc as tb~.: ,, ,,,.~., .,,u.ppe~> ,.,f' " .... • ua~-er> East R i v e r is a g u a r d e d , v":', ' i'-,,ta . . .rYlO . LI.A' l o.-;-" . l ..... . a ..... !.Ca ,*~ :a}i.ax' '"q"¢ i~il Sk!, . . . . . . ~-a£:.~: " . " " e • ' i~l f0, ~~. d;, "~",.,,,,}c,. .... of',ix eatherecl i~a it are piped by gl'avaty ~;~ ~.~!~.,,-mc~ m a . . . . m~ie, l"l]d,'llt.llt")~.~..( F O S C F V ( : ] I F
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t.ion and sgi~nd filtratio;~.. T h e \Vin.<.zlicld.. Rivc.~7 is. ,:,,~,a,,-;--:lar]v-..<.0ii p,:'otec~c~:£ ~xnd had been t a p p e d in t959 by a I0-{nc:}'} mai~'~ reduced ~-> 8 i;w{~c.~, cmp~.yi,:.;~...{~ia~.o " " L.a., :" s' P~AVcF lhe s a m e mLmicipat reservoir in Basscw~-rc tha~ accc:mr',~c:da~.cd t~e " water. Neither' ,,tm,ra/orbi.v no~" ott~c~ aquatic snait:~ we;re t\~u~'t da~, ,,a,:: November, i958, in lhc b, gh-gradient, ve,.~tat~>fl,:,., strca~T~ ~.~ , ~, E!ias~ ~,,k>~'v-r,,above . were . f o. u n d . in cq~c ,.~,tm. ,...... h-the Weir, b m s o m e /lus~ralorb~.r c~ o f ~.hc ~e:-minal municipal reservoir. These werc pi'omp~ly d e s t r o y e d °by by-passm44 and dryi,,~g the c h a m b e r . It is o f interest to t-,otto hov~.cvcr, t h a t dw:ilag 1932 th.c reservoirwas. to.med-r by .Jones " a splendid a q u a r i u m &~r artyonc anxious W collect ... " s ~cd - some part p t a n o r b i d s. (sp. antii~ue~lsis]". "17ta~s,. " ~'" snaits p r e s u m a b l y l~avc' ~nfe. o f the t r e a t m e n t facility., t:br dc..,d,.s.~e'~.- Small lakes o f volcanic origit~ on Mr. Misery and Ve-rdaild's Mr. are mapped. These iakes are inaccessible ~o residents and have x~eve.t been surveyed fo~7 s~aaits. D u r i n g the e n d e m i c period, contact with Witag(:ield River water probably c o n t r i b u t e d to most o f the h u m a ~ inl%ctions..s'~,.c~.~-~' i~ 1932,. 36t',~.. o f treated cases lived n e a r that stream. At present, this n a r r o w .shallow stream has a highgradient., large, b o u l d e r type o{" chaw:~ei, sut2jec~ ~o e x t r e m e wastloms duriJ~g heavy rains, a conditio~ n o r m a l l y unsuitable f:.~r ,4,sfralorbis. N o living speci- ~.ch,.s, . . . ~ n o r were sh.eit signs, or mens o f Au,rrralorbis were seen duvintz,.. careffd sea vegetated pools likely to s u p p o r t it." West F a r m G u t is tapped at an altitude o f abotii 1.500 feet a n d piI~d for all d o m e s t i c uses on u..c large sugar-cane p l a n t a t i o n o f l h a t n,~m-. S o m e 13 7,, o f t r e a t e d cases were t~rmerIy reported f~'om this eommuni{y, a n d it was the source, o f the last two k n o w n clinicat cases. Small a n d medkm~ size .4ustralorbis were present d u r i n g M a r c h , 1958, a{ a density o f 6 to 20 p,~r square y a r d m a stream bed p o t h o l e s o m e 500 yards do n s u e a m f r o m the water supply i m p o u n d m e n t , at w h i c h p o i m the str¢ m wen{ trader"ground, not to reappear. T h e u p s t r e a m reservoh" consists of a c o n c r e t e t a n k o f a b o u t 2 0 square feet with w a t e r a b o u t 3 feet deep, a n d in it a n d a b o v e it, f o r a b o u t ~ ) y a r d s , :the host snail thrives. This watershed is now g u a r d e d , a n d }~o b a t h i n g or clothes.washing has been p e r m i t t e d there :[q)r about 10 years, All samples :of saaits collected then a n d at subsequent visits t e a e d negative for S. mansoni c e m a r i a e . T h e single stream on the ~orti~ coast h a v i n g a small flow. o f wa~er in * A few specimens of the foUewiJtg snai|s were taken: Physa sp,, F e ~ s i a ,~., ~ d Neritina sp.
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PUBLIC
HEALTH
VOI,.
I..XXIV
NO.
7
upland sections only is the Cayon River. which is tapped near its source, at :m altitude of 1,000 feet,/'or agricultural and village usage. No living snails or shell siNas have been observed in the lower rocky dLv stream bed, and only Pto'sa was found in the upper part. As noted above, Buchanan had tested by direct saline smears faecal samples of children in a former hyperendcmic area in 1946 and revealed no cases of schistosomiasi~ but all ascariasis index of 30~,~ among 200 chiMren of both sexes, with an age range of 6 to I6 years. Samples were again collected during December. t95g, and April 1959, fi'om all ages mad both sexes in former endemic f'oci (,~ ~I'.,c,,-atl i co;~st cast of Basseterrc (Palmetto Point, Old Road Village, and Chali,:~}g,c~ '.,'~i,'.gc) N~,~ c,f ~he l gg samples ~ere positive for sdfistosome ova upon use of the M.1,F.C. ,:cchniquc, However, 46.8 }'o Ascaris, 82.4~/o Trichocephalus, and 2"6,90 Necator infections x~re recorded. The majority of those persons tested (77%) were 20 years old or younger, as intehded. A few cases of Giardia lamblia, Balantidium coli, Enterobius vermicularis, and Endamoeba histolylica were detected. MOLLVSCIClr~ING T~ZALS AS cited above, snails in the city reservoir were eliminated bythe simple expedient of drying up lheir habitat. The chemical control of the other colonies was complicated by the fact that West Farm Gut water is used for domestic purposes. Accordingly, two applications of sodium pentachlorophenate were made in the headwater section, presumably above snail colonies, at the rate of 7 p.p:m, for 24 hours according to meflmds standardised by the Bilharzia Control Unit, Puerto Rico Department of Health (Sebastian, I0,~;9). Although living snails were not evident following mollusciciding, they r~t;;reed in force two to three months following each treatment. About 200 adult specimens of the biological control snail, Marisa cotvmarietis (Ferguson and Palmer, 1958), were introduced during April, 1959, throughout the course of West Farm Gut, including the sections harbouring Australorbt~, as an alternative to chemical treatment, and colonisation in the stream was accomplished. DISCUSSION
The cessation of schistosomiasis as a health problem on the island of St. Kitts about 1946 is a singular instan(~e. Granted that this is a result of unplanned environmental changes, it is neverflle]ess valid natural abatement o f schistosomiasis among the island's people. As a result, the level of rural public health has been raised significantly: Concentration of scarce surface water supplies into aqueducts has all but eliminated the intermediate host snail, Am'tralorbis glabratus. Complete destruction of Australorbis is planned o n the basis of either chemical, or biological moiluseiciding.ilTests indicate t h a t r e m a i n i n g snail colonies are notcurrently infected: W i l d mor-~key populations; :whict~ contributed to the epidemiological picture duringtlie endemieperiod; are" stated to
A|JATt
M! NT
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SCIII~I'()S()M1AS1S
MA:N.v, O N I
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be or~ the increa-c. Presence of clean snails in much-reduced breeding foci indicate th'.tt St. ~.~ittsjungle monl.,cy.~ ~Iso arc probably now di~ase free. but proof of this would be a formidable task. At the peak of the problem during 1920-32 thcrc were an estima{cd 5.600 active human cases. Cliniccd cases are now absent and two copro scopic survcys showing negative tests of 1946 and 1958-9 m:~de in former cndemic villages indicate lhat the disease is either greatly reduced or absent in both old a~d young persons. Unfortunately, no utilisable instrument may be forged on the basis of these epidemiological disclosures for the control of this disease clsewhere. ACKNOWLEDGMENTS
These investigations were performed through the gracious assistance of the following: Lt.-Col. thc Hen. H. A. C. Howard, administrator; Hen. C. A. Paul Southwell, Minister of Commtmications and Works; Dr. George I. Shay,, senior medical officer: Dr. G. D. McLean, physician; Mr. Christopher G. Wigley, West Farm Estate; Dr. L:~wrence S. Ritchie, U.S. Army Antilles Command; and Capt. J. W. Ryssy. commant~:;', Greater Antilles Section, U.S. Coast Guard. R liFE R ENCES B u c l~ A r~ ,x N, t. C. (1958-9). O~crsonal communications.) B u g D O N, J. A. (1920). "Topographic Map, St. Kitts". Geographical .~ction, General Staff, W a r Office, No. 2941. CA M t R O r q , T. W. M. (1929). "Observations on a parasitologieal tour o f the Lower Antilles". Prec. r¢~)'. Soc. Med., 22, 933. F ^ u s ' r , E. C. (1933). " T h e history of schistosomiasis in Puerto Rico". Puerto R i ~ J. Pub!. Hhh. 9 (2), 154-61. F I ~ R G U S O N , F. F., R O W A N , W. B., & I ) A L M E R ; J. R. (1958). "'l~ibliogralia seleccionada sobre la bilhar-zia Antillana, o esquistosomiasis mansoni". Talleres Artes Grafieas, Dept. de Inst. Pub., E. L. A. de P. lq., San Juan, P. R., 66 pp. . . . . . . . & PALMER, J. R. (1958). "Biological notes on Marisa cornuarietis, a predator of Australorbis glabratus, the snail intermediate best o f schistosomiasis in Puerto Rico". Amer. J. trop. Med. 7 (6), 640-2. 1-~o F F M A rq, W. A. (1939). " T h e distribution of Schi~'tosoma mansoni in the Western Hemisphere". Ana&s de la Esc. ~'C de Ciencias Biolog., p. 2. .! o tq E S, S. B. (1922). "'Some notes on intestinal bilharTiasis in the West Indies". J. trop. Med. Hyg., 35 (3), 25-7. • (1923). "Intestinal bilharziasis in the West Indies: Intermediate host, Ibid., 26, 253--4. ---. (1932). "Intestinal bilharziasis in St. Kitts, B.W.I." 1bid., 9 (35), 129-36. K E L S t C K, R. E. (1955). Meteorological report for 1954, Agricuiiural Department, St. Kitts. (Personal communication, 1958.) M c L E ^ N, G. D., physician and f o r m e r acting senior medical o~cer, St. Kitts, B.W.I., 1959. (Personal communications.) R l "r c 11 x E, L. S. (1959). Chief, Parasitology Section, U.S. Army Tropical R e . ~ a ~ h Medical Laboratory, San Juan. (Personal communication.) S E e A s T x x N, S. T. (1958-9). (Personal communications.)
THE natural decline and probable completc disappcarancc of mansonian schistosomiasis..in transmissible foml from the Island o f S t . K~t~,., "s B.W.t., is an unique instance in the history o f t b e epidemi.ology of this disease. It is a.,;sumed to have been .imported in African slaves during the 17th and 18th centuries to this and other Caribbean Islands (Faust. 193_~, 1 ergu.t ~ et al., 195.8; Hoffman, 1939). Locally termed [:dbarz,a , it became established in several wa.tcrshcd communities in a coastal strip extending west of Basseterre to the Wingfield River, and in the Cayon River area. on the north-east const. During 1920, S. B. Jones, government medical otficer of St. Kitts. became {nte.rcs~cd in the problem and followed, it with perspicacit.v for about t2 years (J,:nes, 192z: 1923; 1932). During that period, several "guts", o; creeks, had permanent annuai flows and others had residual mountait~, pools, atl of which had man), planorbid snails, then classified as Phmorbis antiguensis Reeve. Positive snails were rarely collected. Chronic cases with enlarged livers and spleens were common, and in the public healti~ clinic the~ were I25 gross cases under tartar .emetic treatment during 1932. The insular infection prevMence was estimated at. about 2570 of tbe island population_ of 22,415. Since shnptc faecal smear techniques reveal only about 10 ~'//oof the total positives deicetable by a variety of sedimentati~a and ccntrifugation methods, probably at least half of the rural population was infected. Two factors strengthen this vi~v: (1) streamside residents were not only subject to man-made seh,stosome pollution, but also. t o t h a t from upstream cercariae originating fiom the monkey-tomonkey parasitic cycle in the mountains; and (.2), unlike other s~m~lar .~ar~bbean islands, couatry people of St. Kitts do not live sca.ttercd at random over the hillsides but are congregated i n t o a village cuI.tt~re from which, in this.lnstance, the potential for infection was ever presem. ,
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i Contribution of the Ministry of Health, the Ministry oi"Comm~niaafions and Works, Government .of St. Kitts, B.WA., ~ and the l~iology Section.. T~hnie.al lDevclo,pmem.Lab~ra~ tories, Technology Branch, .Comr~mnicz~blc Disease Comte, Bureau of Stme~S~mcic~ t~abli¢ Health Service, U:S,.t~partment of HcMth, EducaIion.and Welfl~re,"Sava~n~I~.,:Georgia, •-"PuMic HeMth Sclcntist~, Pu.erto Rico Field Station, Pub~#cHealth.Ser~ce,.San Juan, Puerto Rico. 3 Public Health Engineer, Water Scrvi~s Depa~rn.ent~ B~s~err¢~ S{, KRts, CTdef Inspector, Ministry of Heahh, Basseterr¢, St. Ki2tS.
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}'k t~l 1~-" H ~ A I ' ~ H
"~ol
~XXtv
NO. 7
Since !932. ~.hc incidence has dropped as based on number of clinical
c~.,cs seen Ncgatixc I]ndi~'~gs er~ scl~istosome eggs during a sludy of ascariasis i~: 194(, ,:it Oh! Road \iIia~zc scl',ool conslilulcd the first ex idcnce thai transmission had ceased f l~uehanar~, 1959). TSe gradual disappearance of clinical cases darling ti~e pas'., decade is doc~:mentcd in bo~h public health arid privale medical records (McLean, t959i. The last Iwo known acute cases in St. Ki{~ fi'om lhe West I':mm ~staIc ~ere |rested by McLean, who reported that heavy infectio~ls in ~wo ~ecnagc boys (one of whom lives in Jamaica; the other in Canada) resMed both Faadin and anlhiomaline treatment, and still persisl strongiy in them t0 years later~ Thcre is no addiIional infom~alion on infection among feral monkeys, reported bu~ once (Cameron. 1929). That these monkeys are still capable of caroim,z infec~km with egg passage is midenced by recent posilive results obtained by cxposing specimens to cmvariae of Puerto Rican &'histosoma ,;w~soni (Ritchic, 1959). At preseta~,, these West African green monkeys (Cereopithecus sabaeus) populate thickly the central forested mountains, invading lower farm areas as energetic scaverlgers during dry seasons. There they are commonty seet~ on roads. There is no p~&~ent response of the public to a small head bounty placed upon them for reason of crop conservation. FIELD SURVEYS Traditionally, non-chlorinated water has been used on the two large plantations on St. Kitts and in Basseterre. During 1957, only 50.4 inches of rain fell, similar trends being reported for 1958. During March-April, 1957, only 1 inch of rain fell on ~hree of the subject watersheds--West Farm, Cayon~ and Wing,field. The average annual rainthtl for the past 42 years was 58.9 inches (Kelsick, 1955). Sleep slopes, high-gradient stream beds, and limited cut-over attuvium eoml~ine to dissipate this precipitation, Which is above average for most of the lesser Antilles islands. Three snail surveys made during March and November, 1958, and April, 1959, revealed Austratorbis glabratus (Say)? There are six "permanent" streams on the small island (68 square miles): Winglield River, East River, Stone Fort River, Phillips Gut, West Farm Gut, and Cayon River; and, of these, only the Wing'fieid River now flows continuously to the sea from its source. This condition has persisled for approximately the ]asi 15 years. No hydrologic surveys have been made ol~ St. Kitts and lopographic data are not detinitiye (Burdon, 1920} bu~ reveal ~t *oial of 28 named "guts" which have water temporarily as a Laboratory lasts executed during 1958-9 revealed that tile St. Kitts planorbid was in fac~ A. ,¢labragtts,the ~rineipal imermediate host of schistosomiasis in the Western Hemisphere. Sueces'sful crosses were made with an albino strain from Venezuela. Laboratory cx~lonisationof ',his planorbid was affected and studies of morphology, growth rates, and egg laying yielded resatls within the intra-specifie variations of Puerto Riean ,4. glabralu& The St, Kitts planorbid accepted Puerto Riean S. mansorff infection efficiently,
. , g a r - ~ , , .... ptardations, the " "" ' .. .,~ ° o ! [-::ast River anti Wingfield R.ive~ .~c;wc as tb~.: ,, ,,,.~., .,,u.ppe~> ,.,f' " .... • ua~-er> East R i v e r is a g u a r d e d , v":', ' i'-,,ta . . .rYlO . LI.A' l o.-;-" . l ..... . a ..... !.Ca ,*~ :a}i.ax' '"q"¢ i~il Sk!, . . . . . . ~-a£:.~: " . " " e • ' i~l f0, ~~. d;, "~",.,,,,}c,. .... of',ix eatherecl i~a it are piped by gl'avaty ~;~ ~.~!~.,,-mc~ m a . . . . m~ie, l"l]d,'llt.llt")~.~..( F O S C F V ( : ] I F
ill: \VFItL:; "i }.~.~, ~,t~.dt.l .
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a
t.ion and sgi~nd filtratio;~.. T h e \Vin.<.zlicld.. Rivc.~7 is. ,:,,~,a,,-;--:lar]v-..<.0ii p,:'otec~c~:£ ~xnd had been t a p p e d in t959 by a I0-{nc:}'} mai~'~ reduced ~-> 8 i;w{~c.~, cmp~.yi,:.;~...{~ia~.o " " L.a., :" s' P~AVcF lhe s a m e mLmicipat reservoir in Basscw~-rc tha~ accc:mr',~c:da~.cd t~e " water. Neither' ,,tm,ra/orbi.v no~" ott~c~ aquatic snait:~ we;re t\~u~'t da~, ,,a,:: November, i958, in lhc b, gh-gradient, ve,.~tat~>fl,:,., strca~T~ ~.~ , ~, E!ias~ ~,,k>~'v-r,,above . were . f o. u n d . in cq~c ,.~,tm. ,...... h-the Weir, b m s o m e /lus~ralorb~.r c~ o f ~.hc ~e:-minal municipal reservoir. These werc pi'omp~ly d e s t r o y e d °by by-passm44 and dryi,,~g the c h a m b e r . It is o f interest to t-,otto hov~.cvcr, t h a t dw:ilag 1932 th.c reservoirwas. to.med-r by .Jones " a splendid a q u a r i u m &~r artyonc anxious W collect ... " s ~cd - some part p t a n o r b i d s. (sp. antii~ue~lsis]". "17ta~s,. " ~'" snaits p r e s u m a b l y l~avc' ~nfe. o f the t r e a t m e n t facility., t:br dc..,d,.s.~e'~.- Small lakes o f volcanic origit~ on Mr. Misery and Ve-rdaild's Mr. are mapped. These iakes are inaccessible ~o residents and have x~eve.t been surveyed fo~7 s~aaits. D u r i n g the e n d e m i c period, contact with Witag(:ield River water probably c o n t r i b u t e d to most o f the h u m a ~ inl%ctions..s'~,.c~.~-~' i~ 1932,. 36t',~.. o f treated cases lived n e a r that stream. At present, this n a r r o w .shallow stream has a highgradient., large, b o u l d e r type o{" chaw:~ei, sut2jec~ ~o e x t r e m e wastloms duriJ~g heavy rains, a conditio~ n o r m a l l y unsuitable f:.~r ,4,sfralorbis. N o living speci- ~.ch,.s, . . . ~ n o r were sh.eit signs, or mens o f Au,rrralorbis were seen duvintz,.. careffd sea vegetated pools likely to s u p p o r t it." West F a r m G u t is tapped at an altitude o f abotii 1.500 feet a n d piI~d for all d o m e s t i c uses on u..c large sugar-cane p l a n t a t i o n o f l h a t n,~m-. S o m e 13 7,, o f t r e a t e d cases were t~rmerIy reported f~'om this eommuni{y, a n d it was the source, o f the last two k n o w n clinicat cases. Small a n d medkm~ size .4ustralorbis were present d u r i n g M a r c h , 1958, a{ a density o f 6 to 20 p,~r square y a r d m a stream bed p o t h o l e s o m e 500 yards do n s u e a m f r o m the water supply i m p o u n d m e n t , at w h i c h p o i m the str¢ m wen{ trader"ground, not to reappear. T h e u p s t r e a m reservoh" consists of a c o n c r e t e t a n k o f a b o u t 2 0 square feet with w a t e r a b o u t 3 feet deep, a n d in it a n d a b o v e it, f o r a b o u t ~ ) y a r d s , :the host snail thrives. This watershed is now g u a r d e d , a n d }~o b a t h i n g or clothes.washing has been p e r m i t t e d there :[q)r about 10 years, All samples :of saaits collected then a n d at subsequent visits t e a e d negative for S. mansoni c e m a r i a e . T h e single stream on the ~orti~ coast h a v i n g a small flow. o f wa~er in * A few specimens of the foUewiJtg snai|s were taken: Physa sp,, F e ~ s i a ,~., ~ d Neritina sp.
2(,a
PUBLIC
HEALTH
VOI,.
I..XXIV
NO.
7
upland sections only is the Cayon River. which is tapped near its source, at :m altitude of 1,000 feet,/'or agricultural and village usage. No living snails or shell siNas have been observed in the lower rocky dLv stream bed, and only Pto'sa was found in the upper part. As noted above, Buchanan had tested by direct saline smears faecal samples of children in a former hyperendcmic area in 1946 and revealed no cases of schistosomiasi~ but all ascariasis index of 30~,~ among 200 chiMren of both sexes, with an age range of 6 to I6 years. Samples were again collected during December. t95g, and April 1959, fi'om all ages mad both sexes in former endemic f'oci (,~ ~I'.,c,,-atl i co;~st cast of Basseterrc (Palmetto Point, Old Road Village, and Chali,:~}g,c~ '.,'~i,'.gc) N~,~ c,f ~he l gg samples ~ere positive for sdfistosome ova upon use of the M.1,F.C. ,:cchniquc, However, 46.8 }'o Ascaris, 82.4~/o Trichocephalus, and 2"6,90 Necator infections x~re recorded. The majority of those persons tested (77%) were 20 years old or younger, as intehded. A few cases of Giardia lamblia, Balantidium coli, Enterobius vermicularis, and Endamoeba histolylica were detected. MOLLVSCIClr~ING T~ZALS AS cited above, snails in the city reservoir were eliminated bythe simple expedient of drying up lheir habitat. The chemical control of the other colonies was complicated by the fact that West Farm Gut water is used for domestic purposes. Accordingly, two applications of sodium pentachlorophenate were made in the headwater section, presumably above snail colonies, at the rate of 7 p.p:m, for 24 hours according to meflmds standardised by the Bilharzia Control Unit, Puerto Rico Department of Health (Sebastian, I0,~;9). Although living snails were not evident following mollusciciding, they r~t;;reed in force two to three months following each treatment. About 200 adult specimens of the biological control snail, Marisa cotvmarietis (Ferguson and Palmer, 1958), were introduced during April, 1959, throughout the course of West Farm Gut, including the sections harbouring Australorbt~, as an alternative to chemical treatment, and colonisation in the stream was accomplished. DISCUSSION
The cessation of schistosomiasis as a health problem on the island of St. Kitts about 1946 is a singular instan(~e. Granted that this is a result of unplanned environmental changes, it is neverflle]ess valid natural abatement o f schistosomiasis among the island's people. As a result, the level of rural public health has been raised significantly: Concentration of scarce surface water supplies into aqueducts has all but eliminated the intermediate host snail, Am'tralorbis glabratus. Complete destruction of Australorbis is planned o n the basis of either chemical, or biological moiluseiciding.ilTests indicate t h a t r e m a i n i n g snail colonies are notcurrently infected: W i l d mor-~key populations; :whict~ contributed to the epidemiological picture duringtlie endemieperiod; are" stated to
A|JATt
M! NT
()F
SCIII~I'()S()M1AS1S
MA:N.v, O N I
2~5
be or~ the increa-c. Presence of clean snails in much-reduced breeding foci indicate th'.tt St. ~.~ittsjungle monl.,cy.~ ~Iso arc probably now di~ase free. but proof of this would be a formidable task. At the peak of the problem during 1920-32 thcrc were an estima{cd 5.600 active human cases. Cliniccd cases are now absent and two copro scopic survcys showing negative tests of 1946 and 1958-9 m:~de in former cndemic villages indicate lhat the disease is either greatly reduced or absent in both old a~d young persons. Unfortunately, no utilisable instrument may be forged on the basis of these epidemiological disclosures for the control of this disease clsewhere. ACKNOWLEDGMENTS
These investigations were performed through the gracious assistance of the following: Lt.-Col. thc Hen. H. A. C. Howard, administrator; Hen. C. A. Paul Southwell, Minister of Commtmications and Works; Dr. George I. Shay,, senior medical officer: Dr. G. D. McLean, physician; Mr. Christopher G. Wigley, West Farm Estate; Dr. L:~wrence S. Ritchie, U.S. Army Antilles Command; and Capt. J. W. Ryssy. commant~:;', Greater Antilles Section, U.S. Coast Guard. R liFE R ENCES B u c l~ A r~ ,x N, t. C. (1958-9). O~crsonal communications.) B u g D O N, J. A. (1920). "Topographic Map, St. Kitts". Geographical .~ction, General Staff, W a r Office, No. 2941. CA M t R O r q , T. W. M. (1929). "Observations on a parasitologieal tour o f the Lower Antilles". Prec. r¢~)'. Soc. Med., 22, 933. F ^ u s ' r , E. C. (1933). " T h e history of schistosomiasis in Puerto Rico". Puerto R i ~ J. Pub!. Hhh. 9 (2), 154-61. F I ~ R G U S O N , F. F., R O W A N , W. B., & I ) A L M E R ; J. R. (1958). "'l~ibliogralia seleccionada sobre la bilhar-zia Antillana, o esquistosomiasis mansoni". Talleres Artes Grafieas, Dept. de Inst. Pub., E. L. A. de P. lq., San Juan, P. R., 66 pp. . . . . . . . & PALMER, J. R. (1958). "Biological notes on Marisa cornuarietis, a predator of Australorbis glabratus, the snail intermediate best o f schistosomiasis in Puerto Rico". Amer. J. trop. Med. 7 (6), 640-2. 1-~o F F M A rq, W. A. (1939). " T h e distribution of Schi~'tosoma mansoni in the Western Hemisphere". Ana&s de la Esc. ~'C de Ciencias Biolog., p. 2. .! o tq E S, S. B. (1922). "'Some notes on intestinal bilharTiasis in the West Indies". J. trop. Med. Hyg., 35 (3), 25-7. • (1923). "Intestinal bilharziasis in the West Indies: Intermediate host, Ibid., 26, 253--4. ---. (1932). "Intestinal bilharziasis in St. Kitts, B.W.I." 1bid., 9 (35), 129-36. K E L S t C K, R. E. (1955). Meteorological report for 1954, Agricuiiural Department, St. Kitts. (Personal communication, 1958.) M c L E ^ N, G. D., physician and f o r m e r acting senior medical o~cer, St. Kitts, B.W.I., 1959. (Personal communications.) R l "r c 11 x E, L. S. (1959). Chief, Parasitology Section, U.S. Army Tropical R e . ~ a ~ h Medical Laboratory, San Juan. (Personal communication.) S E e A s T x x N, S. T. (1958-9). (Personal communications.)