INTRODI]CTION It is lmov¡n that tmnsmlssfons ol S. trI¡r- the relative lmpoftanße of tho socio-economic

Ree. Inßt. Med, ttop. São Pøulo 29(1):1-8, joneírc-levere¡ro, 1987

WATER.GONTACT PATTERNS AND SCHISTOSOMA MANSONI INFECTION IN A BURAT COMMUNIW IN NOFTHEAST BFAZIT

(I)

Edu¡ldo MülA (2) & Ái!¡lsn C. SLEIGH (3)

SUMMABY

We evâluated the hJluence.of water-related human activities, contâminative behaviour, house location, education and soslo.economic status on endemic Schis. tosoma mansoni infection. Tlre study T'as conducted in a hi¡ly non-irrigated at€a

of

rural northeast Brazil amongst

a

defined populâtlon

of

subsistence farmers, of whom gBEo _{wete inlected by age 20, Tl:e area wa¡i mapped, water bodies} ,were surveyed, and a detailed questionnaire ll'as performed on each household.

Infec-tion was assessed by duplicate stool examinations using ths sensltlve Bell

tech-nique

to

quantify egg excretion. For each household, and index

of

intensiw ot i¡fection was computed by grouping individual log-transformed egg counts as an age-sex adjusted

Z

score. Few households hâd

â

sanitary installation

or

a do-mestlc water supply, However, neithet water-contact nor contamlnative behavior were lndiscriminate. TTle people made conside¡able effort

to

defaecãte

far

from a water source, to obtatn household dfiBking wate¡ from the cleanest source, and

to bathe only at certein sites vrhele privacy is assured. Land ownership and

lito-racY correlated poorly with the household index of intensiõ¡ of infection. The key influence on infection status \áâs the relative location of the hous€ and snail-freo

or snail colonized water sources.

In

this a¡ea,

a

saie domestic ,water supply is the critical input needed to achieve definitive control of endemic Schistosomiasls.

KEY WORDS; Schlstosûma ¡nônsonl

_-

tnfection; Schistosomiasis

-

rural community; Transmission

_-

watet contact,

INTRODI]CTION

It

is lmov¡n that tmnsmlssfons ol S.

trI¡r-

the relative lmpoftanße

of

tho socio-economic ßOn¡

ln

an endemic areê depends on e

number

_{determinants of house losation, education and}

of

inteÐelated socioecologicâl variables that detemine hum'n rwâter

"ort"d

;;;;;;.

;;;-

water'related human activities'

in

the distñbu-cal contamina on of water sources ând the

pre-

tion

of

the p¡evalence and intenslhr

of

infec-smce

of

suitabte snail hosts s,6,6,r?.

In tJ'is

tion

in

a population of an endemic aÌea ln the stud¡¡, an attempt has b€en made

to quantify

state

of

Bahia, BmdI.

(l) llesenied ât the XVI Conglesso da Socied.adê Brællej¡a de Medicins Tropical, NstÈl, Rlo G¡snds dÞ Norte, BEzil.

3-8 reDn¡¿ry, 1980

(2) Departamento ate M€dlclna Preve¡tivÈ, tþculdade de MedicjrE, Unive¡sialatle rede¡8l da Bshia. Rua PÂdre Feljó, *

- 4P andar, Csneta. 40000 Sslvador, BÂhfa, Braall

l3) Depaüment oI IlopicÊt l,uþtic Healt¡, H¿lvard School of Public lfeelth; BGton, MassBchìls€tis, IISA

The Harvard component was diæcted by Dr, Ilro¡¡ras H. Weller and was sulported by gfê¡ts f¡om the Wellcorû€

TtìEt and ihe EtUrE McCoD¡el Cl¡rk Fou¡ldatlon. Fi€rd activitîès w€'æ pe olmed lû collabo¡atlon wrth Fi¡nd¡çáo Os. w¿ldo Guz (TIOCRUZ) _{a¡d w€le} superviseal f¡ Bahb by D¡. Itslo She ock. Subsidlisry grants ve¡s rec€l!€d from

MOT-A, E, & SLEIGH, A. C. _- WâUe¡-co¡tact patiems ând Schistosoms marsoni inf€ction in s ¡urat connuntty l¿ Northeasü B¡a¿it. Bev, Inst. Meal. t¡op. SÃo P¿ulo, 99(1): 1-8, 198?.

Itris

report forms pârt of a long term pro-ject _{aimed at improving our lrnowledge}

_of

_the epidemiology and control

of

Manson's

schis-tosomiasis. The project extended from l9?4 to

1984 and was conducted

in

the municipaliw of Castro Alves, an areâ tJpical of peâsant farm.

ing

communities

of

the

litoral

of

Northeast Brazil 2,10,11,14,15;18-æ.

îris

_{study ptovides bacXr.}

ground data

on the life

circumstances and

constraints that rclate

to

endemic

Schistoso-miasis, together with

iis

tmptications

fo¡

pto-motion of long term control of the disease.

MAIEBI,AI,S AND MEIIIODS

Sturty Ârea ¡nd Population

The study area lncluded three contiguos fezendas (geopolitical units) caUed Morfo do

llfonso, Graviel and niacho Seco

(figure

1),

,ìÁrhich _{c'e¡e m¿pped}

in

_{19731ó. A, census of the}

resident population Ìeas conducted annually

from 1974

to

1983.

F¡9. I - Map shovri¡g houses Ðd snâil hBbitâts in ¡'Bzendas

Mo o do A-ronso, G¡âviel and Riâcho Seco in the Csst¡o .{lveÄ Stu{y area, Bâhia, B$zil.

Itle

are¿ includes 25 squdr€

Km;

the lati. tude

is

12'45'36"5 and tåe longitude

_is

3$25'

4¡1"W.

Ihe

ter¡ain

is hilly

and temperatures range from l7 to 2$C at night to 26 to 35. dur-ing the day. Rainfall vades from 130

to

180 cm aÐnuall¡r _{'wtth most occulring}

from

á.pril to

Àugust u.

Virtually aU families are engaged

in

non-mechânized

faming of

manioc as the staple ãnd tobacco as a cash

ctoþ.

Itrere

is

no

ùri-gauon. flte

houses are dispeNed âlong the ridges and aæ usually nearby the family plots

,

on the hÍll slopes. Water is available only from small streams, ponds and springs in the valleys except for the few families witJ: storage tanks

fol

lainr,Íater. Most valleys are fenced off for câttle farming.

Household Suwey

-4. questionnaire, after pr+testing, was car-ried out

in

June l9?8

by a

Bahiân physician

(t.M. )

well known

in

the

area.

TtIe survev included 69 of the 72 households; one or more

of

the adults, usually females, plovided the information for each family. tach of the thr€e households not contactable bad one occupant

only.

For

each household information was obtained on domestlc water use (source, sto-rage, treatment before use) water contact

(si-te, duBtion, frequency ând time of dây of ba.

thing and clothes-washing) sanitary practices

(usual place

of

defaecation) and domestic

hy-giene (household cleening, garbage dtsposâl).

Information wâs also obtained on

soc¡o-econo-Ídc

structr¡re (house size and constructlon, number, age and sex of lesidents, fami\y assets,

faming

activities, income and landoEr¡ership status) ând education (number

of

yeaß

ot schooling and $ãded assessment

of

ability to'

reâd and q'rite

for

eâch individual). Each fâ. míly interview lasted 45 minutes

to

one hour" All responses were numelicalll¡ coded, to facili" tate subsequent analysis.

WÐüer SutTev

Using standBrd sampling methods for snâil surveys 16 _each wâterbo{y identifled in the _a¡ea

in January 1980 1r'as examined once

fol

the pre-sence of Blomphâlarl¿

spp.

The only species

found

v'ithin

this study aÌea was B. glabrâta although uninfected B. str¿rnlnea has been de"

tected

in

a nearby area during detalled mal& cological suryeys

of

Castro .Alves ls.

Faecal Examlnaffo[s

Specimens were collected and processed

by a modification

of

the Bell method

rt.

tgg

counts from duplicate papers were averaged for

each stool

sample.

IndividuÊl infection

ras

MOIA, E. & SLEIGE, Á. C. _- Vt¡ate!.contact pâtteús and SchistosoEa mÂnEonl intec0ion in a rural comÍlunity rn Northeast Bmzil. Rev. tDst. lued. trop. São Psulo, ¿9tl): t-8, 198?.

used data from an ea¡liet stool survey (.A.pril l9??) because the population had been lreated

with

oxamniquinêrE, These pre-tr€atment egg counts provided information on the ¡'natu¡al" intensity

of

infection.

It

is

unlikely that the

local

ecology, behaviou¡

o¡

socio-economic

structure changed over

the

14 month period between the stool survey and the questionnal-re.

Data -Analysis

When appropriate individual data were aggregøled,

by

gender, age group, graded

in-tensity

of

infection, household and house

lo-câtion,

Ttre level

of

data agg¡egation chosen

for

each analysis reflected the level of impact

of the variâble under consideration. Thus the

impact on the intensiry of S, ma.nsoni infectioD

of the vadable under consideration.

ïhus

the anâlysed

by

indlvidual

or

age.sex aggregated

dat4 q'heleas _{the impaci}

_of

_the physical

en-vironment, socio-economic status

or

education

were analysed

by

household aggregated data:

Ihe

prevalence

of

infection

for

individuâls in' various age-sex groups was calculated.

As

the

intensiw

of

S, DaEsoni infection vsdes \r'ith age the age structure

of

a family

u¡ill

influence the meãn intensity

of

infection

for

that household. Hence,

to

enable valid comparisons,

a

household index

of

inJection

was created

by

calculating age sex specific Z scores using logarithms

of

egg

counts.

Tlle sco¡e was computed using standard methods

wher€by egg eount values weÌe corrected by subtracting tfre population mean egg count for the age and sex group from the observed hou-sehold age and sex specific mean egg count

and dividÍng

the

difference

by

the standard deviation of egg count c¡ithin the corresponding

age

and

sex

glouþ

_{tz =}

x-l)/sD).

lhe

household index

of

infection \¡¿as the sum of age-sex specific Z scores

Ior

the household.

If

r

Z

score is zero, then that familys value is equal to the e)rpected mea¡

for

tlle popul¿tion age-sex strata represented

within

that

house-hold. Â positive or negative Z score indicates a value that is greater than o¡ less than the mean, reErectively, Household indices of infection va. ried from

-3.82 +116 mean standard deviation

Socio-econordc status (land-ownership, as-sets and income) was compâred to tlle

house-hold index

of

infection. Literacy was defined

as

the âbility

to

read and vrrite

a

message.

T'he prevalence

of

literacy and

the

averag€ amount of schooling were comparcd for adults

(>

15 yea¡s old) and children. The hous€hold indices

of

infection were contrasted

for

those families y'ith zero ¿nd with one literate petson.

House construction, size, crowdlng, sanitary installatlon, defaecation practices and garbage disposal were described.

Ttre source

of

domestic water used for drinhing was compared to the source of water used

for

home bathing. The existence of

per-ceived alternative sources \áas compared to tåe potential sources documented by t}Ie water survey. The mediarì time spent fetcÌìing water per day v¡as compared

to

the avetage amount

of

water stored

fo¡

each household,

Data on indtvidual water contact due to batlìing outside the house v¿ere agregated into

two

age groups

(<

15 and

>

15 years) and the average time spent for outside bâthing wss then calculated

for

each group by the ave¡age

wedrlJ¡ frequency. Data on individual water contact due

to

clothes washing v¿ere analysed

by age, sex, location, duration and time of day.

\I/ater contact due

to

playing was not quanti-fÍed by this study.

&ESIJLTS

Prevalence and Intensit¡r

of

S. mansoni Inlec-tlon

ïlle

overÊll preyalence

of

S. r¡ransoni in-fection

was

71.1% and, was similar

to

that noted

in

tlre 1g¡4 survey

of

the same

popula-tion¡tt. '¡1t" prevâlence and intensity

of

infec-tion rose rapidly after five years of age (Tâble

l).

Over 9370

of

individuals were tnfected by age 20. fndividuals aged 15-25 years v'ere

par-ticularh¡ prone

to

he¿W infections; thereafter the pr€valence ând intensify of infection

in

ol-der individuals beg¿n

to

decline.

Houslng atrd Hygiene

Housdwalls \¡sere constructed

of

mud and

wattle Qíqot

or

adobe QSVo\ and, roofs of lo.

câlly

produced

_{clay tiles}

GÙqo,

ot

l'râtÆþ. GOEor. !'.ost houses had mud floors, two

Do-Mcl[A, E, & SLEIGH, .4. C. _- Water-contact psttoms snat Schislo€oms E¡r€o¡i inlection l¡ a nùal coEJnudty ln Noftheast B¡s'il. R€v, Illst. Med. kop. SÍo P.ldo, 29(r): l'8, 198?.

TABf.E I

Eevalence and intensjty of S. m¡nlord inlectlon jn the study poPulstion, Csstlo Alves' Bshiu, l9l8

Aæ

(yeats) rotâI¡esident

populâtion i

Number with stool OI inf€cüon Cþomet¡ic

EgeÞ P€r G¡am <1 l-4 5 l8

u

2L 112. 6? t0i l8s r69 2tt ltl ?o 89 9¡ 77 59 ¡00 2t 96 59 43 M M M F M M M ¡' M M P M M M l? 2t 26 20 30 2q l9 7 t6 I t2 2l 23 t2 23 8 9 9 ll 3 I

u

18 23

x

n

l8 !2 ll t7 11 12 9 I 14 l0 33.3 115.8 38.8 65.2 65.3 80.0 83.3 91.6 ?5.0 100.0 82.3 86.9 81.8 86.3 ?5.0 lm.0 71.7 17,7 64.2 50.0 10.14 15.19 20'u 25-44 35.44 45-54 55-At 68.5 ?3.5 M 774 192 L43 762

' Population based on the Bn¡u8l census October l9?7

r' _,âp¡il 19?? stool suwey. Stool exåmined by Eell techni$re M=mate,F=lemale

mestic garbage was usually

thrown

on

the house as fertilizer for

fruit

trees

ot

as food or domestic animals.

No

composting

çâs

done.

Only five households had sanitary inst¿llation of which four were

it

privies; the rest

of

the population defaecate on the ground usually at a specific site near the house. Ttre defaecation site was a sensitive subject and was not pursu-ed further

for

this survey.

Houso Looaú¡on, Lsnd-owEersh¡p, Education a,trd fnfeotion

ltre

best predictor

_of

tho household

infec-tion index was house loc8tion (Table

2).

Mo. reover, households

from

faue[da

Morro

do

Afonso (Figure 1) had a mean infectlon lndex (.0.75) substantislly lower than the mean in-fection index

for

lazendas Gr8yiel and Riaoho Seco comblned

(+0.1?).

Land-osrnershlp was a poor predictor

ol

household lnfection indices

{

(an _average

_of

-0,48

for

families orrning land ând -0.33

for

those that did

not)

and this ob-servation held true when compaling

landown-ing and non-landowning families lìving on the same faze¡¡d.a.

We found t}lat 307o

of

adults znd,zz%o c'1,

school-age child¡en were literâte. The meaD

indices

of

infection

for

the .41 families with

one or more litemture persons and for tfre 28

families

wlth

no literate perso¡s were similar (infection indlces

of

-0.10 and .0.36, rêspecti. vely).

lryat€r flse Inside the Hor¡so

water

is

usuatlJ¡ tetched

by

sdolescents

and female

adults. For

ddriki¡g water, 8løe

(56/69)

_of

families used the spdr¡g and only

MOTA, E. & SLEIGH, å. C. _- Wate¡-contact p¿ttems anal Scùtstoso,lla nrnsor¡l iDlectlon Jn s ru¡sl coûìmurity in No¡th€Âst BEzll. Rey. Inst. Med. trop. São Pâùto, 29(r): l-9, 1987.

T¿,BLE 1I

Va¡tstfon of thê ÁSe.especilic p¡evalence aDd i¡t€ùsity of S, mãrsoEt inf€ction accoÍUiìg to bousehold location srithiu

tlÌe study alea

Place of residence

N.. with PÌevalencs

stool of infection

ex8m, r/r

NP eith Prevâlence

stool of infection Nr stool with Prevalence of ùJectlon ECCcount r

AGE

0-4 5.14

t5-u

35+

2l

2t

29 34

145

tu 6t

2l

2A

27 ¡i

25

27

2t.l

52.4

75.O

63.9

l9

42 32 36

5?.1 92.0 r00

88.9

42.9 90.5 90.5 ?9.3

t0 205

146

r Gêomet¡ic mean ege couDt o! thosê nected (eggs _er ga¡n)

TÄBLE¡II

Numbe¡ of fâ¡¡tties according to source of wster u.E€d

ât home

2 2.9

2 2.9

I 1,5

15 2t.7 49 1L0

* _{IriJona¿ion vâs Dot availâþte ior two tâmiues.}

the elderly usually bathed at home, using qrater

most often (48Vo, fetc}:.ed. fÌom streams. .Again,

few

families (297ø, rel,orted,

an

attemative sourse, and 15 families collected tainwâter as a secondary sor¡rce. FiftJ¡ seven peÍcent (lg/25)

of

t}le families using spring water

fo¡

both

drirlking and bathing

at

home lived near a spring, i.e. on fazenda Morro do /llonso.

Water fo¡ domestic use \iyas stored in clay,

tin

or wooden

jars. ltle

median time pel day

spent fetching water wafi 20 minutes

for

the households (387a) storing a one day supply of u'ater, 30 minutes

for

those (35%) stodng e

two

day supÞly and 35 minutes

for

families QTVo) wìl}J water stored

for

a period longel than 48 hours. Only

four

fami¡ies boiled and

12

(177o) filtered

ï¡âter

before drinking it.

fhe filte$

used

for

this

purpose a¡e

of

un"

lmow efficacy.

Five families had tecently spent ItSg 120-180.00 each

to

build large

brick

and cement

ianl(s (5000

-

15000 liters)

to

storc raÍnv/at€r captured

from

the houre roof. T]:ey repofted that the tanks stored enough water,to supply domestic needs duúng the drier months. These

fâmilies were âll landorÃ'ners and lived in hou-ses lwith tiled roofs.

Water-Coúct Outside the Hoüse

The adult and adolescent fem¿le population spent and avemge of si.x hours ââÆh ttme they

wâshed clothes, usu¿lly

in

streams twice a week. The prefered tùne was 10 âm to 4 pm. Tïre yor¡ng childæn often irlâyed ùr the wster at this

time.

Oeerc,ll. 64% of the total

popula-tion

bathed outside the house using sFeams almost exclusively (927¿

)

_regardless of _{age and} sex (Table

4).

Privacy

at

bathing sites lwâs maintained by erecting thatched scleens aror¡nd

or slightly

belüÍ

¿ strearn and diverting watel along wooden spouting

to

create

a

crude

shswer inside the screened È!ea. virtually

eve-rybody bathed between 10 atn and 6 pm. T À B.L E IV

wâter souæe used by individuals for bathing outsid€ rfte bouse

Sí[e of b8thiDg Drinklng Bsthing

of ¡i¡st SecoÌld Fi¡st Seco¡d

N.o % N.o % N.' % N} %

Pond

Raln

56 81.2

5 7.2

4 5.8

4 5.8

4 5.8 2ø 4A.6

r 1.5 I 1.5

0 - 33 4?.8

2\ 30-4 6 7.2

43 62.3

-Sprl¡a

q"

Mo¡lo do âJonso r

G¡aviel

Riacho Sleco

103 95.4 5

80 94.1 5

32 ?8.0 I

4.õ 220

* _{Most individusl8 in Mo o do Afonso bBühe ln ê 6[fteri¡}

MmA, E. & SLEIGH, Á. C. _- Wate¡-contsct pâtterns and Schistosoma Eâ.so¡i inlection ¡n a rulal corununity ià No¡t¡ìËast _tt., Bmzll. ßev. Itrst. Mei¡. trop. são Pâuto, 29(r): 1-8, 198?,

Bathe 1-70 minutes pe! Bathe more t¡¿Ìr ?0

miDr¡tes p€r week ln

¡Íater-Contarú and S, mansoni Infection Most individuals (104,/141) _{aged less than} 15 years bathed in streams (Table 5). The mean

time spent

for

stream bathlng was pædictive

of

the prevalence of S. maDsoni infection: in. dividuals bathing more than ?0 minutes per week

in

streams were significantly more likely

(X,

₌

11.67;

p

4

0.01) to be jnfected, _<82.5qo p¡evalence) than those spending less than ?0

minutes per week (50.07¿ prevâlence). Ihe intensiw

of

inlection was also corrclated to the amount

of

exposure

to

stfeam wâter; in children 5-14 years

old

there !¡,¡as

a

positive å-ssociation between the individual egg count and the tifne spent bathing (Pearson

correla-tion coeficlent,

r

₌

0.258;

p

<

0.05).

TÁBLE V

Str€âm ÞathiDg and S. rn¡¡sorl tnJ€ction for individual

aged less than 15 yæls old

Bßthi¡g Nmlrer with P¡evalence of siool exâm. S. m¡¡sohl

Afonso presented a lower intensity of infection possibly due

to

the p¡oximity

of

a safe water

source, i.e. the snail-free spring, whereas those

on f&zendÀs Gr¡vlel and Biecho Seoo tÃrere not so ccologically fortunate.

It

hâs been suggested that poorly educaL ed individuals

Ír

rural arcas are necessatily ln discriminate

in

their water-contact and

defa.e-cation behaviour. Horrever, our data indicate that, notwithstanding the extremely low level

of

fomal

education

in

the study area, neither defaecation nor r¡rater contact can be consider-ed indiscriminate. Ttre people make a

conside-rable effort to obtain domestis drinhing water

flom

the cleanest source (the snail-free spring on Morro do AfoDso)

a¡d

only bathe at cer-r

tain

sites where privasy can

be

assured.

It

costs too much for most people to store enough

lainwater to provide for all water needs throug-hout the

yea¡.

fhe

dispe$al of houses along the

hill

c¡ests mall(es

it

prohibitively expensÍve

for individual residents to reticulate safe \,satet

supplies. Thus, regardless

of

their

apprecia-tion of dange$, the people at present have no choice

for

bathing and clothes washing other than using the nearest acrceÞtable water body.

This study design did not allow us to elu-cidate the link behfleen defa€cation habits and

S. maùsoni transmission. However,

it

ïtas

ob-vious that

for

adults privacy and conveniencs

were two major considerations

in

chooslng a defa€cation site. Future studies could ll'eu fo-cus on the defaecation behaviour of the mobile, socially unaware and heavily iniected group.

of children âged 9

to

15 yeârs.

If it

could be

confimed that

this

group

is

responsible for most of the fâecal contamination

ol

the rural environment

it

would be appropÌiate to

ensu-re that educational material stressing the need

to

defaecâ,te below

or

fat

away from bâthing and clothes washing sites, is designed specially

for

this age group. Ttre installation of

house-holds latrines would not be eu)ected

to

have

much inlluence

on

transmission. Ttre fa€cal contâmination

of

tJ:e domestic environment

fr

this rurâl ârea would be most unlikely to teach the distant bathing and clothes washlrlg sites,

although reduclng faecal contamination of the domestic envlronment could have an impact in reducing the transmlssion

of

other infectioug

a¡d

parasitic diseases. DISCUSSION

Reports from Puerto Rico (6), St. Lucia (g), Tanzania (13) and Ghana (4) _{have shown that} the type and duration of individual

water,con-tact is an excellent predlctor of the prevalencr and intensity

of

schistosomal

infection.

Our data on individuals tesident

in

the Castro

.4.1-ves study area confirm this associâtion. Howe-ver, the most striking relationship here rE)orted

emerged at the household level of analysis and

highlighted the extraordinalily focâl natule ol

S.

mansonl transmission

within

an

endemic area.

Ou¡ d¿ta indicate that a key determlnant

of

human infection

is

ecological.

In

Castro .{lves neady all residents used spring or stream water

for

bathing and domestic hygiene, thus, the prevalence and intens¡ty of infection reflect-ed the location

of

the househotd relative to the snail-free or snail colonized watet sources. Residents

of

households on fauÆndâ

Mollo

do

MC[tÀ, E, & SLEIGH, A. C. _- Water-contact pattems and Sclústosoh.¡ ma¡so¡l inJÊciton in a ruÞl cornmu¡ity jn

Norüh€åst BÉzil. Rey. Inst. Med. trop. São P¡ulo. 29(1): 1-8, 198?.

Repetitive use

of

community-based

schis-tosomacidal treatment cân lower the

¡isk

of heaw infections l8 _{and a larga scale chemothe'} râpy,oriented control program throughout Bra-zi1 is aheady underway 12.

It

_is predictable _that

the benefits

of

the control strategy

to

Brâui-lia,ns resident in areas 'with endemic

schistoso-miasis

will

be

considerable ¡0. However, â permanent solution

to

schistosomiasis

will

de-pend on the availability of safe rÃ'ater supplies

throughout

the

endemic zone 1,7-9,2t.

It

will

take many ¡¡ears of economic progress before rural peasants \ùill have the resources to obtain safe domestic water supplies. Programs direct-ed at lowering the cost of adequate supplies of safe water for rural Brazilians would be most appropriate. Possible alternatives include

sub-sidizing the construction

of

large rain-water tanks, the development of a cheaper technique

1o¡ building such tanks,

or

the reticulation ol water supplies on a grand,scale throughout

ru-ral Brazil.

RESUMO

Paalrões de contato com a águe e

ir

ecção por Schistosoma mansoni em com!¡nidade rura,l do

Nordest€ bresileiro

Este estudo analisa a relaçáo entre as

ca-racterísticas da infecção por S, ma.nsonl e o padrão de contato com água, os hábitos de hi-giene, a localização do domicílio,

o

nlvel

edu-cacional

e

as condições sócio,econômicas, em

uma população delinida rcsidente na zona en. dêmica de Castro Alves, Bahia, Brasil,

A

álea de estudo é típica de zonas rurais do

Nordes-te, com relêvo acidentado e sua população de-dica-se à lavoura não iûiga.da de lumo e

man-dioca. Após

o

mapeamento da área e um

in-quérito malacológico completo, foi aplicado um questionário para câda famÍlia com questões referentes às atividades de sontato com água,

tempo de exposiçáo, condições de habitação e

caracteristicas sócio-econômicas. .Á.

ptevalên-cia e a intensidade de infecqáo por S. mansoni

foram obtidas usando'se a técnica de Bell para

a

contagem de ovos nas fezes.

Â

análise dos dados incluiu o cálculo de um lndice de infec-cão da família utilizando'se a contagem de ovos

por gramâ de fezes de cada indivíduo. Poucas' casas tinham instalações sanitárias ou fonte de

ágj.Ja, pala uso doméstico, ent¡etanto, os

h6-bitos de defecação e de contato com água não eram indiscriminados, observando-se que os

l¡Ì-divíduos dispendian esforço considerável em busca de água mais limpa para beber e para tomar banho, evitando defecar próximo às fon. tes de água, ,{ propriedade da terra e o nivel educacional não mostraram-se coEelacionados com o Índice de infecção. O fatoÌ que pareceu

influenciar a maior ou menol prevalência de infecçáo por S. m¿nsoni

foi

a localização das casas em relação à distância de uma fonte de água não colonizada por Biomphalaria glabra-ta.

ACX(NOìtrI]EDGMEIVTS

This study was a collaborÈtive project in-volving the Federal University

of

Bahia, The

F\¡ndação OsrÃ'aldo

cruz,

and

the

Harvard Sshool

of

Public Health, Field v/ork was

sup-ported by Antonio Celso Batista and Tomé

Sil-va Oliveira. Technical support

in

the

laborato-rywas

provided by Vera Lúcia Menezes,

Ro-berto MâgalhãÆs, and Tereza Maish de PaivB'

Ât

Harvard the faculty and staff

of

the De-pafüment

of

T¡opical Public Health furnished logistical, secretarial, and technical a.ssistance;

Dr. Thomas H. lfleller plovided administratlve support and scientijic advice throughout the study. Dr.

oto

Oliveira and Dr. Reinaldo RosB

furnished vital local assistance.

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