R e v i s t a d a S o c i e d a d e B r a s i l e i r a d e M e d i c i n a T r o p i c a l 2 6 ( 3 ) : 1 7 5 - 1 8 0 , j u l - s e t , 1 9 9 3
INTESTINAL HELMINTHIASES IN ECUADOR: THE
RELATÍONSHIP BETWEEN PREVALENCE, GENETIC, AND
SOCIOECONOMIC FACTORS
P h i l i p J . C o o p e r , A n g e l G u e v a r a E . a n d R o n a l d H . G u d e r i a n
P r e v a l e n c e o f i n f e c t i o n w i t h t h e i n t e s t i n a l h e l m i n t h s , A s c a r is lu m b r ic o id e s , T r i c h u r is tr ic h i u r a , A n c y lo s to m a d u o d e n a l e a n á S t r o n g y l o i d e s s te r c o r a lis w a s e x a m i n e d i n 6 3 2 r e s i d e n t s o f c o m m u n i t i e s i n E s m e r a l d a s p r o v i n c e o f E c u a d o r . T h e s e c o m m u n i t i e s w e r e d i v i d e d i n t o t w o g r o u p s a c c o r d i n g t o a r e a o f h a b i t a t i o n w h i c h r e f l e c t e d d i f f e r e n t s o c i o e c o n o m i c c i r c u m s t a n c e s . A t t e m p t s w e r e m a d e t o c o r r e l a t e i n f e c t i o n s t a t u s w i t h r a c e a n d A B O b l o o d g r o u p p h e n o t y p e . T h e r a c i a l g r o u p s i n c l u d e d b l a c k s , C h a c h i a m e r i n d i a n s , a n d m i x e d - r a c e m e s t i z o s . G r e a t e r p r e v a l e n c e s o f i n f e c t i o n w e r e s e e n i n t h e a r e a o f l o w e r s o c i o e c o n o m i c s t a t u s . N o r a c i a l o r b l o o d g r o u p a s s o c i a t i o n s w i t h h e l m i n t h i n f e c t i o n w e r e s e e n c o n t r o l l i n g f o r s o c i o e c o n o m i c s t a t u s .
K e y - w o r d s : H e l m i n t h p a r a s i t e s . R a c e . A B O b l o o d g r o u p p h e n o t y p e s . S o c i o e c o n o m i c s t a t u s .
G a s tr o in te s tin a l h e lm in th ia s e s a re a n im p o rta n t c a u s e o f m o r b id ity w o r ld w id e a n d a f fe c t a la rg e p r o p o r ti o n o f m a n k in d 3. T h e fa c to rs th a t c o n tro l s u s c e p tib ility to g e o h e lm in th ia s e s in m a n a r e p o o r ly u n d e r s to o d b u t i n c l u d e h o s t b e h a v io u r , im m u n ity , g e n e tic s , a n d n u tr itio n .
T h e e v id e n c e f o r a r o l e f o r g e n e tic fa c to rs in d e te r m in in g s u s c e p tib ility to in te s tin a l h e lm in th in fe c tio n s is la rg e ly e p id e m io lo g ic a l. F o r e x a m p le , th e r e is s o m e e v id e n c e o f a f a m ilia l p re d is p o s itio n to h ig h o r lo w w o r m b u r d e n s 6. G e n e tic a s so c ia tio n s w i t h in f e c tio n s ta tu s m a y b e e x a m in e d a t th e p o p u la tio n le v e i u s in g s im p le g e n e tic m a r k e rs s u c h a s r a c e a n d b lo o d g ro u p .
R a c ia l d if f e r e n c e s in th e p r e v a le n c e , a n d th e c o u r s e a n d o u t c o m e o f d i s e a s e h a v e b e e n d o c u m e n t e d in i n f e c t io n s w i t h h o o k w o r m 13, p in w o r m 5, o n c h o c e r c ia s is 15, a n d le is h m a n ia s is 14. M a n y s u c h s tu d ie s s u f f e r f r o m th e d is a d v a n ta g e s o f c o m p a r i n g p o p u l a t i o n s f r o m d i f f e r e n t g e o g r a p h ic a l r e g io n s , m a k in g it im p o s s ib le to c o n tr o l f o r c o n f o u n d in g fa c to rs s u c h a s le v e i o f e x p o s u r e a n d n u tr itio n a l s ta tu s .
T h e r e h a s b e e n r e n e w e d in te re s t in th e r o le o f th e A B O b lo o d g r o u p s y s te m in d e te r m in in g s u s c e p tib ility to p a r a s itic a n d b a c te ria l in f e c tio n s .
N a tio n a l C e n tr e f o r T ro p ic a l D ise a se s - e x te n sio n Q u ilo, H o s p ita l V o z a n d e s, Q u ito , E c u a d o r.
A d d r e s s t o : D r . P h ilip C o o p e r . H o sp ita l V o z a n d e s, C a silla 17- 1 7 -6 9 1 , Q u ito , E c u a d o r.
R e c e b id o p a r a p u b lic a ç ã o e m 0 1 /0 3 /9 3 .
In d iv id u a l A B O p h e n o ty p e s h a v e b e e n a s s o c ia te d w i t h s u s c e p t i b i l i t y t o l y m p h a t i c f i l a r i a s i s 11, g ia r d ia s is 1, c h o le r a 4, a n d m a la r ia 12.
A n o p p o r tu n ity to s tu d y th e r e la tiv e im p o rta n c e o f g e n e tic a n d s o c io e c o n o m ic fa c to rs in in te s tin a l h e lm in th ia s e s e x is ts in th e S a n tia g o r i v e r b a s in o f E s m e ra ld a s p ro v in c e in E c u a d o r . H e r e , th r e e ra c ia l g ro u p s in h a b it a r a in f o r e s t a r e a in c lo s e p ro x im ity to e a c h o th e r; in d ig e n o u s C h a c h i a m e r in d ia n s , b la c k s ( o f A fr ic a n d e s c e n t), a n d m ix e d -ra c e m e s tiz o s . R a c ia l d iffe re n c e s in d is e a s e p r e v a le n c e b e tw e e n C h a c h illa a n d b la c k s h a v e a lre a d y b e e n re p o r te d in m a la r ia 10, y a w s 8, a n d o n c h o c e rc ia s is 7.
T h is s tu d y w a s p e r f o r m e d to in v e s tig a te th e im p o rta n c e o f g e n e tic s , u s in g th e m a rk e rs o f ra c e a n d b lo o d g r o u p , a n d s o c io e c o n o m ic sta tu s in d e te r m in in g th e p re v a le n c e o f in te s tin a l h e lm in th ia s e s in th e S a n tia g o r i v e r b a s in .
M A T E R I A L A N D M E T H O D S
S tu d y a r e a a n d p o p u l a t i o n
T h e p ro v in c e o f E s m e r a ld a s ( la titu d e 1’9 6 S to 1 ’4 3 W a n d lo n g itu d e 7 8 ’4 8 W to 8 0 ’9 W ) is th e n o r th w e s te m C oastal p ro v in c e o f E c u a d o r . T h is re g io n w h e r e th e e le v a tio n ra n g e s a p p r o x im a te ly 0 - 2 0 0 m e tre s , o c c u p ie s 1 4 ,7 lO k m a n d h a s a p o p u la tio n o f 2 8 5 ,6 0 0 (1 9 8 2 c e n s u s ).
C o o p e r P J , G u e v a r a A E , G u d e r i a n R H . I n t e s t i n a l h e b n i n t h i a s e s i n E c u a d o r : t h e r e l a t i o n s h i p b e t w e e n p r e v a l e n c e , g e n e t i c , a n d s o c i o e c o n o m i c f a c t o r s . R e v i s t a d a S o c i e d a ç í e B r a s i l e i r a d e M e d i c i n a T r o p i c a l 2 6 : 1 7 5 - 1 8 0 , j u l - s e t , 1 9 9 3 .
c o a s ta l p a r t o f th e p r o v in c e , m u n ic ip a l o f E lo y A lf a r o . T h e a r e a is p r im a r ily e q u a to r ia l r a m fo re s t.
T h e s tu d y w a s c o n d u c te d in c o m m u n itie s liv in g i n t h i s a r e á . T h e s e c o m m u n itie s in c lu d e ; in d ig e n o u s a m e r in d ia n s , th e C h a c h illa ; b la c k s ( o f a f r ic a n d e s c e n t); a n d m e s tiz o s o f m ix e d e u r o p e a n , in d ia n , a n d a f r ic a n a n c e s tr y . M o s t f a m ilie s in th is re g io n a r e e n g a g e d in a g r ic u ltu r e , l o g g in g , o r fis h in g . T h e
e th n o g ra p h ic fe a tu re s o f th e s e c o m m u n itie s h a v e b e e n d e s c rib e d e ls e w h e r e 9.
T h e s tu d y a r e a in c lu d e d B o rb o n ( th e p rin c ip a l to w n a t th e c o n f lu e n c e o f th e r iv e r s th a t fo r m th e S a n tia g o R i v e r B a s in ) a n d ru r a l v illa g e s w h ic h w e re
a c c e s s ib le b y e ith e r r i v e r o r d i r t r o a d . T h e s tu d y a r e a w a s d i v i d e d i n t o tw o : A r e a 1 ( h i g h e r s o c io e c o n o m ic s ta tu s ) w a s B o rb o n a n d a r e a 2 ( lo w e r s o c io e c o n o m ic s ta tu s ) in c lu d e d a to ta l o f 5 6 v illa g e s . I n h a b ita n ts o f B o r b o n w e r e w e a lth ie r th a n th o s e fr o m a r e a 2 a n d h a d a c c e s s to e d u c a tio n a n d h e a lth f a c i l i t i e s . M o s t h o u s e h o l d s i n B o r b o n h a d ru d im e n ta ry s a n ita iy fa c ilitie s, e le c tric ity , a n d a c cess to c le a n w a te r . T h e s e w e r e a b s e n t in a r e a 2 .
S a m p l e c o l l e c ti o n a n d a n a ly s i s
A s in g le b lo o d s a m p le a n d s to o l s a m p le w e re o b ta in e d f r o m in d iv id u a is in th e stu d y c o m m u n itie s . T o o b ta in a n d a n a ly s e th e s e s a m p le s la b o ra to rie s w e re s e t u p a t h e a lth c e n tr e s in B o rb o n f o r a r e a 1 a n d Z a p a llo G r a n d e f o r a r e a 2 . A to ta l o f 2 9 6 w e re s e le c te d in a r e a 1 a n d 3 3 6 in a r e a 2 . A fie ld te a m s p e n t a to ta l o f 3 w e e k s in a r e a 1 f o llo w e d b y 3 w e e k s in a r e a 2 c o lle c tin g a n d a n a ly s is s a m p le s . In B o r b o n , m e m b e r s o f t h e c o m m u n i t y w e r e e n c o u ra g e d to a tte n d th e h e a lth c e n tr e w h e re sa m p le s w e re ta k e n a n d e x a m in e d im m e d ia te ly . I n a r e a 2 , th e te a m v is ite d th e v illa g e s b y c a n o e a n d b r o u g h t b a c k a p p r o x im a te ly 5 0 v o lu n te e r s d a ily (s e le c te d ra n d o m ly ) to Z a p a llo G r a n d e w h e r e s a m p le s w e re ta k e n a n d e x a m in e d fr e s h . A d a ta s h e e t w a s fille d in f o r e a c h p a tie n t w h ic h in c lu d e d in f o r m a tio n o n a g e , s e x , ra c e , a n d a d d r e s s .
S to o l s u s p e n s io n s w e r e e x a m in e d in s a lin e a n d l u g o l ’s io d in e b y d ir e c t m ic ro s c o p y u s in g lo w a n d h ig h p o w e r. T h r e e s m e a r s (e a c h f o r s a lin e a n d io d in e ) w e r e e x a m in e d f r o m e a c h in d iv id u a l f o r th e p r e s e n c e o f e g g s o r la r v a e o f in te s tin a l h e lm in th s . T h e d ir e c t m e th o d o f s to o l e x a m in a tio n w a s u s e d a s
th e f o r m a lin - e th e r c o n c e n tr a tio n m e th o d 15 o f f e r s little a d v a n ta g e in s e n s itiv ity o v e r t h is m e th o d in a r e a s o f h i g h h e l m i n t h p r e v a l e n c e ( G u e v a r a , u n p u b lis h e d d a ta ).
O n ly in f e c tio n w i t h th e 4 c o m m o n ly fo u n d in te s tin a l h e lm in th s w e r e r e p o r t e d in th is s tu d y . T h e s e w e r e A s c a r i s l u m b r i c o i d . e s , T r i c h u r i s t r i c h i u r a , h o o k w o rm , a n d S t r o n g y l o i d e s s t e r c o r a l i s .
T h e h o o k w o r m s p e c ie s id e n tif ie d i n t h is s tu d y a c c o rd in g to e g g s iz e w a s A n c y l o s t o m a d u o d e n a l e .
T h is is th e d o m in a n t s p e c ie s fo u n d a lo n g th e w e s t c o a s t o f S o u th A m e r ic a 2. A li in d iv id u a is in fe c te d w ith in te s tin a l h e lm in th s w e r e o f f e r e d a p p r o p r ia te a n tih e lm in th ic tr e a tm e n t.
B lo o d s a m p le s w e r e o b ta in e d b y v e n e p u n c tu r e o f a n te c u b ita l v e in s u s in g s te r ile v a c u ta in e r (B e c to n D ic k in s o n , N e w J e r s e y , U S A ) s e ts . R e d c e lls w e r e te s te d f o r A B O b lo o d g r o u p a n tig e n s u s in g th e te s t tu b e m e th o d .
C o n s e n t
E th ic a l c o n s e n t f o r th is s tu d y w a s o b ta in e d b y c o n s u lta tio n o f c o m m u n ity le a d e r s a n d th e C h a c h i F e d e r a tio n a n d a ls o f r o m th e E th ic a l C o m m itte e , H o s p ita l V o z a n d e s , Q u ito .
S t a t i s t i c a l a n a l y s i s
S ta tistic a l a n a ly s is w a s p e r f o r m e d u s in g M in ita b s t a t i s t i c s p r o g r a m m e o n a n A p p l e - M a c i n t o s h C o m p u te r. I n d iv id u a is w i t h m is s in g d a ta w e r e e x c lu d e d f r o m th e a n a ly s is . S ta tis tic a l a s s o c ia tio n s w e r e m e a s u r e d u s i n g P e a r s o n ’ s C h i - s q u a r e . S ta tis tic a l s ig n ific a n c e w a s ta k e n a s a p r o b a b il i t y o f le s s th a n 0 .0 5 .
R E S U L T S
P o p u l a t i o n c h a r a c t e r i s t i c s
C o o p e r P J , G u e v a r a A E , G u d e r i a n R H . I n t e s t i n a l h e l m i n t h i a s e s i n E c u a d o r : t h e r e l a t i o n s h i p b e t w e e n p r e v a l e n c e , g e n e t i c , a n d s o c i o e c o n o m i c f a c t o r s . R e v i s t a d a S o c i e d a d e B r a s i l e i r a d e M e d i c i n a T r o p i c a l 2 6 : 1 7 5 - 1 8 0 , j u l - s e t , 1 9 9 3 .
Population distribution
T h e r e w a s a s k e w in th e ra c ia l d is tr ib u tio n o f th e s tu d y p o p u la tio n b e tw e e n th e tw o s tu d y a re a s. M o s t b la c k s liv e d in a r e a 1 ( 6 0 .3 % ) a n d th e m e s tiz o s ( 6 8 .7 % ) a n d C h a c h illa ( 7 9 .0 % ) liv e d m a in ly in a r e a 2 .
Blood group phenotypes
T h is is b e s t e x a m in e d a c c o r d in g to ra c e . T h e d i s tr ib u tio n o f b lo o d g r o u p p h e n o ty p e s w a s s im ila r
b e tw e e n b la c k s a n d m e s tiz o s w ith 7 0 .6 % a n d 6 2 .7 % re s p e c tiv e ly b e in g b lo o d g r o u p O , 1 4 .6 % a n d 1 9 .4 % g r o u p A , 1 3 .1 % a n d 1 4 .9 % g r o u p B , a n d 1 .8 % a n d 3 .0 % g r o u p A B . A lm o s t a li th e C h a c h illa ( 9 8 .8 % ) w e r e b lo o d g r o u p O w ith o n ly 2 ( 1 .2 % ) b e in g g r o u p B . T h e r e w e r e n o C h a c h illa w ith g r o u p s A o r A B .
Helminth prevalence
A to ta l o f 4 8 0 ( 7 5 .9 % ) o f th e s tu d y p o p u la tio n w e r e in f e c te d w i t h a t le a s t o n e h e lm in th sp e c ie s . I n f e c tio n ra te s f o r in d iv id u a l h e lm in th s p e c ie s w e re a s f o llo w s ; A . l u m b r i c o i d e s 3 6 8 ( 5 8 .2 % ) in fe c te d ,
T . t r i c h i u r a 3 2 0 ( 5 0 . 6 % ) , A . d u o d e n a l e 158 ( 2 5 .0 % ) , a n d S . s t e r c o r a l i s 3 7 ( 5 .9 % ) .
Race and helminth prevalence
P r e v a le n c e ra te s te n d e d to b e h ig h e r in m e s tiz o s a n d C h a c h illa th a n in b la c k s ( T a b le 1). T h is w a s t r u e o f c o m b i n e d i n f e c t i o n ( x 2 = 1 1 . 5 d f = 2 , p < 0 .0 1 ) a n d in fe c tio n w ith A l u m b r i c o i d e s (x 2= 9 .1 d f = 2 , p < 0 . 0 5 ) a n d A d u o d e n a l e(x 2 = 2 1 . 3 d f = 2 , p < 0 . 0 0 1 ) . T h e s e ra c ia l d if f e r e n c e s w e r e n o t sta tistic a lly s ig n if ic a n tin in fe c tio n s w ith T. t r i c h i u r a .
In th e c a s e o f S . s t e r c o r a l i s , p re v a le n c e s w e re to o lo w to d e te c t a n y d iffe re n c e s .
Blood group and helminth prevalence
B lo o d g r o u p a s s o c ia tio n s w e r e se e n in in fe c tio n w i t h A . d u o d e n a l e . G r o u p s O a n d A B w e re see n m o r e c o m m o n ly in in fe c te d in d iv id u a is ( x 2 = 9 . 7
d f = 3 , p < 0 . 0 5 ) . I n f e c tio n ra te s w ith th is p a r a s ite a c c o rd in g to b lo o d g r o u p a r e s h o w n in T a b le 2.
O n ly 9 in d iv id u a is w e r e g r o u p A B .
Area and helminth prevalence
P re v a le n c e ra te s w e r e h ig h e r in a r e a 2 th a n a r e a 1 ( T a b le 1). T h is w a s tr u e o f c o m b in e d in fe c tio n ( x 2 = 6 6 .8 d f = l , p < 0 . 0 0 1 ) , A . l u m b r i c o i d e s
(x 2= 7 . 0 d f = l , p < 0 . 0 1 ) , T. t r i c h i u r a (x 2 = 2 5 .8 d f = l , p < 0 .0 0 1 ) , a n d A . d u o d e n a l e (x 2 = 2 1 . 3 d f = l , p < 0 .0 0 1 ) . S . s t e r c o r a l i s w a s m o r e p r e v a le n t in a r e a 1 (n o t s ig n ific a n t).
Area, race, and helminth prevalence
A n a ly s is o f h e lm in th p r e v a le n c e b y ra c e in th e tw o a re a s s h o w e d m a rk e d ly h ig h e r p re v a le n c e s in a li ra c e s in a r e a 2 ( T a b le 1). T h e s e d iffe re n c e s w e re n o t s ta tis tic a lly s ig n ific a n t in in fe c tio n s w ith A . l u m b r i c o i d e s . S . s t e r c o r a l i s w a s m o re p r e v a le n t in a re a 1 in b la c k s a n d m e s tiz o s (n o t s ig n ific a n t).
T h e r e w e r e n o i n t e r - r a c i a l d if f e r e n c e s in h e lm in th p re v a le n c e in n e ith e r a r e a 1 n o r a r e a 2 (T a b le 1). T h is w a s tr u e f o r c o m b in e d a n d in d iv id u a l h e lm in th in fe c tio n s .
Area, blood group, and helminth prevalence
T h e b lo o d g r o u p O a n d A B a s s o c ia tio n s w ith A . d u o d e n a l e in fe c tio n w e r e c o n f o u n d e d b y a r e a . I f th e p re v a le n c e o f A . d u o d e n a l e in fe c tio n is e x a m in e d a c c o rd in g to b lo o d g r o u p in a re a s 1 a n d 2 , th e a s s o c ia tio n s d is a p p e a r (T a b le 2 ). T h e fín d in g o f 1 00 % p r e v a le n c e in in d iv id u a is w ith g ro u p A B in a r e a 2 is d if f ic u lt to in te r p r e t a s o n ly 2 in d iv id u a is h a d th is b lo o d g r o u p .
D IS C U S S I O N
A r e a o f h a b i t a t i o n w a s th e m a j o r f a c to r d e te r m in in g h e lm in th p r e v a le n c e . In f e c tio n ra te s fo r m o s t h e lm in th s w e r e h i g h e r in a r e a 2 th a n a re a 1. T h e s e f in d in g s w e r e v e r y s tr o n g ly s ta tis tic a lly
s i g n i f i c a n t . G u t h e l m i n t h t r a n s m i s s i o n i s l i k e l y t o
b e g r e a te r in a r e a 2 a s th is a r e a is c h a ra c te ris e d b y p o o r a c c e s s to h e a lth c a re a n d e d u c a tio n , a n d b y th e a b s e n c e o f c le a n w a te r a n d s a n ita tio n a n d th e ir r e g u la r u s e o f fo o tw e a r. T h e s tu d y p a r tic ip a n ts
w e re a n d s a n i t a t i o n a n d t h e i r r e g u l a r u s e o f f o o t w e a r .
T h e s tu d y p a r tic ip a n ts w e r e n o t q u e s tio n e d a b o u t a n tip a r a s itic m e d ic a tio n w h i c h m i g h t a c c o u n t f o r
C o o p e r P J , G u e v a r a A E , G u d e r i a n R H . I n t e s t i n a l h e l m i n t h i a s e s i n E c u a d o r : t h e r e l a t i o n s h i p b e t w e e n p r e v a l e n c e , g e n e t i c , a n d s o c i o e c o n o m i c f a c t o r s . R e v i s t a d a S o c i e d a d e B r a s i l e i r a d e M e d i c i n a T r o p i c a l 2 6 : 1 7 5 - 1 8 0 , j u l - s e t , 1 9 9 3 .
T a b l e 1 - H e l m i n t h i n f e c t i o n p r e v a l e n c e a c c o r d i n g t o r a c i a l g r o u p a n d a r e a o f h a b i t a t i o n .
R a c e A re a N u m b e r C o m b in e d A l T t A d S s
A li g r o u p s
1 2 9 6 6 1 .2 5 2 .7 3 9 .9 8 .8 7 .1
2 3 3 6 8 9 . 4 * * * 6 3 . 1 * *
60
.1
* * * 3 9 3 * * * 4 .8* T 6 3 2 7 6 .0 5 8 .2 5 0 .6 2 5 . 0 5 .9
B la c k s
1 2 4 0 6 0 .8 5 0 .8 4 0 .8 8 .3 6 .3
2 158 8 8 .0 * * * 5 8 .2 5 9 . 5 * * * 3 6 . 1 * * * 2 .5
T 3 9 8 7 1 .6 5 3 .8 4 8 . 2 1 9 .4 4 .8
M e s tiz o s
1 21 5 7 .1 5 7 .1 2 8 .6 4 .8 1 9 .1
2 4 6 9 1 . 3 * * 7 3 .9 6 0 . 9 * 3 7 . 0 * * 8 .7
T 6 7 8 0 .6 6 8 .7 5 0 .8 2 6 .9 1 1 .9
C h a c h is
1 3 5 6 5 .7 6 2 .9 4 0 .0 1 4 .3 5 .7
2 1 3 2 8 9 .4 * * * 6 5 .2 6 0 . 6 * 4 4 . 0 * * 6 .1
T 1 67 8 4 .4 6 4 .7 5 6 .3 3 7 . 7 6 . 0
T = tota l; C o m b in e d = ali 4 h e lm in ts; A l == A . l u m b r i c o id e s ; T I = T. t r i c h i u r a ; A d = A . d u o d e n a le - , S s = 5. s t e r c o r a l i s
T e s t statistic o f c o m p a r iso n o f p re v a le n c e s b e tw e e n a re a s 1 a n d 2 a re sho w n (1 d e g re e o f fre e d o m ): * p < 0 .0 5 * * p < 0 . 0 1 * ** p < 0 .0 0 1
T a b l e 2 - P r e v a l e n c e o fA . d u o d e n a le i n f e c t i o n a c c o r d i n g t o b l o o d g r o u p a n d a r e a .
B lo o d g r o u p B o th a r e a s B o th a r e a s B o th a r e a s
n ° % n ° % n ° %
O 1 3 5 /4 8 8 2 7 .7 1 7 /1 9 8 8 .6 1 1 8 /2 9 0 4 0 . 7
A 1 1 ./7 1 1 5 .5 5 ./ 4 4 1 1 .4 6 . 1 2 1 2 2 .2
B 9 . / 6 4 1 4 .1 3 ./ 4 7 6 .4 6 . / 1 7 3 5 .3
A B 3 ./9 3 3 .3 1 ./7 1 4 .3 2 . 1 2 1 0 0 .0
T o ta l 1 5 8 /6 3 2 2 5 .5 2 6 /2 9 6 8 .8 1 3 2 /3 3 6 3 9 .3
a c c e ss to h e a lth fa c ilitie s .
P o p u la tio n s s u rv e y s h a v e p r o v id e d e m p iric a l
d a ta re la tin g to ra c ia l d iffe re n c e s in p re v a le n c e o f a n u m b e r o f h e lm in th s 5 7 1315. R a c ia l d iffe re n c e s in d is e a s e p r e v a le n c e h a s o f te n b e e n c ite d a s e v id e n c e fo r g e n e tic c o n tr o l o f s u s c e p tib ility . In te r p r e ta tio n o f s u c h d a t a i s c o m p l i c a t e d b y t h e m a n y e n v iro n m e n ta l d if f e r e n c e s th a t m a y in flu e n c e th e s e
su c h a s le v e i o f e x p o s u r e , n u tr itio n , a n d in te rc u rre n t in fe c tio n . In th is s tu d y th e s e fa c to rs w e r e c o n tro lle d a s w e ll a s p o s s ib le . I n e a c h a r e a , th e 3 ra c ia l g ro u p s s h a re d th e s a m e e n v ir o n m e n t a n d w e re o f s im ila r n u tr itio n a l s ta tu s a n d w e r e lik e ly to b e e x p o s e d to s im ila r le v e is o f in f e c tio n w ith g u t h e lm in th s a s
w e ll a s o th e r in f e c tio u s d is e a s e s .
T h e a p p a r e n t ra c ia l d if f e r e n c e s in h e lm in th p r e v a l e n c e s e e n in t h i s s t u d y w e r e s t r o n g l y
c o n f o u n d e d b y a r e a o f h a b ita tio n . F o r e x a m p le , p re v a le n c e ra te s w e re h ig h e r in m e s tiz o s a n d C h a c illa t h a n i n b l a c k s f o r c o m b i n e d i n f e c t i o n , A . l u m b r i c o i d e s , a n d A . d u o d e n a l e . H o w e v e r , w h e n a n a ly s e d b y a r e a , a li ra c ia l d if f e r e n c e s w e r e lo s t.
C o o p e r P J , G u e v a r a A E , G u d e r i a n R H . I n t e s t i n a l h e l m i n t h i a s e s i n E c u a d o r : t h e r e l a t i o n s h i p b e t w e e n p r e v a l e n c e , g e n e t i c , a n d s o c i o e c o n o m i c f a c t o r s . R e v i s t a d a S o c i e d a d e B r a s i l e i r a d e M e d i c i n a T r o p i c a l 2 6 : 1 7 5 - 1 8 0 , j u l - s e t , 1 9 9 3 .
p o s s ib le th a t th e g r o u p A B a s s o c ia tio n is v a lid b u t n u m b e rs w e r e to o s m a ll to e x c lu d e a n a r e a e f fe c t. T h e g r o u p O a s s o c ia tio n w a s s tr o n g ly c o n f o u n d e d b y a r e a : T h e p r o p o r ti o n o f in d iv id u a is w ith b lo o d g ro u p O w a s h i g h e r in a li ra c e s in a r e a 2 w h e r e A . d u o d e n a l e p r e v a le n c e w a s m u c h h ig h e r. In a d d itio n , th e C h a c h is , w h o liv e d p r e d o m in a n tly in a r e a 2 , h a d th e h ig h e s t p r e v a le n c e o f A . d u o d e n a l e a n d w e re a lm o s t e x c lu s iv e ly g r o u p O .
T h i s s t u d y i l l u s t r a t e s t h e i m p o r t a n c e o f c o n tr o llin g f o r s o c io e c o n o m ic c irc u m s ta n c e s in e p id e m io lo g ic a l in v e s tig a tio n s o f g e o h e lm in th ia s e s . A re a o f h a b ita tio n w a s a g o o d in d ic a to r o f b o th s o c io e c o n o m ic fa c to r s a n d th e le v e i o f g e o h e lm in th tr a n s m is s io n a n d p r e v a le n c e . I f th e s tu d y a r e a h a d n o t b e e n d i v id e d in to tw o to re fle c t th e s e d iffe re n c e s , a n u m b e r o f s p u r io u s a s s o c ia tio n s b e tw e e n ra c e a n d b lo o d g r o u p a n d h e lm in th p r e v a le n c e w o u ld h a v e b e e n se e n .
T h e s e f in d in g s d o n o t p r e c lu d e a r o le fo r g e n e tic s i n s u s c e p tib ility to g u t h e lm in th s . T h e u s e o f p r e v a le n c e s tu d ie s to d e te c t ra c ia l a n d g e n e tic d e te r m in a n ts o f in f e c tio n s ta tu s w ith h e lm in th s , th o u g h u s e f u l , m a y b e o f lim ite d p o w e r in re v e a lin g su c h a s s o c ia tio n s . T h e u s e o f s im p le g e n e tic m a r k e rs s u c h a s r a c e a n d b lo o d g r o u p m a y b e to o c r u d e to d e te c t v a lid g e n e tic a s s o c ia tio n s . A lte m a tiv e ly , th e v e r y s tr o n g in f lu e n c e o f e n v ir o n m e n t d e m o n s tra te d in th is s tu d y m a y h a v e m a s k e d w e a k e r a s s o c ia tio n s o f r a c e o r b l o o d g r o u p .
R E S U M O
A p r e v a l ê n c i a d e i n f e c ç õ e s c o m h e l m i n t o s A s c a ris lu m b r ic o id e s , T r ic h u r is tr ic h iu r a , A n c y lo s to m a d u o d e n a le e S tr o n g y l o id e s s te r c o r a lis f o i e x a m i n a d a e m 6 3 2 p e s s o a s e m d i f e r e n t e s c o m u n i d a d e s n a R e g i ã o d e E s m e r a l d a s n o E q u a d o r . E s t a s c o m u n i d a d e s f o r a m d i v i d i d a s e m d o i s g r u p o s c o n f o r m e a á r e a n a q u a l r e s i d e m , o q u e r e f l e t e d i f e r e n t e s c i r c u n s t â n c i a s s ó c i o -e c o n ô m i c a s . I n t -e n t o u - s -e c o r r -e l a c i o n a r o s t i p o s d -e i n f -e c ç ã o c o m a r a ç a e o s g r u p o s s a n g u í n e o s A B O . N e s t e s g r u p o s r a c i a i s e s t ã o i n c l u í d o s n e g r o s , a m e r í n d i o s C h a c h i , e m e s t i ç o s . N o t o u - s e a p r e v a l ê n c i a d e i n f e c ç õ e s n a s á r e a s s ó c i o - e c o n ô m i c a s m a i s b a i x a s . N ã o s e e n c o n t r o u n e n h u m a r e l a ç ã o c o m a i n f e c ç ã o h e l m í n t i c a e r a ç a o u g r u p o s a n g u í n e o d e p o i s d e c o n t r o l a r s e o s t a t u s s ó c i o -e c o n ô m i c o .
P a l a v r a s - c h a v e s : P a r a s i t o s h e l m i n t o s . R a ç a . G r u p o s a n g u í n e o A B O f e n ó t i p o . S t a t u s s ó c i o - e c o n ô m i c o .
A C K N O W L E D G E M E N T S
W e w is h to th a n k D o n B u n d y f o r h e lp fu l c o m m e n ts o n th e m a n u s c r ip t a n d T o n y F u lf o r d fo r sta tis tic a l a d v ic e . W e a ls o th a n k th e in h a b ita n ts o f th e c o m m u n itie s in v o lv e d in th is s tu d y f o r th e ir c o - o p e r a tio n .
R E F E R E N C E S
1. B a m e s G L , K a y R . B lo o d g r o u p s a n d g ia rd ia s is . L a n c e t 1 :8 0 8 , 1 9 7 7 .
2 . B r o w n H W , N e v a F A . B a s ic C lin ic a i P a r a s ito lo g y , 5 th e d itio n . A p p le to n - C e n tu r y C r o f ts , N o r w a lk , C o n n e c tic u t p . 1 2 2 - 1 2 3 , 1 9 8 3 .
3 . B u n d y D A P . P o p u la tio n e c o lo g y o f in te s tin a l h e l m i n t h i n f e c t i o n s in h u m a n c o m m u n i t i e s . P h ilo s o p h ic a l T r a n s a c tio n s o f th e R o y a l S o c ie ty o f L o n d o n 3 2 1 :4 0 5 - 4 2 0 , 1 9 8 8 .
4 . C le m e n s J D , S a c k D A , H a r r i s J R , C h a c k r a b o r ty J , K h a n M R , H u d a S , A h m e d F , G o m e s J , R a o M R , S v e n n e r h o lm A M , H o lm g r e n J . A B O b lo o d g r o u p a n d c h o le r a : n e w o b s e r v a tio n s o n s p e c if ic ity o f ris k a n d m o d if ic a tio n o f v a c c i n e e f f ic a c y . J o u r n a l o f In fe c ti o u s D is e a s e s 1 5 9 :7 7 0 - 7 7 3 , 1 9 8 9 .
5 . C r a m E B . S tu d ie s o n o x y u r ia s is . X X IV C o m p a r a tiv e fin d in g s in th e w h ite a n d n e g r o r a c e s . P r o c e e d in g s o f th e H e lm in th o lo g ic a l S o c ie ty o f W a s h in g to n 7 :3 1 - 3 5 , 1 9 4 0 .
6 . F o r r e s t e r J E , S c o t t M E , B u n d y D A P , G o ld e n M H N . P re d is p o s itio n o f in d iv id u a is a n d f a m ilie s in M e x ic o to h e a v y in f e c tio n w ith A s c a r i s l u m b r i c o i d e s a n d T r i c h u r i s t r i c h i u r a . T ra n s a c tio n s o f th e R o y a l S o c ie ty o f T r o p i c a l M e d ic i n e a n d H y g ie n e 8 4 :2 7 2 - 2 7 6 , 1 9 9 0 .
7 . G u d e r ia n R H , B e c k B J , P r o a n o S J R , M a c k e n z ie C D . O n c h o c e r c i a s i s in E c u a d o r , 1 9 8 0 - 1 9 8 6 : E p id e m io lo g ic a l e v a lu a tio n o f th e d is e a s e in th e E s m e r a l d a s P r o v i n c e . E u r o p e a n J o u r n a l o f E p id e m io lo g y 5 : 2 9 4 - 3 0 2 , 1 9 8 9 .
8. G u d e r ia n R H , G u z m a n J R , C a lv o p in a M , C o o p e r P J . S tu d ie s o n a fo c u s o f y a w s in t h e S a n tia g o B a sin , P r o v in c e o f E s m e r a ld a s , E c u a d o r . T r o p i c a l a n d G e o g r a p h ic a l M e d ic i n e 4 3 :1 4 2 - 1 4 7 , 1 9 9 1 . 9 . G u d e ria n R H , L e o n L A , L e o n R , C o r r a l F , V a s c o n e z
C , J o h n s t o n T S . R e p o r t o n a fo c u s o f o n c h o c e r c ia s is o f E s m e r a ld a s p r o v in c e o f E c u a d o r . T h e A m e r ic a n J o u r n a l o f T r o p i c a l M e d ic in e a n d H y g ie n e 3 1 :2 7 0 - 2 7 4 , 1 9 8 2 .
C o o p e r P J , G u e v a r a A E , G u d e r i a n R H . I n t e s t i n a l h e l m i n t h i a s e s i n E c u a d o r : t h e r e l a t i o n s h i p b e t w e e n p r e v a l e n c e , g e n e t i c , a n d s o c i o e c o n o m i c f a c t o r s . R e v i s t a d a S o c i e d a d e B r a s i l e i r a d e M e d i c i n a T r o p i c a l 2 6 : 1 7 5 - 1 8 0 , j u l - s e t , 1 9 9 3 .
M e d ic i n e a n d H y g ie n e 8 0 :1 6 2 - 1 6 3 , 1 9 8 5 . 11. H ig g in s D A , J e n k in s D J , P a r to n o F . T im o r ia n
f ila ria s is a n d A B O b lo o d g r o u p s . T r a n s a c tio n s o f t h e R o y a l S o c ie ty o f T r o p i c a l M e d ic in e a n d H y g ie n e 7 9 :5 3 7 - 5 3 8 , 1 9 8 5 .
1 2 . H ill A V S . M a la r ia r e s is ta n c e g e n e s : a n a tu ra l s e le c tio n . T r a n s a c tio n s o f th e R o y a l S o c ie ty o f T r o p i c a l M e d ic in e a n d H y g ie n e 8 6 : 2 2 5 - 2 2 6 ,1 9 9 2 . 13. K e ll e r A E , L e a th e r s W S , K n o x J C . T h e p r e s e n t
s ta tu s o f h o o k w o r m in fe s ta tio n in N o rth C a ro lin a . A m e r ic a n J o u r n a l o f H y g ie n e 2 6 :4 3 7 - 4 5 4 , 1 9 37 . 14. W a lto n B C , V a lv e r d e L . R a c ia l d if fe r e n c e s in
e s p u n d i a . A n n a l s o f T r o p i c a l M e d i c i n e a n d P a r a s ito lo g y 7 3 :2 3 - 2 9 , 1 9 7 9 .
1 5 . W o o d r u f f A W , C h o y c e D P , M u c i - M e n d o z a F , H ills M , P e ttit L E . O n c h o c e r c ia s is in G u a te m a la . A . C lin ic a i a n d p a ra s ito lo g ic a l s tu d ie s w ith c o m p a r a s io n b e tw e e n th e d is e a s e t h e r e a n d in E a s t A fr ic a . T r a n s a c tio n s o f th e R o y a l S o c ie ty o f T r o p i c a l M e d ic in e a n d H y g ie n e 6 0 :7 0 7 - 7 1 9 , 1 9 6 6 . 1 6 . W o r ld H e a lth O rg a n iz a tio n . B a s ic la b o ra to r y m e th o d s
