Rev. Inst. Med. trop. São Paulo
31 (2>: 110-118, março-abril, 1989
SCHISTOSOMIASIS MANSONI IN THE MUNICIPALITY OF PEDRO DE TOLEDO (SÃO PAULO, BRAZIL) WHERE THE B i o m p h a l a r i a t e n a g o p h i l a I S T H E S N A I L H O S T . I — P R E V A L E N C E
I N H U M A N P O P U L A T I O N (1)
L . C . S . D I A S ( 2 ) , U . K A W A Z O E ( 2 ) , C . G L A S S E R ( 3 ) , S . H O S H I N O - S H I M I Z U ( 4 ) , H Y. K A N A M U R A ( 4 ) , J . A . C O R D E I R O ( 2 ) , O . F . G U A R I T A {3) & G . J . I S H I H A T A (3)
S U M M A R Y
D u e to the scarce information about the epidemiological features of schistoso¬ miasis in which the vector is B i o m p h a l a r i a tenagophila, an investigation was carried in Pedro de T o l e d o in 1980 where s u c h peculiarity is observed. S t o o l e x a m i n a t i o n s ( K a t o K a t z method) were performed in 4,741 i n d i v i d u a l s (22.8% positive to Schisto-soma m a n s o n i eggs) of this 583 h a d previously received c h e m o t e r a p y and 4,158 remainders, untreated. T h e schistosomiasis prevalence in those two groups where respectively 31.7% and 21.6% . Epidemiological investigation showed that 83.6% were autochthonous cases from the studied area: the autochthonous prevalence rate, and the intensity of infection in the untreated autochthonous cases were higher in males than in females; the intensity in the latter untreated group was low, 58.5 eggs/g feces {geometric mean). Moreover, according to the age groups the intensity of infec-tions correlated well (rs = 0.745) with the prevalence rates. Schistosomiasis was veri¬
fied to occur mostly during the leisure time and by the use of water streams for housework in rural zone. O n l y 0.4% out of 1,137 snails was positive for S . mansoni cercariae, apparently u n c h a n g e d from the 1978 s t u d y when the h u m a n prevalence was 12.0%. T h e studied area presented differences and similarities in relation to the other B r a z i l i a n areas were the m a i n intermediate host is B . g l a b r a t a .
K E Y W O R D S : S c h i s t o s o m a mansoni; B i o m p h a l a r i a tenagophila; E p i d e m i o l o g y .
I N T R O D U C T I O N I n the V a l l e y of R i b e i r a (State of S ã o P a u l o
— B r a z i l ) , the h u m a n schistosomiasis was first recorded in 19532 1, with 43 autochthonous cases
in the D i s t r i c t of A n a D i a s , Municipality of I t a -riri, neighboring the M u n i c i p a l i t y of Pedro de Toledo, where the present study was performed. S i n c e that time only B i o m p h a l a r i a tenagophila
has been found in the m o l l u s c a n breeding sites but, those snails were already positive for S c h i s -tosoma mansoni cercariae in about 1.7%. I n the Municipality of Pedro de Toledo, autochthonous cases of schistosomiasis were also detected as reported by P I Z A & R A M O S2 1, however, in only
6 of the studied population.
(1) S u p p o r t e d b y S U C E N , F A P E S P a n d C N P q .
(2) P r o f e s s o r o f U n i v e r s i d a d e E s t a d u a l d e C a m p i n a s . I n s t . B i o l o g i a , D e p t o . P a r a s i t o l o g i a , C . P . 6 1 0 9 . C E P 13081 C a m p i n a s , S P , B r a z i l .
(3) E p i d e m i o l o g i s t of S u p e r i n t e n d ê n c i a d e C o n t r o l e d e E n d e m i a s . S ã o P a u l o , S P , B r a s i l . (4) P r o f e s s o r o f U n i v e r s i d a d e d e S ã o P a u l o . S ã o P a u l o , S P , B r a z i l .
D I A S , L . C . S . ; K A W A Z O E , U . ; G L A S S E R , C . ; H O S H I N O S H I M I Z U , S . ; K A N A M U R A , H . Y . : C O R D E I R O , J . A . ; G U A R I T A , O . F . & I S H I H A T A . G . J . - S c h i s t o s o m i a s i s m a n s o n i i n t h e m u n i c i p a l i t y o f P e d r o d e T o l e d o ( S a o P a u l o . B r a z i l ) w h e r e t h e B i o m p h a l a r i a t e n a g o p h i l a i s t h e s n a i l h o s t . I — P r e v a l e n c e i n h u m a n p o p u l a t i o n . R e v . I n s t .
M e d . t r o p . S ã o P a u l o , 31 ( 2 ) : 110 1 1 8 . 1 9 8 9 .
More recently (1970), the S u p e r i n t e n d e n c y of E n d e m i c Disease Control ( S U C E N ) of the S ã o P a u l o State H e a l t h D e p a r t m e n t has established a Schistosomiasis Mansoni C o n t r o l P r o g r a m m e in that area. T h i s p r o g r a m m e i n c l u d e s yearly stool e x a m i n a t i o n for all the population exposed to the risk of transmission, chemoterapy of infec-ted i n d i v i d u a l s , periodical snails e x a m i n a t i o n s from the water collection, health education, a n d , application of molluscicide drugs in the streams whenever infected s n a i l s w i t h c e r c a r i a e of S . mansoni are found.
Despite this effort the prevalence has increa-sed from 4.0% (1970) to 12.0% (1978); of the latter percentage 85.0% consisted of autochthonous cases. T h e rate of infected B . tenagophila howe ver seemed u n c h a n g e d since 1970, with 1.0%.
T h e present study was u n d e r t a k e n due to that increasing rate of schistosomiasis m a n s o n i verified in Pedro de T o l e d o a n d also because of the l a c k of studies in relation to the natural history of s c h i s t o s o m i a s i s in regions where B . tenagophila is the intermediate host. T h e whole project which started in 1980 includes a detailed investigation on parasitological an epidemioló gical aspects of u r b a n a n d rural areas during, a period of approximately 8 years. T h e s e studies will be performed as following: prevalence of the infection in the h u m a n population and in the s m a l l m a m m a l s ; prevalence of s n a i l infection with S . mansoni; evaluation of parasitological and i m m u n o l o g i c a l m e t h o d s for d i a g n o s i s of schistosomiasis; c l i n i c a l study of infected i n d i v i duals; specific treatment a n d assessment of p a rasitologic cure of treated patients; application of molluscicide drugs in all natural s n a i l bree ding sites, whenever infected molluscs are detec ted; evaluation of transmission by the incidence of schistosomiasis u s i n g control groups; use of sentinel-mice; infection rate and density of the snail host.
I n this paper, part of the epidemiological stu dies concerning the prevalence of urban and ru ral schistosomiasis, identification of autochtho nous cases and assessment of previously treated subjects will be reported.
M A T E R I A L A N D M E T H O D S 1. D e s c r i p t i o n of the studied area
Pedro de Toledo is located in the Valley of R i b e i r a , near the S o u t h e r n coast of S ã o P a u l o S t a t e , B r a z i l . T h e studied region comprises an area of 631 k m2 and the town is located 43.5 m
above sea level. T h e landscape is hilly with m a n y s m a l l streams which are shallow with m a n y sto-nes on its m a r g i n and plentiful vegetation. T h e I t a r i r i R i v e r is the m a i n stream and belongs to the R i b e i r a de I g u a p e basin. T h e climate accor ding to K o p e n n ' s classification c a n be conside-red as tropical and h u m i d . T h e mean tempera-ture is about 22 C in the hottest month whereas, in the coldest month, 1 8 C . I n the dryest month the rainfall is about 60 m m , however, in J a n u a r y and F e b r u a r y the rainfall is heavier reaching 203 to 220 m m . A c c o r d i n g to the 1980 census of the B r a z i l i a n Institute of G e o g r a p h y and S t a t i s t i c s , Pedro de Toledo has 6,076 inhabitants, with 2,336 l i v i n g in the u r b a n zone and 3,704 in the rural zone. T h e majority of the people is white. T h e m a i n local activity is agriculture, mostly in b a n a n a p l a n t a t i o n . A c c o r d i n g to S U C E N , about 5,000 inhabitants live either in places where the transmission of schistosomiasis has ocurred or is presently occuring. These areas are called F O C I . T h e remaining 1,000 inhabitants live in pla ces where this parasitosis has not been reported yet.
T h e studied population from the F O C I was 2,370 i n h a b i t a n t s from the urban zone and 2,371 from the rural zone. T h e urban inhabitants lived in a s m a l l town with the following facilites: tap water and power supplies, around 85.0% of the dwellings had sewer s y s t e m , and 50.0% of the streets were p a v e d ; the sewage was treated. T h e rural inhabitants, generally, lived in poor houses scattered along nonpaved roads in 15 areas n a -mely: R i o do P e i x e , R i o do P e i x e I, k m 106, k m 110, F a z e n d a S ã o J o s é , B r a ç o do Meio, B r a ç o do Meio I, Mariano, Mariano I, R i b e i r ã o do L u i z , T r ê s B a r r a s , Á g u a P a r a d a , J a r d i m C a j u , Á g u a F r i a a n d V i l a B a t i s t a . T h e r e were no irrigation c a n a l s in the area; there were d r a i n channels a n d s m a l l s t r e a m s i n the b a n a n a p l a n t a t i o n w h i c h were the m a i n breeding places of B . tena-gophila; there was no sewers system available.
D I A S , L C . S . ; K A W A Z O E . U . ; G L A S S E R , C . ; H O S H I N O S H I M I Z U , S . ; K A N A M U R A , H . Y . ; C O R D E I R O , J . A . ; G U A R I T A , O . F . & I S I I I H A T A , G . J . — S c h i s t o s o m i a s i s m a n s o n i i n t h e m u n i c i p a l i t y o f P e d r o d e T o l e d o ( S ã o P a u l o , B r a z i l ) w h e r e t h e B i o m p h a l a r i a t e n a g o p h i l a i s t h e s n a i l h o s t . I — P r e v a l e n c e i n h u m a n p o p u l a t i o n . R e v . I n s t .
M e d . t r o p . S ã o P a u l o , 31 ( 2 ) : 1 1 0 1 1 8 , 1 9 8 9 .
2. L a b o r a t o r y method for diagnosis
Stool e x a m i n a t i o n was carried out in 1980 according to K a t o - K a t z quantitative m e t h o d1 1,
by collecting one fecal sample from each i n d i v i d u a l a n d p r e p a r i n g three slides for s e a r c h i n g eggs of S . mansoni and of other non-related hel-minths.
3. S t a t i s t i c a l analysis
R e s u l t s of laboratory test a n d personal d a t a regarding to sex, age, s k i n color, occupation, p l a ces of birth, living sites, epidemiological classifi cation, as well as, previous chemotherapy were transcribed into i n d i v i d u a l computer cards.
T h e intensity of infection was expressed as geometric mean of number of excreted eggs per gram feces, due to the irregular distribution of e g g s1 5.
T h e following methods were used for the s t a tistical analyses: analyses of variance ( A N O V A ) , T u k e y ' s test for contrasts, K o l m o g o r o v - S m i r n o v goodness-of-fit test a n d confidence i n t e r v a l s . T h e level of 5.0% (p < 0.05) was adopted as m i n i m u m significant difference for rejecting the n u l l hypothesis. S p e r m a n correlation coefficients were
e s t i m a t e d2 5 to verify the correlation between the
intensity of the infection observed in different age groups or localities and the prevalence of schistosomiasis.
R E S U L T S
A total of 4,741 subjects could be studied ( T a b l e 1) and the overall schistosomiasis m a n -soni prevalence in Pedro de Toledo was 22.8% (1083/4741). T h e rural zone presented higher in-fection rate (25.6%) in relation to the u r b a n area (20.2%) but no significant at the 5.0% level. T h i s parasitosis also prevailed in rural even after the separation into two sub-groups, one that recei-ved treatment and other, no-treatment ( T a b l e 1).
T h e prevalence rates verified in rural untrea-ted population to schistosomiasis varied grea-tely according to the locality: 5.9% ( R i o do P e i x e I), 14.5% ( K m 110), 17.8% ( K m 106), 20.9% ( R i o do Peixe), 25.0% ( F a z e n d a S ã o José), 25.5% ( B r a ço do Meio I ) , 27.5% (Mariano I ) , 30.2% ( B r a ç o do Meio), 31.4% (Ribeirão do L u i z ) , 31.6% (Maria-no), 31.9% (Três B a r r a s ) , 36.9% ( Á g u a P a r a d a ) , 42.9% ( J a r d i m C a j u ) , 43.6% ( Á g u a F r i a ) a n d 61.2% (Vila B a t i s t a ) .
I n respect to 4,158 i n d i v i d u a l s without any previous treatment to S . mansoni, the
prevalen-T A B L E 1
Prevalence of schistosomiasis m a n s o n i in urban a n d rural areas of the m u n i c i p a l i t y of Pedro de T o l e d o ( S ã o P a u l o S t a t e — B r a z i l — 1980) by p a r a s i t o l o g i c a l K a t o - K a t z m e t h o d , a c c o r d i n g to
the treatment to the disease.
Stool T r e a t m e n t Untreated E x a m i n a t i o n T o t a l T o t a l U r b a n R u r a l U r b a n R u r a l A r e a A r e a A r e a A r e a % % % % Positive 26.4* 41.6 185 18.9 24.1 898 ( ± 4.4) ( ± 6.7) ( ± 2.1) ( ± 1.8) Negative 73.2 58.4 398 81.1 75.9 3,260 ( ± 4.4) ( ± 6.7) ( ± 2.1) ( ± 1.8) T o t a l 385 198 583 1,985 2,173 4,158 * Confidence interval 95%
D I A S , L . C . S . ; K A W A Z O E , U . : G L A S S E R , C . ; H O S H I N O S H I M I Z U , S . ; K A N A M U R A , H . Y . ; C O R D E I R O , J . A . ; G U A R I T A , O . F . & I S H I H A T A , G . J . — S c h i s t o s o m i a s i s m a n s o n i i n t h e m u n i c i p a l i t y o f P e d r o d e T o l e d o ( S ã o P a u l o , B r a z i l ) w h e r e t h e B i o m p h a l a r i a t e n a g o p h i l a i s t h e s n a i l h o s t . I — P r e v a l e n c e i n h u m a n p o p u l a t i o n . R e v . I n s t .
M e d . t r o p . S ã o P a u l o , 31 ( 2 ) : 110 1 1 8 , 1 9 8 9 .
ce rates of helminthiasis were: T r i c h u r i s t r i c h i u -ra, 42.3%, A s c a r i s l u m b r i c o i d e s , 40.4% a n d S . mansoni, 21.6%. T h e r e also were one case of in fection with E n t e r o b i u s v e r m i c u l a r i s a n d one with T a e n i a sp.. Multiple p a r a s i t i s m w i t h two or more species was observed in 36.4% of the cases.
E p i d e m i o l o g i c a l investigation was possible to be done in 884 (81.6%) out of 1083 carriers of S . mansoni, of these 83.6% (739) were autoch-thonous cases in P e d r o de T o l e d o , 3.8% from other m u n i c i p a l i t i e s of S ã o P a u l o S t a t e , 1.3% from other B r a z i l i a n S t a t e s and 11.2% undeter-mined. T h u s , the number of i n d i v i d u a l s acquired schistosomiasis only in S ã o P a u l o S t a t e was 772 (87.3%).
A l l the statistical analyses were performed in untreated population or in autochthonous c a -ses.
T h e analysis of variance could not be done in the total e x a m i n e d inhabitants (4,741) becau se the full information (sex, age, domicile and epidemiological classification) were not obtai-ned; from 3,407 residents w i t h complete informa-tions for this analysis was performed.
T h e A N O V A test i n d i c a t e differences bet ween the prevalence of autochthonous schistoso-miasis in 1,765 males (28.1%) and in 1,642 females (14.7%), as well as, a m o n g age groups c o m p r i s i n g from 0 to over 60 years ( F i g u r e 1 and T a b l e 2).
T A B L E 2 R e s u l t s o b t a i n e d b y t h e s t a t i s t i c a l a n a l y s i s o f v a r i a n c e ( s c a l e : a r c s e n / ~ p ) f r o m d a t a o f F i g u r e 1, c o r r e s p o n d i n g to t h e p r e v a l e n c e o f S . m a n s o n i i n f e c t i o n d e t e r m i n e d b y p a r a s i t o l o g i c a l m e t h o d ( K a t o K a t z ) a c c o r d i n g t o t h e a g e g r o u p s , s e x a n d z o n e , i n t h e p o p u l a t i o n of P e d r o d e T o l e d o , S ã o P a u l o S t a t e , B r a z i l (1980). A G E G R O U P V A R I A N C E 0 t o o v e r 60 y e a r s 5 to 29 y e a r s D e g r e e of F D e g r e e of F f r e e d o m f r e e d o m Z o n e 1 2.92 1 1.53 S e x 1 4 1 . 0 91 1 6.73 A g e g r o u p 12 7.71" 4 9.49 Z o n e x S e x 1 0.13 1 5.89 Z o n e x A g e g r o u p 12 1.42 4 1.08 S e x x A g e g r o u p 12 0.76 4 2.85 S i g n i f i c a n c e a t t h e 5 . 0f r l e v e l
I n F i g u r e s 1 and 2, higher prevalence rates a n d intensity of infection c a n respectively be seen w i t h i n the age groups from 5 to 29 years.
80 20-A -tzr A -rzM PREVALENCE RATE • i IN RURAL ZONE • 9 PREVALENCE RATE A
/
IN URBAN ZONE A 9TOTAL PREVALENCE RATE _
5£
0 - 4 I 5 - 9 1 10 ~ I 4 | 15 — 19 I 2 0 - 2 4 J 2 5 - 2 9 | 3 0 - 3 4 | 3 5 ~ 3 9 | 4 0 - 4 4 | 4 5 - 4 9 | 5 0 - S 4 | 5 5 - 5 9 | 60 and + | A G E GROUP 1 P r e v a l e n c e r a t e s o f a u t o c h t h o n o u s s c h i s t o s o m i a s i s m a n s o n i b y t h e K a t o K a t z m e t h o d , a c c o r d i n g to a g e g r o u p , r u r a l a n d u r b a n z o n e s , i n P e d r o d e T o l e d o , S ã o P a u l o , B r a z i l (1980). F i g . s e x .D I A S , L . C . S . : K A W A Z O E . U . : G L A S S E R , C . ; H O S H I N O S H I M I Z U , S . ; K A N A M U R A , H . Y . ; C O R D E I R O , J . A . ; G U A R I T A , O . F . & I S I I I I I A T A . G . J . — S c h i s t o s o m i a s i s m a n s o n i i n t h e m u n i c i p a l i t y o f P e d r o d e T o l e d o ( S ã o P a u l o , B r a z i l ) w h e r e t h e B i o m p h a l a r i a t e n a g o p h i l a i s t h e s n a i l h o s t . I — P r e v a l e n c e i n h u m a n p o p u l a t i o n . R e v . I n s t . M e d . t r o p . S ã o P a u l o , 31 ( 2 ) : 1 1 0 1 1 8 , 1 9 8 9 . A G E G R O U P F i g . 2 — G e o m e t r i c m e a n of t h e n u m b e r of. S . m a n s o n i e g g s p e r g r a m o f f e c e s b y t h e K a t o - K a t z m e t h o d , i n 307 a u t o c n t h o n o u s n o n t r e a t e d i n d i v i d u a l s f r o m P e d r o d e T o l e d o , S a o P a u l o . B r a s i l (1980). O b s . T h e 25 to 29 f e m a l e a g e g r o u p i n t h e u r b a n z o n e a l s o i n c l u d e s i n d i v i d u a l s f r o m s u b s e q u e n t g r o u p s . N u m b e r s p l a c e d a b o v e t h e c o l u m n s i n d i c a t e t h e n u m b e r of s u b j e c t s e x a m i n e d .
A N O V A was also applied for these age groups and the results obtained ( T a b l e 2) were similar to the afore mentioned study for all age groups, besides the significant difference verified in the interaction between zone a n d sex. More detailed studies done using T u k e y ' s test showed that, in general, the age groups 10-14, 15-19 and 20 24 h a d significantly higher prevalence rates than the remainder age groups. However, these three groups did not differ among them. T h e age group 5 9 had significantly higher prevalence than the 0-4 and those more t h a n 45 years of age a n d lower than the age group 10-14 ( T u k e y ' s test difference 5% - 7.308; k - 11 and v - 7.1).
T h e intensity of infection in 307 untreated autochthonous cases was 58.5 eggs/g feces (geo-metric mean). T h e confidence intervals test sho-wed statistically significant diference (p value less than 0.01) for the following conditions: in the r u r a l zone the i n t e n s i t y of infection (66.7 eggs/g) was higher than in the u r b a n area (44.6 eggs/g); the m a l e s presented higher infection (61.8 eggs/g) than females (53.3 eggs/g), while the males from the rural area h a d the egg excretion
rate (69.9 eggs/g) higher than those from u r b a n area (49.8 eggs/g); the males from the rural zone also eliminated more eggs (61.4 eggs/g) than tho-se from u r b a n zone (32.1 eggs/g).
T h e data which provided F i g u r e 2 were analy-sed by K o l m o g o r o v S m i r n o v test and it was ob-served that the distribution of the intensity of infection, expressed in terms of geometric mean of excreted eggs per g r a m feces, between sexes in the rural zone was significantly different [ Dm a x
(0.2498) D5,/ f (0.1972); = 130 and n2 - 75] and
this phenomenom did not occur in u r b a n area. A good correlation was obtained (rs = 0.745)
between the intensity of infection and prevalen ce rate according to the age groups ( F i g u r e 3) Nevertheless, this correlation was poor (rs = 0.196)
between the same parameters in relation to the town and 15 studied areas in Pedro de Toledo.
D I S C U S S I O N
T h e overall prevalence rate (22.8%) found in Pedro de Toledo in 1980 was considerably higher
D I A S , L . C . S . ; K A W A Z O E , U . ; G L A S S E R , C . ; H O S H I N O S H I M I Z U , S . ; K A N A M U R A , H . Y . ; C O R D E I R O , J . A . ; G U A R I T A , O . F . & I S H I H A T A , G . J . — S c h i s t o s o m i a s i s m a n s o n i i n t h e m u n i c i p a l i t y o f P e d r o d e T o l e d o ( S ã o P a u l o , B r a z i l ) w h e r e t h e B i o m p h a l a r i a t e n a g o p h i l a i s t h e s n a i l h o s t . I — P r e v a l e n c e i n h u m a n p o p u l a t i o n . R e v . I n s t . M e d . t r o p . S ã o P a u l o , 31 ( 2 ) : 110 1 1 8 , 1 9 8 9 . o z UJ - J
3
UJ a: a. • 41 S T O O L E X A M I N A T I O N ( K A T O - K A T Z ) T GM ( G E O M E T R I C M E A N ) O F E G G S P E R GRAM O F F E C E S 0 - 4 5 - 9 10 - 14 15 - 19 20 - 24 25 - 29 30 - 3 4 35 - 39 4 0 - 4 4 45 - 49 50 - 54 55 - 59 60 and • 2E CD A G E G R O U P F i g . 3 — P r e v a l e n c e r a t e s of a u t o c h t h o n o u s c a s e s of s c h i s t o s o m i a s i s m a n s o n i o b t a i n e d b y K a t o K a t z m e t h o d a n d i n t e n s i t y o f i n f e c t i o n a c c o r d i n g to a g e g r o u p s , i n P e d r o d e T o l e d o , S ã o P a u l o , B r a z i l (1980).t h a n the rate of 12.0% observed in 1978 when S U C E N performed stool e x a m i n a t i o n s by K a t o ' s qualitative methods in 1,000 inhabitants.
T h i s prevalence is considered h i g h , specially by the fact that, B . tenagophila is k n o w n to be an intermediate host of low suceptibility for S .
m a n s o n i1 9 2 3. I n that area, from March to May
of 1980, only 5 specimens out of 1,137 B . tenago-p h i l a collected were r e a l i s i n g c e r c a r i a e of S . mansoni. T h o s e positive snails were collected from two breeding sites, one located in rural and other in u r b a n areas. S i n c e h i g h prevalence rate of schistosomiasis in non-treated cases was de-tected in V i l a B a t i s t a , the causes of h i g h trans-m i s s i o n in that population are now under inves-tigation.
I n areas of B r a z i l where the schistosomiasis is endemic, and where B . g l a b r a t a and B . strami-nea, are considered the intermediate hosts, the h u m a n prevalence is u s u a l l y higher than the one observed in this s t u d y1 6 1 8. T h e autochthony of
endemic cases in Pedro de T o l e d o is contrary to those found in other regions of S ã o P a u l o S t a -te, where 88.4% of the infections are imported and only 10.0% are a u t o c h t h o n o u s2 6. I t should
be emphasized that the t r a n s m i s s i o n of this p a -rasitic disease in S ã o P a u l o S t a t e is found in isolated foci. F o r instance, the F a z e n d a C o l m e i a F o c u s , in the county of P i n d a m o n h a n g a b a , sho-wed a h u m a n prevalence of 17.5%, whereas the
rate for the entire Municipality was only 3.3%. Therefore, it is difficult to compare prevalence rates of the endemic diseases in the different re-gions of the State.
Other h e l m i n t h i a s i s reported for Pedro de Toledo showed similar rates to those found in other areas of B r a z i l8. A l t h o u g h the more specific
method for the diagnosis for each parasites not used.
T h e f i n d i n g of 73.2% ( T a b l e 1) p r e v i o u s l y t r e a t e d i n d i v i d u a l s p r e s e n t e d n e g a t i v e e g g counts in feces, as well as, the relatively lower intensity of infection associated to a lower preva-lence rate in u r b a n area in relation to the rural area (58.4%) m a y be e x p l a i n e d by the improve-ments of the levels of basic sanitation and educa tion received and by other epidemiological fac-tors e x i s t i n g in the region. O n the other h a n d , in rural area w h i c h h a v e not receive sanitation improvements the prevalence of schistosomiasis became higher.
T h e p e r s i s t e n c e of egg e x c r e t i o n s a m o n g previously treated subjects appears to be rein-fections and probaly development of some drug tolerance or resistence, since the population h a d been successively submitted to Niridazole, H y -c a n t h o n e a n d O x a m n i q u i n e treatments. T h i s last aspect is also now under investigation. T h e prevalence rate of schistosomiasis in Pedro de
D I A S , L . C . S . : K A W A Z O E , U . : G L A S S E R , C . , H O S H I N O S H I M I Z U . S . ; K A N A M U R A , H . Y . ; C O R D E I R O , J . A . ; G U A R I T A , O . F . & I S H I H A T A , G . J . — S c h i s t o s o m i a s i s m a n s o n i i n t h e m u n i c i p a l i t y o f P e d r o d e T o l e d o ( S ã o P a u l o , B r a z i l ) w h e r e t h e B i o m p h a l a r i a t e n a g o p h i l a i s t h e s n a i l h o s t . I — P r e v a l e n c e i n h u m a n p o p u l a t i o n . R e v . I n s t .
M e d . t r o p . S ã o P a u l o , 31 ( 2 ) : 110 1 1 8 , 1 9 8 9 .
T o l e d o , according to the sex was higher in males than in females ( T a b l e 2). T h i s m a y be e x p l a i n e d by the fact that in the studied area, men u s u a l l y enter water streams more frequently than wo-men. I n the M u n i c i p a l i t y of R o s e i r a (São P a u l o State), where the s n a i l host is B . tenagophila, S A N T O S2 4 observed that among schoolchildren
of the u r b a n area, 90.0% of infected people were boys. However, in schoolchildren of the lowland area there was no difference related to the s e x . I n another M u n i c i p a l i t y vicinity of R o s e i r a , the-re was a higher pthe-revalence rate in m a l e s1 0.
Howe-ver, in B r a z i l i a n S t a t e s where the disease is more endemic, settled for a longer period of time, most investigators agree that there is no significant difference in regard to sex1- 2 4 1 8 2 2 2 4. T h e
fre-quency distribution of prevalence according to the age groups determined by stool e x a m i n a -tion, showed an early prime infection (0-4 age group) in 4.8% ( F i g u r e 1). T h e age group between 5-24 years presented the highest prevalence rate (Figures 1 and 2). T h i s is comparable to the re-sults found by others authors in several B r a z i l i a n S t a t e s1-5 13- 1 4 l l-2 0. I n S ã o P a u l o S t a t e , F R Ó E S
et a l1 0 found a higher prevalence rate in 10-20
age group and suggested that the disease in the Municipality of S ã o J o s é dos C a m p o s , where the B . t e n a g o p h i l a is the i n t e r m e d i a t e host, w a s usually acquired during recreational activities. I n Pedro de Toledo there was a decrease in the prevalence rates among i n d i v i d u a l s of 25 years and older ( F i g u r e s 1 a n d 2). T h e s e d a t a do not agree with the results presented by S A N T O S2 4
who reported the highest percentages a m o n g ol der i n d i v i d u a l s working in rice fields and clea ning ditches in the lowland. A c c o r d i n g to this author, the disease h a s a professional character. B u t apparently, this is not the case for Pedro de T o l e d o , where the schistosomiasis is acquired m a i n l y d u r i n g r e c r e a t i o n a l a c t i v i t i e s s u c h as s w i m m i n g , fishing, etc. I n the rural zone, trans-mission is also consequence of the use of water for housework.
T h e r e is no record of differences between prevalence rates of rural a n d u r b a n zones in au-tochthonous cases ( F i g u r e 1 and T a b l e 2). I n the present area of study there are no clearcut beha v i o r a l b o u n d a r i e s for the i n h a b i t a n t s of b o t h areas a l t h o u g h the p h y s i c a l boundaries between the rural and u r b a n zones are well defined. A g r i
-culture is the m a i n activity of the population; b a n a n a is the predominant type of agriculture, followed by vegetables. T h e m e a n intensity of infection of 58.5 eggs/g feces was low to the usually found in other B r a z i l i a n endemic areas. C O U -R A & C O N C E I Ç Ã O6 recorded the mean values
of 207 and 138 eggs/g feces respectively in of 1973 and 1974 in a rural c o m m u n i t y , in the S t a t e of Minas G e r a i s , where the B . g l a b r a t a is the major vector. I n Pedro de T o l e d o , the highest intensity rate was observed more in the rural than in the u r b a n area. Male i n d i v i d u a l s presented a higher number of eggs in the feces than women.
T h i s indicatives that the men of the rural zone have greater contact with the foci of infec-tion. I n regard to age groups ( F i g u r e 2) the hi-ghest intensity of eggs was found in the groups r a n g i n g from 5 to 24 years old. I n the subsequent age groups, no further attempt was made to car-ry out any comparison because of the relatively s m a l l size of the sample. A n interesting fact is that in the 10-14 age group, women of the rural zone showed a geometric mean of 212 eggs/g of feces ( F i g u r e 2). T h i s value is m u c h higher than the geometric mean of 58.5. I t was expected that females would generally show a lower intensity rate of infection than men. However, intensity of infection in men was 61.8 and women 52.3 eggs/ g of feces. T h e h i g h geometric mean found in the 10-14 women group is probably related to the fact that these girls frequently enter water streams to wash clothes or cookware, t a k i n g the place of their mothers who u s u a l l y go to the work in the fields. I n spite of an irregular excretion of eggs in the feces, their countings in popula-tional studies should be of some value, consi-dering that the m a s s evaluation offsets the cau-ses for error1 3 1 4 1 5 2 1. T h e intensity of infection
in previously treated patients was not, described here because is well know that intensity decrea-sed in those patients.
T h e d a t a here o b t a i n e d r e g a r d i n g to the existence of p o s i t i v e correlation between the geometric mean of egg counts and the preva-lence rate w i l l be of v a l u e in determining the conversion factor or of the forecast the intensity and prevalence of the infection through the K a -t o - K a -t z me-thod.
D I A S , L . C . S . ; K A W A Z O E , U . ; G L A S S E R , C . ; H O S H I N O S H I M I Z U , S . ; K A N A M U R A , H . Y . ; C O R D E I R O , J . A . ; G U A R I T A , O . F . & I S H I H A T A , G . J . — S c h i s t o s o m i a s i s m a n s o n i i n t h e m u n i c i p a l i t y o f P e d r o d e T o l e d o ( S ã o P a u l o ,
B r a z i l ) w h e r e t h e B i o m p h a l a r i a t e n a g o p h i l a i s t h e s n a i l h o s t . I — P r e v a l e n c e i n h u m a n p o p u l a t i o n . R e v . I n s t .
M e d . t r o p . S ã o P a u l o , 31 ( 2 ) : 1 1 0 - 1 1 8 , 1 9 8 9 .
However, in h i g h l y endemic area of schisto-somiasis, h a v i n g B . g l a b r a t a as the vector, s u c h correlation was not verified1 5. T h e results here
obtained w i l l offer a base line for similar epide-m i o l o g i c a l w o r k s carried out under the s a epide-m e conditions in other areas.
T h e sensitivity of K a t o - K a t z method is known to be h i g h intensity of infections7 but as verified
in previous s t u d i e s1 2, the parasitological test is
not relible, m a i n l y in areas of low and m e d i u m p r e v a l e n c e r a t e s . T h i s f a c t w a s o b s e r v e d b y D I A S et a l .9, who h a d to repeat the
parasito-l o g i c a parasito-l test 4 to 5 times to confirm some positive results provided by serological tests. T h e e x a c t sensitivity of K a t o - K a t z method is now beeing estimated in relation to s k i n test and immunofluorescence test. T h e preliminar results i n d i c a -te that its sensitivity is lower than 50.0%.
I n spite of the problem presented by the K a t o - K a t z method, as to the degree of the sensiti-vity, it demonstrated that, in Pedro de T o l e d o , infection starts before 4 years of age. It was veri-fied that in the areas w h i c h t r a n s m i s s i o n of the parasite occurs v i a B . tenagophila, epidemiolo-g i c a l characteristics are not so m u c h different from those of other B r a z i l i a n areas in which B . g l a b r a t a is the intermediate host. T h e m a i n dif-ference is related to the intensity of infection, which now is still low in Pedro de T o l e d o .
I t is concluded that:
a) the prevalence rate of schistosomiasis m a n -soni in Pedro de T o l e d o , as determined by stool e x a m i n a t i o n , was 22.8%. T h e a u t o c h t h o n o u s carriers were 80.8%;
b) a c c o r d i n g to the tests e m p l o y e d , y o u n g e r people (5 to 24 years old) were more affected by the infection and the prevalence was higher in males than females;
c) the prevalence rate in the u r b a n zone was the same as in the rural zone when determined by stool e x a m i n a t i o n in autochthonous cases; d) more than 70.0% previously treated cases pre sented parasitologically negative;
e) the intensity of infection was low, w i t h a geo-metric mean of 58.5 eggs/g of feces;
f) t r a n s m i s s i o n of s c h i s t o s o m i a s i s u s u a l l y oc-curred during leisure time and also d u r i n g the use of water streams for housework in the rural zone;
g) a positive correlation between intensity of in-fection a n d prevalence rates a c c o r d i n g to the age groups was observed.
R E S U M O
Esquistossomose m a n s ô n i c a no m u n i c í p i o de Pedro de Toledo (São Paulo, B r a s i l ) onde B i o m ¬ p h a l a r i a tenagophila é hospedeiro
intermediá-rio. I — P r e v a l ê n c i a na população h u m a n a . D e v i d o à escassez de dados epidemiológicos sobre esquistossomose m a n s ô n i c a onde B i o m -p h a l a r i a t e n a g o -p h i l a é vetor foi desenvolvido em 1980 o presente trabalho, no m u n i c í p i o pau-lista de Pedro de Toledo. F o r a m e x a m i n a d a s fe-zes de 4741 pessoas (Método de K a t o - K a t z ) com prevalência de 22,8%; entre essas, 583 foram tra-tadas p a r a a endemia anteriormente e 4158 não m e d i c a d a s ; as prevalências nos dois grupos fo¬ r a m , respectivamente, 31,7% e 21,6%. Por inves-tigação epidemiológica constatou-se que 83,6% dos casos foram autóctones d a área estudada. P r e v a l ê n c i a dos a u t ó c t o n e s e i n t e n s i d a d e de infecção nos portadores autóctones não tratados foram maiores no homem do que n a mulher; a intensidade no último grupo foi b a i x a : 58,5 ovos/ g de fezes (média geométrica). D e acordo com g r u p o s e t á r i o s , se c o r r e l a c i o n a r a m b e m (rs =
0,745) as i n t e n s i d a d e s de infecção e as preva-lências. A infecção ocorreu, n a zona rural, princi-palmente, durante lazer e trabalho doméstico. Somente 0,4% de 1137 moluscos foram positivos p a r a S c h i s t o s o m a mansoni. E s s e índice foi, apa-rentemente, o mesmo em estudo de 1978 quando a prevalência h u m a n a era de 12,0%. A área estu-d a estu-d a apresentou estu-diferenças e semelhanças epi¬ demiológicas em relação às áreas onde B . gla-brata é o p r i n c i p a l hospedeiro intermediário.
A C K N O W L E D G E M E N T S
T o D r . A n t o n i o G u i l h e r m e de S o u z a for sup-port given throughout all stages of the study; to D r s . A . E . P i e d r a b u e n a and L. K . H o t t a for help w i t h the s t a t i s t i c a l a n a l y s i s ; to Prof. D r .
D I A S , L . C . S . ; K A W A Z O E , U . G L A S S E R , C . : H O S H I N O S H I M I Z U , S . : K A N A M U R A , H . Y . . C O R D E I R O , J . A . ; G U A R I T A , O . F . & I S H I I I A T A . G . J . — S c h i s t o s o m i a s i s m a n s o n i i n t h e m u n i c i p a l i t y o f P e d r o d e T o l e d o ( S ã o P a u l o .
B r a z i l ) w h e r e t h e B i o m p h a l a r i a t e n a g o p h i l a i s t h e s n a i l h o s t . I — P r e v a l e n c e i n h u m a n p o p u l a t i o n . R e v . I n s t .
M e d . t r o p . S ã o P a u l o , 31 ( 2 ) : 110 1 1 8 , 1 9 8 9 .
L u i z Caetano da S i l v a for suggestions in writting the text; to Mrs. R o s a Maria de J e s u s P a t u c c i and other S U C E N c o l l a b o r a t o r s for v a l u a b l e help in the field work; to Mr. L u i z Henrique Alle ment a n d M r . J o s u e N a z a r e n o de Lima in trans¬
c r i b i n g d a t a . R E F E R E N C E S 1. B A R B O S A , F . A . S . — M o r b i d a d e d a e s q u i s t o s s o m o s e . R e v . b r a s . M a l a r . , (nº. e s p ) : 3-159. 1966. 2. B A R B O S A , F . S . — E p i d e m i o l o g i a . I n : C U N H A , A . S . d a — E s q u i s t o s s o m o s e m a n s o n i . S ã o P a u l o , E d i t o r a d a U n i ¬ v e r s i d a d e d e S ã o P a u l o , 1970. p. 31-59. 3. B A R T H O L O M E W , R . K . ; P E T E R S , P . A . S . & J O R D A N . P . — S c h i s t o s o m a m a n s o n i i n S t . L u c i a n a n d K e n y a n c o m ¬ m u n i t i e s — a c o m p a r a t i v e s t u d y u s i n g t h e K a t o s t o o l e x a ¬ m i n a t i o n t e c h n i q u e . A n n . t r o p . M e d . P a r a s i t . , 7 5 : 4 0 1 - 4 0 5 , 1981. 4. B R E N E R , Z . & M O U R Á O , O . G . — I n q u é r i t o c l í n i c o e p i ¬ d e m i o l ó g i c o e m f o c o s e n d ê m i c o s d e e s q u i s t o s s o m o s e e m M i n a s G e r a i s . 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