Rev. Inst. Med. trop. São Paulo
31 (2): 103-109, rnarço-abrü, 1989
RELATIONSHIP BETWEEN THE PREVALENCE OF ANTIBODIES TO ARBOVIRUS AND HEPATITIS B VIRUS IN THE VALE DO RIBEIRA REGION, BRAZIL
C l á u d i o S é r g i o P A N N U T I ( 1 , 3 ) , L y g i a B u s c h I V E R S S O N ( 2 ) , J o ã o S i l v a d e M E N D O N Ç A ( 3 ) , A m é l i a P . A , T R A V A S S O S D A R O S A (4) & C e l s o F r a n c i s c o H c r n a n d e s G R A N A T O ( 5 ) .
S U M M A R Y
2 8 0 students, between 6 and 1 4 years old, residents in the I g u a p e county, southern coast of the S t a t e of S ã o P a u l o , were studied in order to identify the existence of a possible association between the prevalence of specific antibodies to the hepatitis B v i r u s a n d the e x p o s u r e to h a e m a t o p h a g o u s m o s q u i t o e s , e v a l u a t e d indirectly through the prevalence of antibodies to 1 7 arboviruses isolated in B r a z i l .
T h e children were from 4 areas with different topographical characteristics: 89 of the children were from the u r b a n zone of the town of I g u a p e , 89 were from the p e r i u r b a n zone, 3 0 were from the rural area with extensive b a n a n a plantations, and 7 2 were from the jungle zone. P r e v i o u s studies h a d shown significantly higher prevalence of antibodies to different arboviruses in the c u l t i v a t e d zone and the jungle zone, when compared to the urban and peri urban zones of I g u a p e . T h e detec¬ tion of antibodies to the H B V surface a n t i g e n ( H B s A g ) was done t h r o u g h the r a d i o i m m u n o a s s a y ( A u s a b , A b b o t t L a b o r a t o r y ) . T h e cases considered positive were confirmed through the presence of anti-core H B V antibodies (anti H B c E I A Roche). A significantly higher prevalence of anti H B V antibodies was observed in c h i l ¬
dren from the jungle zone ( 2 6 / 7 2 = 3 6 , 1 % ) when compared to those from the u r b a n
zone ( 5 / 8 9 = 5 , 6 % ) , peri-urban ( 6 / 8 9 = 6 , 7 % ) or from the cultivated zone ( 0 / 3 0 =
0r% ) .
T h e result suggest the existence of a c o m m o n factor in the dissemination of the arboviruses and the hepatitis B virus, supporting the hypothesis that mosquitoes may play an important role in the H B V transmission in tropical forested region.
K E Y W O R D S : H e p a t i t i s B t r a n s m i s s i o n ; H e p a t i t i s B seroepidemiology. A r b o v i r u s and H e p a t i t i s B
I N T R O D U C T I O N
T h e higher prevalence of hepatitis B virus regions3 3 4 suggested that, along with
conven-( H B V ) markers in h u m a n populations in tropical t i o n a l t r a n s m i s s i o n m e c h a n i s m s observed in
(1) I n s t i t u t o d e M e d i c i n a T r o p i c a l e L I M d o H o s p i t a l d a s C l í n i c a s d a F a c u l d a d e d e M e d i c i n 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 . S ã o P a u l o . S P , B r a s i l . (2) F a c u l d a d e d e S a ú d e P ú b l i c a d a U n i v e r s i d a d e d e S a o P a u l o , S ã o P a u l o , S P , B r a s i l . (3) H o s p i t a l d o S e r v i d o r P ú b l i c o d o E s t a d o d e S ã o P a u l o . S ã o P a u l o . S P , B r a s i l . (4) I n s t i t u t o E v a n d r o C h a g a s . M i n i s t é r i o d a S a ú d e . B e l é m , P a r á , B r a s i l . (5) I n s t i t u t o A d o l f o L u t z . S e c r e t a r i a d o E s t a d o d a S a ú 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 s i l . A d d r e s s f o r c o r r e s p o n d e n c e : D r . C l á u d i o S é r g i o P a n n u t i . I n s t i t u t o d e M e d i c i n a T r o p i c a l d e S ã o P a u l o . A v . D r . E n é a s d e C a r v a l h o A g u i a r . 470 05403 S ã o P a u l o . S P . B r a s i l .
other parts of the world, a d d i t i o n a l modes of transmission m i g h t be present i n the tropics.
T h e h i g h prevalence i n some of these regions of d i s e a s e s t r a n s m i t t e d b y h a e m a t o p h a g o u s arthropods and the low frequency of blood trans-fusion or i n j e c t i o n s a m o n g their i n h a b i t a n t s , raised the first suspicion of H B V transmission v i a mosquitoes and other insects as reported b y
B L U M B E R G et al.4. Detection of H B A g s in various
species of mosquitoes and other h a e m a t o p h a
-gous arthropods captured i n tropical r e g i o n s6
8. i7, 27. 35, 40, 41. 42 a n cj e ve n u r b a n areas of the
United S t a t e s1 3, has somehow corroborated this
hypothesis. E x p e r i m e n t a l studies showed that
when various species of m o s q u i t o e s2 6 7 2 8 3 0
3i, 38a n d 0t h e r h a e m a t o p h a g o u s arthropods1 2 2 6
3i, 37, 39, 40w er e fe cj blood containing H B s A g , it
was possible to detect this m a r k e r in mosquitoes for a p p r o x i m a t e l y u p to 4 d a y s , i n most of the studies, a n d for periods up to several weeks i n the other arthropods. I t was observed, however, that the H B s A g disappears once the blood is fully digested, i n d i c a t i n g that no viral replica-tion occurred i n the a n i m a l6 , 7-3 1.
A c c o r d i n g to these results, infections of H B V v i a arthropods would be the result of m e c h a n i c a l t r a n s m i s s i o n . I n t h i s m o d e of t r a n s m i s s i o n , which was already been described for several ty-pes of p l a n t and a n i m a l viruses, s u c h as the my-x o m a virus i n rabbits and certain a r b o v i r u s e s1 1,
the virus would remain viable i n the structure of the s u c k i n g apparatus of the arthropods and m i g h t be transmitted p a s s i v e l y from a contami-nated host to a susceptible one, of the refeeding time for the mosquito, or when it completed a
feeding which h a d been interrupted5. A s is the
case with certain viruses s u c h as the Venezuelan equine e n c e p h a l i t i s1 1 or R i f t V a l l e y fever viruses
which reach very h i g h concentration i n blood; the likehood of m e c h a n i c a l t r a n s m i s s i o n of H B V , which is h i g h l y infectious and h i g h l y resistant to i n a t i v a t i o n3 6, appears possible.
T h i s m e c h a n i c a l transmission should occur more frequently i n tropical regions, where there is i n t e n s i v e t h e a c t i v i t y of h a e m a t o p h a g o u s arthropods.
A seroepidemiologic survey to H B V , carried out i n S ã o P a u l o S t a t e , B r a z i l2 9, demonstrated
a n u n u s u a l l y h i g h p r e v a l e n c e of a n t i - H B S among children l i v i n g i n a c a m p i n g area near S e r r a do Mar, a rural area near the c o a s t a l region of the S t a t e . T h e study showed a prevalence of 31.2% (10/32) a m o n g children whose age ranged from 1 to 5 years, and 48.7% (19/39) among those in the 6 to 11 years group. T h e s e children were of low socioeconomical status. However, among the adult population of low socioeconomic status living i n the u r b a n area of the city of S ã o P a u l o ,
the prevalence of a n t i - H B s was only 14.58%2 9,
suggesting that factors other than the socioeco nomic status determined, the h i g h prevalence of i m m u n o l o g i c a l m a r k e r s to H B V i n this loca-lity.
I n order to test the hypothesis that wild culi-cidae m i g h t be involved i n H B V transmission, a seroepidemiologic survey to the H B V was con-ducted in a region w i t h s i m i l a r ecological charac-teristics, namely the V a l e do R i b e i r a , w h i c h is also included in the so called S e r r a do Mar S y s tern. T h i s area i s characterized b y an a b u n d a n t
Culicidae fauna1 5 1 6. Since 1977 the Department of
E p i d e m i o l o g y of the P u b l i c H e a l t h S c h o o l of the University of S ã o P a u l o , i n collaboration with E v a n d r o C h a g a s Institute, has conducted seroe-pidemiological surveys for arboviruses in the hu-m a n population. T h e prevalence of arbovirus an-tibodies should thus provided a n indirect i n d i cator of the r i s k of infections t r a n s m i t t e d by mosquitoes. T h e prevalence of i m m u n o l o g i c a l markers of the H B V should be correlated with that of arbovirus antibodies.
M A T E R I A L A N D M E T H O D S
T H E A R E A . T h e serological survey was car-ried out i n I g u a p e , one of the counties of the Vale do R i b e i r a , located i n the coastal area of the S t a t e of S ã o P a u l o , southeast B r a z i l , i n a region still extensively covered by forests.
I n 1976 a n epidemic of arbovirus encepha-l i t i s r e s u encepha-l t e d i n a m o r b i d i t y i n d e x o f 717.5/100.000 i n h a b i t a n t s i n I g u a p e2 1.
Seroepide-m i o l o g i c a l studies showed that arbovirus as be-longing to the T o g a v i r i d a e a n d F l a v i v i r i d a e
fa-milies, pathogenic for h u m a n2 2 2 5, are circulating
in the region.
Within the l i m i t s of the county, four areas w i t h different t o p o g r a p h i c a l a n d p h y t o l o g i c a l
characteristics, were studied. T h e s e areas, have been described in details p r e v i o u s l y2 5. T h e y are
briefly:
a) U r b a n Zone: i n c l u d i n g I g u a p e , a town lo cated in the coast and a health resort in a large n e i g h b o u r i n g i s l a n d , w h i c h p r e s e n t s u r b a n structure;
b) P e r i - U r b a n Zone: R o c i o D i s t r i c t , in the outshirts of I g u a p e , with rural characteristics, poor houses sparsely located among the vegeta tion; grass and s m a l l bushes predominate.
c) C u l t i v a t e d Z o n e : in the c o a s t a l p l a i n s , w i t h a few areas of r e s i d u a l forest. E x t e n s i v e planting of bananas, and, more recently, of vege tables and grain, is carried out.
d) J u n g l e Zone: still extensively covered by forests, made up of t a l l trees, dense foliage and h i g h degree of heterogenity, where the utiliza tion of l a n d agricultural and cattle-raising pur poses is still limited.
C A S E S T U D Y
I n the 1981-1982 period, blood samples were collected for an arbovirus seroepidemiological study from 337 students (6 to 14 years old) from I g u a p e county. These children proved to have different prevalences of H I antibodies to 17 arbo virus isolated in B r a z i l , according to the locality where they lived. A m o n g , these 337 sera, preser ved at -20°C, 280 presented an enough a m o u n t that permited the research of H B V immunolo gical markers. T h e 280 children resided in diffe rent areas: 89 of them lived in the U r b a n Zone; 89 in the P e r i u r b a n Zone, 30 in the C u l t i v a t e d Zone and 72 in the J u n g l e Zone. T h e majority of the children (70.1%) h a d lived all their lives in the place at which they were residing at the time of the study. O n l y 2.8% h a d lived there for a period of less than one year. T h e 280 children belonged to 233 different families. I n 33 families two or more children were e x a m i n e d .
Socioeconomic status was estimated on the basis of the father's profession, and proved to be low, with no significant difference between the areas of residences, since 71(30.5%) of the fathers were agricultural workers, 58(24.9%) were
m a n u a l l a b o r e r s , 27(11.6%) were f i s h e r m e n , 27(11.6% ) were low level public servants, 13(5.6%) were clerks in commercial establishments, and 4(1.7%) were elementary schoolteachers. I n 33 cases (14.2%) this information was not available. A s to s e x , 51.7% (135/261) were male a n d 48.3 (126/261) were female. I n 19 cases, this informa tion was not available.
A n t i - H B s A g was determined by radioimmu noassay ( A u s a b - A b b o t t Laboratories).
T h e positive sera were tested to a n t i - H B c antibodies by an i m m u n o e n z i m a t i c technique ( R o c h e L a b o r a t o r y ) . T o ensure a c c u r a c y in the results, only cases where both markers were pre sent were considered positive. I n schoolchildren from the C u l t i v a t e d Z o n e a n t i - H B c antibodies were measured in all sera.
R E S U L T S
Of the 280 sera studied, 37 (13.2%) were posi tive for a n t i - H B s . A prevalence of 27/71 (38.0%) was presented by children of farm workers, 3/27 (11.1%) by children of fishermen a n d 7/135 (5.2%) by children whose fathers worked at others acti vities. A s to sex there was no significant diffe rence (p > 0.05) between p r e v a l e n c e i n m a l e (12.6%) and female (15.1%). I n one of the positive cases, this information was not available. A s to age distribution, no statistically significant diffe rence (p > 0.05) was observed in the prevalence of a n t i - H B s A g antibodies among the groups of 6 to 8 years (11.8%), 9 to 11 years (13.3%) and
12 to 14 years (16.0%).
T h e prevalence rates of a n t i - H B s A g and ar bovirus antibodies according to the four diffe rent geographic areas considered m a y be seen in T a b l e 1. I n the J u n g l e area, the rate of sera with positive a n t i - H B s was 36.1% (26/72), signifi c a n t l y higher than other zones (p < 0.001). I n the three localities of this J u n g l e area, preva lence was 36% (9/25) in the P a v o a district, 37.8% (14/37) in the P é d a S e r r a district, and 30% (3/10) in the D e s p r a i a d o district.
None of the cases from the B a n a n a l Zone presented a n t i - H B c or a n t i - H B s antibodies.
When we only considered the families where no more than one child was studied, the
antiH B s prevalences were of 26.7% in the J u n g l e Z o -ne, 8.2% in the P e r i u r b a n Zone a n d 6.1% in Ur-ban Zone showing a significant difference bet-ween J u n g l e Zone and U r b a n and P e r i u r b a n
Zo-nes ( X2 = 10.5050 p < 0.01).
D I S C U S S I O N
There are significant differences in the pre-valence of H B s antibodies according to the geo g r a p h i c a r e a c o n s i d e r e d . T h e p r e v a l e n c e of
T A B L E 1
Prevalence of H B s A g antibodies (anti-Ags H B ) and H I antibodies a g a i n s t 17 arbovirus in school children, aged 6 to 14 years, for different areas of V a l e do R i b e i r a , S ã o P a u l o , B r a z i l .
G e o g r a p h i c area N? tested N? positive (%) A n t i - H B s A g N? positive (%) Anti-arbovirus U r b a n Zone (Iguape and I l h a C o m p r i d a ) 89 5 ( 5.6%) 2 ( 2.2%) P e r i u r b a n Zone (Rocio) 89 6 ( 6.7%) 3 ( 3.4%) C u l t i v a t e d Zone 30 0 ( 0.0%) 7 (23.3^ ) J u n g l e Z o n e 72 26 (36.1%) 13 (18.0%) T o t a l 280 37 (13.2%) 25 ( 8.9%) x2 - 36.2883 p < 0.001
36.1% in children from 6 to 4 years old, the v a s t majority of whom (73% ) were children of farmers who lived in the J u n g l e Zone, is u n u s u a l , both in relation to children from other areas of the present study and in relation to the rates obser-ved in the adult population of low socioeconomic status in the city of S ã o P a u l o , where the
preva-lence of a n t i - H B s antibodies was 14.58%2 9. T h e
rates were s i m i l a r to those of h i g h prevalence (48 7%) observed in 6 to 11 year-old children
li-v i n g in the S e r r a do Mar r e g i o n2 9, also in the
southern coast of S ã o P a u l o S t a t e , which pre-sents climatic and p h y t o l o g i c a l conditions simi-lar to those of the V a l e do R i b e i r a .
I n the present study, the children h a d a ho-mogeneous socioeconomical status. A l s o , there were no significant differences as to sex a n d age of those infected by H B V (p > 0.05). T h u s , it is pro-bable that a factor l i n k e d to the geographic area could be influencing the larger dissemination of the H B V i n the J u n g l e Zone. T h e fact that s i m i l a r rates were found in three different localities of the J u n g l e Z o n e somehow removes the
possi-bility of a local epidemic of infection by H B V , since these populations have almost no contact at all among themselves. Besides even we e x c l u -de 33 families where two or more children were studied (15 from J u n g l e zone), the prevalence of positive sera to a n t i - H B s antibodies remains sig-nificantly higher in the J u n g l e Zone than other areas.
Previous study, carried out a m o n g these ve-ry same children, also detected a clear pattern in the prevalence of H I antibodies to 17 arbovi-ruses in B r a z i l , depending on the geographical area under c o n s i d e r a t i o n2 5. T h e prevalence of
ar-b o v i r u s a n t i ar-b o d i e s w a s s i g n i f i c a n t l y h i g h e r among those l i v i n g in the rural zone ( J u n g l e and C u l t i v a t e d Zones) t h a n observed a m o n g c h i l -dren l i v i n g in the U r b a n a n d P e r i - U r b a n Z o n e s2 5.
T h e results suggest the existence of a com-mon factor in the dissemination of V H B and of the arboviruses in forested areas, one of the pos-sibilities being that of t r a n s m i s s i o n by means
of anthropophilic mosquitoes, extremely abun-dant in that r e g i o n1 5 1 6.
N e v e r t h e l e s s , t h e t r a n s m i s s i o n m e c h a -nisms for both viruses would have totally diffe-rent characteristics. T h u s , is relation to the arbo-viruses, there is a continuous maintenance cycle of these agents in the forest, w i t h p a r t i c i -pation of wild vertebrates, especially m a m m a l s and birds, and of haematophagous mosquitoes in which the virus multiplies. When humans enter this ecosystem, they face a h i g h probability of becoming infected. T h e H B V , on the other h a n d , would be m e c h a n i c a l l y transmitted by haemato-phagous arthropods; this requires, besides the h i g h density of this arthropods, exogenous intro-duction of the virus by infected h u m a n s . T h i s m i g h t occur in one area and not in another, even though the second area m i g h t be j u s t a few kilo-meters away from the first, due to the fact that this transmission depends on the degree of dis-persion of the m e c h a n i c a l vectors. Furthermore, there are no know a n i m a l reservoirs to H B V ex-cept m a n . T h e association between the preva-lence of a r b o v i r u s a n t i b o d i e s a n d a n t i - H B s , which seem to be directed proportional (the hi gher the prevalence of anti arbovirus antibodies, the higher the prevalence of a n t i - H B s A g antibo-dies), is s h a r p l y interrupted in the C u l t i v a t e d Zone, the very place of highest prevalence of ar-bovirus antibodies.
A reasonable e x p l a n a t i o n to this discrepan-cy (0% of a n t i - H B s a n d 23,3% of arbovirus anti-bodies) would be the total absence of H B V car-riers in the C u l t i v a t e d Zone. T h e total absence
of H B V m a r k e r s among children in this zone cor-roborates this hypothesis. S h o u l d H B V be intro-duced in this locality, the expectation would be for an infection prevalence comparable to that of J u n g l e Z o n e since in the open areas of the extraforest environment of I g u a p e there is a h i g h
frequency of different species of C u l i c i d a e1 5 1 6.
A d d i t i o n a l research directed to this area beco-mes necessary. I n the U r b a n a n d P e r i - U r b a n Zo-nes of the town of the I g u a p e , the epidemiolo-gical behavior would be equivalent to that obser-ved in the U r b a n Z o n e of the city of S ã o P a u l o .
Other studies have attempted to s t a b l i s h a correlation between H B V m a r k e r s and the
pre-sence of mosquitoes1 1 4 2 0 3 2; the results are
con-flicting. However, the different conditions under w h i c h these studies were carried out and the different techniques employed for the detection of H B V i m m u n o l o g i c a l m a r k e r s m a k e the com-parison of the results difficult.
U n u s u a l l y h i g h prevalences of H B V i m m u -nological m a r k e r s have been consistently observed a m o n g I n d i a n tribes in the western A m a -zon area, v a r y i n g , in the adult i n d i v i d u a l s from
60,7% to 100%9 1 0 1 8 1 9. A s for inhabitants of the
rural zone i n the V a l e do R i b e i r a these popula-tions live in relative isolation, in close contact with the forest. H i g h rates of infection by arbo-virus, s u c h as Mayaro, have also been observed in the A m a z o n r e g i o n3 3. E v e n if there is a wide
gap between the I n d i a n s of the A m a z o n regions and the inhabitants of the V a l e do R i b e i r a area, both populations have something in c o m m o n : they both live i n close contact with the forest environment and its fauna. T h e present study seems to support the hypothesis that mosqui-toes m a y p l a y an i m p o r t a n t role in the trans-mission of hepatitis B in the tropical forested regions, However, further research becomes ne-cessary to shed further light on the matter.
R E S U M O
Relação entre p r e v a l ê n c i a de anticorpos p a r a a r b o v i r u s e v i r u s de hepatite B na região do
Vale do R i b e i r a , B r a s i l .
280 escolares de 6 a 14 anos de idade, residen¬ tes em I g u a p e , Vale do R i b e i r a , sudeste do E s t a -do de S ã o P a u l o , foram estuda-dos com o objetivo de verificar possível associação entre a preva-lência de anticorpos para hepatite B e a expo¬ sição a mosquitos hematófagos, a v a l i a d a indire-tamente pela prevalência de anticorpos de arbo-virus. A s c r i a n ç a s eram originárias de 4 áreas com c a r a c t e r í s t i c a s topográficas e fitográficas diferentes: 89 residiam em área u r b a n a , 89 em área periurbana, 30 em área de cultivo extensivo de b a n a n a e hortaliças e 72 em área florestal. E s t u d o s prévios m o s t r a r a m significante maior prevalência de anticorpos de arbovirus nas áreas c u l t i v a d a e florestal do que nas áreas u r b a n a e periurbana. A p e s q u i s a de a n t i - H B s foi feita por radioimunoensaio ( A u s a b , Laboratório A b -bott) e de a n t i - H B c por ensaio imunoenzimático (Roche). Observou-se que os escolares residentes
na área florestal apresentaram mais alta preva-lência (26/72 = 36.1%) de anticorpos para hepa-tite B de que os residentes nas áreas u r b a n a (5/89
= 5,6%), periurbana (6/89 = 6.7%) e c u l t i v a d a (0/30 = 0% ). O s resultados sugerem a e x i s t ê n c i a de fator c o m u m n a transmissão de arboviruses e de hepatite B , apoiando a hipótese que nas regiões tropicais com presença de m a t a mosqui-tos p o s s a m desempenhar importante papel n a transmissão da hepatite B . R E F E R E N C E S 1. B A Y L E T , R . ; D I E B O L T , G . ; L I N H A R D , J . & D I O P , S . — F r é q u e n c e d e l ' a n t i g è n e A u s t r a l i a e t u d i é e c o m p a r a t i ¬ v e m e n t a 1 ' a c t i v i t é a n o p h é l i e n n e d a n s s e p t v i l l a g e s s e r e r s a u Sénégal. B u l l . S o c . P a t h , e x o t . , 6 7 : 6 4 - 7 2 , 1974. 2. B E R Q U I S T , K . R . ; M A Y N A R D , J . E . ; F R A N C Y , D . B . ; S H E L L E R , M . J . & S C H A B L E , C . A . — E x p e r i m e n t a l s t u -d i e s o n t h e t r a n s m i s s i o n of h e p a t i t i s B b y m o s q u i t o e s . A m e r . J . t r o p . M e d . 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