Rev. Soc. Bras. Med. Trop. vol.22 número3

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 2 ( 3 ) : 1 1 9 - 1 2 4 , J u l - S e t , 1 9 8 9

U S E F U L N E S S O F SER O LO G Y F O R TH E E V A L U A T IO N O F

T R Y P A N O S O M A C R U Z I

T R A N SM ISS IO N

IN E N D E M IC A R E A S OF C H A G A S ’ D IS E A S E

Roberto Chuit1, Elisabet Subias2 , Analia C. Pérez

₂

Irene Paulone2, Cristina Wisnivesky-Colli

2

and Elsa L. Segura

2

Thirteen com m unities fr o m 7 A rgentinian provinces were selected fo r the

evaluation o f serology as an indicator o f transm ission o f C hagas disease. O f the

com m unities appraised, 6 d id n o t have a history o f previo u s treatm ent with insecticides

a n d 7 h a d received sporadic or continuous insecticide treatm ent. T he inh a b ita n ts o f

2 0 % o f the houses o f each locality were studied by serology. The sam ples were obtained

b y fin g er p ric k in g a n d 5 0 fil o f blood were m ixed with 1 5 0 /il o f 5 0 % glycerine solution in

tissue culture m edia to be assa yed by In d irect H em a g g lu tin a tio n a n d In d irect Im m u n o ­

fluorescence tests. In untreated areas, the prevalence o f infection in in fa n ts 0-4 years o ld

was 17.5% , reaching to over 2 2 % f o r the 5-9 y e a r o ld group, a n d to 3 3 .3 % in 10-14 y e a r

old individuals. T h e prevalence in treated a n d surveyed areas was 2 .6 % in 0-4 y e a r o ld

children, 5 .4 % in 5-9 y e a r o ld a n d 6 ,2 % in 10 -1 4 y e a r o ld youngsters. The differences

between both areas were sta tistica lly sig n ifica n t (p

<

0.005). T h is stu d y fa v o r s serology

as a valid indicator f o r the evaluation o f transm ission o f C hagas disease in rural areas.

Key-words:

T. cruzi

transmission. Prevention and control. Field study. Serodiagnosis.

Chagas’ disease produced by infection with

T.

cruzi,

is widely disseminated through the Americas17.

The triatomine vector

of T. cru zi

may lodge in human

dwellings, and can be found from Rio Colorado, in

Northern Mexico, to the Parallel 42° South in Argen­

tina and Chile^^.

The suggestion of controlling domestic triato­

mine by spraying houses with insecticides as a control

measure of disease transmission, was advanced at the

beginning of the forties in the Continent1^ 20 j n

Argentina, the first steps were undertaken around

1940 a i^ later on, in the mid fifties, control campaigns

were initiated in some provinces4 24 j n

1952

the

programme extended over 9 provinces, and in the

seventies, the whole country was under control. Activi­

ties involved insecticide application in dwellings and

1. Servido Nacional de Chagas. Secretaria de Salud, Ministério de Salud y Acción Social de la Nation. Córdoba, Argentina.

2. Instituto Nacional de Diagnóstico e Investigación de la Enferme-dad de Chagas “ D r Mario Fatala Chabén” (IN D IECH ) Secretaria de Salud-Ministerio de Salud y Acción Social de la Nation. Buenos Aires, Argentina.

This work was supported by the Secretary of Health of the Argentinian Ministry of Health and by U N DP/W ORLD BANK/W HO Special Programme for Research and Training in Tropical Disease (TDR).

Postal Address: IN D IECH , Av. Paseo Colon 568 CP: 1063 Telex 25064 Coopre Ar, Buenos Aires, Argentina.

Recebido para publicação em 23/8/88.

serological control of blood to be transfused23. On that

occasion, the National Control Agency, the Servicio

Nacional de Chagas (ChCA) and the Instituto N a­

cional de Diagnóstico e Investigación de la Enferme-

dad de Chagas (IN D IECH ) were created. The first, to

care for the control of the insect population and the

•second, to control the inter-human transmission of

Chagas’ disease23.

The activity carried out for the control of vectors

consists mainly of insecticide spraying of domiciles

during the chemical attack phase1319. After the attack

phase, periodic entomological evaluations are re­

commended, to be carried out by means of the

man/hour method, as part of the so called “classical

surveillance” method in treated houses19. These

actions, performed by trained personnel of the Control

Agency are costly as they demand 60 minutes of work

of skilled men per house to be completed. Houses

found infested, are sprayed with insecticide13 19

Serology has been one of the powerful tools to

study Chagas’ disease, and to develop control strate­

gies, at first by the use of Complement Fixation and

nowadays by the use of Hemagglutination techniques

among others, which has permitted is to define ende­

mic areas in the Continent9 12. Serology has been also

used by several groups as an alternative method of

retrospective evaluation for the status of Chagas’

disease transmission in populations of endemic areas,

such as in studies carried out in Argentina and the rest

of the Continent 8 23 jt was demonstrated that the

C h u it R , S u b ia s S , P é r e z A C , P a u lo n e I, W is n iv e s k y - C o lli C , S eg u ra E L . U s e f u ln e s s o f s e r o lo g y fo r th e e v a lu a tio n o f T r y p a n o ss o m a cru z i t r a n s m i s s i o n in e n d e m i c a r e a s o f C h a g a s ’ d i s e a s e . 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 2 : 1 1 9 - 1 2 4 , J u l - S e t , 1 9 8 9

pre valence o f C h agas’ d isease in 18 y e a r old m en in

A rg entina d ecreased from 1 0 .3 % 7 in 1968 to 5 .9 % in

198123. S u ch a d e crease inclu ded 18 y e a r old m en

b o m in 19 6 3 , an d show ed the effect th a t th e control

P ro g ram m ay have h a d on tran sm issio n after 19 years

o f application.

O ne o f th e lim itations o f serolo gy fo r field w ork

is related to blood sam pling. A t presen t, a new

p ro cedu re is being applied, w hich en ab les collectio n o f

cap illary blo od sam p les b y finger puncture, rendering

unnecessary , fo r the n ex t 30 d ay s after collection, a n y

special la b o rato ry conditions an d allow ing th e storage

o f sam ples a t ro o m tem p eratu re and hum id ity25.

T h e serolo gical stu d y o f children is relevant

becau se it w ould perm it the detection over sho rt periods

T h is p a p e r o utlines a p ro p o sed schem e fo r

serolo gical studies in ru ral com m unities, w hich could

b e u se d as a pro spective tool fo r the ev aluatio n and

plannin g o f control cam paigns. F o r th a t p u rp o se all

the in hab itants o f e a c h h ouse selected in thirteen are as

from seven A rg en tin ian Pro vinces, w ere serolo gically

studied. S erolo gical resu lts w ere co rrela ted w ith the

activities c a rrie d o u t by the A rg en tin ian C h ag as

d isease C o n tro l A g en cy (C h C A ).

M A T E R IA L S A N D M E T H O D S

T his study w as p erform ed from D ecem ber,

1 983, to M a y , 1985 an d involved th irteen ru ral villa­

ges from th irteen countie s o f seven A rg en tin ian pro­

v inces (F ig u re 1). T h e se selected localities w ere simi­

la r in the n u m b er an d type o f popu lation , housing, geo­

graphical distrib u tio n an d socio -econom ical co ndi­

tions.

T h e are as w ere selected accordin g to the below -

m entioned crite ria, an d w ith d a ta o b tain e d from re­

cords o f the C h C A .

C ateg o ry 1) A re a s w ithou t chem ical tre a tm e n t

A re a s w hich h a d n o t re ceived insecticidal tre­

a tm en t u p to the d a te w hen the stu dy began.

C ate g o ry 2 ) A re a s chem ic ally tre a te d

a) Surveyed: a re a s chem ically tre a te d in the

attack p h ase a n d su rveyed by th e C o n tro l

P ro gram m e m ore th an o nce in a determ in ed

period.

b) R ecen tly treated , o r areas w here n o surveillan­

ce activ ities w ere m ad e fo r a long p erio d o f tim e

(T ab le 1).

S a m p l i n g p r o c e d u r e s :

T h e h ouses selected

w ere con sid ered as th e sam plin g unit, stu dying all th eir

occup ants. A cco rd in g to carto g rap h ic inform atio n

ob tain ed from th e P rim ary H e a lth C a re P ro gram m e

(P H C ), a n average o f 1 5% to 2 0 % o f the houses

F ig u r e 1 - G e o g r a p h i c a l d i s t r i b u t i o n o f t h e A r g e n t i n i a n r u r a l l o c a l i t i e s s t u d i e d : 1. C a l d é n , R e t a m o , A y a c u c h o , S a n L uis; 2 . A m a m á , M o r e n o , S a n tia g o d e l E stero ; 3 . S a n

M a r t i n 2 , P a t i n o , F o rm o sa ; 4 . L o s T e la r e s , Q u e b r a c h o s , S a n tig o d e l E ster o ; 5. S a n t a V i c t o r i a , S a n M a r t i n , S a lta ; 6 .

S o t e l o s , R i o H o n d o , S a n tia g o d e l E ster o ; 7. Y a v i C h ic o , Y a v i, Jujuy; 8 . L a b a t ó n - A c h e r a l , S a n P e d r o , Jujuy; 9 . P a c l i n , E l A l t o , C a ta m a rc a ; 1 0 . C h a n c a n i, P o c h o , C o rd o b a ; 1 1 . P i r q u i t a s - H u a y c a n o , A m b a t o , C a ta m a r ca ; 1 2 . S a n M a r t i n 1, P a ti n o , F o rm o sa ; 1 3 . P a j o n a l , P o m á n , C a ta m a rca .

C h u i t R , S u b i a s S , P é r e z A C , P a u l o n e I , W i s n i v e s k y - C o l l i C , S e g u r a E L . U s e f u l n e s s o f s e r o l o g y f o r t h e e v a l u a t i o n o f

Tiypanossom a cruzi

inhabited in the whole area were selected representing

one of five of the_ houses.existing in.the area15 16.

The first house to be surveyed was selected at

random and then a systematic sampling procedure was

used. Those people absent at the beginning of the study

were included upon their return.

S a m p le collection a n d serological study:

Blood

samples were collected by pricking a fingertip with a

disposable sterile blade, collecting 50jul with a gauged

capillary tube, and mixing the sample with 150

of the

preservative contained in a polypropylene tube with an

hermetic rubber cap25. These tubes were placed in

60-tube trays each one contained in a woodenbox sui­

table for handling. Blood samples collected in the field

were sent by mail to IN D IECH to be analysed. Indirect

Table 1-

D istribution o f serologicalprevalencefor

T. cruzi

infection g ro u p ed by area, age-group a n d category o f

insecticide treatm ent - A rgentina 1983-1985.

Age group (Years) City

Country-Province

0-4

% ( Po s/ Np) 5-9

% (Pos/N.0) 10-14

% (Pos/N.°) 15-19

% ( Po s/ Np) + 20

% (Pos/N.°)

Category of

Treatment

Calden - Retamo

Ayacucho - San Luis 9.5 (2/21) 22.2 (4/18) 33.3 (5/15) 33.3 (4/12) 29.9 (26/87) 1

Amama

Moreno - Sgo. del Estero 13.0 (3/23) 24.2 (8/33) 47.7 (21/44) 48.5 (16/33) 44.4 (20/45) 1

San Martin N?

Patino - Formosa 22.9 (14/61) 40.0 (48/120) 55.9 (33/59) 24.1 (13/54) 42.8 (36/84) 1

Los Telares Quebrachos - Sgo. del

Estero 10.0 (2/20) 34.8 (8/23) 41.2 (7/17) 38.5 (5/13) 60.0 (36/60) 1

Santa Victoria E.

San Martin - Salta 26.7 (4/15) 46.0(58/126) 48.5 (65/134) 35.0 (7/20) N.D. 1

Sotelos

Rio Hondo - Sgo. del

Estero 22.2 (2/9) 42.1 (8/19) 44.4 (4/9) - ( 1 /3 ) 54.5 (18/33) 1

Yavi Chico

Yavi - Jujuy 0.0 (0/12) 0.0 (0/11) 0.0 (0/8) 0.0 (0/10) 19.0 (4/21) 2a

Lobaton - Acheral

San Pedro - Jujuy 2.8 (2/72) 5.5 (4/73) 6.2 (1/16) 17.6 (3/17) 54.5 (30/55) 2a

Paclin

El Alto - Catamarca 0.0 (0/32) 0.0 (0/21) 0.0 (0/24) 0.0 (0/26) .37,5 (18/48) 2a

Chancani

Pocho - Cordoba 2 .8 (1 /3 5 ) 23.8 (15/63) 45.8 (11/24) 52.2 (12/23) 56.4 (35/62) 2a

Pirquitas Huaycamo

Ambato - Catamarca 5.0 (1/20) 19.2 (5/26) 20.0 (3/15) 21.4(3/14) 16.0 (4/25) 2b

San Martin N.° 1

Patino - Formosa 0.0 (0/10) 20.8 (5/24) 21.4(3/14) 2 3 .0(3/13) 18.4 (7/38) 2b

Pajonal

Poman Catamarca 5.7 (2/35) 12.0 (7/58) 8.8 (3/34) N.D. 27.0 (10/37) 2b

N.D. Not Done: 1 — without treatment 2a — with treatment and continuous surveillance 2b = with treatment and no regular surveillance.

C h u it R , S u b ia s S , P é re z A C , P a u lo n e I, W is n iv e s k y -C o lli C, S eg u ra E L . U se fu ln es s o f se r o lo g y f o r th e e v a lu a tio n o f

T rypanossom a cruzi

H em agglutin ation ( I H A )2®, an d In d ire ct Im m uno­

fluorescence ( I F I ) 2 reactions, specific fo r anti

antibod ies w ere u se d as th e serologic tests^ an d n o n

coin cid ent resu lts betw een b o th reactions w ere verified

by the E nzy m e Im m u n o ssay (E L IS A ) using

epim astigote m em b ran e antig ens22. I H A an d I F I

p ro v id e d

a 9 9 .5 % o f specificity w hen perform ed

together a t the m inim um reactive dilution o f 1:325 . T h e

initial serum dilutio n w as 1:16 in all ca se s due to the

1 :4 dilutio n o f th e b lo o d in th e preserver. R eactiv ity o f

blo o d sam ples w ith th e preservative h ad u p to a 9 7 %

correla tion w ith identical sam ples o f serum ob tain ed

from venopunctu re as w as previo usly described2^.

R E S U L T S

A to ta l o f 2 2 2 6 blo o d sam ples w ere collected

from patients o f b o th sex es w ith ages ranging from 6

m onths to 93 years o f age. Serological an alysis show ed

6 7 0 positiv e results (3 0 .0 9 % ).

Serological resu lts o f the stud ied sam ples are

p re sen ted in T able 1, gro uped b y th e origin o f the area:

city, county o r province; b y the age groups o f the

populatio n; an d b y the m odality o f applicatio n o f the

chem ical treatm en ts perform ed in the houses.

A ll are as w hich h a d n o t received insecticidal

tre a tm e n t (C a te g o ry 1) sh ow ed sim ilar results in term s

o f prevalence: in children aging from 0 to 4 years,

higher th an 10% ; a n increasin g prevalence o f m ore

th an 2 2 .2 % in child ren from 5 to 9 y ears o f age,

reachin g its m ax im u m level in child ren aging from 10

to 14 years. N o significant differences were found

am ong p revalence rates show n b y the 10 to 14 years

old group w ith resp ect to child ren 15 to 19 years o f age

o r 2 0 years o r old er (p > 0 .1 ). F o r instance, the resu lts

fo r the S an M a rtin 2 population, in P atin o, in the

provin ce o f F o rm o sa, a locality o f this category, are

p resen ted in F ig u re 2.

T h e pre valence ra te s ob served in areas treated

an d continu ously su rveyed fo r household reinfesta­

tions b y triato m in es (C ateg o ry 2 a) are sim ila r to those

observ ed in the cities o f L o b ato n an d A cheral, S an

P edro, in th e P ro vin ce o f Ju ju y (F igu re 2). In these

areas, children aged from 0 to 4 years, show ed a

prevalence o f 2 .6 % w hile those from 5 to 9 years o f age

h a d a prevalence rate o f 5 .4 % ; those from 10 to 14

years show ed a rate o f 6 .2 % , w hich rose to 17 .6 % in

child ren from 15 to 19 years o f age an d to 5 4 .5 % in

people old er th an 19 years o f age.

W ith in C ate g o ry 2b in th e locality o f P ajo nal, in

the P ro v ince o f C ata m arca, w here control activities

w ere n o t contin uous, children 5-9 years o f age sh ow ed

an in creased p revalence rate o f 12% com pared to

child ren 10 to 14 years o f age (8 .8 % ), but these

differences are n o t statistically significant ( p X ) .l) .

Figure 2 -

T . cruzi

(_______ )

m o s a : w i th o u t c h e m i c a l tr e a tm e n t; b ) ( -

---

s u r v e illa n c e .

Serological reactiv ity o f th o se populatio ns

w hich were ch em ically tre a te d w ith insecticides com ­

p a re d to n o n -tre a te d a re a s are an aly sed in F igu re 3. A

significant difference w as o b serv ed betw een b o th

F ig u r e 3 - D i s t r i b u t i o n o f a v e r a g e s e r o l o g i c a l p r e v a l e n c e to T . cruzi in f e c t i o n o b t a i n e d in A r g e n t i n e in 6 l o c a t i t i e s w i t h o u t c h e m i c a l t r e a t m e n t ( b l a n k c o l u m n s ) a n d 7 l o c a l i t i e s w ith c h e m i c a l t r e a t m e n t ( s t r i p e d c o l u m n s ) .

regions, w here children fro m 0 to 4 years o f age

belonging to chem ically tre a te d are as show an average

pre valence rate o f 2 .3 % , w hereas ch ildren o f the sam e

age living in n o n -treated are as show a pre valence rate

o f 17 .5 % (p < 0 .0 0 5 ).

C h u i t R , S u b i a s S , P é r e z A C , P a u l o n e I , W i s n i v e s k y - C o l l i C , S e g u r a E L . U s e f u l n e s s o f s e r o l o g y f o r t h e e v a l u a t i o n o f

Trypanossom a cruzi

DISCUSSION

The serological prevalence rates for Chagas’

disease in rural areas without insecticidal treatment

shown in this study are coincident with the relative

values obtained by Rosenbaun and Cerisola at the end

of the fifties21 and confirm those obtained by Bonet et

al3. In all cases serological prevalence rates increase

with the age of the individuals, reaching their maximun

in the age groups older than 40.

Data obtained confirm previous findings in

Argentina which show that the highest risk of infection,

in areas of active transmission, is below 10 to 14 years

of age, reflected on the fact that at least 50% of the total

infected population is already infected at this age3 21.

These data are coincident among others with those

found in Bambui, Brasil11 and Venezuela18.

The results shown here present, according to

Rosenbaum, “ Information about what happened in the

past with individuals studied in the present”, where

each individual under study represents, a cross section

of the different stages of the evolutive cycle of the

disease1 21,

This assertion becomes demonstrated by the

increasing prevalence with steeper slopes for areas

without treatment than for chemically treated regions.

In those areas where chemical treatment was

performed, a prevalence rate of 2.3% was found in

children 0 to 4 years of age, whereas in non-treated

areas a prevalence rate of 17.5% was found in this age

group, evidencing the effects of control measures

against domestic triatomine with promotion of

community participation. Once more the use of che­

mical control actions ensures the interruption of

T.

cruzi

human transmission and the surveillance

appears necessary to maintain this condition in the

long-term. These assertions are reflected in locality of

Chancani, Cordoba, where the area was sprayed every

4-5 years, and in Lobaton where surveillance was

performed continuously from 1966 up to the present

time by the current programme of health of the

province of Jujuy. In both localities interruption of the

transmission was successfully achieved, in the early

eighties in the former and at the end of the sixties in the

latter.

Research work on the serological prevalence of

T cruzi

infection in children gives information about

the status of transmission at the moment of sample

collection, about its history and its future evolution, the

latter, depending on the actions to be implemented.

In chemically treated areas where continuous

entomological surveillance activities were carried out,

serological prevalence rates of

T. cruzi

infection in

children up to 4 years of age tended to decrease,

whereas this trend in those areas where no surveillance

measures were taken was not observed. Thus serology

is a suitable indicator of the state of the transmission of

infection by

T. cru zi

in rural communities before or

after any control campaign intervention14.

Control Programmes current surveillance and

evaluation activities are based on the use of the results

of their own entomological surveys as indicators of the

state of transmission. The extent of the endemic area

and control programme constraints concerning trained

personnel and its mobilization to the areas makes it

difficult to achieve regular evaluations by this metho­

dology. Serology, on the other hand, would allow the

undertaking of surveys in the hands of local trained

human resources, becoming a useful tool to help in a

Control Programme current activities.

Control Programmes have, at present, a variety

of improved and new technologies compared with

those available at their origins that open new pos­

sibilities. This fact would permit the beginning of a

gradual change in the philosophy of control Pro­

grammes and the use of new laboratory’s metho­

dologies, like serology in the hands of their own well-

trained field agents, this would effectively accomplish

the scope and objectives of the programmes.

In summary, the results of prevalence of

T. cru zi

infection obtained from serological sampling perfor­

med in rural areas from thirteen departments of seven

endemic provinces for Chagas’ disease in Argentina,

qualify serology as an appropiate technology, easily-

available, economic, and a sensitive indicator of the

status of the transmission, providing a tool for the

evaluation of control actions performed and the plan­

ning of future activities.

RESUMO

Treze co m unidades de 7p ro vín cia s argentinas

fo r a m escolhidas p a ra avaliação de sorologia com o

indicador da transm issão d a D oença de Chagas. D a s

com unidades m encionadas, seis não tin h a m história

p révia de tratam ento com inseticidas e sete tin h a m

recebido tratam ento esporádico ou continuado.

Vinte p o r cento dos m oradores d a s casas de

cada localidade fo r a m estudados p o r sorologia. A s

am ostras fo r a m obtidas p o r p u n çã o da p o n ta do dedo

e 5 0 m icrolitros d e sangue fo r a m m istu ra d a s com 150

m icrolitros de um a solução conservadora de glice­

rina a 5 0 % em m eio de cultivo, p a ra serem estudados

p o r h em aglutinação indireta, e im unofluorescência

indireta. N a s áreas não tratadas a prevalência da

infecção em crianças de 0-4 anos f o i de 17,5 %

chegando a m a is de 2 2 % p a ra as de 5-9 anos e a

3 3 ,3 % no grupo 10-14 anos. A p revalência nas áreas

tratadas e sob vigilância f o i de 2 .6 % em crianças de

0-4 anos, 5 ,4 % an o s de 5-9 anos e de 6 ,2 % em jo v e n s

de 10-14 sendo as diferenças entre os dois tipos de

áreas estatisticam ente significativas ( < 0,005).

C h u i t R , S u b i a s S , P é r e z A C , P a u l o n e I , W i s n i v e s k y - C o l l i C , S e g u r a E L . U s e f u l n e s s o f s e r o l o g y f o r t h e e v a l u a t i o n o f

Trypanossom a cruzi

E ste estudo p ropõe a sorologia com o um indi­

cador válido p a ra a avaliação da transm issão da

D oença de C hagas em áreas rurais.

Palavras-chaves: Transmissão de

T. cruzi.

Prevenção e controle. Estudo de campo. Sorodiagnós-

t i c o .

ACKNOW LEDGEM ENTS

We wish to thank, D r Mirta Carlomagno for her

editorial assistance. Adolfo Contreras and Victor Vigil

gave valuable practical assistance in the field.

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