The objective of this study is to determine if a Chagas disease protocol starting with a serological survey is as reliable at identifying insect-infested areas as one using the gold standard entomological survey. The study found that health center areas infested with Rhodnius prolixus were identified using a threshold seroprevalence of 0.1%. The serological survey took half the time and was 30% less expensive than the entomological survey. Developing countries with limited resources may find this strategy useful in combating Chagas disease. This strategy also identifies seropositive children, which facilitates their treatment

Doust, J

Lucas, R

Spurling, G

English

Spurling, G.

Lucas, R.

Doust, J.

University of Queensland eSpace

Identifying health centers in Honduras infested with Rhodnius prolixus using the seroprevalence of Chagas disease in children younger than 13 years

MSF Field Research

IDENTIFYING HEALTH CENTERS IN HONDURAS INFESTED WITH RHODNIUS
PROLIXUS USING THE SEROPREVALENCE OF CHAGAS DISEASE IN CHILDREN
YOUNGER THAN 13 YEARS
GEOFFREY SPURLING,* ROMUALD LUCAS, AND JENNY DOUST
University of Queensland, Brisbane, Australia; Médecins Sans Frontières, Paris, France
Abstract. The objective of this study is to determine if a Chagas disease protocol starting with a serological survey
is as reliable at identifying insect-infested areas as one using the gold standard entomological survey. The study found
that health center areas infested with Rhodnius prolixus were identified using a threshold seroprevalence of 0.1%. The
serological survey took half the time and was 30% less expensive than the entomological survey. Developing countries
with limited resources may find this strategy useful in combating Chagas disease. This strategy also identifies seropositive
children, which facilitates their treatment.
INTRODUCTION
In 2000–2001, Médecins Sans Frontières (MSF) conducted
a program targeting Chagas disease in Honduras. Chagas dis-
ease is a serious problem in Mexico and the Andean and
Central American countries with approximately 9 million
people infected with the parasite and 25 million remaining at
risk.
1 The prevalence of Chagas disease is reducing in South
America with the success of the Southern Cone initiative
launched in 1991. This initiative aims to eliminate transfu-
sional transmission and to eradicate the principal insect vec-
tor in South America, Triatoma infestans. A similar initiative
aims to eradicate Rhodnius prolixus, the principal insect vec-
tor in Central America. These programs use a World Health
Organisation (WHO) protocol where an entomological sur-
vey identifies infested areas requiring spraying. While effec-
tive, this strategy is resource and time intensive. MSF adopted
a different approach, developing a protocol using a serologi-
cal survey to identify infested areas in need of spraying, which
had the additional advantage of identifying and treating se-
ropositive children. de Andrade and others found that a se-
rological survey of schoolchildren allowed mapping of sero-
prevalence, detected child carriers of the disease, allowed
comparison of different regions, and longitudinally could
evaluate the efficacy of vector control measures.
2 The objec-
tive of this study is to determine if a protocol starting with a
serological survey is as reliable at identifying infested areas as
one using the gold standard entomological survey and to com-
pare protocols for cost and time.
MATERIALS AND METHODS
The study area comprised three adjacent municipalities,
Orica, San Ignacio, and Marale, located in the central moun-
tains of Honduras. Another nongovernment organization in
conjunction with the national vector control authorities was
concurrently conducting a program of home improvement,
including roof replacement in the worst affected parts of
MSF’s project area. The MSF team consisted of two brigades,
each with one supervisor and six members. A process of com-
munity consultation and explanation of our activities was un-
dertaken prior to both entomological and serological surveys.
The brigades first conducted the entomological survey,
searching for the principal insect vector, R. prolixus, in each
village. Data on Triatoma dimidiata infestation were also col-
lected. They then conducted the serological survey, taking a
fingerprick sample of blood from each child under 13 years of
age on Whatman no. 2 filter paper. All blood samples were
taken in the presence of brigade leaders, the MSF social
worker, the MSF doctor or trained local Honduran health
staff. The procedure and the implications of positive and
negative tests were explained to parents or the caregiver
present with the child. It was explained that treatment would
be offered in the event of a positive test. Refusal by parents,
family members, or children was respected. These samples
were analyzed in a central laboratory using a Chagatest
ELISA IgG from Wiener Laboratory in Rosario, Argentina.
The sensitivity of this test is 99.8% and the specificity is 99.2%.
Positive ELISA tests and 10% of negative ELISA tests were
confirmed with an immunofluorescence assay. Facilities al-
lowing parasitological diagnosis were not available. All houses
in health center areas infested with R. prolixus were sprayed
using a pyrethroid insecticide, and seropositive children were
treated with benznidazole in their communities for 60 days
using a dose of 7.5 mg kg
−1 day
−1 in two divided doses.
A cost comparison of entomological and serological sur-
veys was based on the time and running costs required to
complete each survey using the two MSF brigades. Additional
costs such as serological tests, filter paper, and the laboratory
technician were factored into the cost comparison.
RESULTS
Complete results for entomological and serological surveys
were obtained for all 11 health center areas in the three mu-
nicipalities Orica, San Ignacio, and Marale. In this study area,
5,090 houses were searched, and R. prolixus infestation was
identified in 22 communities. In the same area, 9,573 children
were tested for Chagas disease, and 49 returned a positive
result (Table 1). Refusal rates were low except for small clus-
ters in certain communities, usually for religious reasons.
Overall coverage in the serological survey was approximately
93%. In all health center areas, infestation with R. prolixus
could be identified using a threshold seroprevalence of 0.1%
(sensitivity 100%). The specificity at this level was 66%
(Table 2). All health centers with a seroprevalence of more
than 0.2% were found to be infested with R. prolixus. There-
fore, using a threshold seroprevalence of 0.2%, the specificity
of the test was 100%, and the sensitivity was 80%.
In a fourth municipality, Guayape, the serological survey
revealed four health center areas with a seroprevalence
* Address correspondence to Dr. Geoffrey Spurling, MBBS, DTM,
and H, FRACGP, Discipline of General Practice, Level 2, Edith
Cavell Building, Royal Brisbane Hospital, Herston, Qld 4029, Aus-
tralia. E-mail: g.spurling@uq.edu.au
Am. J. Trop. Med. Hyg., 73(2), 2005, pp. 307–308
Copyright © 2005 by The American Society of Tropical Medicine and Hygiene
307greater than 0.2%. Although no formal entomological survey
was performed in this municipality, the brigades reported see-
ing R. prolixus in all four of these health center areas. In
addition, no R. prolixus was seen or reported from the re-
maining two health center areas with a seroprevalence of 0%.
There was no correlation found between health center se-
roprevalence and infestation with T. dimidiata. This vector
appeared to account for 6% of the seropositive children in
our project. All the children with a confirmed positive test
were asymptomatic and were offered treatment with ben-
zonidazole. Seventy percent of these children in treatment
had no side effects. Side effects were common though gener-
ally mild and included loss of appetite, rash, dizziness, stom-
ach pain, headache, and fatigue. Only two children ceased
treatment, both after 1 month and both due to a severe rash.
Local health authorities undertook to follow up children who
were treated with trypanocidal medication. The national vec-
tor control authorities have undertaken to follow up MSF’s
work with repeat spraying to maintain vector eradication.
The running costs of our activities were calculated for the
11 health centers belonging to the 3 municipalities of Orica,
San Ignacio, and Marale. The serological survey took half the
time of the entomological survey representing 50 days less per
municipality. This time saving led to reduced running costs
such that the serological survey was 30% less expensive than
the entomological survey, or US$3,761 per municipality.
DISCUSSION
This study has found that the presence or absence of the
principal insect vector R. prolixus can be predicted using the
seroprevalence of children under the age of 13 years in health
center areas. Health centers were used as our geographical
unit of reference as they are a realistic area in which to spray
all houses if R. prolixus infestation exists. R. prolixus spreads
from house to house and is also spread passively by people
moving along access routes.
3 Local topography often deter-
mines house to house spread, the course of these access
routes, and the boundaries of the local health center. Munici-
palities are large enough to ensure that R. prolixus infestation
will translate into seropositive children; however, it is an un-
realistic area to spray without more specific entomological
data. Individual villages may be infested without seropositive
children. This method does not allow for detection of areas at
risk of T. dimidiata, a sylvatic vector, which is not targeted for
eradication and is a secondary priority to R. prolixus in Cen-
tral America.
4 The serological survey in our project took half
the time and cost 30% less than the entomological survey.
This difference would be greater for local authorities with
existing infrastructure. By inviting children to health centers,
taking fingerprick blood samples and sending these to a cen-
tral laboratory, local authorities would know the Chagas dis-
ease status of a health center within a week. Health centers
could then be prioritized according to seroprevalence with
resources diverted at a seroprevalence less than 0.1%, further
investigation at 0.1% to 0.2%, and spraying of the entire
health center area once seroprevalence rises above 0.2%. The
local health center could then start anti-trypanocidal medica-
tion for seropositive children, which has been shown to im-
prove parasite-related outcomes.
5 The serological survey is a
useful tool in assessing and combating Chagas disease. It de-
serves particular consideration in communities lacking the re-
sources to undertake an entomological survey.
Received January 10, 2005. Accepted for publication March 17, 2005.
Acknowledgments: The authors acknowledge the hard work of the
local Honduran MSF brigades who gathered the information for the
entomological and serological surveys.
Authors’ addresses: Geoffrey Spurling, Discipline of General Prac-
tice, Level 2, Edith Cavell Building, Royal Brisbane Hospital, Her-
ston, Qld 4029, Australia, Telephone: 3346 4831, Fax: 3365 5130,
E-mail: g.spurling@uq.edu.au. Romuald Lucas, 3 Chemin de Gorre-
quer, 29740 Plobannalec, France, E-mail: romualdlucas@minitel.net;
romuald.lucas@laposte.net. Jenny Doust, Discipline of General Prac-
tice, Level 2, Edith Cavell Building, Royal Brisbane Hospital, Her-
ston, Qld 4029, Australia, E-mail: j.doust@uq.edu.au.
Reprint requests: Geoffrey Spurling, Discipline of General Practice,
Level 2, Edith Cavell Building, Royal Brisbane Hospital, Herston,
Qld 4029, Australia, Telephone: 3346 4831, Fax: 3365 5130, E-mail:
g.spurling@uq.edu.au.
REFERENCES
1. Control of Chagas disease. World Health Organ Tech Rep Ser
2002;905:i–vi, 1–109, back cover.
2. de Andrade AL, Zicker F, Luquetti AO, Oliveira RM, Silva SA,
Souza JM, Martelli CM, 1992. Surveillance of Trypanosoma
cruzi transmission by serological screening of schoolchildren.
Bull World Health Organ 70: 625–629.
3. Dujardin JP, Munoz M, Chavez T, Ponce C, Moreno J, Schofield
CJ, 1998. The origin of Rhodnius prolixus in Central America.
Med Vet Entomol 12: 113–115.
4. Dias JC, Silveira AC, Schofield CJ, 2002. The impact of Chagas
disease control in Latin America: a review. Mem Inst Oswaldo
Cruz 97: 603–612.
5. Villar JC, Marin-Neto JA, Ebrahim S, Yusuf S. Trypanocidal
drugs for chronic asymptomatic Trypanosoma cruzi infection.
Cochrane Database Syst Rev 2002(1):CD003463.
TABLE 1
Summary data from the study area
Number
Summary data from the study area
Houses in census 7,303
Houses searched 5,090
Health centers infested with Rhodnius prolixus 5
Children in census 10,283
Children tested 9,573
Seropositive children 49
Overall seroprevalence 0.51%
Municipality of Guayape
Children in census 5,195
Children tested 4,878
Seropositive children 28
Overall seroprevalence 0.57%
TABLE 2
Correlation of seroprevalence of Chagas disease in children younger
than 13 years and the presence of Rhodnius prolixus in health
center areas
Seroprevalence
Insect search for R. prolixus
Positive Negative Total
> 0.1% 5 2 7
< 0.1% 0 4 4
Total 5 6 11
Sensitivity  5/5  100% (95% CI: 57–100%)
Specificity  4/6  67% (95% CI: 30–90%)
Positive predictive value  5/7  71% (95% CI: 36–92%)
Negative predictive value  4/4  100% (95% CI: 51–100%)
Prevalence  5/11  45% (95% CI: 21–72%)
SPURLING AND OTHERS 308

Control of Chagas disease. World Health Organ Tech Rep Ser 2002;905:i–vi, 1–109, back cover.

Surveillance of Trypanosoma cruzi transmission by serological screening of schoolchildren.

Syst Rev 2002(1):CD003463. TABLE 1 Summary data from the study area Number Summary data from the study area Houses in census 7,303 Houses searched 5,090 Health centers infested with Rhodnius prolixus 5 Children in census 10,283

The impact of Chagas disease control in Latin America: a review. Mem Inst Oswaldo

The origin of Rhodnius prolixus in Central America.

Identifying Health Centers in Honduras Infested with Rhodnius Prolixus Using the Seroprevalence of Chagas Disease in Children Younger than 13 Years.

Identifying Health Centers in Honduras Infested with Rhodnius Prolixus Using the Seroprevalence of Chagas Disease in Children Younger than 13 Years.

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