Diminution of the intradomestic reinfestation by Triatoma dimidiata in

Guatemala through an integrated control based on an ecosystem

approach

María Carlota Monroy EscobarDulce María Bustamante ZamoraDulce María Bustamante Zamora

Laboratory of Applied Entomology and Parasitology, Department of Biology, San Carlos University, Guatemala & Cols.

Chagas Disease or American Trypanosomiasis

Trypanosoma cruzi

Invertebrate Host(Hemiptera: Reduviidae:Triatominae)

Vertebrate Host(Mammals)

Phases of Chagas Disease

M ic roscop ica l tes tB lood cu ltu re

X en od iag n os isP C R

P aras ito log ica l

Ig M D etec tion

S ero log ica l

L ab ora to ryd iag n os is

3-4 m on ths

AC U TE PH ASE

Might last for several yearsIt is asym ptom atic

IN TER MED IATE PH ASE

B lood cu ltu reX en od iag n os is

P C R

P aras ito log ica l

Ig G d e tec tion

S ero log ica l

L ab ora to ryd iag n os is

It the longest period

C R O N IC PH ASE

IN FEC TIO N

Chagas in Guatemala

Chagas vectors in Guatemala

• Rhodnius prolixus*

• Triatoma dimidiata

• Other triatomines: Triatoma nitida, Triatoma ryckmani.

Triatoma dimidiata

3.5 cm

2.4 cm

Triatoma dimidiata

• It is a versatile species, with high capacity of adaptation (sylvatic, domestic, peridomestic).

• Various subpopulations geographically (genetically?) isolated.

It is present in different scenarios: – sylvatic, – domestic-peridomestic, – domestic-peridomestic-sylvatic.

• T. dimidiata intradomestic density is higher in red areas (low forest coverage, mud wall houses).• Is there a higher risk in highly deforested areas (south-west)?

1:250,000

T. dimidiata Control

• Native species non eradicable: reinfestation (from sylvatic foci?).

• Is then necessary to learn how to coexist with this bug, preventing the contact with it (inside the house).

• Long term control must be based on physical and ecological methods.

• Active participation of the community is a priority. (Zeledón 2002)

Chagas Control in C.A.

Central America Initiative (1998)• Vectorial transmission (95%):

– Massive attack with insecticides (pirethroid)– Epidemiological and entomological surveillance* – Home improvement and community

surveillance*• Transfusional transmission:

– Blood screening in blood banks (mandatory by law)

Challenges for Control in C.A.

• House reinfestation: T. dimidiata – Residual or real immigrants? – From peridomestic or sylvatic environments?

• Communitary participation– Home improvement– Surveillance

• Epidemiological/Entomological permanent surveillance

• The loss of T. dimidiata natural ecotopes

An Ecosystem Approach for Chagas Disease Control in

Guatemala

Why an ecosystem approach?• Triatominae long term control demands:

– appropriate management of the domestic and peridomestic environments to avoid colonization; and of the sylvatic environments to avoid lost of natural ecotopes better management of the ecosystem.

• Transdisciplinarity to confront the variety of constraints of the problem.

• The research must be oriented with the vision of developing a policy (involvement of the Ministry of Health).

The Proposal

General Objective

• Test in a pilot project, an improved T. dimidiata control strategy, integrating

a) chemical control;

b) community participation in house improvement (domicile and peridomicile), entomological surveillance, and environmental management; to reduce the risks of Chagas disease transmission, for the better management of the ecosystem and to improve human health.

Specific Objectives

• To gather key information from the ecosystem, necessary to comprehend the factors who difficult the elimination of T. dimidiata from the domicile and peridomicile.

• To integrate a work team (researchers, Public Health workers and community), to propose, analyze, discuss and conclude, which is the best strategy for integrated control against T. dimidiata, according to everyone's expectative and real possibilities.

Specific Objectives

• To execute an integrated control intervention, considering managements in the domestic, peridomestic and sylvatic environments.

• To evaluate and disseminate the results of the integrated control.

Study Site• Jutiapa (eastern Guatemala)

– T. dimidiata situation: 50% dispersion, 35% infestation, >20% population in risk

– Reinfestation: could be three months after sprayings; the infestation increases with time and can reach its original levels

- >15% population positive to T. cruzi infection- Agriculture and cattle, Spanish speakers, houses

built of mud walls (adobe), communitarian forests and beekeeping

- 4 villages (150 houses each, 3000 people)

2 villages with integrated control (ecosystem approach)

2 villages with chemical control (traditional approach)

Experimental Design

36 months

Traditional Approach

• Entomological surveillance

• Insecticide application in the positive houses

• Information to the community (school teachers)

• Entomological monitoring for reinfestation –selected houses-

• Second insecticide application

Ecosystem Approach• Transdisciplinary Research Team

– Biological Component (Ecology, Entomology)– Social Component– Engineering Component– Ministry of Public Health (ETV)Ministry of Public Health (ETV)

• IV Phases of Intervention– Characterization– Analysis, Consensus and Design – Execution of Interventions– Evaluation and Dissemination

Domestic and peridomestic environments (suitable places for T. dimidiata – infestation, colonization)

Humans

Chemical control

Disease discomfort

shame

T.d.

T.d.Reinfestation

Domestic and peridomestic environments (suitable places for T. dimidiata – infestation, colonization)

Humans (socioeconomic situation, social organization, behavior, constructive systems.)

Natural environment

Agriculture, deforestation

Chemical control

Disease discomfort

shame

T.d.

T.d.

T.d.Loss of

T. dimidiata natural ecotopes

Reinfestation

Environmental ManagementReforestation

Home Improvement

Phase I: Characterization

• Presentation of the project to the community– Establishment of the project possibilities

• Social diagnostics– Understand the populations perspective on

the problem: people’s knowledge, attitudes, culture, expectations

– Identify leaders and channels for communication

• Ecological and Biological diagnostics– Entomological evaluation (dom-peridom)– Vectors’ sylvatic ecotopes; mobility– Vegetation and land use; diagnostic of the

communitarian forests

• Engineering diagnostics– Constructive systems

• Insecticide application

Phase II: Analysis, Consensus and Design

• Analysis of the diagnostics• Design of the strategy for:

– Management in the domestic, peridomestic, sylvatic environments

– Communitarian system for reinfestation monitoring

• Presentation of the proposed actions to the community. Consensus. – Who? When? How?

Phase III: Execution of interventions

• Motivational activities for an improved ecosystem management– Workshops of techniques for house

improvement, meliponiculture, forestry seedbeds, medicinal plants (others).

• Execution of house improvements (domestic and peridomestic) by the community

• Establishment of the communitarian system for reinfestation monitoring

• Promotion of an ecological restoration: sylvatic environment management (seedbeds and reforestation, meliferous plants gardens, medicinal plants gardens)

• Intermediate evaluation: social, entomological, housing

Phase IV: Evaluation and Dissemination

• Entomological monitoring for reinfestation.• Evaluation of:

– Number of houses improved (domestic, peridomestic)

– Number of trees planted, reforested area– Number of hives in good conditions for production– Number of houses with gardens (medicinal or

meliferous plants)– Number of bugs reported by the community

• Analysis of the communitarian organization for the sustainability of the entomological monitoring and reforestation.

• Comparison of results with the control villages.

• Presentation of results. Recommendations for the National Control Program of the Ministry of Health.

Expected Results with the Ecosystem Approach

• Reduce and maintain the infestation index of T. dimidiata lower than 5%, the colonization index between 0-5%, and the density index lower than 1.

• Improve the structural and sanitary conditions of at least, 50% of the houses in the villages.

• Improve the management of the sylvatic environment surrounding the villages.

• Inform an recommend the National Control Program, about the advantages of the ecosystem approach for the control of T. dimidiata.