Impact of Residual Spraying on Rhodnius prolixus and Triatoma dimidiata in the Department of Zacapa in Guatemala

Vol. 98(2): 277-281, March 2003

J Nakagawa/⁺, C Cordón-Rosales*, J Juárez**, C Itzep**, T Nonami

Japan International Cooperation Agency, Oficina de Voluntarios Japoneses, 18 Calle, 5-56 Zona 10 Unicentro 12 nivel Oficina 1203, Guatemala, Guatemala *Universidad del Valle de Guatemala/Center of Disease Control-Medical Entomology Research and Training Unit/Guatemala, Guatemala **Ministerio de Salud Pública y Asistencia Social de Guatemala, Guatemala

As a vector control program to control Chagas disease in Guatemala, residual spraying of Rhodnius prolixus and Triatoma dimidiata was performed, and its impact was measured in the department of Zacapa. In order to identify infested villages and determine the degree of infestation, a baseline entomological survey to identify municipalities infested with vectors followed by an additional vector survey in areas known to be infested was conducted. Residual spraying using pyrethroid insecticides was performed at all the villages identified as being infested with the vectors. The residual spraying was shown to be highly effective against both vectors by the decrease in infestation indices after spraying. Analysis of the cost-effectiveness of the spraying showed that the average cost of insecticides per house is high when compared with that in Southern Cone countries.

Key words: Chagas disease - Rhodnius prolixus - Triatoma dimidiata - vector control - cost analysis - Guatemala

Chagas disease is one of the most serious vector-born diseases in Guatemala. It is estimated that in Guatemala 4,000,000 people are at risk for Chagas disease, 730,000 people are currently infected, and 30,000 people are infected annually (Hayes & Schofield 1990, OPS 2000, Schofield 2000). Chagas disease is a parasitic infection that in its chronic stage produces irreversible organ damage. It is caused by a flagellate protozoan, Trypanosoma cruzi, which is transmitted to humans through the feces of blood-sucking triatomine bugs. There are three domiciliated triatomine species in Guatemala: Rhodnius prolixus, Triatoma dimidiata, and Triatoma nitida, with the main vector species being R. prolixus and T. dimidiata (Schofield & Dujardin 1997).

R. prolixus is a much more efficient vector than T. dimidiata in transmitting T. cruzi (Ponce 1999). It appears to be exclusively domestic in Central America and can be eliminated (Schofield & Dujardin 1997, Dujardin et al. 1998). On the other hand, T. dimidiata has reported silvatic ecotopes, and is widespread in peridomestic and domestic habitats (Zeledon 1981).

Through a national survey of triatomine infestation of 236 villages in 22 departments between 1995 and 1997, it was shown that the populations in the departments in the Eastern part of the country were at highest risk of Chagas disease transmition (Tabaru et al. 1999). T. dimidiata is reported to be distributed in 21 of 22 departments (OPS 2002), while R. prolixus is limited to five departments (Tabaru et al. 1999) with infestation indices between 0 and 34.5%, and dispersion indices from 0 to 85.7% (Tabaru et al. 1999). In 1997, World Health Organization (WHO) and the Central American countries set a goal for the elimination of the transmission of Chagas disease by the end of 2010 through the elimination of R. prolixus, reduction in the distribution of T. dimidiata, and elimination of the transmission of T. cruzi through blood transfusion. In January 2000, the Ministry of Health of Guatemala initiated a vector control program directed at eliminating Chagas disease transmission in five departments (Zacapa, Chiquimula, Jutiapa, Santa Rosa, and Jalapa) in the Eastern region of Guatemala under the decentralized health system in collaboration with Japan International Cooperation Agency (JICA), the Pan American Health Organization, the University of San Carlos of Guatemala, and the Medical Entomology Research and Training Unit/Guatemala, the Center for Disease Control of the United States and the Center for Health Studies/University of Valle of Guatemala (UVG/CDC-MERTUG). Under the health area integrated system (SIAS: Sistema Integral de la Atención en Salud) which is a decentralized health administration system, each department is administered as a "health area (area de salud)". Each health area is responsible for executing health programs such as the vector control operation in each department.

The objective of the study is to evaluate the feasibility of our vector control operation by determining the impact on the vectors of residual spraying, which is evident by change in the house infestation rate in the department of Zacapa.

MATERIALS AND METHODS

RESULTS

DISCUSSION

ACKNOWLEDGEMENTS

To the ETV section of the health area of Zacapa and the survey team of UVG/CDC-MERTUG for their contribution to the operational survey. To Drs Chris Schofield, Yoichi Yamagata, Robert Klein, and Yuichiro Tabaru for their advice.

REFERENCES

Figure | Table I | Table II | Table III | Table IV

⁺Corresponding author. Fax: 81-54-643-3439. E-mail: junnakagawa@hotmail.com

Received 8 August 2002

Accepted 24 January 2003