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Modeling Chagas disease in Chile: From vector to congenital transmission
Mauricio Canals1, Dante Cáceres2, Sergio Alvarado2
1Programa de Salud Ambiental, Escuela de Salud Pública, Facultad de Medicina, Universidad de Chile, Chile; Departamento de Medicina, Facultad de Medicina, Universidad de Chile, Chile.
Insights
Chagas disease dynamics were modeled, revealing vector transmission is key to eradication. Interrupting domestic transmission and controlling wild vectors are crucial for eliminating Chagas disease.
Area of Science:
- Epidemiology
- Mathematical Modeling
- Public Health
Background:
- Chagas disease is a significant public health issue in Latin America, particularly in northern Chile.
- Vector transmission of Chagas disease was interrupted in 1999 with the elimination of Triatoma infestans.
- The epidemiologic dynamics of Chagas disease require updated modeling following vector control efforts.
Purpose of the Study:
- To model the dynamics of Chagas disease incorporating both vector and congenital transmission.
- To analyze the contributions of vector and congenital transmission to the overall disease burden.
- To identify key parameters influencing Chagas disease transmission and eradication.
Main Methods:
- Development of a mathematical model integrating vector and congenital transmission pathways.
- Simulation of disease dynamics based on the proposed model.
- Derivation and analysis of the basic reproductive number (R0) and sensitivity analyses.
Main Results:
- The basic reproductive number (R0) is a sum of vector (R0V) and congenital (R0C) contributions, with R0V being dominant.
- Chagas disease transmission declines exponentially within 2-3 generations if vector transmission is eliminated.
- Human bite rate, vector density, and insect vector mortality are critical parameters.
Conclusions:
- Interruption of domestic vector transmission is essential for Chagas disease eradication.
- Post-eradication strategies must focus on preventing wild vector domiciliation and re-infestation.
- Adequate treatment coverage for congenital Chagas disease cases is vital.
Abstract:
Chagaś disease is a human health problem in Latin America. It is highly prevalent in northern Chile between the Arica-Parinacota and Coquimbo regions, with reported incidence of 3-11/100000 inhabitants and mortality of 0.3-0.4/100000. The interruption of vector transmission was reported in 1999 by means of the elimination of the primary vector, Triatoma infestans, from human dwellings, thus the epidemiologic dynamics of this disease should be modified. Here we model the dynamics of Chagaś disease based on previous models for vector and congenital transmission, propose a model that includes both transmission forms and perform simulations. We derive useful relationships for the reproductive number (R0) showing that it may be expressed as the sum of the vector (R0V) and congenital (R0C) contributions. The vector contribution is larger than the congenital one; without the former Chagaś disease vanishes exponentially in two to three generations. Sensitivity analyses showed that the main parameters that intervene are the human bite rate, the density of vectors per human and the mortality rate of the insect vectors. Our model showed that the success of the eradication of Chagaś disease is based on the interruption of domestic transmission. Once this is obtained, the control strategies should focus on avoiding the domiciliation of wild vectors, re-colonization by the primary vector, and an adequate coverage of congenital case treatment.
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