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An agent-based model of tsetse fly response to seasonal climatic drivers: Assessing the impact on sleeping sickness transmission rates

An agent-based model of tsetse fly response to seasonal climatic drivers: Assessing the impact on sleeping sickness transmission rates
An agent-based model of tsetse fly response to seasonal climatic drivers: Assessing the impact on sleeping sickness transmission rates
ackground

This paper presents the development of an agent-based model (ABM) to incorporate climatic drivers which affect tsetse fly (G. m. morsitans) population dynamics, and ultimately disease transmission. The model was used to gain a greater understanding of how tsetse populations fluctuate seasonally, and investigate any response observed in Trypanosoma brucei rhodesiense human African trypanosomiasis (rHAT) disease transmission, with a view to gaining a greater understanding of disease dynamics. Such an understanding is essential for the development of appropriate, well-targeted mitigation strategies in the future.

Methods

The ABM was developed to model rHAT incidence at a fine spatial scale along a 75 km transect in the Luangwa Valley, Zambia. The model incorporates climatic factors that affect pupal mortality, pupal development, birth rate, and death rate. In combination with fine scale demographic data such as ethnicity, age and gender for the human population in the region, as well as an animal census and a sample of daily routines, we create a detailed, plausible simulation model to explore tsetse population and disease transmission dynamics.

Results

The seasonally-driven model suggests that the number of infections reported annually in the simulation is likely to be a reasonable representation of reality, taking into account the high levels of under-detection observed. Similar infection rates were observed in human (0.355 per 1000 person-years (SE = 0.013)), and cattle (0.281 per 1000 cattle-years (SE = 0.025)) populations, likely due to the sparsity of cattle close to the tsetse interface. The model suggests that immigrant tribes and school children are at greatest risk of infection, a result that derives from the bottom-up nature of the ABM and conditioning on multiple constraints. This result could not be inferred using alternative population-level modelling approaches.

Conclusions

In producing a model which models the tsetse population at a very fine resolution, we were able to analyse and evaluate specific elements of the output, such as pupal development and the progression of the teneral population, allowing the development of our understanding of the tsetse population as a whole. This is an important step in the production of a more accurate transmission model for rHAT which can, in turn, help us to gain a greater understanding of the transmission system as a whole.
1935-2735
e0006188
Alderton, Simon
ec893713-8c3f-465e-8a22-c719744d9f8c
Macleod, Ewan T.
339781ee-33f7-4dd1-8f28-0854491cb5ef
Anderson, Neil E.
366fb85a-744a-4824-a201-4ce5cffe9e3e
Palmer, Gwen
42e739c0-539b-487d-a4fc-120eb234f668
Machila, Noreen
de89dfd5-8994-4d40-9338-26dac8a8846c
Simuunza, Martin
07638302-eb50-428d-b418-83bcfae9a0c4
Welburn, Susan C.
531d82a4-0190-4ff9-a7bb-576ae38fa0b3
Atkinson, Peter M.
96e96579-56fe-424d-a21c-17b6eed13b0b
Alderton, Simon
ec893713-8c3f-465e-8a22-c719744d9f8c
Macleod, Ewan T.
339781ee-33f7-4dd1-8f28-0854491cb5ef
Anderson, Neil E.
366fb85a-744a-4824-a201-4ce5cffe9e3e
Palmer, Gwen
42e739c0-539b-487d-a4fc-120eb234f668
Machila, Noreen
de89dfd5-8994-4d40-9338-26dac8a8846c
Simuunza, Martin
07638302-eb50-428d-b418-83bcfae9a0c4
Welburn, Susan C.
531d82a4-0190-4ff9-a7bb-576ae38fa0b3
Atkinson, Peter M.
96e96579-56fe-424d-a21c-17b6eed13b0b

Alderton, Simon, Macleod, Ewan T., Anderson, Neil E., Palmer, Gwen, Machila, Noreen, Simuunza, Martin, Welburn, Susan C. and Atkinson, Peter M. (2018) An agent-based model of tsetse fly response to seasonal climatic drivers: Assessing the impact on sleeping sickness transmission rates. PLoS Neglected Tropical Diseases, 12 (2), e0006188. (doi:10.1371/journal.pntd.0006188).

Record type: Article

Abstract

ackground

This paper presents the development of an agent-based model (ABM) to incorporate climatic drivers which affect tsetse fly (G. m. morsitans) population dynamics, and ultimately disease transmission. The model was used to gain a greater understanding of how tsetse populations fluctuate seasonally, and investigate any response observed in Trypanosoma brucei rhodesiense human African trypanosomiasis (rHAT) disease transmission, with a view to gaining a greater understanding of disease dynamics. Such an understanding is essential for the development of appropriate, well-targeted mitigation strategies in the future.

Methods

The ABM was developed to model rHAT incidence at a fine spatial scale along a 75 km transect in the Luangwa Valley, Zambia. The model incorporates climatic factors that affect pupal mortality, pupal development, birth rate, and death rate. In combination with fine scale demographic data such as ethnicity, age and gender for the human population in the region, as well as an animal census and a sample of daily routines, we create a detailed, plausible simulation model to explore tsetse population and disease transmission dynamics.

Results

The seasonally-driven model suggests that the number of infections reported annually in the simulation is likely to be a reasonable representation of reality, taking into account the high levels of under-detection observed. Similar infection rates were observed in human (0.355 per 1000 person-years (SE = 0.013)), and cattle (0.281 per 1000 cattle-years (SE = 0.025)) populations, likely due to the sparsity of cattle close to the tsetse interface. The model suggests that immigrant tribes and school children are at greatest risk of infection, a result that derives from the bottom-up nature of the ABM and conditioning on multiple constraints. This result could not be inferred using alternative population-level modelling approaches.

Conclusions

In producing a model which models the tsetse population at a very fine resolution, we were able to analyse and evaluate specific elements of the output, such as pupal development and the progression of the teneral population, allowing the development of our understanding of the tsetse population as a whole. This is an important step in the production of a more accurate transmission model for rHAT which can, in turn, help us to gain a greater understanding of the transmission system as a whole.

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More information

Accepted/In Press date: 22 December 2017
e-pub ahead of print date: 9 February 2018
Published date: 9 February 2018

Identifiers

Local EPrints ID: 418147
URI: https://eprints.soton.ac.uk/id/eprint/418147
ISSN: 1935-2735
PURE UUID: 324342c3-79dc-418b-a08d-85f64797d295

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Date deposited: 22 Feb 2018 17:30
Last modified: 23 May 2018 16:31

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Contributors

Author: Simon Alderton
Author: Ewan T. Macleod
Author: Neil E. Anderson
Author: Gwen Palmer
Author: Noreen Machila
Author: Martin Simuunza
Author: Susan C. Welburn

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