Journal Article

Quantifying geographic accessibility to improve efficiency of entomological monitoring

Longbottom, Joshua, Torr, Stephen J., Krause, Ana, Stanton, Michelle C.

2020

Overview

Vector-borne diseases are important causes of mortality and morbidity in humans and livestock, particularly for poorer communities and countries in the tropics. Large-scale programs against these diseases, for example malaria, dengue and African trypanosomiasis, include vector control, and assessing the impact of this intervention requires frequent and extensive monitoring of disease vector abundance. Such monitoring can be expensive, especially in the later stages of a successful program where numbers of vectors and cases are low. We developed a system that allows the identification of monitoring sites where pre-intervention densities of vectors are predicted to be high, and travel cost to sites is low, highlighting the most efficient locations for longitudinal monitoring. Using remotely sensed imagery and an image classification algorithm, we mapped landscape resistance associated with on- and off-road travel for every gridded location (3m and 0.5m grid cells) within Koboko district, Uganda. We combine the accessibility surface with pre-existing estimates of tsetse abundance and propose a stratified sampling approach to determine the most efficient locations for longitudinal data collection. Our modelled predictions were validated against empirical measurements of travel-time and existing maps of road networks. We applied this approach in northern Uganda where a large-scale vector control program is being implemented to control human African trypanosomiasis, a neglected tropical disease (NTD) caused by trypanosomes transmitted by tsetse flies. Our accessibility surfaces indicate a high performance when compared to empirical data, with remote sensing identifying a further ~70% of roads than existing networks. By integrating such estimates with predictions of tsetse abundance, we propose a methodology to determine the optimal placement of sentinel monitoring sites for evaluating control programme efficacy, moving from a nuanced, ad-hoc approach incorporating intuition, knowledge of vector ecology and local knowledge of geographic accessibility, to a reproducible, quantifiable one.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Abundance / Accessibility / African trypanosomiasis / Algorithms / Animals / Biology / Biology and Life Sciences / Control / Costs / Costs and Cost Analysis / Data collection / Dengue / Dengue fever / Disease / Disease transmission / Efficiency / Engineering and Technology / Entomology / Environmental monitoring / Environmental Monitoring - methods / Geographic Information Systems / Health informatics / Human diseases / Humans / Image classification / Imagery / Infectious diseases / Insect Vectors / Intervention / Livestock / Malaria / Medicine / Medicine and Health Sciences / Methods / Models, Biological / Models, Statistical / Monitoring / Morbidity / People and Places / Pest Control / Physical Sciences / Public health / Remote monitoring / Remote sensing / Remote Sensing Technology / Research and Analysis Methods / Roads / Roads & highways / Satellites / Sentinel health events / Stratified sampling / Surfaces / Travel time / Traveltime / Tropical climate / Tropical diseases / Tropical environments / Trypanosoma / Trypanosomiasis, African / Tsetse Flies / Uganda / Vector Borne Diseases / Vectors / Vectors (Biology)