Predicting where blackflies live
Where in Nigeria are blackflies, the insects that spread river blindness, most likely to be found?
The background
Blackflies breed in fast-flowing rivers. Their bites spread onchocerciasis, also called river blindness. WHO reports that over 99% of people with the disease live in 31 African countries, and Nigeria is one of them.
The trouble is, nobody had a clear map of where the flies are in Nigeria. Without one, survey teams spend a lot of time and money searching in the wrong places.
What I did
I started with 1,732 locations where teams had checked for blackflies, marking whether they found them or not. Then I pulled in climate data (temperature and rainfall) and elevation maps for the whole country.
Using R, I trained two kinds of model, a statistical model and a machine learning model called random forest, to learn which conditions blackflies like. The models then predicted the chance of finding flies everywhere else.
I presented this first version to the national steering committee in 2023. In 2024 I worked with other modellers on a stronger version that added a binomial geostatistical model.
The numbers that matter
survey points used to train the model
of sampled sites had blackflies
accuracy of the random forest model
of sites without flies correctly identified
Elevation and the heaviest rainfall were the strongest clues to where blackflies live.
The model correctly picked out about 65% of sites with flies and about 80% of sites without them.
A map like this tells entomology teams where to go first, which saves time and money in the field.
It also supports the bigger effort to assess how river blindness is being transmitted in Nigeria.
Slides and figures
These come straight from my presentations and model outputs. Tap any one to see it bigger.
