This article was written by Andy Hardy, Aberystwyth University and first published on The Conversation.

On a typically hot and humid July day in Stonetown, the capital of Zanzibar, a gaggle of children, teenagers and the odd parents watched our small drone take flight. My colleagues Makame Makame, Khamis Haji and I had finally found the perfect launch spot.

With a high-pitched humming, the drone took to the air. It sounded like a big mosquito – appropriate, since we were testing the use of drones for mapping aquatic malaria habitats. These shallow sunlit water bodies teem with mosquito larvae. In a matter of days, the larvae will emerge as adult mosquitoes in search of a blood meal. If one of those mosquitoes bites a human infected with malaria, it will become a vector for the disease and continue its deadly transmission cycle.

Zanzibar is a Tanzanian archipelago off the coast of East Africa. Both it and mainland Tanzania have fought a long, well documented battle with malaria. Globally, the disease infects over 200 million people annually and is responsible for killing approximately 500,000 people each year.

The Millennium Development Goals prompted a number of large scale campaigns across sub-Saharan Africa to combat malaria. Millions of bed nets were distributed. Insecticide was supplied to spray in homes across communities. The aim was to stop people getting bitten, interrupting the transmission cycle.

It’s been a real success story, leading to a notable decrease in the disease’s prevalence. Some areas of Zanzibar have seen prevalence levels drop from 40% of the population having malaria to less than 1%.

Now epidemiologists and public health managers are looking to complement indoor-based nets and spraying with outdoor based solutions. In effect, they’re taking the battle to mosquitoes. And drones are a crucial part of their armoury. One of the main challenges to disease managers is finding small water bodies that mosquitoes use to breed. This is where drones come in – for the first time, drone imagery can be captured over large areas which can be used to create precise and accurate maps of potential habitats.

Tracking mosquitoes

We know that once an adult mosquito has fed and rested, it will typically go in search of a mate. Then it moves on to a suitable location – an aquatic habitat like the fringes of river channels, roadside culverts and irrigated rice paddies – to lay its eggs.

Public health authorities need to be able to locate and map these water bodies so they can be treated using a larvicide like DDT. This process is known as larval source management, and was successfully used in Brazil and Italy many decades ago. There, the DDT killed mosquito larvae – but could also be devastating for local ecology as well as having adverse effects on human health.

Today much safer, low toxicity replacements have been developed. The problem is that they come at a cost. Resources are also needed to disseminate the larvicide and to locate the water bodies that host the mosquito eggs and larvae. Some of these hideaways are tough to find on foot, and if water bodies are accurately mapped a larvicide campaign could end up being a waste of time.