How drones and monkeys are helping malaria research
A malaria parasite once thought confined to macaque monkeys is infecting humans more and more. Hot on its tail are researchers from the London School of Hygiene and Tropical Medicine, who are using drones to map forest changes in South East Asia, as well as tracking malaria-carrying monkeys themselves. Katherine Nightingale takes a look at the project in pictures.
You might have heard of drones being used to track herds of large animals, or in search and rescue operations, but in Sabah in Malaysian Borneo, it’s trees they’ve got their eye on.
Historically, malaria in Borneo was caused by Plasmodium falciparum, a tiny parasite which hitches a ride in mosquitoes and is transmitted to people through its bite. But now people in Borneo are more likely to be infected with a parasite called Plasmodium knowlesi, which is just as severe in people as Plasmodium falciparum, even though the infection is mild in its usual targets of short-tailed and pig-tailed macaque monkeys.
But how has P. knowlesi made this leap from monkeys to humans and is it really on the increase or has it always been there? Infectious diseases often make their way from animals to people at frontiers between wild, natural environments and human settlements. It appears that changes in land use in Borneo ― from forest to rubber plantation ― have driven monkeys and people closer together, and changed the habitats of mosquitoes. Together these are likely to have created more opportunities for infected mosquitoes to reach humans.
But no one has pinpointed exactly which changes lead to an increase, and without that knowledge it will be difficult to either prevent the transmission of malaria from happening or to prepare health services serving at-risk populations. That’s why researchers from the Monkeybar project are surveying Sabah from the skies. 
The drones they used are an off-the-shelf model called the senseFly eBee. Lightweight and compact, they are fitted with a 16-megapixel camera which takes images that can be used to create maps and three-dimensional models of the area. Being able to produce this data in real-time and track rapidly changing environments is key.
Researchers from the Monkeybar project flew 158 drone flights between December 2013 and May 2014.
The drones don’t require much specialist knowledge ― for example, they are launched by simply throwing them into the air. This means they can be used by many members of the research team. They fly at about 350-400 metres above their launch site. Most flights were successful, but some had to repeated because of wind, rain and battery failure.
Some of the land changes that the team picked up were startlingly rapid. The images above show an area in Sabah, Borneo, in February 2014 and again in May 2014 after clearing for a rubber plantation has begun.
The researchers then combined the land maps produced from the drones with data from humans carrying GPS trackers and monkeys wearing GPS collars. They also added data on P. knowlesi cases in hospitals, and mosquito abundance.
In the map above, yellow spots indicate the presence of a macaque, red spots a case of P. knowlesi, and the crosses are houses.
Together, this tracking of people, monkeys and mosquito habitats will build up a picture of the human activities most likely to lead to increases in disease, and begin to answer the question of where the increase in P. knowlesi is coming from.
The Monkeybar project is funded by the Environmental and Social Ecology of Human Infectious Diseases Initiative, a collaboration between the MRC, the Natural Environment Research Council (NERC), the Economic and Social Research Council (ESRC) and the Biotechnology and Biological Sciences Research Council (BBSRC).
 Mapping infectious disease landscapes: unmanned aerial vehicles and epidemiology. Cox. J. et al (2014), Trends in Parasitology 30 (11)