Mosquito man: Dave Chadee

Most people don’t think of entomology as a life-saving profession, but going by per capita impact, mosquitoes may be the most dangerous animals on Earth. And Trinidadian scientist Dave Chadee stands in the middle of a “perfect swarm” of the tiny bloodsuckers. Nazma Muller learns about his groundbreaking research, with the potential to save millions of lives

Dave Chadee. Photograph by Alex Smailes

Consider this: mosquitoes kill more people (and livestock) than any other animal on the planet. The Dracula of the insect world transmits a range of diseases — including malaria, dengue, yellow fever, and filariasis — to more than seven hundred million people across Africa, Asia, Latin America, and the Caribbean annually, killing two million of them.

And climate change (or climate variability, as some prefer to see it) is only making things worse. Hurricanes and flooding create ideal conditions for mosquitoes to breed. Though not all 3,500 species of mosquito transmit diseases, the ones that do — like Aedes aegypti, which carries the dengue and yellow fever viruses — are often the first ones to fly in when natural disaster strikes.

In the middle of a seemingly perfect storm (or swarm, if you like) of biting blood bandits stands Dave Chadee, professor of environmental health at the University of the West Indies in Trinidad — whose work involves a lot of mosquitoes. In fact, you could call him the Steve Irwin of mosquitoes. And although, compared to crocodiles and lions, it may not be as TV-worthy to battle an almost invisible midge-like fly, Chadee’s research subjects are real havok-wreakers. “There’s actually a species of mosquito whose proboscis can penetrate denim, you know,” Chadee mentions in passing, an aside to the fact that he works with the Smithsonian Institution on developing their biodiversity database, and has already identified two species of mosquito previously unknown to exist in Trinidad.

From 1979 to 1997, Chadee had the invaluable experience of doing fieldwork and collecting specimens as an entomologist and parasitologist with the Insect Vector Control Division of the Ministry of Health in his native Trinidad and Tobago. The job gave him the opportunity to study mosquitoes in households across Trinidad and Tobago, in the forests, on the wharves, wherever they were biting and spreading diseases. Having worked in public health, and been involved in controlling epidemics and outbreaks of dengue, Chadee can appreciate the rapid response of spraying chemicals such as malathion in affected communities, which can stop the spread of the disease within a week. “You’re always going to have a need for spraying,” he admits, “especially if you have an outbreak.”

But his focus is finding an alternative method to insecticides, with their possible side effects. In 2008, the International Atomic Energy Agency awarded him a research grant to pilot the use of the Sterile Insect Technique (SIT) against Aedes aegypti mosquitoes, to prevent dengue transmission in the tropics. This involves sterilising immature male mosquitoes via radiation, and releasing them back into the wild to mate. Since the eggs produced are not viable, the population eventually collapses. Two aspects of the project — investigating whether the sterile males maintained mating patterns similar to virile males from the field, and identifying wild females inseminated by sterile males following release — were successfully completed and proven to work in Mauritius and Reunion Island, while pilots are being done for the Seychelles, Madagascar, and Brazil.

With a US$1.5 million grant from the Bill and Melinda Gates Foundation, and in collaboration with researchers at Tulane University in New Orleans, Chadee also developed a special trap that collects the eggs of mosquitoes and kills the adults as they lay. While the Tulane team is continuing with the initial design, Chadee is pioneering another and “far more effective” version he has refined in collaboration with scientists at James Cook University in Australia. Trials of the device began in Trinidad and also Down Under in January.

Should the testing yield the expected results — a massive reduction in the number of breeding mosquitoes and their eggs — the trap will be marketed by a German company. This crucial link, which will transform his idea and data into a commercially viable product that can be marketed and sold across the mosquito-ridden world, was procured by the Australian university. “That’s the reason you need to develop good collaborations,” Chadee points out.

Chadee’s expertise is, understandably, in great demand — by the World Health Organisation, the Pan American Health Organisation, CARICOM, and various governments (for example, Burkina Faso asked him for help in dealing with dengue). Chadee was also appointed a member of the Intergovernmental Panel on Climate Change (IPCC) in 2010, and since 2004 he’s been an adjunct professor in the Department of Epidemiology and the Global Public Health Programme at the University of Miami.

His current list of research projects includes the impact of cell tower radiation on the health and well-being of three study populations in Trinidad, and the rearing of Philornis downsi, a parasite that affects Darwin finches, which are now endangered. The International Atomic Energy Agency awarded Chadee and his compatriot John Agard — a fellow UWI professor and member of the IPCC — a research grant to help colonise the flies so biological controls could be developed. And in 2013 Chadee was awarded an Anthony N. Sabga Caribbean Award for Excellence, which came with a US$80,000 prize.

The idea of, say, taking a cruise with some of that award money makes Chadee burst into laughter. “I don’t go on vacation,” he explains. “Work is pleasure for me. I am absolutely delighted that people pay me to do this job and reward me for it.” And there are many productive ways to use the award, he says.

At the top of the list: completing a book on flooding and climate change, with a special focus on the Caribbean. Although the region suffers annually from hurricanes and storms, and the urbanisation of our islands is multiplying the effects of torrential rains and flash floods, very little data has been collected, and there is no literature to draw on. “We are hoping to change that with this book,” Chadee says, and given his track-record for groundbreaking science with big real-life impact, there’s no reason to doubt him.