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DISCOVER


MOSQUITO MAN


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 Photography by Alex Smailes


C


onsider 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.


84 WWW.CARIBBEAN-BEAT.COM 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 Internat ional 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 ster i l ising 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 ref ined in collaboration with scientists at James Cook University in Australia.


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