Honduras has prevented dengue illness by educating people to fear insects and avoid their bites for decades. Hondurans are learning about a more effective disease control method that goes against all they’ve learnt.
Which is why a dozen people celebrated last month when Tegucigalpa resident Hector Enriquez hoisted a glass jar full of mosquitoes above his head and released them. Mason Enriquez, 52, volunteered to promote a dengue suppression scheme by releasing millions of unique insects in Honduran capital.
The mosquitoes Enriquez released in his dengue-endemic El Manchen neighborhood were developed by scientists to carry Wolbachia germs. These mosquitoes carry the bacterium to their offspring, limiting epidemics.
The charity World Mosquito Program developed this dengue technique over the last decade and is testing it in over a dozen nations. With more than half the world’s population at danger of dengue, the WHO is closely monitoring mosquito releases in Honduras and elsewhere and ready to promote the plan globally.
Over the next six months, Doctors Without Borders will release over nine million Wolbachia-carrying mosquitoes in Honduras, where 10,000 people contract dengue annually.
“There is a desperate need for new approaches,” mosquito programme founder Scott O’Neill said.
Recent decades have seen scientists reduce the threat of infectious diseases, especially mosquito-borne viruses like malaria. Dengue is the exception: infection rates keep rising.
Models anticipate 400 million dengue infections each year in 130 countries. Despite its low mortality rate (40,000 per year), dengue outbreaks can overwhelm health services and cause many individuals to miss work or school.
“When you come down with dengue fever, it’s often akin to getting the worst case of influenza you can imagine,” said Johns Hopkins mosquito researcher Conor McMeniman. McMeniman explained why it’s called “breakbone fever”.
Traditional mosquito-borne illness prevention hasn’t worked as well against dengue.
The most prevalent dengue mosquitoes, Aedes aegypti, are resistant to pesticides, which have only short-term effects. Dengue virus has four types, making vaccinations tougher to control.
Because they bite throughout the day, Aedes aegypti mosquitoes are difficult to control with bed nets. Climate change and urbanization will make dengue fighting harder because these insects flourish in warm, moist conditions and congested cities.
“We need better tools,” said WHO Global Neglected Tropical Diseases Program researcher Raman Velayudhan. Wolbachia is a long-term, sustainable remedy.”
As early as this month, Velayudhan and other WHO specialists will advocate testing the Wolbachia method in other countries.
Bacteria shock scientists
The Wolbachia method took decades.
The bacteria are found in 60% of insect species excluding the Aedes aegypti mosquito.
“We worked for years on this,” said O’Neill, 61, who using microscopic glass needles and his Australian students transferred bacterium from fruit flies into Aedes aegypti mosquito embryos.
Scientists tried to utilize Wolbachia to control mosquitoes 40 years ago. Scientists would release sick male mosquitoes into the wild to pair with uninfected females, whose eggs would not hatch.
O’Neill’s research discovered that Wolbachia-carrying mosquitoes didn’t spread dengue, yellow fever, Zika, or chikungunya.
Infected females carry Wolbachia to their progeny, “replace” a local mosquito population with one that harbors the virus-blocking bacteria.
Oliver Brady, an epidemiologist at the London School of Hygiene and Tropical Medicine, said the replacement method has changed mosquito control thinking.
“Everything in the past has been about killing mosquitoes, or preventing them from biting humans,” Brady said.
Since 2011, when O’Neill’s lab tested the replacement technique in Australia, the World Mosquito Program has tested it on 11 million people in 14 countries, including Brazil, Mexico, Colombia, Fiji, and Vietnam.
The results are promising. A large-scale field trial in Indonesia in 2019 found that releasing Wolbachia-infected mosquitoes reduced dengue cases by 76%.
O’Neill noted issues remain regarding the replacement strategy’s global efficacy and cost. The three-year Tegucigalpa study will cost $900,000, or $10 per person Doctors Without Borders aims to protect.
Scientists don’t know how Wolbachia prevents viruses. Bobby Reiner, a University of Washington mosquito researcher, said it’s unclear if the bacteria will work against all viral strains or if some may grow resistant.
Reiner remarked, “It’s certainly not a one-and-done fix, forever guaranteed.”
COLOMBIAN MOSQUITOES
The World Mosquito Program’s factory in Medellín, Colombia, produces 30 million Wolbachia-infected mosquitoes per week.
The factory imports dried mosquito eggs from around the world to ensure local mosquitoes have similar traits, such as insecticide resistance, according to Edgard Boquín, a Doctors Without Borders project leader in Honduras.
The dried eggs are soaked with powdered food. After hatching, they can breed with the “mother colony”—a Wolbachia-carrying lineage with more females than males.
A steady buzz fills the mosquito net-cube room where insects breed. Caregivers ensure the best diet: Females “bite” into 97 Fahrenheit pouches of human blood, while males drink sugared water.
“We have the perfect conditions,” manufacturing coordinator Marlene Salazar remarked.
After workers establish that the young mosquitoes possess Wolbachia, their eggs are dried and placed in pill-like capsules for release.
Honduran doctors help
Doctors Without Borders went door-to-door in a steep Tegucigalpa neighborhood to ask locals to incubate Medellin factory-bred mosquito eggs.
Glass jars with water and mosquito egg capsules were allowed to hang from tree branches at six dwellings. Mosquitoes hatch and fly after 10 days.
That day, a dozen young Doctors Without Borders employees rode motorcycles across Northern Tegucigalpa with jars of dengue-fighting insects and released thousands of them at selected spots.
Doctors and volunteers have spent the previous six months training neighborhood leaders, including significant gang members, to acquire their consent to work in their regions since community engagement is vital to the program’s success.
Community members frequently asked if Wolbachia will harm people or the environment. Workers said unique mosquitoes and their offspring bites were harmless.
María Fernanda Marín, a 19-year-old student, works for Doctors Without Borders, hatching Wolbachia-infected mosquitoes for release. She proudly shows neighbors a snapshot of her arm covered in bites to gain their trust.
Another Doctors Without Borders volunteer, Lourdes Betancourt, 63, was initially sceptical of the new tactic. Betancourt, who has been dengue-stricken multiple times, now advises her neighbors to breed “good mosquitoes” in their yards.
“I tell people not to be afraid, that this isn’t bad, to trust,” Betancourt added. “They’ll bite, but you won’t get dengue.”
