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The world spends at least $22 billion every year to kill mosquitoes that spread malaria, dengue and other devastating diseases.
With that money, billions of liters of insecticides, millions of kilograms of larvicides and 75 million mosquito nets treated with insecticides are purchased. Hundreds of millions of dollars more are invested each year in research into new ways to kill mosquitoes.
But as quickly as humans invent new ways to control them, insects develop ways to resist.
What if we left the mosquitoes alone? What if we focused on fixing the things that make people vulnerable to being bitten?
The area around Ifakara town has one of the highest malaria rates in the world. The Ifakara Health Institute, a tropical disease research center, has been studying ways to combat the disease for more than half a century. Some scientists believe that simple, relatively inexpensive changes in people’s homes can make a huge difference in preventing malaria and other mosquito-borne diseases that sicken millions of people a year.
That difference is illustrated by two houses located about 200 meters apart in the village of Chikuti, about 30 kilometers south of Ifakara.
One, at the top of a small hill, houses the kalalu family. Joram Kalalu, 54, and his wife, Malisa Uchaweli, live there with their 13-year-old daughter Omega. They are farmers and Mr. Kalalu also has a part-time job driving a bus to the city, where he pays the equivalent of $85 a month.
The other house, just down the hill and on the other side of the main road, belongs to the mtwaki family: Faustina Mtwaki, 37 years old, her husband, Matías Benjamín, and their seven children. They are also farmers, and Mtwaki brews a type of beer with dried corn that she sells in the neighborhood and earns $65 a month.
Malaria takes its toll on the Mtwaki family. The children develop their characteristic high fever and throbbing headache every two to three months, and Ms Mtwaki has to take time off work to care for them. Trips to the clinic for diagnoses and pills to kill the parasite consume much of the family’s income.
But now Kalalu and his family rarely get malaria. This year, his only fight came after Kalalu was badly bitten by mosquitoes while he was sleeping in a parking lot during a night bus shift.
Why has the Mtwaki family been so sick and the Kalalu family relatively spared?
Two houses, a huge difference in health
Both the Kalalus and the Mtwakis live in houses that they built themselves. The base material of each of them is made up of bricks, made with local earth. But there are some key differences between them, and they add up to critical protection.
Kalalu had worked for years as a miner, living in fields where malaria was a big problem, and saw his colleagues die from the disease. So protecting against malaria was a priority when the family set out to build their house. They bought sand and cement to cover the brick walls with plaster and sealed the gaps where mosquitoes would have entered.
But the Mtwakis stopped at bricks: the walls of their house are made of rough bricks with many gaps, and the unplastered walls keep the house dark and damp, a lure for mosquitoes.
Screened windows: $140
Sealed eaves: $50
Ventilation is important in these houses: it is hot and people often cook inside over a charcoal fire. An opening where the walls meet the ceiling can provide crucial air flow and an entry point for mosquitoes.
Mr. Kalalu’s sense that he was building a malaria-proof home is confirmed by more than just the relative absence of the disease in the family. Entomology teams from the Ifakara Health Institute are studying Chikuti and its malaria-carrying mosquitoes. In fact, they have carried out a nighttime mosquito census in the houses of Kalalu and Mtwaki, counting the insects that are active inside while the family sleeps.
There was 133 mosquitoes inside Mtwaki’s house one afternoon in May, but just 54 inside the Kalalu house.
In total, the Kalalu family spent $4,203 to build your house.
The Mtwaki family would like a similar house: like most families in the village and elsewhere, they have been saving money to make improvements when they can.
What would it take to convert the Mtwaki house into the Kalalus house?
Lina Finda, researcher at the Ifakara Health Institute, has done the calculations – for hundreds of families in this region.
A brand new house: $4,967
For Mtwaki’s house, the cheapest thing would be to start from scratch, he said, building a house with plaster walls, framed doors and windows and a metal roof. The total cost would be just under $5,000.
That is much more than the Mtwakis can afford. And Dr. Finda said the government of Tanzania and other national governments in Africa also consider the bill too high for their anti-malaria budgets.
“When we talk to the government, they say, ‘Oh no, we can’t afford to build a house for everyone,’” Dr. Finda says.
But not everyone needs new housing: 80 percent of malaria cases in Tanzania occur among the population living in the 20 percent of poorest quality houses, according to surveys by the health institute.
And most homes, Dr. Finda said, don’t need a complete rebuild; in fact, nearly 90 percent of the homes in her survey only needed framed and screen-covered windows. Most of the rest of the improvements the families have already made themselves, saving to make changes one by one.
The cost of upgrading a typical house around Ifakara to the point where it provides good protection against malaria is barely $258.
“But when we meet with the big donors, they want a new intervention, a new product, a silver bullet,” Dr. Finda said.
Compare that to the millions of dollars invested in developing insecticides or testing genetically modified mosquitoes. Or with the estimated economic impact of malaria in sub-Saharan Africa: 12 billion dollars a year. So $258 per house starts to seem more feasible.
But subsidizing some or all of the building materials would still be a big bill for governments or donors, and a growing bill as populations grow in sub-Saharan Africa.
There’s no doubt that housing improvement works, said Sarah Moore, a medical entomologist at the Ifakara Health Institute: It was essential to the elimination of malaria in the northern hemisphere. “But in terms of resources, my God, it’s huge,” she said, while Tanzania’s total annual health budget is just two dollars per person.
Experiments with all kinds of mosquito interventions are being carried out around Ifakara, and Dr Finda has observed that some of them help reduce the number of mosquitoes and cases of malaria. But in every village, he meets families like the Mtwakis, who do everything they can to save the money they need to make the changes they know will keep them safe.
“When we survey communities about what method people want, they ask: Can the government help us with this last step?” I have made this effort, now can we get a little push so we can maybe install mosquito nets on the window or door?
Produced by Matt McCann, Sean Catangui and Josefina Sedgwick.