miércoles, mayo 22

One Village, Two Houses — and a New Tactic to Win the War on Mosquitoes

The world spends at least $22 billion every year to kill mosquitoes that spread malaria, dengue and other devastating diseases.

That money buys billions of liters of insecticides, millions of kilograms of larvicides and 75 million insecticide-treated bed nets. Hundreds of millions more dollars are poured into research each year on new ways to kill mosquitoes.

But as quickly as humans invent new ways to control them, the insects evolve ways to resist.

What if we left mosquitoes alone? What if we focused instead on fixing the things that make people vulnerable to getting bitten?

The area around the town of Ifakara has one of the highest malaria rates in the world. The Ifakara Health Institute, a tropical disease research center, has been studying ways to fight the illness for more than a half century. Some scientists there believe that simple, relatively inexpensive changes to people’s homes can make an enormous difference in preventing malaria and other mosquito-borne diseases that sicken millions of people a year.

That difference is illustrated by two houses that sit about 200 yards apart in the village of Chikuti, about 30 miles south of Ifakara.

One, at the top of a small hill, is home to 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 town, which pays the equivalent of $85 a month.

The other house, just down the hill and across the main road, belongs to the Mtwaki family: Faustina Mtwaki, 37, her husband, Matias Benjamin, and their seven children. They are farmers, too, and Ms. Mtwaki makes a type of beer out of dried corn that she sells in the neighborhood, earning $65 a month.

Malaria takes a huge toll on the Mtwaki family. The children develop its signature high fever and pounding headache every two or three months, and Ms. Mtwaki has to set aside her work to care for them. Trips to the clinic for diagnoses, and pills to kill the parasite, eat up much of the family’s income.

But Mr. Kalalu and his family rarely get malaria now. This year, their only bout came after Mr. Kalalu was badly bitten by mosquitoes when he slept in a parking lot on an overnight bus shift.

Why has the Mtwaki family been so sick, and the Kalalu family relatively spared?

Both the Kalalus and the Mtwakis live in homes they built themselves. The base material of each is composed of bricks, made from local soil. But there are a few key differences between them — and they add up to critical protection.


Mr. Kalalu had worked for years as a miner, living in camps where malaria was a huge problem, and he saw colleagues die from the disease. So malaria-proofing was a top priority when the family set out to build their home. They bought sand and cement to cover the brick walls with plaster and they sealed the gaps where mosquitoes would have flown through.

But the Mtwakis stopped at bricks: The walls of their house are made of rough brick with plenty of gaps, and the unplastered walls keep the house dark and damp — a lure for mosquitoes.


Ventilation is important in these houses: It’s hot, and cooking often happens inside over a charcoal fire. An opening where the walls meet the roof can provide crucial air flow — and an entry point for mosquitoes.

Mr. Kalalu’s sense that he was building a malaria-protected home is borne out by more than just the family’s relative freedom from the disease. Entomology teams from the Ifakara Health Institute are studying Chikuti and its malaria-carrying mosquitoes. In fact, they have taken a nighttime mosquito census of both the Kalalu and Mtwaki homes, counting the insects that are active inside while the family sleeps.

There were 133 mosquitoes inside the Mtwaki home on a May evening, but just 54 inside the Kalalu home.

All told, the Kalalu family spent $4,203 to build their house.

The Mtwaki family would like a similar house: Like most families in the village, and families everywhere, they’ve been saving up money to make improvements when they can.

What would it take to turn the Mtwaki home into the Kalalus’?

Lina Finda, a researcher at the Ifakara Health Institute, has done the math — for hundreds of families in this region.

For the Mtwaki home, the cheapest thing to do would be to start from scratch, she said, building a house with plaster walls, framed doors and windows and a metal roof. The total cost would come in at just under $5,000.

That’s way more than the Mtwakis can afford. And Dr. Finda said the government of Tanzania and other national governments in Africa also view the bill as too steep for their malaria budgets.

“When we talk to government, they say, ‘Oh no, we can’t pay to build everyone a house,’” Dr. Finda says.

But not everyone needs a new home: 80 percent of malaria cases in Tanzania happen within the population that lives in the 20 percent of houses that are of the lowest quality, according to surveys from the health institute.

And most homes, Dr. Finda said, don’t need a complete rebuild — in fact almost 90 percent of houses in her surveys needed only framed, mesh-covered windows. Most of the rest of the improvements, families have already done themselves, saving up to make changes one by one.

The cost to upgrade the typical house around Ifakara to the point that it provides good malaria protection is just $258.

“But when we meet with the big donors, they want a new intervention, a new commodity, a silver bullet,” Dr. Finda said.

Compare that with the millions of dollars being thrown into developing insecticides or testing genetically modified mosquitoes. Or with the estimated economic impact of malaria on sub-Saharan Africa: $12 billion a year. Then $258 per house starts to sound more feasible.

But subsidizing part or all of the building materials would still be a big bill for governments, or donors, and an expanding one, as populations grow across sub-Saharan Africa.

There’s no question that improved housing works, said Sarah Moore, a medical entomologist at the Ifakara Health Institute — it was essential for the elimination of malaria in the Northern Hemisphere. “But in terms of resources, my God, it’s enormous,” she said — while Tanzania’s total health budget annually is just $2 per person.

There are experiments with all kinds of mosquito interventions underway around Ifakara, and Dr. Finda has seen some of them help to lower mosquito numbers and malaria cases. But in every village, she meets families such as the Mtwakis, doing their best to save up the money they need to make the changes they know will keep them safe.

“When we do surveys in communities about what method people want, they ask: Can the government help us through this last step? I have made this effort, now can we get a little push so that we can install maybe screens on the window or the door?”

Produced by Matt McCann, Sean Catangui and Josephine Sedgwick.