Building a Cure for Malaria
Some experts believe eradication is impossible without major socio-economic development.
Chang’ombe, a rural village in the Tanga region of Tanzania. Image: Kaleigh Rogers/Motherboard
Malaria's Last Stand is an expository look at the ongoing burden of one of humanity's oldest diseases. Staff writer Kaleigh Rogers travelled to Tanzania to capture the scope of malaria's impact on the road to elimination. Read more here.
Kombo Juma gave me a feeble smile as he propped himself up on the hospital bed, his forehead slightly damp with sweat, and told me he's "feeling fresh now." The 23-year-old serviceman in the Tanzania People's Defence Force had been in the medical ward at the army training center in Mgambo for the last two days, sick with malaria. It's the first time he's ever had the illness.
"It's because he's from Zanzibar," explained the army officer giving me a tour. The officer then spun on his heels and called to another slim boy, resting in a bed across the room, and asked where he was from.
"Zanzibar," the soldier croaked. Same as the young man at the other end of the room, and the serviceman beside him.
In Tanzania, training in the National Service is compulsory upon graduation from high school, so young men and women from all over the country are often shipped to rural Mgambo—a moderately malaria-endemic part of the country. If they're from Zanzibar, they usually get sick, because unlike the rest of Tanzania, Zanzibar has virtually eliminated malaria. This was achieved through education efforts, distributing insecticide-treated mosquito nets, rapid diagnosis and treatment, and indoor insecticide spraying. These techniques have also been used across mainland Tanzania, and have contributed to cutting the malaria prevalence, but they achieved particular success in Zanzibar due to the realities of being an island—small, manageable, and easily quarantined from the rest of East Africa.
"But on the mainland ...we have too many neighbors and they're so closely linked geographically that you cannot separate them," said Dr. Yadon Kohi, a Major General with the TPDF who works on the military's malaria program. "There's no way you can prevent malaria in the Democratic Republic of Congo from coming here, for example. The mosquitoes don't have borders. They don't know these borders. They're everywhere."
Kohi is a proponent of the strategies that have been successfully cutting down the rates of malaria in Tanzania, and thinks we ought to continue investing in these life-saving efforts across sub-Saharan Africa, where malaria still kills hundreds of thousands of people each year. But when I pushed him on the topic, standing in an empty office down the hall from where the Zanzibari soldiers lay fevered, he admitted these efforts will only ever do so much. To truly achieve elimination locally (and, one day, global eradication), there's another essential piece to the puzzle: economic development.
"Why is the country of the United States malaria free? Because they are dealing with the vector. Clear the vector and you end malaria," Kohi told me. "Dealing with the parasite alone and not the vector, I don't think [malaria elimination] is something we can achieve. We must make our efforts towards that, but that's a big dream."
It was once a big dream in the United States, too. In 1933, nearly 125,000 Americans contracted malaria locally, mostly in the south. Five thousand died. Now, it's such a distant memory that many people don't even realize malaria was ever endemic to the US (or that we occasionally still have small, locally-transmitted outbreaks of the disease). In fact, the malaria rates in the US steadily declined after peaking in 1933, and by 1949 the country was considered free of malaria as any kind of significant health problem.
This is a disease that has plagued humankind since Ancient Egypt, and is estimated by some experts to have killed half of all humans who ever lived. Yet the US—where malaria thrived for generations after being first introduced by European settlers—wiped it out locally in less than two decades. In Europe, malaria rebounded in the 1980s and 90s, but it had similar success defeating the disease, and was recently declared malaria free once again, dropping from 90,000 cases per year to zero in just 20 years.
How did we make such short work of eliminating this deadly scourge in some parts of the world while struggling to whittle down its effects in others? The answer is, naturally, complicated. But it has just as much to do with economic development as it does with climate or culture.
The experts who spend their days trying to figure out how to defeat malaria often talk about attacking different parts of the "malaria cycle." The malaria parasite is transmitted from human to mosquito to human. Mosquitoes suck up gametocytes—adult versions of the parasite that are able to reproduce—circulating in the blood of an infected human. Inside the mosquito, these gametocytes produce sporozoites—kind of like baby parasites—which can then travel into a new human when the mosquito feeds. Inside the human, the sporozoites hide out in the liver, and then inside blood cells, where they mature and multiply, infecting the body.
Each strategy for combating malaria interrupts a different part of this cycle: insecticide treated bednets stop infectious mosquitoes from biting humans and releasing sporozoites into the body, while rapid diagnostic tests and treatment help nip an infection in the bud before it turns deadly. If we could fully interrupt the cycle, even temporarily, we could eliminate malaria in endemic areas.
In the US, the strategy to achieve this was brute force: attacking the mosquito and driving its numbers down to disrupt the cycle. We created a new government branch, the Office of Malaria Control in War Areas, in Atlanta, which later became the Centers for Disease Control. We sprayed long-lasting DDT inside people's homes, drained ditches so mosquitoes couldn't lay their eggs, and coated ponds with larvicide so even if they did, the hatchlings would die. It was effective, but it wasn't the only thing we were doing in the 1940s and 50s.
"What went unrecognized at the time, but had a huge impact on reducing malaria here in the southern US, was socio-economic development," said Dr. Patrick Kachur, the malaria branch chief for the division of parasitic diseases at the CDC Center for Global Health.
The electrification of the rural south meant people started spending evenings indoors. Soon radios gave an excuse to stay inside, then the TV, Kachur told me. Screened doors and windows became common. Houses were better insulated for weather and, by extension, mosquitoes. Fans were used to cool homes, and eventually air conditioners, making them both more enticing for humans and less accessible to mosquitoes. So while we were making a huge effort to diminish malaria-carrying mosquito populations, we were simultaneously spending less time around mosquitoes anyway.
"We did not eliminate the mosquitoes that carry malaria; they're still here," Kachur said. "We were able to eliminate the parasite by keeping the mosquitoes in very low numbers long enough to interrupt the transmission cycle."
Kachur said it's important to point out that we had a bit of an easier fight than in sub-Saharan Africa when it came to malaria. This is in part due to our temperate climate, which keeps mosquito populations at bay during the cold parts of the year. It's also because the type of mosquito that carries malaria in North America isn't picky about what it bites, while the species that spreads malaria in Africa loves humans. But Kachur said socio-economic development undeniably assisted the US's fight to rid the country of malaria.
"You can live in the heart of malaria territory, and if you are wealthy enough, it's not a problem."
Yet the global aid community has focused on simpler solutions for fighting malaria in the developing world: bed nets, insecticide, and education campaigns. This has unequivocally helped—annual global malaria deaths dropped from 839,000 in 2000, to 438 000 in 2015, according to the World Health Organization—but it hasn't eliminated malaria. And these methods are facing mounting pressure as the parasite develops resistance to each intervention. Many experts believe economic development is the only long-term solution.
"It's everything," said Sonia Shah, a science journalist and author of The Fever: How Malaria Has Ruled Humankind for 500,000 Years. "All of the other methods are essentially band-aid methods that work in the short term. They're a distant second to development."
Shah said aside from developing a potent vaccine—our best candidate is only 50 percent effective, and only in small children—she isn't convinced there's any way to eradicate malaria without prioritizing development. Though she said this approach takes longer, and isn't as easy as handing out free bed nets, it's proven to be effective not only in the US, but even in some of the most malaria endemic parts of the planet. Shah said when she travelled Blantyre, Malawi, she saw wealthy people who live in air conditioned houses, drive air conditioned cars, and work in air conditioned offices and don't take any kind of malaria prophylaxis.
"There's tons of malaria in Malawi—I mean just a ton, ton, ton ton," Shah told me over the phone. "To me that's really telling; You can live in the heart of malaria territory, and if you are wealthy enough, you don't even have to bother. It's not a problem."
Shah argued that prioritizing development as a malaria fighting strategy is also more effective because people locally will be more likely to embrace it. Though malaria kills 438,000 people a year, it annually infects 214 million, which means the percentage of people who die from malaria is extremely low. And because it's so common and frequent in some parts of the world, locals aren't as concerned about eradicating it. Shah compared it to the yearly flu here in the US, which kills thousands of Americans every year. We're aware of this, but it's so common, most people can't even be bothered to get a flu shot to prevent it. The only difference is that there's a lot more malaria in the world than there is flu, so the total number of people who die is exponentially higher.
The ubiquity of malaria in some parts of the world means cheap, easy strategies like bed nets may not always be embraced. But development? That's something everyone can get behind. Shah pointed to case studies like in Dar es Salaam, Tanzani's most populous city, where a pilot project focused on waste management after pinpointing garbage-clogged ditches as breeding hotspots for mosquitoes.
"Everyone liked it because that's useful for so many reasons, but it also was an effective malaria intervention," Shah said. "The problem is the political will and the money is coming from this movement of a one-size-fits-all solution when the things that are going to last are these little things."
But many malaria endemic countries already recognize this strategy, even if the global aid community doesn't. Back at the military training center, Kohi told me he hopes support will continue for the short-term solutions, to help keep malaria numbers as low as possible while the country develops. And he believes with time, Tanzania will build itself a cure for malaria.
"This country is lucky with natural resources," he said, pointing to the ground. "Where we are, I think there is gas and oil even where we are standing because there's gas 200 kilometers that way and there's gas 500 kilometers that way. Why wouldn't there be gas here? There probably is. When we get there, I think we will be able to solve this problem more practically."
Travel expenses while reporting this series were funded through a fellowship provided by the International Center for Journalists and Malaria No More.