The Staggering Success of Vaccines

To Fight Malaria, Scientists Want To Poison Mosquitos—with Human Blood

Malaria causes more than 600,000 deaths each year, and is just one of numerous deadly human diseases transported by mosquitoes. But what if we could make our blood poisonous to the parasites that crave it?

While it sounds like science fiction, the idea isn't as far-fetched as it might sound.

In a study published today in the journal Science Translational Medicine, scientists report that a drug known as nitisinone can turn human blood so toxic to mosquitoes that they die within a few hours of feeding on samples from patients who received even relatively low doses. What's more, the drug remains effective for up to 16 days after the initial dosing. 

It's important to note that nitisinone does not itself protect against malaria infection. However, by killing the mosquitoes before they can lay eggs, the drug might be able to knock down disease-transmitting mosquito populations to the point that it breaks the chain of infection.

Like a vaccine that relies on herd immunity then, the promise isn't in being individually immune to malaria, but rather working together as a community to snuff out an outbreak.

(What would the world look like without mosquitoes?)

While the researchers caution that such a tool is not intended to fully eradicate mosquito-borne diseases, it may prove helpful in conjunction with other strategies, such as insecticide-laced bed nets, malaria prevention drugs, and vaccines themselves. The new tool might prove especially effective in areas where mosquitoes have already developed resistance to other treatments.

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"The interesting thing about this is that we're using a drug that is already FDA-approved, because it's used to treat rare genetic diseases," says Álvaro Acosta Serrano, a parasitologist, vector biologist and coauthor of the study.

A drug with an interesting history 

Inspired by a toxin in the Australian bottlebrush plant, nitisinone was originally intended for use as an herbicide. It worked by targeting an essential amino acid known as tyrosine.

A family of rare genetic disorders, such as tyrosinemia type I and alkaptonuria, occur when the body can't properly metabolize that same amino acid. Researchers found that nitisinone could be an effective treatment, so the U.S. Food and Drug Administration approved it for use in humans in 1992.  

"This is the only thing that has kept children with tyrosinemia type I alive," says Acosta Serrano. "It's not a perfect solution, but it's the only thing." While nitisinone causes an array of side effects in patients with such disorders, he says these populations typically have to take much higher quantities of the drug than would be needed for effective mosquito control.

Interestingly, in 2016 a pair of researchers in Brazil named Marcos Sterkel and Pedro Oliveira discovered that blood-feeding insects, such as fleas, flies, and mosquitoes have evolved the ability to rapidly process tyrosine, which their bodies are flooded with after a blood-meal.

More importantly, they also learned that if you can disrupt that process, the insect will die.

Knowing that Acosta Serrano's lab at the Liverpool School of Tropical Medicine in the United Kingdom worked on another disease-transmitting, blood-sucking parasite known as the tsetse fly, the researchers contacted him to see if nitisinone might have a role to play. Shortly after, the team expanded their work to look at nitisinone's effect on mosquitoes. 

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And that's how nitisinone went from killing plants to saving kids to potentially fighting against a deadly disease. 

(Are we entering a new era of mosquito control?)

No silver bullets for malaria

Because nitisinone has already passed rigorous safety standards, repurposing the drug to combat mosquito-borne diseases would also require fewer approvals, says Acosta Serrano, who is now at the University of Notre Dame. For instance, nitisinone is currently cleared for use in newborns and young children, and no harmful events have been recorded in pregnant people. That's one reason the results are promising.

"I think the study is very interesting," says George Dimopoulos, a molecular biologist specializing in mosquito-borne diseases at the Johns Hopkins Bloomberg School of Public Health.

For starters, the idea that nitisinone might be useful in combatting mosquito-borne diseases is entirely new, he says. It's also intriguing that side effects seem to be less than those seen in ivermectin, a drug which can also be used to prevent malaria transmission, and the efficacy greater.

Of course, Dimopoulos also pointed to several drawbacks.

"Malaria is a disease of poverty," says Dimopoulos. "Anything that becomes expensive or costly is not going to work, especially for an intervention method like this, where you don't actually protect the individual from malaria, but you protect the population." 

The rarity of the diseases that nitisinone treats means the drug is still too expensive for widespread deployment. With more research interest, though, Acosta Serrano hopes that the costs of nitisinone could be reduced by as much as 80 percent.

The indirect nature of prevention could also be a roadblock. "It's always tricky to convince people to take a drug that doesn't protect them," says Dimopoulos.

However, it may be possible in the future to combine a nitisinone treatment with an anti-malarial medication, he says. Likewise, the treatment might be made more effective by applying it to nearby livestock, which in effect work kind of like mosquito bait.

Similarly, because mosquitoes also rely upon nectar as a food source, scientists have also experimented with creating bags of nectar laced with insecticide that could target mosquitoes without exposing other pollinators to the poison.

"So in theory, you could also use this drug to expose mosquitoes through that technology," says Dimopoulos. "You would not necessarily have to administer it to humans."

Resistance is also a worry with any mosquito control method. But only time will tell if the critters could evolve to tolerate the toxin. 

Whatever role nitisinone might play in the future, both Acosta Serrano and Dimopoulos agree that it will be most effective as part of a multi-faceted approach that is tailored to each population.

 "In some places, drugs combined with the vaccines could work better. In other places, insecticide spraying and new technologies, like genetically engineered mosquitoes, for example, could have greater efficacy," says Dimopoulos. "It's a little bit like personalized medicine."

"There is no silver bullet for malaria," he says. "And I don't think there will ever be a silver bullet."

A Faster Rollout Of Malaria Vaccines Would Save Many Lives

WHEN PAULINE OTIENO'S second child caught malaria, a decade ago, it meant an anxious, feverish week in hospital. When her third-born fell sick recently, he recovered after being given some pills and a few days' rest. The difference might have been luck, or it might have something to do with the world's first malaria vaccine. It has been available at Ms Otieno's local clinic in Migori county, in south-western Kenya, since 2019. Her third child had received it; the second had not.

No Disease Is Deadlier In Africa Than Malaria. Trump's U.S. Aid Cuts Weaken The Fight Against It

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KAMPALA, Uganda — Malaria season begins this month in a large part of Africa, and no disease is deadlier on the continent, especially for children. The Trump administration's decision to terminate 90% of USAID's foreign aid contracts has local health officials warning of catastrophe in some of the world's poorest communities. The U.S. Has been the top bilateral funder of anti-malaria efforts in Africa. Africa's 1.5 billion people accounted for 95% of an estimated 597,000 malaria deaths worldwide in 2023, according to the World Health Organization (WHO).

The USAID stop-work orders issued in late January left Dr. Jimmy Opigo, who runs Uganda's malaria control program, and others "focusing on disaster preparedness," he told the Association press.

Anti-malarial medicines and insecticide-treated bed nets that help control the mosquito-borne disease are "like our groceries," Opigo said. "There's got to be continuous supply."

Related: Trump's ending of 90% of USAID foreign aid contracts slams programs around the world

As those resources dwindle with the termination of U.S. Contracts, Opigo said he expects a rise in cases of severe malaria later this year, including problems like organ failure. There is no cure. Vaccines being rolled out in parts of Africa are imperfect, but are expected to largely continue with the support of a global vaccine alliance.

The Washington, D.C.-based Malaria No More said new modeling shows that just a year of disruption in the malaria-control supply chain would lead to nearly 15 million additional cases and 107,000 additional deaths globally. The organization has urged the Trump administration to "restart these life-saving programs before outbreaks get out of hand."

Health workers in the three African nations most burdened by malaria — Nigeria, Congo, and Uganda — described a cascade of effects with the end of most U.S. Government support. The U.S. Has provided hundreds of millions of dollars every year to the three countries alone through the USAID-led President's Malaria Initiative. The U.S. Funding has often been channeled through a web of non-governmental organizations, medical charities, and faith-based organizations in projects that made malaria prevention and treatment more accessible, even free, especially for rural communities.

Uganda had 12.6 million malaria cases in 2023 and nearly 16,000 deaths, many of them children under 5 and pregnant women, according to WHO.

Opigo said the U.S. Has been giving between $30 million and $35 million annually for malaria control. He didn't say which contracts have been terminated but noted that field research was also affected.

Some of the USAID funding in Uganda paid for mosquito-spraying operations in remote areas, which were supposed to begin in February before the rainy season, when stagnant water becomes a breeding ground for the wide-ranging anopheles mosquito. They have been suspended.

"We have to spray the houses before the rains, when the mosquitoes come to multiply," Opigo said.

Long lines of malaria patients can be seen outside clinics in many areas every year. Malaria accounts for 30% to 50% of outpatient visits to health facilities across the country, according to the Uganda National Institute of Public Health.

Nigeria and Congo

Nigeria records a quarter of the world's malaria cases, but authorities have reduced malaria-related deaths there by 55% since 2000 with the support of the U.S. And others. That support is part of the $600 million in health assistance the west African country received from the U.S. In 2023, according to U.S. Embassy figures. It was not immediately clear whether all of that funding has stopped.

The President's Malaria Initiative has supported Nigeria's malaria response with nearly 164 million fast-acting medicines, 83 million insecticide-treated bed nets, more than 100 million rapid diagnostic tests, 22 million preventive treatments in pregnancy, and insecticide for 121,000 homes since 2011, the embassy says.

In Congo, U.S government funding has contributed about $650 million toward malaria control since 2010. Now, some of the successes in fighting malaria in Congo are being threatened, which will complicate already difficult efforts to identify and track disease outbreaks across the vast country as supplies and expertise for malaria testing are affected.

Worsening conflict in Congo's east, where some health workers have fled, has raised the risk of infection, with little backup coming.

With the loss of substantial U.S. Support, "a lot of people are going to be affected. Some people are really poor and cannot afford (malaria treatment)," said Dr. Yetunde Ayo-Oyalowo, a Nigerian who runs the Market Doctors nonprofit, which provides affordable local healthcare services.

Up to 40% of her organization's clients are diagnosed with malaria, Ayo-Oyalowo said.

There is hope among health workers in Africa that, even after the dismantling of USAID, some U.S. Funding will continue flowing via other groups, including the Global Fund to Fight AIDS, Tuberculosis and Malaria — but that group also received U.S. Support and has not issued a public statement about the dramatic cuts in U.S. Aid or whether its services will be affected.

Opigo said the U.S. Centers for Disease Control and Prevention and the National Institutes of Health might be sources of help.

However, "we need to manage the relationship with the U.S. Very carefully," he added.

___

Chinedu Asadu reported from Abuja, Nigeria. AP journalist Dan Ikpoyi in Lagos, Nigeria, contributed.

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