What will a single-dose malaria drug mean for people in rural Brazil?

José de Souza Nogueira is 63 and says he has had malaria more than 130 times. It is an exceptionally high number, even for a country like Brazil, where the mosquito-borne disease is endemic. But doctors agree that it is quite possible for a smallholder farmer who has spent his entire life in rural areas – the mosquito’s preferred breeding ground.
“I work and live alone, selling what I grow: bananas, oranges, sugarcane, cassava … When I have malaria, I can’t tend to the plants,” he says.
Malaria causes misery for tens of thousands of people in Brazil every year. The most common type, Plasmodium vivax, is less deadly than the malaria typical in Africa, but can be trickier to combat.
The parasite can lie dormant in the liver before it once again flares up and causes symptoms – including fever, chills, muscle and joint pain, profuse sweating, nausea and vomiting.
Officials hope that the rollout of a new test and treatment regimen, now in its infancy, will help them eliminate the disease from Brazil by 2035.
Since the 1990s, the country has used two drugs to treat P. vivax: chloroquine for three days and primaquine for at least seven.
But because chloroquine combats the symptoms, many stop taking the medication after the first three days when they feel better, leaving the parasite in the liver to “wake up” after a few weeks or months.
Patients’ reticence to continue with treatment is understandable, says Eliana Pasini, the municipal health secretary of Porto Velho, the capital of the Amazon state of Rondônia, where Nogueiro lives.
“They need to work, they want to get back to work quickly,” she says. “Usually, these are small farmers, self-employed individuals, people who come from everywhere to this region in search of new opportunities.”
But it stores up future costs. “When a patient has a malaria relapse, you need to give them more medication, they may need to be hospitalised,” she says. “That’s why treatment abandonment is very bad for us, but also for the patient who will end up bedridden for days.”
So, Brazil is trying something new: it is the first malaria-endemic country in the world to adopt tafenoquine – a medicine taken as a single dose – for treating P. vivax cases.
When possible, primaquine will be replaced and the treatment will include chloroquine for three days and two pills of tafenoquine on the first day only.
The “new” drug was discovered in 1978 at the US Walter Reed Army Institute of Research but developed over the past 15 years by GlaxoSmithKline (GSK) and the Medicines for Malaria Venture (MMV).
Research conducted in Brazil – co-sponsored by the Brazilian and UK governments, MMV, the Bill & Melinda Gates Foundation and Newcrest Mining – between 2021 and 2022 showed tafenoquine was a feasible option for the country.
However, the new drug is not a silver bullet. It is unsuitable for infants under two years old and breastfeeding women. Although approved by the Brazilian Health Regulatory Authority for children weighing between 10kg and 35kg, it has not yet been introduced in those groups – and some of the areas it is being used in have high rates of malnutrition.
It also cannot be safely used without an accompanying test for a genetic quirk called G6PD enzyme deficiency, which means both primaquine and tafenoquine can be harmful.
Nogueira is among the 5% of people with the deficiency. The last time he had malaria was the worst: in early June, he spent five days in hospital in Porto Velho.
“I went days without being able to work, with a lot of dizziness; so I couldn’t make money,” he says. “I was feeling exhausted, with pain in my legs and head.” Doctors diagnosed him with high haemoglobin levels, apparently provoked by taking primaquine.
At the time, the tests for G6PD enzyme deficiency were not available. Only now – along with the implementation of tafenoquine – is the ministry of health distributing them, as a result of another study conducted by the same team. A fingertip drop of blood is placed in a portable device, with results in two minutes.
Making the tests available has required MedAccess, a British social enterprise, and Path, a US nonprofit, to provide a volume guarantee for the test manufacturer, the South Korea-based SD Biosensor.
Although primaquine can also be harmful to those with G6PD deficiency – as in Nogueira’s case – if doctors are aware, they can change and spread out doses and increase monitoring to reduce the risk. Tafenoquine, being a single-dose drug, cannot be spread out.
Brazil registered 131,000 cases of malaria (84% caused by P. vivax) in 2022 and is far from its goal of eliminating the disease by 2035. About 99% of Brazil’s malaria cases are concentrated in the Amazon states.
Nogueira lives in the Flor do Amazonas settlement in Candeias do Jamari , 15 miles (25km) away from Porto Velho’s centre. Porto Velho has 460,000 inhabitants but is spread over 13,000 sq miles, a larger area than Belgium. Parts can only be reached by river.
Pasini says the geography adds to the challenge of fighting malaria.
“There are many people living spread out over the vast territory, and there’s also a population that moves around a lot in search of work,” she says. “Some go to mining, others as small farmers.
“People start living where no one lived before. They start cutting down trees and come into contact with the mosquito, which infects one person, then another, and it becomes a network that is difficult to control, because these are not places you can reach quickly due to their difficult access,” she adds.
Since April, the government has provided training on tafenoquine and G6PD tests to more than 850 healthcare professionals from five cities. It insists that distribution is proceeding according to plan, although by 21 June the drugs and tests had yet to be used in patients.
In its first contract, the Brazilian government bought 15,000 tafenoquine doses from GSK for £4.30 each. This amounts to less than 15% of the total P. vivax cases in 2022.
Officials say another purchase of 103,000 doses was under way, and that the treatment should reach all the endemic cities “by the second half of 2026”.
Marcus Lacerda, a malaria researcher, says the cost of treatment may be an “achilles heel”. “The drug itself is not expensive, but the test is,” he says.
The government bought 1,400 devices from SD Biosensor for £210 each and 87,000 test slides for £2.35 each. According to the company’s representative in Brazil, about 5% of them have been delivered so far.
“When someone asks, ‘Brazil started using tafenoquine, will other countries do the same?’ I don’t know,” says Lacerda. “Because I don’t know if everyone will be able to invest in the G6PD test.”