Some overlooked good news from 2023: Six countries knock out 'neglected' diseases

The patient – a man in his mid-30s – was languishing in a hospital in Bangladesh, infected with a disease called visceral leishmaniasis. He was so close to death he wasn't even eligible for the inadequate treatment then available: Thirty painful injections with a drug that often didn't work.

The disease, which is caused by a parasite spread by the bite of sandlies, had swelled his organs, recalls Dr. Dinesh Mondal, of the Dhaka-based research institute icddr,b. "His spleen was so big. His liver was not functioning. He was just left to die."

So Mondal asked the man if he was willing to be the first Bangladeshi to try a new option – an antifungal drug that the U.S. pharmaceutical company Gilead Sciences had originally developed for patients battling cancer and AIDS.

"He told us that, 'I don't know if this will work. But this is the only hope for me. So I agree.' "

The transformation was immediate. "It was amazing," says Mondal. "Within three days he was feeling so good." Today, he says of the man, "He's alive. He's working. He's healthy now. I will never forget that moment."

It proved a pivotal one not just for the patient but for Bangladesh as a country – which in 2023 was one of six nations that were able to eliminate virtually all cases of at least one of the illnesses on the World Health Organization's priority list of "neglected tropical diseases."

Plenty of global health challenges await in 2024. But it's worth taking heart from these nations' success over the past year.

Neglected does not mean negligible

Dr. Albis Gabrielli is a top official in the World Health Organization's program for neglected tropical diseases. He stresses that the fact that for decades they'd been ignored does not mean they are obscure.

"We calculate that approximately 1 billion people are affected," says Gabrielli. And he adds that another 600 million people currently require interventions to ensure they are not infected. "So it's a significant proportion of the global population."

The trouble is the people who contract these diseases are among the world's lowest income citizens, living in some of the world's lowest resourced nations.

"People with no voice," says Gabrielli, "living in poverty in remote rural areas. And therefore the diseases are not, let's say, prioritized."

This historic indifference had extended to not just the health systems of the countries in which the diseases are found but also international donors as well as private pharmaceutical companies – who don't stand to make as much of a profit addressing them compared to diseases prevalent in wealthy countries.

But in the early 2000s, WHO and other global health partners came up with a plan to change that dynamic. They created an official list of neglected tropical diseases – currently covering 21 illnesses – to target with international research and cooperation.

Stopping the spread of trachoma has other consequences

Last July the effort hit a major milestone: Iraq became the 50th nation in the world to eliminate the threat from at least one of the diseases on the list by stamping out a bacterial infection called trachoma that causes blindness. And its certification came four months after two other nations, Benin and Mali, were also verified to have stopped trachoma's spread.

Neutralizing the disease has enormous benefits, says Gabrielli. "It's one of the leading causes of preventable blindness in many parts of the world."

He adds that the strategy for attacking trachoma has implications for other diseases. Trachoma can be transmitted when flies land on an infected person's eyes and nose, coming into contact with contaminated discharge and then spreading it to surfaces touched by other people. So health officials focused on administering antibiotics en masse to practically everyone in areas where trachoma was endemic.

"If you do it for one person the implication will be minimal," says Gabrielli. "But if you treat thousands of people at the same time, you decrease the transmission rate in the environment where these people live."

A landmark in the fight against visceral leishmaniasis

Bangladesh's victory against visceral leishmaniasis marks another step, because it's the first time a country afflicted with the disease has been able to end transmission.

Mondal, the Bangladeshi scientist, notes that the visceral leishmaniasis had been a scourge in Bangladesh for at least two centuries.

"The first reported outbreak was in 1824. The disease killed 75,000 people within three years," he says.

Mondal himself saw the consequences firsthand during an outbreak in the mid 2000s.

"When I visited, all the hospitals were full. Patients were lying on the floor," he recalls.

Yet Mondal says he also saw a glimmer of hope: A large majority of people exposed to the parasite manage to fight it off. It suggested to Mondal that more could be done to help those who were infected. And it motivated him to work with Bangladesh's government on eradicating the disease in coordination with WHO.

The result of that campaign has now exceeded his best expectations: It was the global focus on visceral leishmaniasis that led some scientists in the United Kingdom and India to look into the potential of Gilead's antifungal drug. A trial in India found it was almost 100% effective against visceral leishmaniasis.

Even then there was concern that it would be difficult to distribute the drug in Bangladesh's rural areas because it requires cold storage and special preparation just before it's administered.

But Mondal put together a new trial that showed that this obstacle could be overcome through outreach to health workers. "It was simple training," he says. "You explain everything. And it works."

WHO officials then helped negotiate a deal to drastically reduce the price of the new drug in low-income countries and followed up by donating doses to Bangladesh.

Other diseases on the ropes

Gabrielli, the WHO official, says it's also worth celebrating Bangladesh's other accomplishment in 2023: tackling lymphatic filariasis, better known as elephantiasis – which a second country, Laos, also eliminated in 2023.

"It's a disfiguring disease leading to swollen limbs and disfiguration of the human body," he notes. "So it's a disease that is associated with a lot of, not only physical suffering, but psychological suffering."

Lastly, adds Gabrielli, 2023 also saw Ghana triumph over gambiense human African trypanosomiasis.

"This is the 'sleeping sickness,' " says Gabrielli, "caused by a parasite transmitted by the tsetse fly." Essentially, the parasite kills an infected person by comprising their central nervous system. "So this is also a very severe disease."

For all the progress, in 2023 the WHO added a new entry to the neglected tropical disease list: A gangrenous illness called "Noma" that mostly afflicts malnourished young children.

Meanwhile, Mondal is concerned that Bangladesh's achievement against visceral leishmaniasis has already led to a drop in international funding to ensure the disease doesn't return.

"There's still a lot to do," he says.

For instance Mondal is currently researching an associated skin disorder that as many as 20% of recovered patients may go on to develop.

"These people are healthy clinically. But they harbor the parasite," he says. "So now the challenge is to search for them very actively and also bring them under treatment so that they cannot transmit the disease to others."

Mondal also worries that Bangladesh's government may find it harder to justify the expense of continuing one of the other strategies that proved successful against visceral leishmaniasis: frequent widespread fumigation of homes against sandflies.

So Mondal and collaborators are working on a potentially more cost-effective solution: a paint that contains insecticide that can be applied to walls. In trials he says, the impact was shown to last at least two years. And he hopes to develop it into a practical option for people to apply in their homes themselves.

It's too soon to relax the vigilance against this disease, he says. "We have to continue to prepare ourselves."