11 September 2024

How the fight against sleeping sickness was won

We are closer than ever before to consigning the “the colonial disease” to history.

As we grapple with the ongoing threat of Mpox and the scars of Covid remain raw, there is reason for cautious celebration: we are on the brink of eradicating a brutal disease that has tormented Africa for generations. The World Health Organisation’s (WHO) technical advisory group on human African trypanosomiasis – commonly known as sleeping sickness – has confirmed that elimination by 2030 is within sight.

Sleeping sickness has been termed “the colonial disease” because of its inextricable links with the European scramble for Africa. When the British established Uganda as a protectorate, they displaced local communities to cultivate seemingly fertile land. The disaster that followed made clear why locals had avoided the tsetse-fly-infested regions for centuries. Between 1901 and 1906, more than 250,000 Ugandans died from this parasite-driven illness, which attacks the bloodstream in its first stage and later wreaks havoc on the central nervous system, disrupting the sleep cycle (hence its colloquial name) and causing profound neurological deterioration. During a 1907 visit, Winston Churchill was appalled by this “scourge”, and called for urgent action in his book My African Journey.

Colonial powers across West Africa and the Belgian Congo enacted similar strategies with equally tragic results. By the end of the 19th century, sleeping sickness had solidified its place in the European imagination as an exotic, faraway affliction of others. Joseph Conrad’s Heart of Darkness alluded to the horrors of the disease, while Henry Seton Merriman’s lesser-known but equally visceral novel 1894 novel With Edged Tools dealt directly with the scourge of colonialism, with sleeping sickness taking centre-stage.

In 1902 a Royal Society commission set out to investigate the Ugandan epidemic. Aldo Castellani, a young Italian doctor studying at what was then called the London School of Tropical Medicine, first detected the disease’s culprit, trypanosomes, in the cerebrospinal fluid of patients, but overlooked their importance, blaming a streptococcal bacterium instead. It was the Scottish physician David Bruce, who attended Edinburgh Medical School alongside Arthur Conan Doyle, who got credit for attributing the disease to the parasite. Bruce had earlier made a decisive link between tsetse flies and trypanosome transmission. Bruce’s sleuth-like instincts – well suited for a Sherlock Holmes novel – led to crucial breakthroughs in understanding the disease.

Once the tsetse fly was identified as the vector, colonial authorities initiated aggressive interventions. Tsetse, alongside other wildlife thought to harbour the parasite, were killed, and those people forcibly resettled into tsetse-prone areas were removed with equal vigour and confined to high-density camps. Efforts to find a cure began, and even arsenic – administered in crude formulations – was employed. Remarkably, the arsenic-based drug melarsoprol, notorious for its severe toxicity, remains in occasional use today though, thankfully, new and safer treatments are now available.

As European powers withdrew from Africa in the mid 20th century, many left behind fragile infrastructures, though sleeping sickness levels had fallen to manageable levels. However, by the late 20th century, competing health crises – malaria, tuberculosis and HIV/Aids – eclipsed efforts to control sleeping sickness, which resurged with a vengeance. By 1999, estimates put the number of cases at 300,000, and overwhelmed health systems were struggling to cope. It seemed the “colonial disease” was back.

In the 1980s, the development of eflornithine, a drug which was originally designed to combat cancer but proved effective in treating sleeping sickness even in its advanced stages, offered hope. However, eflornithine is expensive to manufacture and pharmaceutical companies weren’t prepared to make it for sleeping sickness patients in rural Africa, who comprised the world’s poorest populations. However, when it was serendipitously discovered that eflornithine could inhibit hair growth, Western pharmaceutical companies, uninterested in producing the drug for impoverished African patients, rushed to commercialise it for cosmetic use, offering it to women as a solution to the embarrassment of unwanted facial hair. This scandal laid bare the priorities of the global pharmaceutical industry.

Outrage over this disparity spurred change. The French pharmaceutical giant Aventis (now Sanofi) answered the WHO’s plea to produce eflornithine for free. It also provided the WHO with the funds needed to screen patients and distribute the drug. Sanofi now provides all its sleeping sickness drugs to the WHO without charge, and Bayer has joined in too. Médecins Sans Frontières and partners created the Drugs for Neglected Diseases initiative (DNDi) with the goal of developing treatments for diseases overlooked by profit-driven pharmaceutical companies. New diagnostic tools have become available, and other pharmaceutical companies, notably GSK and Novartis, have brought sleeping sickness, along with several other neglected tropical diseases, into their portfolio. The Gates Foundation picked sleeping sickness as one of its earliest target diseases and has provided millions of dollars to help the fight.

By 2018, DNDi had developed fexinidazole, a safe, orally administered drug that lacks the toxicity of the arsenical drugs and avoids the need for injections. Fexinidazole’s anti-trypanosomal activity had first been shown at the University of Glasgow 41 years earlier but with no investment its development had stalled. Being suitable for both stages of the disease, fexinidazole also avoids invasive diagnostic procedures previously required (including sticking a needle into the spinal cord to determine if the disease has progressed to the second, neurological stage). Another drug, acoziborole, which cures even advanced cases with a single dose – a truly remarkable advance – is expected to be available soon. The arduous and often dangerous treatments of the past will, hopefully, soon be relics of history.

Thanks to international cooperation, sleeping sickness is no longer considered a public health problem (the threshold is defined as affecting fewer than one in 10,000 people in endemic areas). Full eradication by 2030 remains the goal, but challenges persist. Guinea worm, for example, which in the 1980s afflicted some 3.5 million people, has had fewer than 60 cases reported annually for nearly a decade. However, reduction to zero has been incredibly difficult to achieve. The last mile in elimination campaigns is often the hardest. The drive to end sleeping sickness may yet face a similar struggle.

Still, we are close – closer than ever before – to consigning this horrific “the colonial disease” to history, alongside smallpox, as an affliction eliminated through deliberate and determined human intervention.

[See also: Medicine wars]