Sleeping sickness

ALSO KNOWN AS: West African trypanosomiasis, Gambian sleeping sickness, East African trypanosomiasis

ANATOMY OR SYSTEM AFFECTED: Brain, heart, lymphatic system, nervous system, psychic-emotional system

DEFINITION: A parasitic disease caused by protozoa and transmitted to humans by the bites of infected tsetse flies

CAUSES: Parasitic infection transmitted by tsetse flies

SYMPTOMS: Painful sore at bite, swollen lymph nodes, high fever, severe headache, joint pain, fatigue, rashes, liver and spleen enlargement, edema, weight loss, debilitation, heart failure; in late stage, appetite loss, listlessness, personality changes, insomnia, tremors, slurred speech, unsteady gait, uncontrollable drowsiness, coma, and death

DURATION: A few weeks to months; progressive and fatal if untreated

TREATMENTS: Toxic drugs (suramin, melarsoprol) for both types; nontoxic drug (eflornithine) for West African type

Causes and Symptoms

Sleeping sickness is a vector-transmitted parasitic disease caused by Trypanosoma. These protozoa are transmitted to humans by the tsetse fly, Glossina, which is found only in moist savannas and forests in parts of sub-Saharan Africa. Rarely, can occur from a mother to her unborn child or through blood or organ transplantation. There are two types of sleeping sickness. West African trypanosomiasis is found in both Central and West Africa. Also called Gambian sleeping sickness, it is caused by Trypanosoma brucei gambiense. East African trypanosomiasis is caused by T. brucei rhodesiense. Another human form of trypanosomiasis, Chagas disease, is found in the Western Hemisphere.

Symptoms of the East African type emerge in three stages. Untreated victims of this acute form of the illness may die within weeks or one year later. The first stage begins with the reaction to the tsetse fly’s bite. A painful sore, called a chancre, appears about forty-eight hours after the bite and lasts from two to four weeks. It is accompanied by swollen lymph nodes. The second or early stage includes high fever, severe headache, joint pain, and fatigue; symptoms appear in waves, with symptom-free periods that can last up to two weeks. Rashes, swollen lymph nodes, enlargement of the liver and spleen, and may also occur. As the disease progresses, weight loss and debilitation increase. Heart involvement may appear early; some patients succumb to before the parasites invade the central nervous system. In the late stage, which appears within a few weeks to months of the infection, loss of appetite, personality changes, headache, listlessness, and are seen, along with tremors, slurred speech, and unsteady gait. Uncontrollable drowsiness occurs late in the course of the disease, progressing to and finally death, often from secondary infections.

West African sleeping sickness is a chronic illness, though just as deadly as the East African variety if left untreated. Instead of three distinct stages, there is usually a long symptom-free period. Often, no chancre appears, and the early stage may be so mild as to be overlooked, although swollen lymph nodes on the back of the neck, called Winterbottom’s sign, may be visible. Symptoms gradually appear weeks or years later but are often so subtle that they continue to be ignored. Ironically, the lack of symptoms can be very dangerous for the patient because early treatment of sleeping sickness is critical in avoiding disability or death.

Treatment and Therapy

Most of the drugs used to treat sleeping sickness are highly toxic. Mortality from drug toxicity can reach 5 to 10 percent. In addition, some of the drugs cannot cross the blood-brain barrier, so they are useless in late-stage illness. One nontoxic drug, eflornithine, not only crosses the barrier but also is highly effective in treating both early-stage and late-stage West African infection. It is not used for East African illness, however, because it is not consistently effective for that type. In addition, it is expensive and difficult to administer correctly. Thus, for both types of early-stage infection, intravenous suramin (or suramine) is often used after giving a test dose to see how patients will tolerate the drug, with intravenous melarsoprol given for late-stage disease of both types. With treatment, most patients recover. However, irreversible damage or death is common when therapy is attempted at the later stage.

Perspective and Prospects

Sleeping sickness had been endemic in about one-third of Africa’s total land area and infected between 300,000 and 500,000 people were annually. However, the reported that efforts to contain the disease in the twenty-first century have made significant strides toward eradicating sleeping sickness. The WHO estimated incidents of the disease have decreased 97 percent in the first two decades of the century. According to the WHO, there were fewer than one thousand cases reported in 2018. As of 2022, the WHO reported cases had not crossed that threshold. Prior to the medical successes of the century, in some areas of Angola, the Democratic Republic of Congo, and southern Sudan, sleeping sickness was the first or second greatest cause of mortality during an epidemic of the disease, ahead of human immunodeficiency virus (HIV) or AIDS. Its worst effects were felt in remote, rural areas where health infrastructure is often nonexistent.

Suramin was discovered in 1921. Pentamidine, sometimes used in treating the early stage of West African sleeping sickness, was discovered in 1941. Melarsoprol, the last arsenic-based medicine still in use, was discovered in 1949. Eflornithine was registered for use in sleeping sickness in 1990 and is approved in the United States for topical use in removing facial hair. None is an ideal drug, and most are difficult to administer under less-than-ideal conditions. Early diagnosis is likewise not easy or inexpensive.

The tragedy is that sleeping sickness had almost disappeared by the early 1960s, but strict and control efforts were allowed to lapse, allowing the disease to reestablish itself and become endemic in many areas. In an effort to once again reverse the spread of the disease, WHO created the Program for Surveillance and Control of African Trypanosomiasis (PSCAT), which unites national programs, nongovernmental organizations, private foundations, universities, regional centers, and donor countries in an effort to reach the common goal of permanent eradication.

Bibliography

Dumas, Michel, et al., editors. Progress in Human African Trypanosomiasis, Sleeping Sickness. Springer, 1999.

Hoppe, Kirk Arden. Lords of the Fly: Sleeping Sickness Control in British East Africa, 1900–1960. Praeger, 2003.

Lyons, Maryinez. The Colonial Disease: A Social History of Sleeping Sickness in Northern Zaire, 1900–1940. Cambridge UP, 1992.

"Parasites—African Trypanosomiasis (Also Known as Sleeping Sickness)." Centers for Disease Control and Prevention, 6 June 2023, www.cdc.gov/parasites/sleepingsickness/. Accessed 8 Apr. 2024.

Ramen, Fred. Sleeping Sickness and Other Parasitic Tropical Diseases. Rosen, 2002.

"Trypanosomiasis, Human African (Sleeping Sickness)." World Health Organization, 2 May 2023, www.who.int/news-room/fact-sheets/detail/trypanosomiasis-human-african-(sleeping-sickness). Accessed 9 Apr. 2024.

"Sleeping Sickness." MedlinePlus, medlineplus.gov/ency/article/001362.htm. Accessed 8 Apr. 2024.

World Health Organization. Control and Surveillance of African Trypanosomiasis: Report of a WHO Expert Committee. World Health Organization, 1998.