Written by Ashley Fang, Peer Reviewed by Nikhil Chakravarty, Edited by Courtney Coleman
African trypanosomiasis, more commonly known as African sleeping sickness, is a vector-borne parasitic disease, which is a disease resulting from an infection transmitted by blood-feeding arthropods, such as mosquitoes. There are currently two categories of African trypanosomiasis: East African and West African (1, 2). While East and West African trypanosomiasis are caused by two different species of parasite (Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense, respectively), both can cause serious, potentially fatal, illness (1). West African sleeping sickness is much more common, accounting for 98% of cases documented in humans (3). It also unfortunately induces more chronic effects than East African sleeping sickness, which mainly infects wild animals and cattle (3). Although only one U.S. citizen is infected each year, on average, with infection being linked to traveling to Africa, it is crucial to become more well-informed on this topic, as this disease is categorized as a neglected tropical disease by the World Health Organization (2). This designation implies that, while the disease is treatable and preventable, it does not receive the attention or funding needed to significantly improve the livelihoods of the infected. Since African trypanosomiasis primarily affects those in poverty and the African economy at large through disrupting agricultural productivity and local markets (3), it’s the responsibility of those less at risk of being affected to be an ally, or even directly contribute resources (such as donating to the World Health Organization), to help support those suffering from the consequences of African trypanosomiasis.
Statistics
Approximately 40,000 cases of African sleeping sickness were reported in 1998 (4). When Africa experienced a trypanosomiasis epidemic in the early 2000s, 50% of villages in Angola, Democratic Republic of the Congo, and South Sudan were affected, experiencing a mortality rate greater than that of HIV/AIDS (4). As shown in Figure 1, after continued control efforts by the World Health Organization and financial donors, only 663 cases were reported in 2020.
Figure 1. Number of reported cases for African trypanosomiasis depicting a 96% reduction in cases: Africa, 2000-2020. (Source: World Health Organization)
Transmission
Both types of African trypanosomiasis are transmitted by a species of tsetse fly found only in rural Africa, particularly in savanna woodland thickets and streams with dense vegetation (1, 2). To transmit disease, tsetse flies infected with either the Trypanosoma brucei rhodesiense or Trypanosoma brucei gambiense parasites bite humans (1). Though the proportion of tsetse flies infected with parasites is not very high, the consequences for the infected host can be dire, including potential re-infection. Disease transmission between humans, albeit poorly documented and rare, can occur through several mechanisms, including from an infected pregnant woman to her baby, through sexual intercourse, blood transfusion, and organ transplants (1). Furthermore, population displacement, war, and poverty facilitate disease transmission (4). Poor documentation of this disease is due to its higher occurrence in rural settings with limited access to healthcare. Overall, an estimated 60-70 million people across 36 sub-Saharan African countries, including Central Africa Republic, Congo, and Democratic Republic of the Congo, are at risk of infection (2, 3).
Figure 2. Map of Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense parasite spread across sub-Saharan Africa and infections per km2 per year: 2000-2017. (Source: Buscher et al., Lancet, 2017)
Symptoms and Diagnoses
Infection with African trypanosomiasis occurs in two stages. First, parasites target the blood and lymphatic system, and second, proceed to invade the central nervous system (CNS) (1). Early on, individuals exhibit more mild symptoms, such as fever, headache, and muscle/joint pain (3). As the disease progresses to the CNS, mental impairment, seizures, and difficulty moving manifest (3). In addition, those infected experience a disruption of their sleep-wake cycle, often suffering from daytime sleepiness and nighttime insomnia – hence why it is called African sleeping sickness. It is important to note, though, that not all individuals report this symptom (2, 3). Those with East African trypanosomiasis typically observe symptoms within 1-3 weeks after initial infection and progress to the second phase in a few weeks. Because of its rapid progression, death can occur within several months if left untreated. On the other hand, those with West African trypanosomiasis can experience symptoms intermittently, with symptoms becoming apparent in a few months to a year. If untreated, it can be fatal within three years (1).
Luckily, there are diagnostic tests available to evaluate the presence of infection and stage of disease. Blood and lymph fluid tests can be used to detect the presence of both the West and East African variants (3). To determine if the parasite has reached the central nervous system, doctors may also utilize a cerebrospinal fluid test (3).
Treatment and Prevention
Treatment of West and East African trypanosomiasis can also be divided into two stages (3). For West African trypanosomiasis, first stage treatment involves intravenous or intramuscular injection of the drug pentamidine. In second stage treatment, when the CNS is affected, the drug eflornithine is administered intravenously four times daily for two weeks. Though this drug is very effective, frequently, it is difficult to treat patients due to the poor organization of clinics and hospitals in rural Africa. As such, eflornithine is usually used with nifurtimox to balance the positive effects of eflornithine with its inconsistent administration. For East African trypanosomiasis, the suramin drug is used to treat first-stage infection. It is known to have mild but reversible side effects, such as nausea, diarrhea, rash, and fatigue. The only drug available to treat second-stage East African trypanosomiasis is melarsoprol, but it can cause severe, life-threatening adverse reactions in patients, such as encephalopathy (negative effects on brain function/structure), and therefore, it should be given with caution. There is no vaccine or medicine to prevent African trypanosomiasis. The only prevention method is to avoid attracting tsetse flies by not wearing bright or extremely dark-colored clothes, and avoiding where tsetse flies live in the daytime, such as bushes near streams and thickets (3).
While African trypanosomiasis appears to be declining as a public health problem, there is still much more work to be done to reach long-term eradication and control of the disease. Becoming more informed is an important first step to helping improve the livelihoods of those affected by African trypanosomiasis.
References
1. Division of Parasitic Diseases and Malaria, Global Health. “CDC - African Trypanosomiasis.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 16 Feb. 2022, www.cdc.gov/parasites/sleepingsickness/.
2. Medicine, Johns Hopkins. African Trypanosomiasis (African Sleeping Sickness), Johns Hopkins Medicine, 19 Nov. 2019,
www.hopkinsmedicine.org/health/conditions-and-diseases/african-sleeping-sickness#:~:text=African%20sleeping%20sickness%20is%20a,the%20tsetse%20fly%20is%20found.
3. Medicines, Access to. “Human African Trypanosomiasis .” A Social Issue: Neglected Tropical Diseases and Three Major Infectious Diseases, Access to Medicines, 2014,
atm.eisai.co.jp/english/ntd/africa.html#:~:text=When%20left%20untreated%2C%20the%20m ortality,from%20this%20disease%20every%20year.
4. Organization, World Health. “Trypanosomiasis, Human African (Sleeping Sickness).” World Health Organization, World Health Organization, 10 Jan. 2022,
www.who.int/news-room/fact-sheets/detail/trypanosomiasis-human-african-(sleeping-sickness ).
5. Buscher, Philippe, et al. “Human African Trypanosomiasis.” The Lancet, vol. 390, no. 10110, 30 June 2017, doi:https://doi.org/10.1016/S0140-6736(17)31510-6.
6. Organization, World Health. “Sustained Decline in Sleeping Sickness Cases Puts Elimination within Reach.” World Health Organization, World Health Organization, 23 June 2020, www.who.int/news/item/23-06-2020-sustained-decline-in-sleeping-sickness-cases-puts-elimina tion-within-reach.
This post is not a substitute for professional advice. If you believe that you may beexperiencing a medical emergency, please contact your primary care physician, or go to the nearest Emergency Room. Results from ongoing research is constantly evolving. This post contains information that was last updated on April 10, 2023.
Ashley Fang is currently a Molecular and Cell Biology major undergraduate at UC Berkeley.
Nikhil Chakravarty is currently a second-year MPH student specializing in Epidemiology at UCLA.
Courtney Coleman is a master's degree candidate in biology at Harvard and Co-President of Students vs Pandemics.
Excellent!!!
Very educational and informative.