African trypanosomiasis

African trypanosomiasis is an insect-borne parasitic infection of humans caused by the protozoan Trypanosoma brucei, specifically the subspecies T. b. gambiense and T. b. rhodesiense, and transmitted by the bite of infected tsetse flies ^[2]. It is a bloodstream protozoan parasite infection that leads to sleeping sickness and is almost invariably progressive to death without treatment ^[1][4].

After a tsetse fly bite, early-stage infection involves parasite replication in blood and lymph, producing fever, headache, itchiness, and joint pain within one to three weeks ^[2]. Weeks to months later, the parasite crosses the blood–brain barrier and neurological manifestations emerge, including confusion, poor coordination, numbness, and disturbed sleep ^[2]. The associated pathology is largely inflammatory, contributing to anemia and brain dysfunction, and T. b. gambiense yields chronic disease over months to years whereas T. b. rhodesiense produces symptoms within weeks to months ^[4][2].

The disease caused major epidemics in the 20th century and accounted for around 9000 deaths in 2010, down from 34,000 in 1990 ^[1][2]. From 2010 to 2014, an estimated 55 million people were at risk for gambiense and over 6 million for rhodesiense disease, with 3797 cases reported in 2014 representing an 86% reduction from 2000 ^[2]. It remains endemic in sub-Saharan Africa, especially rural central Africa, and has been recorded in 37 countries; cases are also reported from non-endemic nations via travellers, tourists, migrants, and expatriates ^[1][2].

Transmission occurs through the bite of tsetse flies infected with T. b. gambiense or T. b. rhodesiense in sub-Saharan Africa ^[3][2]. T. b. gambiense is principally transmitted among humans, while T. b. rhodesiense is zoonotic with cattle and wild animals as reservoirs ^[2]. Long-lasting infection supports parasite transmission between hosts, and animal reservoirs may contribute to endemic persistence and resurgence in historic foci ^[4][2].

With no vaccine available, control relies on case detection, treatment, and vector control ^[1][3]. Avoiding tsetse fly bites through insect repellents and protective clothing, plus vector measures such as insecticide spraying and release of sterilized flies, has lowered incidence ^[2]. Introduction of simple rapid diagnostic tests facilitates gambiense screening in primary health care, and screening at-risk populations helps prevent severe disease ^[3][2].

1. 1 Büscher P et al. Human African trypanosomiasis. Lancet. 2017 Nov 25. PMID: 28673422. doi: 10.1016/S0140-6736(17)31510-6. PubMed: https://pubmed.ncbi.nlm.nih.gov/28673422/
2. 2 Wikipedia contributors. African trypanosomiasis - Wikipedia [Internet]. Wikipedia. cited 3 Sept 2026. Available from: https://en.wikipedia.org/wiki/African_trypanosomiasis
3. 3 Lejon V et al. Human African trypanosomiasis. Lancet. 2025 Mar 15. PMID: 40089378. doi: 10.1016/S0140-6736(25)00107-2. PubMed: https://pubmed.ncbi.nlm.nih.gov/40089378/
4. 4 Pays E et al. The Pathogenesis of African Trypanosomiasis. Annu Rev Pathol. 2023 Jan 24. PMID: 36055769. doi: 10.1146/annurev-pathmechdis-031621-025153. PubMed: https://pubmed.ncbi.nlm.nih.gov/36055769/