Author(s): Sharon Roy, Rebecca Chancey, Paul Cantey, Anne Straily

Infectious Agent

Trypanosomiasis is caused by 2 subspecies of the protozoan parasite Trypanosoma brucei (T. brucei rhodesiense and T. brucei gambiense).

Transmission

Trypanosomiasis is transmitted by the bite of an infected tsetse fly (Glossina spp.). Bloodborne, congenital, sexual, and transfusion or transplantation transmission are rare.

Epidemiology

African trypanosomiasis is endemic to rural sub-Saharan Africa. T. brucei rhodesiense is reported from eastern and southeastern Africa, mainly Malawi, Tanzania, Uganda, Zambia, and Zimbabwe. T. brucei gambiense is reported from central and west Africa, particularly in parts of the Democratic Republic of the Congo, as well as Angola, Cameroon, Central African Republic, Chad, Congo, Côte d’Ivoire, Equatorial Guinea, Gabon, Guinea, South Sudan, (northern) Uganda, and other countries. See World Health Organization (WHO) maps and tables of African trypanosomiasis cases, by country.

In 2018, WHO received 4,977 reports of sleeping sickness cases from African countries; T. brucei gambiense accounted for 98% of cases. Many cases, however, are likely not recognized or reported; exported cases also have been reported in expatriates, immigrants, refugees to countries outside of Africa, and tourists. Cases imported into the United States are rare; most cases in international travelers are due to T. brucei rhodesiense, typically acquired during visits to national parks or game reserves.

Tsetse flies inhabit rural areas, including forests and savannah areas, and areas of thick vegetation along rivers and waterholes, depending on the fly species. Travelers to urban areas are at minimal risk, although transmission has been observed in some urban settings in the past. Tsetse flies bite during the day, and <1% are infected. Risk for infection in travelers increases with the number of fly bites, which does not always correlate with duration of travel. People most likely to be exposed to African trypanosomiasis infection are hunters and villagers with infected cattle herds. Tourists and other people working in or visiting game parks are at risk for contracting African trypanosomiasis if they spend long periods in rural areas where the disease is present.

Clinical Presentation

T. brucei rhodesiense

Clinical manifestations generally appear within 1–3 weeks after the infective bite and can include a chancre at the bite site that appears within a few days of the bite; high fever; headache; myalgia; skin rash; thrombocytopenia; and less commonly, cardiac dysfunction, renal failure, or splenomegaly. Central nervous system (CNS) involvement can occur within a few weeks of the exposure and results in sleep cycle disturbance, mental deterioration, and, if left untreated, death within months.

T. brucei gambiense

Clinical manifestations of T. brucei gambiense generally appear months to years after exposure, but the incubation period can be <1 month. Signs and symptoms are nonspecific and can include arthralgia, facial edema, intermittent fever, headache, lymphadenopathy, malaise, myalgia, pruritus, and weight loss. CNS involvement occurs after several months to years of infection and is characterized by daytime somnolence and nighttime sleep disturbance, headache, and other neurologic manifestations (e.g., behavioral changes, mood disorders, focal deficits). In residents of endemic areas, the clinical course of disease caused by T. brucei gambiense generally progresses more slowly (estimated average total duration of 3 years) than that caused by T. brucei rhodesiense, but if not treated, both forms of African trypanosomiasis typically are fatal.

Diagnosis

Tsetse fly bites are characteristically painful, and a chancre can develop at the bite location. No serologic tests for Trypanosoma brucei are available in the United States. Diagnosis of T. brucei rhodesiense is made by microscopic identification of parasites in specimens of blood, chancre fluid, or tissue; cerebrospinal fluid (CSF); bone marrow aspirates; or lymph node aspirates. The level of parasitemia is lower in T. brucei gambiense than T. brucei rhodesiense infections. Microscopic identification generally requires serial examinations of samples concentrated by techniques such as centrifugation followed by buffy coat examination, microhematocrit centrifugation, or mini-anion exchange centrifugation.

Serologic testing for T. brucei gambiense, available outside of the United States, can assist in diagnosis; the Centers for Disease Control and Prevention (CDC) can provide contact information. All patients diagnosed with African trypanosomiasis must have their CSF examined on a wet preparation to look for motile trypomastigotes and white blood cells (WBC) to determine whether the CNS is involved; the choice of treatment drugs depends on the disease stage. Patients with ≤5 WBC/mL and no trypomastigotes in CSF are in the first stage, and those with >5 WBC/mL or trypomastigotes in CSF are in the second stage.

Diagnostic assistance is available from CDC’s Division of Parasitic Diseases and Malaria DPDx laboratory (dpdx@cdc.gov), and from the Parasitic Diseases Hotline for Healthcare Providers (404-718-4745; parasites@cdc.gov).

Treatment

Treat people diagnosed with African trypanosomiasis with a drug course specific to the type of infection (T. brucei rhodesiense or T. brucei gambiense) and disease stage (i.e., presence or absence of CNS involvement). Pentamidine, the recommended treatment for first-stage T. brucei gambiense infection, is available in the United States. Nifurtimox was approved by the US Food and Drug Administration in August 2020 and is commercially available. Other drugs used to treat African trypanosomiasis (e.g., eflornithine [used in combination with nifurtimox], melarsoprol, suramin) are not commercially available in the United States but can be obtained from CDC. Physicians can consult with CDC staff to obtain otherwise unavailable treatment drugs (parasites@cdc.gov, 404-718-4745).

No test of cure is available for African trypanosomiasis. After treatment, closely follow patients for 24 months and monitor for relapse. Recurrence of symptoms will require examination of body fluids, including CSF, to detect the presence of trypanosomes.

Prevention

No vaccines or prophylactic drugs against African trypanosomiasis are available. To reduce the risk for infection, travelers should minimize contact with tsetse flies by wearing long-sleeved shirts and long pants made of medium-weight fabric in neutral colors. Tsetse flies are attracted to bright or dark colors, especially blue and black, and can bite through lightweight clothing. Travelers should inspect vehicles before entering, because the flies are attracted to the motion and dust from moving vehicles. Travelers should avoid bushes, because tsetse flies are less active during the hottest part of the day but will bite if disturbed. Although permethrin-impregnated clothing and insect repellent have not proven to be particularly effective against tsetse flies, travelers should use DEET repellent to prevent other insect bites that can cause illness (see Sec. 4, Ch. 6, Mosquitoes, Ticks & Other Arthropods).

CDC website: African trypanosomiasis