Two subspecies of the protozoan parasite Trypanosoma brucei (T. b. rhodesiense and T. b. gambiense ).
The bite of an infected tsetse fly (Glossina spp.). Bloodborne and congenital transmission are rare.
Endemic to rural sub-Saharan Africa. T. b. rhodesiense is found in eastern and southeastern Africa, mainly Tanzania, Uganda, Malawi, Zambia, and Zimbabwe. T. b. gambiense is found in central Africa and in limited areas of West Africa, particularly in parts of Democratic Republic of the Congo, as well as Central African Republic, Angola, South Sudan, Guinea, Gabon, Congo, Chad, (northern) Uganda, and other countries. World Health Organization (WHO) maps of African trypanosomiasis cases, by country, are available at www.who.int/trypanosomiasis_african/country/foci_AFRO/en.
In 2016, the WHO received 2,184 reports of sleeping sickness cases; T. b. gambiense accounted for 98% of them. Many cases, however, are likely not recognized or reported. Tsetse flies inhabit rural, vegetated areas. 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. Cases imported into the United States are rare; almost all are due to T. b. rhodesiense , typically during visits to national parks or game reserves.
Clinical manifestations generally appear within 1–3 weeks after the infective bite and may include high fever, a chancre at the bite site (within a few days of the bite), skin rash, headache, myalgia, thrombocytopenia, and less commonly, splenomegaly, renal failure, or cardiac dysfunction. Central nervous system involvement can occur within a few weeks of the exposure and results in sleep cycle disturbance, mental deterioration, and (if not treated) death within months.
Clinical manifestations generally appear months to years after exposure, but the incubation period may be <1 month. Signs and symptoms are nonspecific and may include intermittent fever, headache, malaise, myalgia, arthralgia, facial edema, pruritus, lymphadenopathy, and weight loss. Central nervous system involvement occurs after several months to years of infection and is characterized by daytime somnolence and nighttime sleep disturbance, headache, and other neurologic manifestations (such as mood disorders, behavioral changes, and focal deficits). In residents of endemic areas, the clinical course of disease caused by T. b. gambiense generally progresses more slowly (with an estimated average total duration of 3 years) than that caused by T. b. rhodesiense , but both forms of African trypanosomiasis typically are fatal if not treated.
Tsetse fly bites are characteristically painful, and a chancre may develop at the bite location. Diagnosis is made by identifying parasites in specimens of blood, chancre fluid or tissue, lymph node aspirate, or cerebrospinal fluid. Buffy-coat preparations concentrate the parasite, enabling easier visualization for diagnosis. All patients diagnosed with African trypanosomiasis must have their cerebrospinal fluid examined to determine whether there is involvement of the central nervous system, since the choice of treatment drugs depends on the disease stage. Diagnostic assistance is available through CDC (www.cdc.gov/dpdx; 404-718-4745; firstname.lastname@example.org).
Infection can usually be cured by a course of antitrypanosomal therapy, although long-term sequelae, including permanent damage to the central nervous system, may occur. In the United States, particular treatment drugs (suramin, melarsoprol, eflornithine) are available through CDC under investigational protocols. Choice of treatment drug depends on species causing infection (T. b. rhodesiense or T. b. gambiense ) and stage of disease. Clinicians can consult with CDC for assistance with treatment.
Avoid tsetse fly bites. Travelers should wear wrist- and ankle-length clothing made of medium-weight fabric in neutral colors, as tsetse flies are attracted to bright or dark colors (especially blue and black) and can bite through lightweight clothing. Permethrin-impregnated clothing and use of DEET repellent might provide partial protection by reducing the number of bites—see Chapter 3, Mosquitoes, Ticks & Other Arthropods.
CDC website: www.cdc.gov/parasites/sleepingsickness/
Sharon L. Roy, Barbara L. Herwaldt, Christine Dubray, Anne Straily