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 in 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, primarily in Democratic Republic of the Congo, Central African Republic, Angola, South Sudan, Guinea, Cameroon, Gabon, Côte d’Ivoire, Congo, Chad, and northern Uganda. World Health Organization (WHO) maps of African trypanosomiasis cases, by country, are available at www.who.int/trypanosomiasis_african/country/foci_AFRO/en.
In 2014, 3,796 sleeping sickness cases were reported to the World Health Organization; T. b. gambiense accounted for >98% of cases. Many cases, however, are probably not recognized nor reported. Tsetse flies inhabit rural, densely vegetated areas; people who only travel to urban areas are not at risk. Flies bite during the day, and <1% are infected. Risk of infection increases with the number of fly bites, which is not always directly correlated with duration of travel. Cases imported into the United States are rare.
Clinical manifestations generally appear within 1–3 weeks of the infective bite and may include high fever, a chancre at the bite site, skin rash, headache, myalgia, thrombocytopenia, and less commonly, splenomegaly, renal failure, or cardiac dysfunction. Central nervous system involvement can occur within a month of infection and results in sleep cycle disturbance, mental deterioration, and eventually death.
Clinical manifestations generally appear months to years after infection and are nonspecific. Signs and symptoms 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, severe headache, and a range of neurologic manifestations including mood disorders, behavior change, focal deficits, and endocrine disorders. The clinical course of disease caused by T. b. gambiense is generally less severe than that caused by T. b. rhodesiense , but both are fatal if not treated.
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. Diagnostic assistance is available through CDC (www.cdc.gov/dpdx; 404-718-4745; parasites@cdc.gov).
Infection can usually be cured by a course of antitrypanosomal therapy, although long-term sequelae, including permanent damage to the central nervous system, may remain. Treatment drugs (suramin, melarsoprol, eflornithine) are provided by 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 clothing of wrist and ankle length made of medium-weight fabric in neutral colors, as tsetse flies are attracted to bright or dark colors and can bite through lightweight clothing. Permethrin-impregnated clothing and use of DEET repellent may reduce the number of fly bites.
CDC website: www.cdc.gov/parasites/sleepingsickness
Francisca Abanyie