Human African trypanosomiasis

Human African trypanosomiasis (HAT, sleeping sickness) is caused by two subspecies of the protozoan parasite Trypanosoma brucei: T. b. rhodesiense is prevalent in East Africa among many wild and domestic mammals; T. b. gambiense causes an anthroponosis in Central and West Africa. The disease is restricted to tropical Africa where it is transmitted by the bite of infected tsetse flies (Glossina spp.).

Although well under control in the mid 20th century, HAT has returned to Africa in epidemic proportions since the 1980s, causing a severe public health problem in countries such as the Democratic Republic of Congo, Angola, Sudan, and Uganda. A joint effort by national, international, and nongovernmental organizations, as well as the pharmaceutical industry, is required to reverse this trend.

Clinical features

HAT progresses through distinct clinical stages that invariably lead to death if left untreated. Progress is fast in rhodesiense HAT, often resembling the clinical picture of malaria or septicaemia, and slow—sometimes lasting years—in gambiense HAT.

Outside Africa, HAT is a rare diagnosis as an imported infection in travellers, but has to be considered in any patient with fever, chronic lymphadenopathy, or neurological changes returning from HAT endemic areas.

Diagnosis, staging, and treatment

Diagnosis—this is established by the detection of trypanosomes (usually by direct microscopy) in chancre aspirate, blood, lymph, or cerebrospinal fluid. Serology is useful for rapid screening under field conditions, but does not necessarily imply overt disease.

Staging—this is crucial for correct management: the cerebrospinal fluid must be examined in every patient found positive for trypanosomes in blood or lymph aspirate.

Treatment—HAT is curable, but many factors make this difficult: the disease is found in remote places, diagnosis is difficult, treatment is costly and complicated, and many drugs are not easily available. Aside from supportive care, specific treatment depends on the trypanosome subspecies and the stage of the disease, including (1) stage 1—pentamidine, and suramin; (2) stage 2—melarsoprol, eflornithine, and nifurtimox. There are no generally accepted recommendations on drug combinations, but—especially in late stages—treatment is difficult and dangerous to the patient; all of the drugs used are toxic and have many side effects, some potentially lethal.

Prevention

Control can be achieved by a combination of mass screening programmes, treatment of patients, and vector control, which together can lead to a complete break of the transmission cycle. There is no vaccine.