Between August 2024 and January 2025, four cases of Human African trypanosomiasis (HAT), were reported in travelers from nonendemic countries who were bitten by tsetse flies in the Zambezi Valley (see also EpiNews 9.1.2025).
African trypanosomiasis, also called sleeping sickness, is endemic in many Subsaharan countries. It is transmitted by Tsetse flies. These flies are mainly attracted by bright, dark (especially blue) colours. They inhabit rural areas, including forests and savannah areas, and areas of thick vegetation along rivers and waterholes, depending on the fly species. Tsetse flies bite during the day, <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. Travelers to urban areas are at minimal risk, although transmission has been observed in some urban settings in the past.
Regions highlighted within Zambia and Zimbabwe depicting the approximate risk area for the disease.
All travellers should be informed that sleeping sickness is endemic in Africa. Tsetse flies, the carriers of sleeping sickness, are mainly attracted by bright, dark (especially blue) colours. To prevention sleeping sickness, travelers should:
- Wear well-covering, light-coloured clothing impregnated with permethrin. In addition, use repellents to also protect against mosquitoes.
- Inspect vehicles for tsetse flies before entering. Tsetse flies are yellow to dark brown in color, about the size of a housefly, and hold their wings over their back when at rest.
- Pay attention to posted signs warning about tsetse flies or fly spraying in the area.
- Avoid areas where black or blue tsetse fly traps are present.
In case of a suspicious skin lesion, immediately consult a doctor as a rapid therapy as well as a supportive therapy must be initiated as soon as possible.
Clinicians should urgently consider HAT caused by T.b. rhodesiense in travelers with fever arriving from an endemic area, even if cases have not been reported from that area recently. Delayed treatment can be fatal, so if rhodesiense HAT is suspected, clinicians should promptly obtain a peripheral blood smear to assess for trypanosomes.