What is African trypanosomiasis?
African trypanosomiasis, or sleeping sickness as it is more commonly known, is a protozoan parasitic infection caused by Trypanosoma brucei, transmitted by the tsetse fly (genus: Glossina spp). There are two sub-species; T. brucei rhodesiense predominates in East Africa and usually causes an acute infection, whereas T. brucei gambiense predominates in Central and West Africa and causes a slower progressive, chronic infection. In the UK, travel-associated cases are rare but those that have been reported, are usually caused by T. brucei rhodesiense and have been associated with travel to the game parks of East Africa.
Where does sleeping sickness occur?
Sleeping sickness occurs in countries of Africa where the tsetse fly vector (Glossina spp.) occurs. Tsetse flies infest approximately one-third of the African continent; their distribution is ecologically limited to a band between 14 degrees north from Senegal in the west to 10 degrees north in southern Somalia in the east and 20 degrees south corresponding to the northern fringes of the Kalahari and Namibian deserts; 36 countries in western, central and eastern Africa are therefore endemic for sleeping sickness. In 2009, the WHO reported 9,877 cases of sleeping sickness compared with more than 17,600 in 2004 and almost 38,000 in 1998. This was the first time in 50 years that the number of reported cases had dropped below 10,000 rekindling the hope of elimination with continued improvements in surveillance and control. In the UK, cases are occasionally reported in travellers returning from game parks in East Africa. Most recently, a case was reported in a UK traveller who had returned from Zambia and Zimbabwe.
What are the symptoms?
Sleeping sickness generally occurs in two stages:
During the first stage of East African sleeping sickness, a skin lesion develops after 5-15 days at the site of a tsetse fly bite, which may disappear after 2-3 weeks. Local lymphadenopathy (swollen lymph nodes) and cellulitis may also occur. Fever and parasitaemia (parasites in the blood) occur approximately 1-3 weeks after the infective bite. East African sleeping sickness progresses much more rapidly than West African sleeping sickness and for the West African form, the first sign of trypanosome infection may be the appearance of an irregular fever that does not respond to antimalarials.
During the second stage, trypanosome parasites cross the blood-brain barrier and cause encephalopathy (brain disorder) with headache and personality changes. This occurs within weeks for East African trypanosomiasis and within months or years for the West African form. As the disease progresses to the terminal stage, patients experience disruption to their normal sleep pattern, and become progressively drowsy, which gives the disease its name of "sleeping sickness". The disease can be fatal if untreated.
How do you catch sleeping sickness?
The trypanosome parasite is transmitted by the bite of an infected tsetse fly. Tsetse flies are fairly large insects around the size of a honey bee. In West Africa, the main reservoir for T. brucei gambiense is humans. Tsetse flies within the Glossina palpalis group are the main vector and tend to inhabit damp river areas. In East Africa, the main reservoirs for T. brucei rhodesiense are domestic and wild animals such as antelope and cattle. Tsetse flies within the Glossina morsitans group are the main vectors and tend to inhabit savannah and woodland areas. Tsetse flies, once infected, only need to bite a human once to infect them; they can transmit the disease to many humans in a relatively short space of time. Trypanosomiasis cannot be spread directly from person to person.
How long can you have the infection before developing symptoms?
For East African trypanosomiasis, first symptoms (skin lesion around the bite with lymphadenopathy) will occur 5-15 days after the bite, with fever occurring after 1-3 weeks. For West African trypanosomiasis, symptoms may not present for some weeks after the infective bite. East African trypanosomiasis is a much faster progressing disease than the West African form which can progress over a number of years.
How can you avoid getting sleeping sickness?
There is no vaccine or drug to prevent sleeping sickness. The only way to prevent sleeping sickness is to avoid tsetse fly bites and be aware of the risk. Tsetse flies are attracted by movement and by dark colours, particularly blue. They have been known to follow moving vehicles, therefore windows should remain closed when driving through endemic areas. Tsetse flies are also capable of biting through loose weave fabrics and are unaffected by many insect repellents. Travellers are advised to wear insecticide-treated close weave and loose fitting clothing and use a good repellent containing N, N-diethylmetatoluamide (DEET) on exposed skin. If sunscreen is also being used, repellent must be applied after sunscreen. More information about insect bite avoidance is available from the NaTHNaC website.
How is sleeping sickness treated?
There are drugs available to treat sleeping sickness; administration of these drugs is complex and associated with a range of side effects. If you suspect you may have sleeping sickness you should consult your doctor who will refer you to a tropical disease unit as soon as possible for specialist treatment.
Is sleeping sickness catching?
If you acquire sleeping sickness abroad and become ill on your return to the UK, you cannot pass the infection on to anyone else. The tsetse fly needed to transmit the parasite is not present in the UK. Sleeping sickness cannot be passed directly from person to person.
Sources of information
NaTHNaC information sheet on trypanosomiasis.
Burri C, Brun R. Chapter 73: Human African Trypanosomiasis. In: Cook GC, Zumla A. Manson's Tropical Diseases. London; Saunders, 2003
Last reviewed: 22 October 2010