Geographic risk areas
This leaflet is to inform citizens from the Nordic countries about the risk of Trypanosomiasis. Within the last few years there have been several reported cases of Trypanosomiasis (African sleeping sickness) in visitors to eastern Tanzania. All cases have been visiting either Serengeti or Tarangire national park. Regretfully there seems to be a lack of information from the Tanzanian Ministry of Health to visitors of national parks in northern Tanzania. I have made enquiries about the situation in Serengeti with a veterinary doctor, who is working at the Serengeti Research Centre in Serengeti. He confirmed recently that there don't exist any official reports on the extent on sleeping sickness in Tanzania. Official statistics from 1998 mention that some 200 cases of African sleeping sickness have occurred in Tanzanians. The real number may be much higher.
The population of tsetse flies seems to be on the increase in the Serengeti. About 10% of the tsetse fly population is assumed to be infected with trypanosomes, the parasite which causes African sleeping sickness. However, most of the different types of tsetse flies don't cause disease in human beings or wild animals.
Two types of African sleeping sickness
The rhodesian form of African sleeping sickness in humans occurs in East Africa. In Tanzania this type is found between lake Victoria up to Arusha. The gambian form is found in West- and Central Africa. Both types are dangerous and lead to death untreated. Infections with T. rhodesiense have an incubation time of three days to a few weeks only and are more rapidly progressing. It may cause infection in internal organs, even before the parasite invades the brain. During this stage the patient may, without treatment, become sleepy, apathic and then unconscious. By this time treatment is difficult. Infections with T. gambiense have a longer incubation time (from several months to years) and are often chronic. Typical African sleeping sickness is often connected with this type, which after several years leads to coma, prostration and eventually the patient may die of pneumonia.
The disease is confined to tropical Africa between 200 N and 200 S latitude, corresponding to the distribution of the tsetse fly. Outbreaks can occur when, for any reason, human-fly contact is intensified, or when virulent strains of trypanosomes are introduced into a tsetse-infested area by movement of infected flies or reservoir hosts. Where flies of the Glossina palpalis group are the principal vectors, as in West and Central Africa, infection occurs mainly along streams where forest border rivers and brooks. In these areas we find the gambiense form of African sleeping sickness. In East Africa and around Lake Victoria, where the main vectors are of the Glossina morsitans group, disease occurs over the broader dry savannas. Here we find the rhodesiense type of African sleeping sickness. Wild animals, especially bushbuck and antelopes, and domestic cattle are the chief animal reservoirs of Trypanosoma rhodesiense. In the gambiense type, humans, cattle and pigs are the main reservoir.
Sleeping sickness is a systemic parasitic disease. In the early stages, a painful swelling of the skin (chancre) may be found at the bite site. This may resemble ringworm or beginning abscess, but in contrast with ringworm, there is usually swelling. Also there may be fever, headache, muscle and joint pain, loss of appetite, difficulties with sleeping and irritability, painless enlarged lymph nodes, especially in the neck and further anaemia.
The diagnosis is made by finding trypanosomes in blood, lymph fluid and spinal fluid. The parasites can be found in a blood slide made and stained the same way as a malaria slide. Often several blood tests have to be taken and examined before the diagnosis can be confirmed. Only a few hospitals and clinics in Eastern Africa can diagnose African sleeping sickness reliably through microscopic examination of a blood slide ("thick blood drop") In Dar es Salaam the Nordic Clinic (included in Lonely Planet) can be consulted when there is a suspicion of infection with either malaria or African sleeping sickness.
Suramin is the drug of choice for T. rhodesiense infections and Pentamidine for T. gambiense infections. Since these drugs don't cross the natural barrier to the brain, the spinal fluid needs to be examined to rule out infection of the brain. If this is the case, another drug, Melarsoprol, is used to treat patients with infections of the central nervous system. The drugs mentioned are not available at hospitals in Tanzania. Therefore, the visitor in which infection with African sleeping sickness is diagnosed or suspected is strongly advised to consult hospitals which are specialised in treating tropical infectious diseases. In Norway these are Ullevål and Haukeland hospital.
Appropriate measures of prevention must be based on knowledge of the local ecology of the vectors and infectious agents. We therefore hope that health authorities in Tanzania will carry out investigations and issue reports on the extent and cause of sleeping sickness and strengthen control measures and will advice tourists which "hotspots" in the Serengeti and other national parks in Northern-Tanzania they should avoid. In the meantime, the only way to prevent sleeping sickness is to prevent being bitten by tsetse flies. Tsetse flies often hide in dense acacia bushes and trees to find shade. They are about twice the size of a house-fly, and are active during daylight hours, have a painful bite and are attracted to blue. They come out from bushes or forest and fly in vast swarms with large moving objects, like buffalo's, antilopes but also vehicles. Therefore, when driving through dense bushes or forest, keep car windows closed and kill those that have come into the car. The role of repellents is highly unsure. Avoid blue coloured clothes. One should preferably use long trousers og light khaki material and two pair of socks. Remember that the tsetse fly bites through thick buffalo skin!
Vil du vite mer?
- Trypanosomiasis - for helsepersonell
- Dr. E. Boonstra, District Medical Officer, 6980 Askvoll, Norway