African Trypanosomiasis aka African Sleeping Sickness

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African Trypanosomiasis aka African Sleeping Sickness


Human African Trypanosomiasis (HAT) is an infectious parasitic disease transmitted by vectors. The main problem biologists are trying to solve for this disease is to find a cure or at the very least, prevent it by controlling the spread of it. The parasites that cause this disease are Trypanosoma brucei rhodensiense in Southern/Eastern Africa and Trypanosoma brucei gambiense in Northern/Western Africa. Tsetse fly (Glossina genus) bites are the primary biological vectors for this. The bites can only transport the disease if they have already acquired the infection from animals or human beings affected by the protozoa.

Tsetse flies are only found in Sub-Saharan Africa but only particular species transmit the disease. Moreover, in many regions the flies are found but sleeping sickness is not. People living in rural populations where transmission does occur are most exposed to the disease. This is usually because they depend on agriculture, fishing or hunting and are more unprotected to the tsetse fly.

The sleeping sickness develops when a tsetse fly bites an infected person. “Flies can remain infected for life (2-3 months). Tsetse flies inject over 40,000 metacyclic trypanosomes when they take a blood meal. The minimum infective dose for most hosts is 300-500 organisms, although experimental animals have been infected with a single organism.” [2] [see figure 1 for more detail]

Inside the fly the parasites then divide to reproduce, maturing in the fly’s gut. After they have matured, they move to the salivary glands and become infectious. The next time the tsetse fly bites another person, they will become infected by either the T.b.gambiense (T.b.g) or T.b.rhodesience (T.b.r). [3] “T.b.g. accounts for 95% of reported cases of sleeping sickness.” [1] [see figure 2 for more detail].


  • It causes a chronic infection.
  • The symptoms may take months or even years to appear.
  • When the symptoms do emerge, the disease is most likely in its advanced stage where the central nervous system (CNS) is affected. [1]
  • The symptoms include fever, severe headache, extreme fatigue, aching muscles and joints and swollen lymph nodes.
  • This particular species of the parasite, when untreated, will usually takes 3 years to kill and very rarely lasts longer than 6-7 years.


  • It causes an acute infection.
  • Symptoms generally appear in 1-2 weeks of the infective bite.
  • The actual symptoms are very similar to those of T.b.gambiense; nonetheless some patients may also develop a rash. [2]
  • Due to the speed of the disease, the effects on the heart can become fatal before the disease has a chance to spread to the brain. [3]
  • The parasite can attack the CNS only after a few weeks of contamination
  • This will eventually cause mental health problems. An untreated infection will mean death within months. [2]

Diagnosis is made in three steps. Firstly, a person is screened for any potential infections. This means using serological tests (only for T.b.g) and checking for medical signs – typically swollen cervical glands. The next step in the diagnosing process is confirming if the parasite is present. The final step includes determining how far the disease has progressed – what stage it is at. This can be done through analysing the result cerebrospinal fluid tests. Using the results, the method of treatment is decided.

A problem with the diagnosis procedure is that it requires highly trained professionals and major investment. [1] These types of resources are limited in Africa and that is why “despite the WHO projection of 60 million people at risk in Africa, only a fraction of the population at risk is currently under surveillance, and relatively few cases are accurately diagnosed annually (Knudsen and Slooff, 1992).” [2] (WHO – World Health Organisation)

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Solutions: Main – Drugs

Currently the main method used to treat people with the condition of HAT is drugs. At the first stage the drugs used are not very toxic and are easier to allocate with correct dosages. The earlier HAT is identified, the more probable the cure becomes. Pentamidine is used for the first stage of T.b.g. Although it produces some side-effects, “it is well tolerated by patients”. Suramin is used to treat the first stage of T.b.r and produces side-effects, such as, allergic reactions and undesirable effects in the urinary tract. The second stage treatment drugs are much more ...

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