AFRICAN TRYPANOSOMIASIS OR SLEEPING SICKNESS

Definition of the disease

Human African trypanosomiasis, known as sleeping sickness, is a vector-borne parasitic disease. Trypanosoma, the parasites concerned, are protozoa transmitted to humans by tsetse flies (glossina). In Africa Tsetse flies  are found in vegetation by rivers and lakes, gallery-forests and vast stretches of wooded savannah.

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• Sleeping sickness occurs only in sub-Saharan Africa
• The rural populations depending  on agriculture, fishing, animal husbandry or hunting are the most exposed - along with their livestock –
• It develops in foci whose size can range from a village to an entire region. Within a given focus, the intensity of the disease can vary considerably from one village to the next.

Human African trypanosomiasis takes two forms, depending on the parasite involved:

• Trypanosoma brucei gambiense (T.b. gambiense) is found in central and West Africa. It causes chronic infection, which does not mean benign. A person can be infected for months or even years without obvious symptoms of the disease emerging. When symptoms do emerge, the disease is already at an advanced stage.
• Trypanosoma brucei rhodesiense (T.b. rhodesiense) is found in southern and east Africa. It causes acute infection that emerges after a few weeks. It is more virulent than the other strain and develops more rapidly, which means that it is more quickly detected clinically.

Animal trypanosomiasis

Animals can carry parasites, especially T.b. rhodesiense; domestic and wild animals are a major reservoir. The two human and animal forms of the disease remain a major obstacle to the development of rural regions of sub-Saharan Major epidemics

There have been three severe epidemics in Africa over the last century: one between 1896 and 1906, mostly in Uganda and the Congo Basin, one in 1920 in several African countries, and one that began in 1970 and is still in progress. The 1920 epidemic was arrested due to mobile teams systematically screening millions of people at risk. The disease had practically disappeared between 1960 and 1965. After that success, screening and effective surveillance were relaxed, and the disease has reappeared in endemic form in several foci over the last thirty years.

The Geographical distribution of the disease

Sleeping sickness threatens over 60 million people in 36 countries of sub-Saharan Africa..

In certain villages of many provinces of Angola, the Democratic Republic of Congo and southern Sudan, the prevalence is between 20% and 50%. Sleeping sickness has become the first or second greatest cause of mortality, ahead of HIV/AIDS, in those provinces.

Countries are placed in four categories in terms of prevalence. In each country the spatial distribution of the disease is very diverse; it is found in foci and micro-foci.

• Countries where there is an epidemic of the disease, in terms of very high cumulated prevalence and high transmission: Angola, Democratic Republic of Congo and Sudan; Red zones
• Highly endemic countries, where prevalence is moderate but increase is certain: Cameroon, Central African Republic, Chad, Congo, Côte d'Ivoire, Guinea, Mozambique, Uganda and United Republic of Tanzania. Dark bleu
• Countries where the endemic level is low: Benin, Burkina Faso, Equatorial Guinea, Gabon, Kenya, Mali, Togo and Zambia; Green
• Countries whose present status is not clear: Botswana, Burundi, Ethiopia, Liberia, Namibia, Nigeria, Rwanda, Senegal and Sierra-Leone. Yellow

Risk in travelers:

Risk of infection increases with the number of times a person is bitten by the tsetse fly. Therefore, tourists are not at great risk for contracting African trypanosomiasis unless they are traveling and spending long periods of time in rural areas of Africa.

These would include long-term travelers, foreign workers, persons on safari, off the beaten track travel.

Infection and symptoms

The disease is transmitted with the bite of the tsetse fly.

At first the trypanosomes multiply in the blood, and that process can last for years with T.b. gambiense.

• Mother-to-child infection: the trypanosome can cross the placenta and infect the fetus, causing abortion and perinatal death.
• Accidental infections can occur in laboratories, for example, through the handling of blood of an infected person, although this is fairly rare.

Early phase: fever, headaches, pains in the joints and itching.

Second Phase: begins when the parasite crosses the blood-brain barrier and infests the central nervous system: confusion, sensory disturbances and poor coordination. Disturbance of the sleep cycle  is the most important feature. Without treatment, the disease is fatal. If the patient does not receive treatment before the onset of the second phase, neurological damage is irreversible even after treatment.

Diagnosis

• The only early sign, one that has been known for centuries, is swollen cervical glands.
• Second Phase diagnosis shows the state of progression of the disease. It entails examination of cerebro-spinal fluid obtained by lumbar puncture and is used to determine the course of treatment.

The long, asymptomatic first phase of T.b. gambiense sleeping sickness is one of the factors that makes treatment difficult. Diagnosis must be made as early as possible in order to preclude the onset of irreversible neurological disorders and prevent transmission. Case detection is difficult and requires major human, technical and material resources. Since the disease is rife in rural areas among poor people with little access to health facilities, this problem is all the more difficult.

Prevention

• Wear protective clothing, treated with permethrin,  including long-sleeved shirts and pants. The tsetse fly can bite through thin fabrics, so clothing should be made of thick material.
• Wear khaki or olive colored clothing. The tsetse fly is attracted to bright colors and very dark colors.
• Use DEET  insect repellant. Though insect repellants have not proven effective in preventing tsetse fly bites, they are effective in preventing other insects from biting and causing illness.
• When sleeping, use bednets.
• Inspect vehicles for tsetse flies before entering.
• Don’t ride in the back of jeeps, pickup trucks or other open vehicles. The tsetse fly is attracted to the dust that moving vehicles and wild animals create.
• Avoid bushes. The tsetse fly is less active during the hottest period of the day. It rests in bushes but will bite if disturbed.
• Attend painful insect bites.

Treatment

If the disease is diagnosed early, the chances of cure are high. The type of treatment depends on the phase of the disease: initial or neurological. Success in the latter phase depends on having a drug that can cross the blood-brain barrier to reach the parasite. Four drugs have been used until now.

First phase treatments

• Pentamidine: discovered in 1941, it is used in treatment of the initial phase of T.b. gambiense sleeping sickness. In spite of a few undesirable effects, it is well tolerated by patients. 4mg/kg im  q daily x10 doses.
• Chemoprophylaxis : Pentamidine 3mg/kg IM q6 months

Alternate:

• Suramine: discovered in 1921, it is used in treatment of the initial phase of T.b. rhodesiense. There are certain undesirable effects, especially on the digestive tract. 20mg/kg   IV x 5 doses over 21 days.

Second phase treatments

Melarsoprol: It is the last arsenical derivative in existence. The undesired effects can be serious. T.b. rhodesiense  resistance to the drug, rising to 30% in parts of central Africa.

Eflornithine:. for resistant T.b. rhodesiense 100 mg /kg q6h  iv  x14 days

Dr. Assad