The tsetse fly bite erupts into a red sore and within a few weeks the person can experience fever, swollen lymph glands, aching muscles and joints, headaches and irritability.
In advanced stages, the disease attacks the central nervous system, causing changes in personality, alteration of the biological clock (the circadian rhythm), confusion, slurred speech, seizures, and difficulty walking and talking. These problems can develop over many years in the Gambiense form and some months in the Rhodesiense form; if not treated, the person will die.
Control of sleeping sickness is based on reduction of the reservoirs of infection by early diagnosis and control of tsetse flies.
Prevalence
In 1995, WHO Expert Committee estimated that 60 million people were at risk with an estimated 300 000 new cases per year in Africa, with fewer than 30,000 cases diagnosed and treated.
In 2004, the number of new reported cases fell to 17 616 and WHO considered in that due to increased control, estimated cumulative rate to be between 50 000 and 70 000 cases .
In 2009, the number of new cases reported dropped below 10 000 (9 878) for first time in 50 years and the estimated number of actual cases is currently 30 000. This trend has been maintained in 2010, with 7139 cases reported.
Symptoms
Following the bite of the infected fly, the parasite multiplies in the lymph and the blood, causing headaches, fever, weakness, pain in the joints, and stiffness. People who become infected may or may not show signs of illness immediately. With time the parasite crosses the blood-brain barrier and migrates to the central nervous system. Here it causes various neurological changes which include psychiatric disorders, seizures, coma and ultimately death.
In the case of T.b. rhodesiense infections, the disease is acute, lasting from a few weeks to several months while in T.b. gambiense infections the disease is chronic, generally lasting several years without any major signs or symptoms.
Diagnosis
Diagnosis of the disease requires confirming the presence of the parasite in any body fluid, usually in the blood and lymph system. Early diagnosis is difficult because of the lack of specific signs or symptoms in the first stage of the disease and also because of the lack of sensitivity of the parasitological methods available.
Serological tests for screening available today are only useful for T.b.gambiense infections (Card Agglutination Trypanosomiasis Test or CATT) and establishing suspicion of infection only. Confirmation of infection requires the performance of parasitological tests to demonstrate the presence of trypanosomes in the patient. The parasites can be present in any body fluids. However, the number of parasites can be so low (mainly in the gambiense form of the disease) that available parasitological methods may not be sensitive enough to find them. Thus a negative parasitological result in the presence of a positive serological test does not necessarily indicate absence of infection, and tests may have to be repeated over time to achieve diagnosis.
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Treatment
Only four drugs are registered for the treatment of human African trypanosomiasis: pentamidine, suramin, melarsoprol and eflornithine. However, none of them are anodyne as all have a certain level of toxicity. Pentamidine and suramin are used in the first or early stage of T.b.gambiense and T.b. rhodesiense infections respectively.
Melarsoprol is used in the second or advanced stage of both forms of the disease, being the only treatment available for late stage of T.b. rhodesiense.
Eflornithine can be use in monotherapy but only in the second stage of the T.b.gambiense infections since it has been found not to be effective against the disease due to T.b rhodesiense.
After its inclusion in the WHO 'Essential Medicines List' in April 2009, the combination of eflornithine and nifurtimox has been adopted as first line treatment for second stage gambiense human African trypanosomiasis in major disease endemic countries (Cameroon, Central African Republic, Chad, Congo, Côte d'Ivoire, Democratic Republic of the Congo, Equatorial Guinea, Gabon, Guinea, South Sudan, and Uganda). The combination of both drugs reduces the duration of eflornithine monotherapy treatment and is easier to administer, while maintaining the same level of efficacy and safety.
All drugs current used for the treatment of human African trypanosomiasis are donated to WHO for free distribution by the manufacturers: Sanofi and Bayer. Drugs are stored in and shipped by MSF-Logistics.
Drugs can be requested to: simarrop@who.int or francoj@who.int