Human African Trypanosomiasis (HAT), also known as sleeping sickness, is a life-threatening disease caused by parasites transmitted by infected tsetse flies. According to WHO, the number of cases of HAT has substantially decreased. The current trend suggests that elimination of HAT is possible, and the efforts in the past decade by WHO and National Control Programmes, with MSF, Sanofi, Bayer, DNDi, and others contribute to this.

However, HAT is still a threat to millions in 36 countries in sub-Saharan Africa.

There are two forms of HAT caused by related parasite strains, Trypanosoma brucei (T. b.) gambiense and T. b. rhodesiense, with different geographical distribution.

 

 

Patients with stage 1 disease present with non-specific symptoms such as fever and weakness, and often go undiagnosed. If patients are not treated, stage 2 HAT develops when the parasite crosses the blood-brain barrier and invades the central nervous system. This occurs months to years after initial infection by T. b. gambiense or within weeks for T. b. rhodesiense.At this point the patient develops neurological and psychiatric symptoms such as confusion, lethargy, and convulsions. If left untreated, this disease is usually fatal.

HAT diagnosis requires a complicated series of specialized, invasive tests, including lumbar puncture, to detect the parasite in body fluids and to differentiate between stages 1 and 2 of the disease. For this reason, and because HAT is highly focalized, primarily in rural areas, most endemic countries have organized HAT control into vertical programmes.

These programmes consist of a series of specifically equipped and trained diagnosis and treatment centres togerther with mobile teams in endemic areas. Systematic control measures put in place during the colonial era led to the virtual disappearance of the disease between 1960 and 1965. A variety of reasons since then, including social unrest and war, have led to the relaxation of active screening, treatment, and effective surveillance programmes; and, over the last forty years, the disease has reappeared in endemic form in several foci.

The primary goal of HAT control activities is to save the lives of infected patients through accurate diagnosis and effective treatment. In addition, two complementary approaches are used to reduce disease transmission:

  • Vector control to reduce the number and spread of tsetse flies (through fly traps)
  • Identification and treatment of HAT cases to reduce the reservoir of infectious individuals. Because (asymptomatic) stage 1 cases are unlikely to passively present at a treatment centre, active case-finding campaigns are necessary to detect as many patients as possible at an early-as-possible stage. In these screening campaigns, mobile teams regularly travel to villages known or expected to have HAT–infected individuals; the population is then screened for HAT with a rapid serological test followed by screening for parasites in blood, lymph node aspirates and white cells in CSF from lumbar puncture.

 

References:

[1] WHO Map Production NTD – Distribution of HAT: http://gamapserver.who.int/mapLibrary/Files/Maps/HAT_rh_2013.png?ua=1