African Trypanomiasis

African trypanosomiasis is caused by species of Trypanosoma brucei parasites. The disease is also known as African Sleeping Sickness.

Transmission is through the bite of tsetse flies, and these flies are only found in Africa. There are three morphologically identical parasite species which cause African Sleeping Sickness – (i)T. brucei brucei (ii) T. brucei gambiense and (iii)T. brucei rhodesiense.

Tsetse Fly - The Vector

Tsetse Fly – The Vector

Trypanosoma brucei - The Parasite

Trypanosoma brucei – The Parasite

 

 

 

 

 

 

 

 

When trypanosomes are injected during a tsetse fly’s feeding period, they multiply and eventually disseminate through the bloodstream. A ‘trypanosomal chancre’ often then appears 3 or more days after the bite.

Trypanosomal_chancre

Trypanosomal chancre on a patient’s throat.

As the parasites multiply in the patient’s lymphatic system, parasitaemia of 5 – 12 days results. Waves of parasitaemia are associated with fever. Parasites may then cross the blood brain barrier, to enter into the CNS. CNS involvement is typically at the late stage of the disease.

Epidemiology

Control efforts have make remarkable reductions in case numbers of the last 15 years. In 2009, cases notified to the WHO fell below 10,000 for the first time in 50 years. In 2013 there were 6314 cases recorded, although it is estimated many more individuals were infected.

T. b. gambiense is distributed throughout West and Central sub-Saharan Africa.

T. b. rhodesiense is distributed throughout East and Southern Africa.

 

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