Human African Trypanosomiasis

Human African Trypanosomiasis (a.k.a. HAT), (a.k.a. African Sleeping Sickness), is one of the two diseases I will be studying in Oxford.  Here is some background information gleaned from www.bvgh.org as well as http://www.who.int/topics/trypanosomiasis_african/en/.

HAT is caused by a bite from a tsetse fly infected with the parasite trypanosoma brucei, which is largely

found on the banks of shaded streams in Gambian/West Africa.  Once bitten, the parasite enters your bloodstream where it is immediately attacked by your immune system.  This battle continues as the parasite spreads throughout your body until finally breaking the blood-brain barrier and causing a coma, resulting in death.

The disease can be divided into two parts.  Stage one has nondescript symptoms, such as fever, rash, and fatigue, however it is paramount that the disease be caught during this stage, as there is no cure once the disease reaches stage two.  Stage two is characterized by mental deterioration, personality change, increased sleep, coma, and eventually death.

So then why is this a problem?

While practically all of the reported cases are in Africa, with 70% in the Democratic Republic of Congo, there is no cure.  Infecting both cattle and humans, HAT has a devastating economic affect.  Once in the bloodstream, the parasite is attacked by antibodies that recognize the protein on the outside of the cell. However, just when it appears things are looking up, the parasite sheds its outer layer, revealing a completely different protein that the antibodies have never seen before.

Graph showing the concentration of the parasite in the bloodstream as the disease progresses

The dips indicate times when the antibodies have recognized and are successfully attacking 

the disease but the spikes are when the parasite sheds its protein coating and 

becomes unrecognizable to the antibodies

The process of recognizing and fighting the invader must begin all over again.  This process repeats until the parasite is able to break the blood-brain barrier and cause the infected to become comatose and ultimately results in death.