'sleeping Sickness' Human African Trypanosomiasis

The name sleeping sickness is a vague description of just one of the symptoms caused by the parasite trypanosome brucei. Human African Trypanosomiasis is what the disease is more commonly referred to, and is found in a confined part of the vast continent Africa. More specifically the sub-Sahara region.

Human African Trypanosomiasis is one of the most neglected tropical infections that is re-emerging as a public health issue in most parts of rural Africa. It is caused by a protozoan called trypanosome brucei, which is a sub species of the trypanosome parasite. The vector-borne parasite is transmitted through the bite of tsetse fly when animals and humans become in contact with the fly. The single celled protozoa have complex life cycle spent partly in the tsetse fly and partly in the mammalian bloodstream.

Human African trypanosomiasis is responsible for infecting and attacking more than 10,000 people each year and kills hundreds of thousands of domesticated animals and prevents livestock production in many areas of Africa. About 500,000 people already carry the trypanosome parasite and will die if left untreated, which is commonly the case as many people are unable to seek treatment. There are two types of African sleeping sickness in which the trypanosome parasite exists in - the East African trypanosomiasis and the west trypanosomiasis. The East African trypanosomiasis is caused by the trypanosome brucei rhodesiense, while the West African trypanosomiasis is caused by a similar parasite called trypanosome brucei gambiense. I will be focusing more on the East African trypanosomiasis as it is most commonly found in infected people and animals.

Human African trypanosomiasis is disease that evolves through distinct clinical stages, with a fatal outcome if symptoms persist and is left untreated. The disease develops as a result of protozoa being carried through the blood and lymphatic circulation of the host, and is characterised by a fever which rises quite high, headaches and mental confusion may occur. The first symptoms begin at the painful site of the tsetse fly's bite after a minimum of 5 days. The skin reaction after the bite is called a chancre and it is typically accompanied by regional lymphadenopathy. After the initial bite, spurs of fevers and headaches occur, while joints become painful and some experience itching. If untreated the disease slowly overcomes the defences of the infected person, and symptoms spread to anaemia, endocrine problems and cardiovascular and kidney disorders.

The disease then enters the neurological phase when the trypanosome parasite passes through the blood brain barrier, which phases into the second stage of the African trypanosomiasis. It begins after a few weeks of being infected. African trypanosomiasis has a clear delineated phase in which the predominant symptoms involve the brain. This involves the nervous system, which affects the patient's speech, the mental process slows down, and the patient sits and stares for long periods of time, or sleeps. Other symptoms that are associated with the second stage resemble those of Parkinson's disease, including imbalance, trembling of the limbs, involuntary movements, muscle tightness, and increasing mental confusion. Eventually the patients are unable to cope with their surroundings and enter a terminal somnolent state, which gives the disease its name. If left untreated the symptoms lead to coma and eventually death.

The heightened activity of the cells of the immune system results in damage to the patients owns organs. The blood vessels are also known to leak as the severity of the illness increases. The leaks in the blood vessels result in the protozoa being spread even more throughout the person's body. Many of the symptoms of sleeping sickness are the result of attempts by the patient's immune system to get rid of the invading parasite.

A high degree of training expertise is required in order to diagnose Human African

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