Parasitology - TRYPANOSOMES

Trypanosomes belong to the order KINETOPLASTIDA, so-called because of the large DNA-containing structure, the kinetoplast, found at the base of the flagellum

AFRICAN TRYPANOSOMIASIS

The vector for African trypanosomiasis is theTsetse fly and the distribution of the disease parallels the distribution of the vector.

The symptoms of African trypansomiasis depend on host and the sub-species of trypanosome. In T. gambiense infections there is massive stimulation of immune system and complement-mediated lysis of host cells (gives characteristic anemia). 

Generalized pain, weakness, cramps and swelling of neck lymph nodes. Parasites invade all organs of the body including heart and CNS. 

The latter leads to apathy, mental dullness, tremors, convulsions and sleepiness, coma. There is rapid weight loss and death a few months later from malnutrition, heart failure, pneumonia or a parasitic infection. 

In the case of T. brucei rhodesiense infections, there is no coma or nervous system symptoms as probably patient dies before these can develop.

Recently on the increase, there are a minimum of 20,000 new cases a year; 50,000,000 people are at risk. Nagana prohibits cattle raising in a large area of Africa causing further malnutrition.

Structure of an African Trypanosome

Trypanosomes are unicellular protozoans (figure 1) with a single flagellum that contains microtubules in the 9+2 arrangement typical of other flagella. At the base of the flagellum is the kinetoplast which contains DNA in the form of about 6000 catenated circles. The kinetoplast DNA is 10% of the total cellular DNA and is the important site of action of some anti-trypanosome drugs such as ethidium. The kinetoplast is part of the single long mitochondrion which changes morphology during various stages of life cycle.

Most other organelles are those typical of any eucaryotic cell. At  surface of the cell are sub-membranous pellicular microtubules which give the trypanosome its shape. These underlie a typical  plasma membrane which is often covered by an electron-dense surface coat.

 Epimastigotes grown in culture; kinetoplast (KP) is anterior to the nucleus (N). In most species of Trypanosoma, this stage reproduces in the gut of the vector.

Trypomastigotes in blood smear; kinetoplast is posterior to the nucleus. 

This stage is found in all species of Trypanosoma,

 and in most species it is the only stage that reproduces in the vertebrate (human) host.

http://www.youtube.com/watch?v=7q9PTljtRhE&feature=autoplay&list=PL0390D29087A8EDFF&lf=results_video&playnext=2