Trypanosoma evansi

Trypanosoma evansi is a type of single-celled parasites of the genus Trypanosoma, which occurs as pathogens of Surra, an epizootic disease, especially in horses and camels in North Africa, the Middle East, Asia and Latin America. The parasite is usually transmitted by bites of brakes; However, a proliferation of the parasite does not take place in the insect. Even the originally -called pathogen Trypanosoma equinum the Mal de Caderas, a disease in horses in South America, is now counted for evansi Trypanosoma species. A case of Trypanosoma evansi infected by humans was described in India; usually people are resistant to this pathogen.

Discovery and description

Trypanosoma evansi was built in 1880 by the British Veterinary Griffith Evans ( 1835-1935 ) discovered in India in the Surra diseased horses. According to Evans, the kind from the vet JH Steel was only mistakenly called spirochete evansi, assuming it were bacteria from the group of spirochetes. 1888 this was corrected for today valid name Trypanosoma evansi. The discovery of Trypanosoma evansi was the first case in which a parasite was detected from the kind of trypanosomes as pathogens.

The protozoa have a single flagellum which extends on the cell surface with an undulating membrane to the front end of the cell and there is a free-running scourge. The cells also have a small kinetoplast, an accumulation of deoxyribonucleic acid inside a large mitochondrion; in some isolates lack the kinetoplast. The parasite occurs only in an up to 33 microns long trypomastigotes cell shape. Microscopically the parasite Trypanosoma brucei or Trypanosoma not equiperdum is to be distinguished.

Currently, the type Trypanosoma evansi is classified in the subgenus Trypanozoon. With Trypanosoma equinum a separate species was described originally described in South America as a causative agent of Mal de Caderas or cross paralysis in horses. This species is now considered a form of Trypanosoma evansi.

According to molecular studies are all representatives of the subgenus Trypanozoon, which in addition Trypanosoma evansi and Trypanosoma equiperdum and the three subspecies of Trypanosoma brucei are very similar. Trypanosoma evansi is different from Trypanosoma brucei practically only by complete absence of kDNA maxi Circles, occurring in many copies in kinetoplast mitochondrial DNA. This difference is the reason that Trypanosoma evansi can not reproduce in tsetse flies. From the mitochondrial DNA encoded genes among other cytochromes are essential for oxidative energy metabolism, which is required by Trypanosoma brucei for propagation in tsetse flies. In mammals, trypanosomes is limited to glycolysis for energy. Detailed molecular studies came to the conclusion that T. evansi is not monophyletic, but a set of multiple spontaneous mutations caused by Trypanosoma brucei group; it was concluded that a classification as a separate species was not warranted. It has been proposed to classify the subtype of parasite Trypanosoma brucei, Trypanosoma brucei evansi labeled.

Distribution and host animals

Trypanosoma evansi is in North Africa, the Middle East, in Asia and in Latin America before. As a natural hosts besides horses and camels and cattle, buffalo, deer, the Asian elephant and tiger are called. The most important vector are braking, but also contribute to stable flies were disseminated. In South America, vampire bats are involved in the transmission; these can serve as a reservoir host in which the parasite multiplies in the blood. In South America, also does the capybara as a wild reservoir.

A single case of a diseased secured by a Trypanosoma evansi infection in humans has been described in India. Detailed analysis showed that the patient had mutations in both alleles of the gene Apoli. The protein encoded by this gene Apoli protein is an apoprotein that is responsible for the resistance of the human serum against many trypanosomes. After this case was found in the local population that is obviously a greater number of people with the parasite had contact without getting sick though.

Life cycle

Trypanosoma evansi has a simple life cycle of trypanosomes; multiplication takes place only in mammals, a change of form, as with other trypanosomes does not occur. The transmission by blood-sucking insects is by mechanical means by remaining in the mouth parts of the brake cells of the last blood meal on an infected mammal. After the engraving of a vector which had recently taken a blood meal from an infected animal, get trypanosomes into the tissue of the mammal, and from there into the lymphatic system and into the bloodstream where they multiply by longitudinal division.