African trypanosomiasis in the context of "Reservoir host"

A chancre (/ˈʃæŋkər/ SHANG-kər) is a painless genital ulcer most commonly formed during the primary stage of syphilis. This infectious lesion forms around 21 days after the initial exposure to Treponema pallidum, the gram-negative spirochaete bacterium causing syphilis, but can range from 10 to 90 days. Without treatment it may persist for two to six weeks before healing. Chancres transmit syphilis through direct physical contact. These ulcers usually form on or around the anus, mouth, penis and vulva.

Chancres are also associated with the African trypanosomiasis (sleeping sickness), surrounding the area of the tsetse fly bite.

Protozoan infections are parasitic diseases caused by organisms formerly classified in the kingdom Protozoa. These organisms are now classified in the supergroups Excavata, Amoebozoa, Harosa (SAR supergroup), and Archaeplastida. They are usually contracted by either an insect vector or by contact with an infected substance or surface.

Protozoan infections are responsible for diseases that affect many different types of organisms, including plants, animals, and some marine life. Many of the most prevalent and deadly human diseases are caused by a protozoan infection, including African sleeping sickness, amoebic dysentery, and malaria.

Trypanosoma brucei is a species of parasitic kinetoplastid belonging to the genus Trypanosoma that is present in sub-Saharan Africa. Unlike other protozoan parasites that normally infect blood and tissue cells, it is exclusively extracellular and inhabits the blood plasma and body fluids. It causes deadly vector-borne diseases: African trypanosomiasis or sleeping sickness in humans, and animal trypanosomiasis or nagana in cattle and horses. It is a species complex grouped into three subspecies: T. b. brucei, T. b. gambiense and T. b. rhodesiense. The first is a parasite of non-human mammals and causes nagana, while the latter two are zoonotic infecting both humans and animals and cause African trypanosomiasis.

T. brucei is transmitted between mammal hosts by an insect vector belonging to different species of tsetse fly (Glossina). Transmission occurs by biting during the insect's blood meal. The parasites undergo complex morphological changes as they move between insect and mammal over the course of their life cycle. The mammalian bloodstream forms are notable for their cell surface proteins, variant surface glycoproteins, which undergo remarkable antigenic variation, enabling persistent evasion of host adaptive immunity leading to chronic infection. T. brucei is one of only a few pathogens known to cross the blood-brain barrier. There is an urgent need for the development of new drug therapies, as current treatments can have severe side effects and can prove fatal to the patient.

Tsetse flies (/ˈsiːtsi/ SEET-see, UK: /ˈtsɛtsə/ TSET-sə or US: /ˈtsiːtsi/ TSEET-see) (sometimes spelled tzetze; also known as tik-tik flies) are large biting flies that inhabit much of tropical Africa. Tsetse flies include all the species in the genus Glossina, which are placed in their own family, Glossinidae. The tsetse is an obligate parasite that lives by feeding on the blood of vertebrate animals. Tsetse flies have been extensively studied because of their role in transmitting disease. They have pronounced economic and public health impacts in sub-Saharan Africa as the biological vectors of trypanosomes, causing human and animal trypanosomiasis.

Tsetse flies can be distinguished from other large flies by two easily-observed features: primarily, tsetse flies fold their wings over their abdomens completely when they are resting (so that one wing rests directly on top of the other); Secondly, tsetse flies also have a long proboscis, extending directly forward, which is attached by a distinct bulb to the bottom of their heads.