How does Trypanosoma brucei cause African sleeping sickness?

Trypanosoma brucei is a flagellate protozoan that causes African sleeping sickness, a disease transmitted to humans through the bite of an infected tsetse fly (Glossina).12

Mechanism of Infection

When a tsetse fly feeds on human blood, it transmits the parasites, which then multiply in the host's bloodstream. A key factor in the parasite's ability to cause disease is its sophisticated method of evading the human immune system. The parasite possesses a glycoprotein coat that it can periodically shed and replace with a new coat containing different amino acid sequences. These "antigenic variants" force the host to constantly produce new sets of antibodies, allowing the parasite to survive and replenish its numbers while the immune system struggles to keep pace.13

Disease Progression

The infection typically proceeds in two stages:
* First Stage: The parasites circulate in the blood and invade the lymph nodes and spleen, causing fever, headache, and pain.1
* Second Stage: The parasites eventually invade the brain and spinal cord, leading to severe neurological symptoms, including personality changes, sleep disturbances, profound lethargy, coma, and, if untreated, death.12