African trypanosomiasis: treatment-induced invasion of brain and encephalitis.

Histological sections of the brain from Microtus montanus infected with Trypanosoma rhodesiense and treated after the initial infection period showed that trypanosomes promptly invade the brain tissue and induce a severe encephalitis within a very short time. These findings suggest that the brain invasion and encephalitis that occur after treatment in sleeping sickness must be considered an effect of the treatment. The results illustrate that the brain invasion is probably not hematogenic but rather due to a process of parasite migration from the subarachnoidal space over the Virchow-Robin spaces into the brain.