The pathogenesis of trypanosomiasis of the CNS. Studies on parasitological and neurohistological findings in trypanosoma rhodesiense infected vervet monkeys.

Parasitological examinations of the cerebrospinal fluid of 20 vervet monkeys (Cercopithecus aethiops), that had been infected with Trypanosoma rhodesiense, revealed that the CSF was regularly infested with trypanosomes in the early phase of the disease, at the earliest on the 13th day, in most of the animals in the 3rd or 4th week, after infection. Follow-up examinations of the CSF during the further course of the disease also regularly proved positive for trypanosomes. Histological studies in the animals that died at a mean of 65 days after infection (range 35 to 107 days) revealed encephalitis in the animal with the longest course of the disease. In all the other animals, meningitis alone was found. This was accompanied by a modified early encephalitic reaction, characterized by lympho-plasma-cellular infiltrates exclusively in the adventitial sheaths of those blood vessels passing into the brain from the leptomeninges affected by inflammatory infiltration. The early encephalitic reaction is interpreted as the morphological manifestation of an infestation of the perivascular spaces (Virchow-Robin spaces) with parasites. It indicates that CSF parasitosis in the early phase represents the point of departure for the encephalitis that develops in the late phase of the disease, and that the encephalitis presumably develops as a result of the migration of the trypanosomes out of the subarachnoid space into the perivascular spaces, and from there into the brain.