Relapse infection after chemotherapy in goats experimentally infected with Trypanosoma brucei: pathological changes in central nervous system.

Fourteen goats were experimentally infected with Trypanosoma brucei with the following results: Four animals became terminally ill 24 to 47 days after inoculation of trypanosomes and were killed for necropsy. A second group of four goats became sick, had signs of systemic trypanosomiasis, were treated with diminazine aceturate (Berenil) and recovered showing no signs of disease over observation periods of 151 to 163 days. A third group of six goats, were treated with Berenil and temporarily recovered and in 60 to 79 days after therapy; four of these goats underwent relapse infection characterized by severe central nervous system (CNS) disease. Two of these goats were necropsied 45 days after chemotherapy, before clinical signs were evident, to show early neurological lesions. In group 3 (the relapse group), the microscopic changes became more severe as relapse infection progressed. Microscopically, the central nervous system lesions were edema, hyperemia, and infiltration of plasma cells, small lymphocytes, and some macrophages in the leptomeninges, choroid plexus, and brain parenchyma. Relapse infection is discussed from the standpoint of an occult phase of the disease where parasites are protected from the effects of trypanocidal drugs by the blood-brain barrier.