Abstract:
Background: There are three subspecies of Trypanosoma brucei: T. b. gambiense, T. b. rhodesiense
and T. b. brucei. The first two are infectious to humans, whilst T. b. brucei is not. Identifying an
animal model of T. b. brucei that mimics human African trypanosomiasis (HAT) would enable
researchers to study HAT without subjecting themselves to undue risks such as accidental
infection.
Objectives: This study assessed the sequential clinical, parasitological and haematological
changes in vervet monkeys infected with T. b. brucei.
Methods: Three vervet monkeys were infected with a 104 inoculum of T. b. brucei (isolate
GUTat 1). Late-stage disease was induced by subcurative treatment with diminazene
aceturate 28 days post-infection. The animals were treated curatively with melarsoprol upon
relapse. Parasitaemia and clinical signs were monitored daily and, at weekly intervals, the
monkeys’ blood and cerebrospinal fluid (CSF) were sampled for haematology and parasitosis
assessments, respectively.
Results: The first-peak parasitaemia was observed between seven and nine days postinfection.
Clinical signs associated with the disease included fever, dullness, pallor of mucous
membranes, lymphadenopathy, splenomegaly and oedema. Late-stage signs included
stiffness of joints and lethargy. The monkeys developed a disease associated with microcytic
hypochromic anaemia. There was an initial decline, followed by an increase, in total white
blood cell counts from early- to late-stage disease. Trypanosomes were detected in the
CSF and there was a significant increase in white cell counts in the CSF during late-stage
disease. Infected vervet monkeys displayed classical clinical symptoms, parasitological and
haematological trends that were similar to monkeys infected with T.b. rhodesiense.
Conclusion: The T. b. brucei vervet monkey model can be used for studying HAT without
putting laboratory technicians and researchers at high risk of accidental infection.
