Studies of hyperalgesia induced by Trypanosoma brucei brucei infection in rats

Sprague-Dawley rats were infected by intraperitoneal injections of a strain of Trypanosoma brucei brucei. This parasite spreads early to areas in the nervous system which lack a so-called blood-brain or blood-nerve barrier including spinal ganglia. Signs of sensory disturbance in the form of hyperalgesia were observed already seven days post infection, using a hot plate analgesimeter. The sensory disturbances progressed and the rats started to lose weight about 3 weeks post infection, and died about one week later. Immunohistochemistry showed no reduction in density of calcitonin gene-related peptide or substance P immunoreactive fibres in the skin or spinal cord. It is suggested that the sensory disturbances are mediated via release of kinin or interleukin-1 which are known as potent hyperalgesic agents. The hot plate analgesimeter is a simple and reliable method and may be useful in experimental trypanosomiasis to test drugs developed to combat this disease.