The involvement of endotoxins in Trypanosoma brucei brucei infection in CD-1 mice was investigated by the Limulus amoebocyte lysate (LAL) test. At 7 days post-infection mean serum endotoxin level was elevated by 2·5 times (36·4 pg/ml cf. control 14·25 pg/ml, P < 0·001) and a similar increase was maintained throughout the infection (survival 28–35 days). Purified disrupted parasites contained significant endotoxin activity (mean value 280 pg/mg protein). The mouse infections were also associated with progressive Gram-negative bacteraemia (present in 4 Out of 5 infected animals by day 28 p.i.). The increased endotoxin levels may be due to parasite products, the products of intercurrent bacterial infections, other unidentified sources (e.g. from the gut), or a combination of these. It is concluded that the raised endotoxins may be important contributive factors in the pathogenesis of experimental murine trypanosomiasis.
