Searching for antibodies against Trichinella spiralis in the sera of patients with fever of unknown cause

Human cases of trichinellosis are often difficult to identify because the signs and symptoms of the disease, if the infection produces any at all, are non-specific, being similar to those observed in several other infectious diseases. In an investigation of Mexican patients with fever of unknown aetiology, attempts were made to develop a serodiagnostic test for the detection of antibodies specific for Trichinella spiralis. The excretory and secretory products of T. spiralis larvae (from the muscle tissue of experimentally infected rats) were used as the antigens in an enzyme-linked immuno-electrotransfer blot assay. The sera tested came from patients with fever of unknown cause (N=250), patients confirmed to have infectious or parasitic diseases other than trichinellosis (N=134) and 168 apparently healthy subjects. Overall, 4% of the samples from the febrile group, 1.8% of those from the healthy subjects but none of the sera from those with 'other diseases' reacted with the antigens of interest (of 45, 49 and 55 kDa). The results not only confirm that human infection with T. spiralis may be asymptomatic but also indicate that such infection may be mis-diagnosed.