Twenty-six Laotian refugees infected with Clonorchis or Opisthorchis liver flukes, and 15 uninfected controls, were assessed clinically by history, physical examination, serum 5′nucleotidase level, and serum immunoglobulin E level. Ultrasound studies of the biliary tract were also done on a subset of six infected subjects. The results showed no differences between subjects and controls with respect to clinical symptoms, physical findings, 5′nucleotidase, or biliary ultrasound. Mean serum IgE levels were four times higher in fluke-infected individuals than uninfected controls (P < 0.002). Even when those infected with other parasites in addition to Clonorchis were excluded from the analysis, serum IgE levels remained three times higher in fluke infected individuals (P = 0.06). This study provides some evidence that the fluke provokes a mild immune response in the asymptomatic human host but may not require eradication.
Present address: Comprehensive Child Health Program, Children's Hospital Medical Center, 300 Longwood Avenue, Boston, Massachusetts 02115.