Objectives: To examine the utility of the different elements of screening expatriates and travellers returned from the tropics for parasitic disease (exposure history, symptoms, examination and laboratory tests).
Methods: In phase 1 (conducted prospectively 1990-91), 1029 asymptomatic returnees had a detailed questionnaire and interview on risk-behaviour, physical examination and laboratory tests. In phase 2 (1997-98), 510 consecutive patients referred for routine screening (276 symptomatic and 234 asymptomatic) were screened with laboratory tests.
Results: Exposure history did not correlate reliably with parasite burden. In phase 1 physical examination revealed 387 abnormalities, only three of which indicated parasitic disease. Schistosomal serology was positive in 11% (CI 9-13) of these asymptomatic cases including patients with light or no reported freshwater exposure. Stool microscopy was positive in 19% (CI 16-22) of cases not correlated with reported eating habits, and eosinophilia was present in 8% (CI 6-10). In phase 2 reported symptoms did not correlate with parasitic disease. Schistosomiasis was present in 15% (CI 13-24) of asymptomatic and 18% (CI 13-22) of symptomatic individuals (OR 1.2 P = 0.46); stool microscopy was positive in 14% of both symptomatic and asymptomatic patients, and eosinophilia in 9% of symptomatic and 6% of asymptomatic individuals.
Conclusion: Potentially serious asymptomatic infection is common in travellers. Detailed exposure history, symptom history and physical examination added little to detecting cases. Stool microscopy, schistosomal serology and eosinophil count all had good yield. Filarial serology had low yield in patients without eosinophilia.