SummaryOBJECTIVES 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 ϭ 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.keywords health screening, parasites, tropics correspondence Dr P. L. Chiodini,

1. Skeletal and other clinical features in twenty-three patients with homocystinuria have been compared with those in sixteen patients with Marfan's syndrome. 2. The two diseases are clinically similar but florid arachnodactyly and scoliosis are commoner in Marfan's syndrome, whereas widening of epiphyses and metaphyses of long bones is a distinctive feature of homocystinuria. 3. Patients with homocystinuria frequently have osteoporosis at a young age with a high incidence of vertebral involvement including biconcavity and flattening. Patients with Marfan's syndrome do not have osteoporosis and may have excessively tall vertebrae. 4. Mental retardation and thrombosis are common in homocystinuria and uncommon in Marfan's syndrome. 5. Homocystinuria is most probably inherited as an autosomal recessive and Marfan's syndrome as an autosomal dominant. 6. The two diseases should be differentiated because of the thrombotic risk in homocystinuria, and also because in this disease there is a possibility of treating the biochemical defect. 7. Although patients with homocystinuria may present to the orthopaedic surgeon with osteoporosis, severe genu valgum or scoliosis, the disease is an uncommon cause of these defects.

While the morbidity in FCO personnel is low in comparison to other expatriate groups, the higher risk of morbidity in employees and unaccompanied individuals merits further research, particularly to ascertain whether work demands, isolation or risk-taking behaviour are contributory factors.

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Travellers to the tropics worry about catching "tropical" diseases. Those