Effect of screening and treatment on imported intestinal parasite infections: results from a randomized, controlled trial.

A randomized, controlled trial was undertaken to evaluate the effects of a screening program for intestinal parasite infection in newly arrived Southeast Asian refugees to Montréal, Québec, Canada, during 1982-1983. Families assigned to the screened groups were examined, infected persons were treated and followed until they were infection-free, and all screened families were reexamined at six months. Families assigned to the control groups were examined at six months only. Statistically significant prevalence differences in unadjusted and adjusted estimates over the six-month study period were found between screened persons and controls for each of three groups of refugees from Kampuchea, Laos, and Vietnam, respectively. In general, the greatest prevalence differences ascribed to the screening program were observed in hookworm and Ascaris lumbricoides infections. Continued high levels of Giardia lamblia and Strongyloides stercoralis infection were observed at six months; this raises concerns over the effective therapeutic management of infected persons, the risk of local transmission, and the relevance of screening for intestinal parasites in new arrivals from endemic areas.