Outbreak of Entamoeba histolytica and Giardia lamblia infections in travellers returning from the tropics.

Of 160 travellers from various regions in Italy who had taken part in a five-day organized trip to Phuket, Thailand, and been accommodated in the same luxury hotel, 17 showed either amebic abscess or colitis. A pretested questionnaire that focused on the consumption of foods and beverages well known to be a source of intestinal infection in endemic areas was available from these 17 patients as well as from 41 out of 74 asymptomatic travellers. Stool samples for parasitological examination were also available. In patients affected with amebic abscess, antibodies to Entamoeba histolytica were also determined. Overall, parasitological examinations were negative in eight (13.8%) patients, and 50 out of 58 (86.2%) were found to be positive. The prevalence of Giardia lamblia and E. histolytica infections was 67.2% and 72.4%, respectively, and 28 subjects (48.3%) were stool-positive for both of these protozoa. No other intestinal parasites were found. No particular food or beverage was consumed by all of the parasitized subjects and by none of the stool-negative individuals. However, the consumption of drinks with ice, ice cream and raw fruit in ice was significantly associated with E. histolytica and/or G. lamblia infections (Fisher's exact test, p ranging from 0.03 to 0.003).