Giardiasis in American Travelers to Madeira Island, Portugal

Abstract

A high incidence of diarrhea was reported in a group of approximately 1,400 Americans who traveled to the Portuguese island of Madeira in October 1976. A mail questionnaire survey revealed that 39% of the responding 859 travelers experienced diarrhea; in 42% of these diarrhea lasted for longer than 1 week. The most frequent accompanying symptoms were abdominal cramps (75%), abdominal distention (72%), nausea (70%), and weight loss (40%). Of all travelers surveyed, 33% developed an illness resembling giardiasis with a median incubation period of 4 days. Of 35 ill patients who had a stool culture, enteric pathogens were recovered from 4 (3 Shigella and 1 Salmonella). On the other hand, of 58 ill patients whose stools were examined for parasites, Giardia lamblia was recovered from 27 (47%). Analysis of the epidemiologic data showed that drinking tap-water on the island was significantly associated with illness; eating ice cream or raw vegetables on the island was also implicated. There was no evidence of continuing transmission of giardiasis in American tourists visiting Madeira 8–12 months after the outbreak.