Failure of an ointment based on IR3535 (ethyl butylacetylaminopropionate) to prevent an outbreak of cercarial dermatitis during swimming races across Lake Annecy, France.

Cercarial dermatitis, a re-emerging disease world-wide, may affect those engaged in water sports. Many of those who swim in the annual cross-lake races at Annecy in France, for example, develop such dermatitis. In an attempt to see whether ethyl butylacetylaminopropionate (IR3535) would protect swimmers from the dermatitis, the exposed skin on the right side of each of 78 participants in the cross-lake races of 2001 was treated with IR3535-based ointment. When contacted by telephone during the week following the races, 64 (82%) of the subjects reported that they had developed cercarial dermatitis. Subjects with a past history of cercarial dermatitis were more likely to report an attack in 2001 than those who said that they had never had such dermatitis prior to 2001 (P=0.001). The skin lesions were scattered all over the body in 89% of the cases and limited to the left side of the body in 11%. Of the 63 cases who reported time of onset, 32 (51%) had noticed lesions within an hour of the race. The mean duration of clinical manifestations was 4.8 days (range=30 min-18 days). The clinical manifestations were significantly more severe in the subjects aged >16 years than in the younger subjects, although these two age-groups swam in separate races. Thirty-one of the affected subjects attempted to cure their dermatitis, using any of five different treatments. Overall, the results were disappointing, with the IR3535-based ointment, which had initially been developed as an insect repellent, appearing to offer little, if any, protection against cercarial dermatitis.