Risk of otitis externa after swimming in recreational fresh water lakes containing Pseudomonas aeruginosa

BMJ 1995;311:1407-1410 (25 November)

General practice

Risk of otitis externa after swimming in recreational fresh water lakes containing Pseudomonas aeruginosa

Ilse A van Asperen, epidemiologist,^a Carolien M de Rover, epidemiologist,^b Jack F Schijven, researcher,^a Suparto Bambang Oetomo, physician,^b Joop F P Schellekens, medical microbiologist,^a Nan J van Leeuwen, microbiologist,^a Cees Colle, environmentalist,^c Arie H Havelaar, microbiologist,^a Daan Kromhout, professor in epidemiology,^a Marc W J Sprenger, medical microbiologist ^a

^a National Institute of Public Health and Environmental Protection, Bilthoven, Netherlands, ^b District Health Authority de Achterhoek, ^c Provincie Gelderland

Correspondence to: Ms I A van Asperen. Department of Infectious Diseases Epidemiology, National Institute of Public Health and Environmental Protection, PO Box 1, NL-3720 BA, Bilthoven, Netherlands.

Abstract

Objective: To determine whether an outbreak of otitis externawas due to bathing in recreational fresh water lakes and toestablish whether the outbreak was caused by Pseudomonas aeruginosain the water.
Design: Matched case-control study.
Setting: The Achterhoek area, the Netherlands.
Subjects: 98 cases with otitis externa and 149 controls matchedfor age, sex, and place of residence.
Main outcome measures: Odds ratios for type of swimming waterand frequency of swimming; presence of P aeruginosa in ear swabsand fresh water lakes.
Results: Otitis externa was strongly associated with swimmingin recreational fresh water lakes in the previous two weeks(odds ratio 15.5 (95% confidence interval) 4.9 to 49.2) comparedwith non-swimming). The risk increased with the number of daysof swimming, and subjects with recurrent ear disease had a greatlyincreased risk. The lakes met the Dutch bathing water standardsand those set by the European Commission for faecal pollutionin the summer of 1994, but P aeruginosa was isolated from allof them, as well as from the ear swabs of 78 (83%) of the casesand 3 (4%) of the controls.
Conclusions: Even when current bathing water standards are met,swimming can be associated with a substantial risk of otitisexterna because of exposure to P aeruginosa. People with recurrentear disease should take special care when swimming in waterscontaining P aeruginosa.

Key messages

Key messages
Most attention has been given to faecal pollution of such water
In this study a relation was found between otitis externa and swimming in fresh water lakes, due to Pseudomonas aeruginosa that was present in the lakes
All the lakes met current bathing water standards, which, however, do not cover P aeruginosa
Persons with recurrent ear disease should take special care swimming in waters containing P aeruginosa because they have an increased risk of otitis externa

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