Legionella risk assessment in cruise ships and ferries.

The increasing development of marine traffic has led to a rise in the incidence of legionellosis among travellers. It occurs in similar environments, especially closed and crowded, and aboard ships Legionella survives and multiplies easily in water pipes, spreading into the environment through air conditioning systems and water distribution points. Although in recent years in the construction of cruise ships preventive measures aimed at curbing the proliferation of Legionella (design, materials, focus on the operation and maintenance of the water system), have been taken account, little or no attention has been paid to small ships which, in many cases, are old and not well maintained. The aim of the study was to evaluate the frequency and severity of Legionella contamination in ferries and cruise ships in order to adopt more specific control measures. A prevalence study was carried out on 10 ferries and 6 cruise ships docking or in transit across the port of Messina (Sicily, Italy). Water and air samples collected from many critical points were tested for qualitative and quantitative identification of Legionella. Legionella pneumophila sg 1 was isolated from the samples of shower and tap water in 7 (70%) of the 10 ferries examined, and in 3 (33%) of the 6 cruise ships examined, and L. pneumophila sg 2-14 in 8 (80%) and 1 (16.7%) of these ships, respectively. No Legionella contamination was found in whirlpool baths, air and ice samples. In conclusion, the data obtained confirm higher levels of Legionella contamination in local ferries and cruise ships, underlining the need to adopt corrective actions more specific for these smaller vessels.