Legionnaires diseases and the water environment in Israel

Using systematically evaluated methods, 39 strains of Legionella were isolated from 302 samples of water from surface sources, fishponds, cooling systems and wastewater stabilization ponds. Most isolations were made during the warm irrigation season (May to October). Legionella pneumophila was the most frequent species isolated. Evidence that Legionella can infect and survive for long periods, at low temperatures, in a natural aquatic protozoan (Acanthamoeba palestinensis), may provide a possible explanation for the over-wintering mechanism during which period the organisms are rarely identified in free form in water samples. Antibody levels to Legionnaires disease bacteria were determined on a total of 2,410 blood samples drawn from 1,335 individuals residing in rural agricultural cooperative villages (Kibbutzim). The population studied included irrigation and other water contact workers exposed to aerosolized water from sprinkler irrigation systems using clean water, wastewater and non-water contact individuals as controls. Water contact workers carried antibodies to Legionella pneumophila 7 times more frequently than the non-water contact control group (2.8% vs 0.4%). There was no difference between those exposed to sprinkler irrigation with clean water or wastewater effluent. It is concluded from this study that under the conditions in Israel where Legionella spp. are ubiquitous in irrigation water sources, workers exposed to aerosols from sprinkler irrigation have a high occupational risk of infection with Legionnaires disease bacteria.