Environmental studies on the survival of leptospires in a farm creek following a human leptospirosis outbreak in Iowa.

Environmental studies were conducted to determine survival potential of leptospires in a farm creek. The creek was the swimming site involved in two previous outbreaks of human leptospirosis. Finding infected mammals in the area and the isolation of pathogenic leptospires from the water supported the theory that an endemic foci existed. Precipitation was sufficient to cause numerous floodings of the creek and surface run-off was evident. The water temperature data indicates that for several months each year the temperature range was adequate for survival of pathogenic leptospires. Saprophytic water leptospires were found during the total year. Although the pH of the creek water ranged from 6.9 - 8.7 the majority of samples were slightly alkaline and considered adequate for maintenance of leptospires. Several nutrients were found in the water including NH3, B1, B12, considered essential for leptospiral growth. If infected mammals are shedding leptospires, it is likely that the creek environmental conditions herein determined are usually adequate for survival. The creek water becomes a vehicle and an ecologic foci for transmission of leptospires to animals and man.