Epidemiology of Leptospirosis

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Abstract
Studies were made on streams contaminated by infected cattle to determine 1) the degree of infectivity of the water (for guinea pigs), 2) how long the water might remain infective and 3) whether down-stream distribution of the organism could be detected. In one area only the 3 original water samples, and only those collected within the pasture area, were infective (2.0 ml but not 0.5 ml). The rapid disappearance of leptospirae from this stream was attributed to removal of the herd from the area and to the adverse effect of gross pollution of the small, sluggishly flowing stream with excreta from the large herd of cattle. L. pomona was isolated from water samples collected from a small stream (140 gal./min.) flowing through another infected pasture on 3 successive weeks after the herd was vaccinated. As little as 0.1 ml. but not 0.01 ml. was infective. Samples collected about 300 and 1000 yards down-stream were also positive (though irregularly) while those from the 1.8-mile sampling station were consistently negative.