The occurrence of salmonella in waste water from Danish slaughterhouses. A quantitative study

In waste water from 11 slaughterhouses, the occurrence of salmonellas were followed continually during a whole week. Thirty-eight samples out of 66 were contaminated. The mean concentrations of salmonellas varied between 0.9 and 668 per 100 ml. Only 4 different serotypes were found viz., S. agona, S. indiana, S. senftenberg, and S. typhimurium. This distribution of serotypes is incompatible with epidemiological data from humans, animals, and feed-stuffs. It is suggested that certain serotypes of Salmonella may become established in sewage systems of slaughterhouses or that propagation of salmonellas may take place in the sewer rats. In one particular plant, large numbers of S. senftenberg were found during the whole period of sampling. It is pointed out that discharge of such heavily polluted waste water into water courses may constitute a public health hazard if the recipient is used for irrigation of vegetables or pastures.