The occurrence and significance to animal health of salmonellas in sewage and sewage sludges

SUMMARY A total of 882 samples of settled sewage, sewage sludges and final effluents from eight sewage treatment plants were examined for the presence of salmonellas. Of these samples 68 % were positive, isolations being made most frequently from settled sewage (85 %), raw sludge (87 %) and anaerobically digested sludge (96 %). Fewer isolations were made from final effluent (24%) and processed sludges (58%). Samples usually contained less than 200 salmonellas/100 ml and arguments are presented that such concentrations should not lead to disease in animals if suitable grazing restrictions are followed.