A RETROSPECTIVE CASE-CONTROL STUDY OF RISK-FACTORS ASSOCIATED WITH SALMONELLA-ENTERICA SUBSP ENTERICA SEROVAR ENTERITIDIS INFECTIONS ON DUTCH BROILER BREEDER FARMS

The organized control of Salmonella enterica subsp. enterica serovar E nteritidis (Se) in the Dutch poultry sector aims to prevent vertical t ransmission by the top-down approach, but its effectiveness is now und ermined by the increasing role of horizontal transmission, so that pre ventive hygiene on the poultry farm gains significant importance. In o rder to assess the actual level of preventive hygiene and to identify risk factors, an inquiry was held among a representative number of bro iler breeder farms. It became evident that the hygiene conditions on D utch broiler breeder farms can and must be improved. From a matched ca se-control study, carried out among Se-infected and Se-free farms, the occurrence of Se infection could be explained for about 30% by factor s concerning preventive hygiene, the surroundings of the farm and the farm itself. Thus, other factors, not included in the study, may also be important. No particular key factors were found. Preventive hygiene can certainly reduce the infection risk, but only a comprehensive pac kage of measures can do so. The Dutch Product Board for Poultry and Eg gs and the Dutch Organization of Poultry Farmers have now agreed to st rict hygiene programmes to control horizontal transmission of Se, but these will require considerable technical and financial investments.