SEROPREVALENCE OF PORCINE EPIDEMIC DIARRHEA VIRUS-INFECTION AMONG DIFFERENT TYPES OF BREEDING SWINE FARMS IN SPAIN

A cross-sectional study for determining the seroprevalence of porcine epidemic diarrhea virus (PEDV) infection among swine breeding farms in the Castilla y Leon region (Spain) was carried out. Breeding farms we re stratified according to size and type of production (intensive or e xtensive). The number of farms to be sampled in each stratum was calcu lated from the latest census data available and the prevalence of sero positive farms obtained in other countries. Within each herd, the numb er of sows needed to detect the presence of the disease were sampled, according to within-herd seroprevalence data obtained by us in previou s studies. A total of 5098 sow serum samples from 794 different farms were collected during 1992-1993 and tested for the presence of PEDV-sp ecific antibodies, using a blocking ELISA with monoclonal antibodies; 55.9% of herds had at least one positive animal; 29.6% of sera were po sitive. Seropositive farms were detected throughout the sampled region , indicating that the infection was widespread. Higher farm-level prev alence rates were found in farms with more than 20 sows compared with small ones (less than or equal to 20 sows) and in intensive than in ex tensive herds. On the other hand, within-farm seroprevalence and mean blocking percentage of positive sera decreased with increasing size of the farm.