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 León region (Spain) was carried out. Breeding farms were stratified according to size and type of production (intensive or extensive). The number of farms to be sampled in each stratum was calculated from the latest census data available and the prevalence of seropositive farms obtained in other countries. Within each herd, the number of sows needed to detect the presence of the disease were sampled, according to within-herd seroprevalence data obtained by us in previous studies. A total of 5098 sow serum samples from 794 different farms were collected during 1992–1993 and tested for the presence of PEDV-specific antibodies, using a blocking ELISA with monoclonal antibodies; 55.9% of herds had at least one positive animal; 29.6% of sera were positive. Seropositive farms were detected throughout the sampled region, indicating that the infection was widespread. Higher farm-level prevalence rates were found in farms with more than 20 sows compared with small ones (≤ 20 sows) and in intensive than in extensive herds. On the other hand, within-farm seroprevalence and mean blocking percentage of positive sera decreased with increasing size of the farm.