Groundwater surveillance of endemic swine pathogens on Iowa swine farms via dead-end ultrafiltration

Groundwater is a plausible medium for transmission of pathogens on and between swine farms that is not addressed in current biosecurity practices. Waterborne disease transmission is uninvestigated for swine. Typical assessments of farm water quality include basic microbial measures, which may not reveal pathogens of concern. This study aimed to assess endemic swine pathogens and manure markers in private wells supplying 40 Iowa swine farms. Wells were sampled in spring (n = 20) or fall (n = 20) using dead-end ultrafiltration, which improves sensitivity of groundwater-borne pathogen detection and allows sampling of viruses, bacteria, and protozoa. Samples were analyzed by quantitative polymerase chain reaction for porcine reproductive and respiratory syndrome virus, porcine epidemic diarrhea virus, porcine circovirus 2, rotavirus group C, enteropathogenic Escherichia coli, Salmonella spp., swine Bacteroides (Pig-1-Bac and Pig-2-Bac), and Cryptosporidium spp. Ten of 40 wells tested positive for at least one microbe. Detection of swine Bacteroides markers in seven wells indicated that a pathway existed from manure to groundwater. Pathogen detections included porcine circovirus type 2 on three farms and Cryptosporidium spp. at two farms. Five samples contained two or more target organisms. Field controls were collected with all samples, and laboratory controls were included for all manipulations and analyses. This study suggests the possibility of waterborne pathogen transmission to swine populations and motivates development of water biosecurity measures on swine farms.