Effects of different animal waste treatment technologies on detection and viability of porcine enteric viruses

Abstract

Enteric pathogens in animal waste that is not properly processed can contaminate the environment and food. The persistence of pathogens in animal waste depends upon the waste treatment technology, but little is known about persistence of porcine viruses. Our objectives were to characterize the porcine enteric viruses (porcine noroviruses [PoNoVs], porcine sapoviruses [PoSaVs], rotavirus A [RV-A], RV-B, and RV-C) in fresh feces or manure and to evaluate the effects of different candidate environmentally superior technologies (ESTs) for animal waste treatment on the detection of these viruses. Untreated manure and samples collected at different stages during and after treatment were obtained from swine farms that used conventional waste management (CWM) and five different candidate ESTs. The RNA from porcine enteric viruses was detected by reverse transcription-PCR and/or seminested PCR; PoSaV and RV-A were also detected by enzyme-linked immunosorbent assay. Cell culture immunofluorescence (CCIF) and experimental inoculation of gnotobiotic (Gn) pigs were used to determine RV-A/C infectivity in posttreatment samples. The PoSaV and RV-A were detected in pretreatment samples from each farm, whereas PoNoV and RV-C were detected in pretreatment feces from three of five and four of five farms using the candidate ESTs, respectively. After treatment, PoSaV RNA was detected only in the samples from the farm using CWM and not from the farms using the candidate ESTs. RV-A and RV-C RNAs were detected in four of five and three of four candidate ESTs, respectively, after treatment, but infectious particles were not detected by CCIF, nor were clinical signs or seroconversion detected in inoculated Gn pigs. These results indicate that only RV-A/C RNA, but no viral infectivity, was detected after treatment. Our findings address a public health concern regarding environmental quality surrounding swine production units.

FIG. 1.

Detection of PoNoV, PoSaV, RV-A, RV-B, and RV-C in pre- and posttreatment samples as well as different steps following treatment in different candidate ESTs and CWM. □, negative; ▒ positive by RT-PCR, seminested PCR, and/or ELISA; ▪, positive by seminested PCR and CCIF.