The stability of porcine rotavirus in feces

Rotaviruses are known as major causal agents of diarrhea in humans and anim als. They affect young animals in intensive rearing and cause great economi c losses. This study evaluated the infectivity of porcine rotavirus maintai ned for 32 months at approximately 10 degrees C in the original stool speci mens. Thirty stool specimens of 1-4-week-old piglets from breeding farms lo cated in the southwest of the State of Parana were selected for this study. They were randomly chosen from stool samples positive for rotavirus RNA by polyacrylamide gel electrophoresis (PAGE) at the time of collection. The t hirty stool samples maintained for 32 months were re-tested by PAGE and 11 out of 30 were still positive showing physical integrity of the eleven segm ents of viral RNA. In order to demonstrate the maintenance of viral infecti vity processed fecal homogenates were inoculated in MA-104 cell cultures. A fter an average of three blind passages 5 out of 11 samples demonstrated cy topathic effect similar to that of a simian rotavirus (SA-11) used as posit ive control. To confirm these findings an immunofluorescence test was perfo rmed and typical cytoplasmatic granular fluorescence was observed. Electron microscopy of stool samples showed that most of the virus particles were s ing le-shelled and some were found to be in advanced state of degradation. The viral nucleic acid extracted from six fecal specimens out of those that showed physical integrity of rotavirus RNA by PAGE were also amplified whe n submitted to RT-PCR demonstrating stability of viral RNA. We therefore co ncluded that porcine rotavirus infectivity is maintained for a long period of time in stool specimens at low temperature. (C) 2000 Elsevier Science B. V. All rights reserved.