The infectivity of pig rotavirus in stools

Rotaviruses are the major pathogen for both human and animal. They affect young animals in intensive rearing and cause great economic losses. This study intended to evaluate the infectivity of porcine rotavirus maintained for 32 months at approximately 10ºC. in the original stools specimens. Thirty stools specimens of 1-4-week-old piglets originating from breeding farms located in the southwest region of the Paraná State were selected for this study. They were randomly chosen from stools samples positive for rotavirus by polyacrylamide gel electrophoresis (PAGE) at the time of collection. The thirty stools samples maintained for 32 months at approximately 10ºC were re-tested by PAGE and 11 out of 30 were still positive showing the integrity of the eleven bands of viral RNA. To demonstrate the maintenance of viral infectivity, clarified and trypsin-treated stools specimens homogenates were inoculated in MA-104 cell cultures. After an average of 3 blind passages 5 out of 11 samples demonstrated cytophathic effect similar to that of standard simian rotavirus (SA-11). To confirm these findings, a immunofluorescent test was used and demonstrated typical cytoplasmic granular fluorescence. Electron microscopy of stools samples showed that most of the virus particles were single- shelled and some were found to be in an advanced state of degradation. Therefore the conclusion was that porcine rotavirus infectivity is maintained for a long period of time in stool specimens at low temperature. This certainly is an important aspect for the maintenance of viable virus in natural condition as well as for the transmission of the disease. Os rotavírus constituem-se nos principais patógenos da diarréia em humanos e animais. Afetam os animais jovens em criações intensivas e causam grandes perdas econômicas. Este estudo avaliou a infecciosidade do rotavírus suíno mantido por 32 meses a aproximadamente 10ºC nas amostras originais de fezes. Trinta amostras de fezes de leitões de 1-4 semanas de idade, provenientes de granjas da região sudoeste do Paraná, foram selecionadas para o estudo. As amostras foram colhidas no período de março a outubro de 1991 e selecionadas ao acaso dentre as positivas para rotavírus pela eletroforese em gel de poliacrilamida (EGPA), à época da colheita. Estas foram retestadas por EGPA 32 meses após manutenção à temperatura de aproximadamente 10ºC. Onze das 30 amostras ainda foram positivas, mostrando a integridade das 11 bandas de RNA viral. Com o intu