Characterization of epidemic diarrhea outbreaks associated with bovine torovirus in adult cows.

Bovine torovirus (BToV) is recognized as an enteric pathogen of calves, but its etiological role in diarrhea and epidemiological characterization in adult cows remain unclear. In 2007-2008, three outbreaks of epidemic diarrhea occurred in adult cows at three dairy farms in Niigata Prefecture, Japan. BToV was the only enteric pathogen detected in these outbreaks, as determined by electron microscopy, reverse transcription-PCR, bacteria and parasite tests of fecal samples, and antibody tests with paired sera. The epidemiological features of the three outbreaks were similar to those of bovine coronavirus infection, except for the absence of bloody diarrhea, with diarrhea spreading among most adult cows, but not in calves, within several days and diarrhea lasting for 3-5 days with anorexia. Decreased milk production and mild respiratory symptoms were also observed in two of the outbreaks. Nucleotide sequence analysis of the BToV nucleocapsid, spike, and hemagglutinin-esterase (HE) genes revealed a close relatedness among the detected BToV strains from each outbreak and those of Japanese BToV strain Aichi/2004. Furthermore, we isolated a BToV strain, designated Niigata (TC), from a fecal sample using a human rectal tumor cell line. Sequence analysis of this isolate and Aichi/2004 indicated that both strains have truncated HE genes with deletions in the 3' region that occurred through cell culture-adaptation. The short projections that are believed to be formed by the HE protein on virus particles were not observed in these cultured strains by electron microscopy. Taken together, these results suggest that BToV causes epidemic diarrhea in adult cows and should be included in the differential diagnosis of diarrhea in adult cows. In addition, our findings indicate that the HE protein of BToV may not be necessary for viral replication.

Development and application of one-step multiplex reverse transcription PCR for simultaneous detection of five diarrheal viruses in adult cattle.

A one-step multiplex reverse transcription (RT)-PCR method was developed for the simultaneous detection of five viruses causing diarrhea in adult cattle: bovine group A rotavirus (GAR), bovine group B rotavirus (GBR), bovine group C rotavirus (GCR), bovine coronavirus (BCV), and bovine torovirus (BToV). The detection limit of the one-step multiplex RT-PCR for GAR, GCR, BCV, and BToV was 10(2), 10(0), 10(1), and 10(2) TCID(50)/ml, respectively, and that for GBR was 10(6) copies/ml. The one-step multiplex RT-PCR with newly designed primers to detect GAR had higher sensitivity than a single RT-PCR with conventional primers, with no false-positive reactions observed for ten other kinds of bovine RNA viruses To assess its field applicability, 59 of 60 fecal samples containing one of these five viruses from all 25 epidemic diarrhea outbreaks in adult cattle were positive in the one-step multiplex RT-PCR assay. Furthermore, using four additional fecal samples containing two viruses (GBR and BCV or BToV), two amplified products of the expected sizes were obtained simultaneously. In contrast, all 80 fecal samples lacking the five target viruses from normal adult cattle were negative in the multiplex assay. Taken together, our results indicate that the one-step multiplex RT-PCR developed here for the detection of GAR, GBR, GCR, BCV, and BToV can be expected to be a useful tool for the rapid and cost-effective diagnosis and surveillance of viral diarrhea in adult cattle.

First report of mixed Entamoeba polecki (ST 1) and E. suis infection in piglets shedding abnormalfeces by histopathological and molecular surveys.

Of the three species of Entamoeba found in swine, namely E. histolytica, E. polecki and E. suis, E. histolytica can also infect humans, producing colitis or abscesses of liver and leading to death. However, the pathogenicity of other species of Entamoeba has not been fully characterized. Here, we conducted histopathology and molecular surveys on a pig farm where piglets had blackish feces or muddy diarrhea. Histopathological examination of two piglets showed necrosis of the mucous surface at the ileum, cecum, or colon, infiltration of neutrophils, and formation of ulcers. Based on morphological characteristics, E. polecki and E. suis trophozoites were mainly detected at lamina propria and surface of the lesion, respectively, and Lawsonia intracellularis, a bacterial pathogen, was also detected. Molecular analysis using the small subunit ribosomal RNA gene on other piglets and a sow revealed infection with both E. polecki and E. suis. These findings corroborate our previous reports that the two Entamoeba spp. are pathogenic in pigs as aggravations of symptoms with L. intracellularis. This is the first report about mixed infection with E. polecki and E. suis.