No abstract

Direct electron microscopy (EM) and enzyme-immunoassay (rotazyme) results for the detection of rotaviruses in 346 enteric specimens from calves, lambs, piglets and foals were compared. The rotazyme test was at least 3 times more sensitive than direct EM in diagnosing infection. Rotavirus antigen was demonstrated by rotazyme in 22% of 280 scour samples and in 27% of 66 samples from non-scouring animals. There was an association between diarrhoea and higher amounts of rotavirus antigen. This prevalence of rotaviruses detected in animals with diarrhoea highlights the significant involvement of other pathogens identified in the study including Eimeria, Cryptosporidia, Escherichia coli, Campylobacter, and other viruses.

Healthy feedlot beef cattle were surveyed for the presence of Listeria spp. in fecal grab samples taken over 3 months. Composite samples were made from 224 individual animals each month. Listeria monocytogenes was isolated from one composite sample (4%) from the first sampling and not from the subsequent two. Listeria innocua was found in composite samples from all three samplings at levels of 17, 9, and 35%, respectively. From the individual samples comprising the Listeria spp.--positive composites, L. monoytogenes was isolated from one sample (3%) in the second sampling but not in the first or third samplings. L. innocua was found in 9, 8, and 10% of the individual samples comprising Listeria--positive composites in the first, second, and third samplings, respectively. The two L. monocytogenes isolates were pathogenic to mice. Further characterization of these isolates revealed atypical rhamnose fermentation patterns. These results indicate that the frequency of isolation of L. monocytogenes from feedlot beef cattle is low.