Abstract
Enteritis is the major cause of mortality in neonatal calves. Diagnostic work to detect the pathogens involved and identification of risk factors for such infections are imperative to improve calf health. Bovine norovirus (BNoV) and nebovirus prevalence was investigated using RT-PCR in 50 dairy herds in five geographic regions of Sweden. BNoV and nebovirus were found to be common infections in young dairy calves. BNoV was detected in 20% of 250 calves in 48% of the herds. Nebovirus was detected in 5% of the calves in 16% of the herds. Both infections were present in three herds (6%). BNoV-infected calves were younger (median age 7 days) than nebovirus-infected calves (median age 21 days). These infections were not detected in adult cows and young stock over 6 months of age tested in selected herds. Risk factors identified for BNoV infection were a high number of preweaned calves present at the time of sampling, colostrum uptake by suckling the dam only, calf kept in a single pen, and geographic location of herd, while no risk factors for nebovirus infection were identified in the multivariable analysis. Univariable analysis suggested risk factors for nebovirus infection to be geographic location and early separation from the dam.
Highlights
Bovine norovirus (BNoV) and nebovirus are genetically distinct enteric caliciviruses [1].BNoV are closely related to human noroviruses which are considered the worldwide leading cause of non-bacterial gastroenteritis [2]
Both BNoV and nebovirus are frequently detected in naturally occurring calf diarrhea cases and an association has been shown between calf diarrhea and these infections [6]
A high proportion of BNoV- and nebovirus-positive calves were co-infected with other enteritis agents when such infections were analyzed
Summary
Bovine norovirus (BNoV) and nebovirus are genetically distinct enteric caliciviruses [1].BNoV are closely related to human noroviruses which are considered the worldwide leading cause of non-bacterial gastroenteritis [2]. Experimental infections with nebovirus in gnotobiotic calves caused intestinal lesions and diarrhea [1,3]. Experimental infections with BNoV in gnotobiotic calves (strain CV186-OH/00/US) produced lethargy and mild to moderate diarrhea with minute intestinal lesions but with prolonged fecal shedding [4]. Infection with BNoV-type strain Jena virus in conventional calves resulted in severe watery diarrhea and villous atrophy [5]. Both BNoV and nebovirus are frequently detected in naturally occurring calf diarrhea cases and an association has been shown between calf diarrhea and these infections [6]. Previous work on BNoV and nebovirus has been focused on molecular studies, but little information on management risk factors for infection is available
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