Final Risk Analysis - Biosecurity New Zealand

9. Bovine Calicivirus Infection
9.1. HAZARD IDENTIFICATION
9.1.1. Aetiological agent
Family: Caliciviridae; Genus: Norovirus, bovine enteric calicivirus and possibly other calicilike
viruses.
9.1.2. OIE list
Not listed.
9.1.3. New Zealand status
Not reported to occur in New Zealand.
9.1.4. Epidemiology
Two genotypes of the virus, the Jena and Newbury agents, occur in Europe (Knowles and
Clarke 2004) and a third type has been described in the USA (Oliver et al 2003).
Despite identification of the viruses in calves nearly 40 years ago (Woode and Bridger 1978),
the role of bovine enteric caliciviruses in calf diarrhoea is not well understood. Experimental
infection of gnotobiotic calves and new born calves caused diarrhoea and intestinal pathology
(Hall et al 1984). However, in naturally occurring cases of diarrhoea, calves are often infected
with several viruses including rotaviruses and coronaviruses that are isolated in higher
numbers than the caliciviruses (Knowles and Clarke 2004). Descriptions of diarrhoea
associated with the virus are restricted to calves. Adult animals are apparently resistant or
immune to infection.
The virus has been described in England (Knowles and Clarke 2004; Woode and Bridger
1978), Germany (Deng et al 2003), the Netherlands (van der Poel et al 2000), and the USA
(Smiley et al 2003). Investigations to identify virus or virus antibodies in countries where the
virus is known to occur generally indicated a high prevalence of infection. In Germany virus
was identified in 8.9% of 381 cases and antibody was found in 99.1% of 824 samples (Deng
et al 2003). In the USA 72% of 75 calf faecal samples were positive in an RT-PCR assay
(Smiley et al 2003). In the Netherlands 44% of pooled faecal samples from 75 veal farms
were found to be positive in an RT-PCR assay, and it was suggested that calves may be a
source of infection for humans. However, a recent study suggests that calf strains differ from
human isolates and calves are unlikely to be a source of infection for humans (Oliver et al
2003). The virus has been known for almost 40 years but attracts little attention from
diagnostic laboratories and research workers. This suggests that it is of minor economic
importance.
It is not known whether the virus occurs in New Zealand. However, since it is widely
distributed in the world and is a trivial pathogen for which active surveys have not been done,
it is likely that the virus may already be present in New Zealand.
MAF Biosecurity New Zealand Import Risk Analysis: Cattle from Australia, Canada, the EU & the USA ● 29