VIRAL ZOONOSES AND FOOD OF ANIMAL ORIGIN - CALICIVIRUSES AND HUMAN-DISEASE

Caliciviruses are important veterinary and human pathogens. The viruse s gain their name from characteristic cup-shaped structures seen on th e virion surface by negative stain electron microscopy. In humans cali civiruses are a major cause of diarrhoeal disease. There are two funda mentally different genome structures amongst human caliciviruses. The Norwalk-like or small round structured viruses (SRSVs) are viruses tha t have an amorphous structure when viewed by EM, they have a genome co mposed of 3 major open reading frames (ORFs). These viruses cause epid emic gastroenteritis amongst all age groups. In contrast, the 'classic ' human caliciviruses (HuCVs) display the typical calicivirus surface structure and have their capsid ORF fused to and contiguous with the n on structural proteins forming one giant polyprotein. HuCVs are predom inantly associated with paediatric infections and are only a minor cau se of disease in humans. Spread of disease for both SRSVs and HuCVs is usually by faecal oral transmission. SRSVs are a major cause of foodb orne gastroenteritis especially linked to the consumption of sewage-co ntaminated shellfish. However, there is no evidence that these viruses replicate in shellfish or that they originate from an animal source.