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Abstract:
The name astrovirus was used by Madeley and Cosgrove in 1975 to describe a small round virus (approximately 28 nm diameter) with star-like appearance on electron microscopy. It was first seen in faeces from a few children with gastroenteritis. An aetiological role in gastroenteritis has since been confirmed. The virus causes a mild illness after an incubation period of 3-4 days. Antibody studies indicate that infection is widespread and, in Britain, mainly occurs in the 2-5 year age group. Outbreaks occur in, for example, institutions and paediatric wards. The virus usually spreads by the faecal-oral route but food- or water-borne outbreaks have occurred. Strains of astrovirus have been isolated from many animals including calf, lamb, pig, cat, dog, duck and turkey. The lamb strain can cause gastroenteritis but the bovine strain did not cause diarrhoea in gnotobiotic calves. Infected turkeys have scours, and infection in ducklings causes haemorrhagic hepatitis with a mortality up to 25%. Five human serotypes have been described, all antigenically distinct from the bovine and ovine strains. The human astrovirus does not replicate in conventional tissue cultures but undergoes a non-productive cycle in human embryo kidney cells, and productive replication in the presence of trypsin. It is a positive-strand RNA virus, which is acid stable (pH3), survives at 60 degrees C for five but not 10 minutes and, like the enteroviruses, resists inactivation by alcohols. It has a density of 1.35-1.37 g/ml in caesium chloride.
Insights
Astrovirus, a small, star-shaped virus, causes mild gastroenteritis in children and spreads through the fecal-oral route. It has been identified in various animal strains, with differing effects on hosts.
Area of Science:
- Virology
- Gastroenterology
- Public Health
Background:
- Astrovirus, identified in 1975, is a small, round virus (~28 nm) with a distinctive star-like appearance under electron microscopy.
- It is a significant etiological agent of gastroenteritis, particularly in young children, causing mild illness after a 3-4 day incubation period.
- Infections are widespread, with outbreaks noted in institutional settings and pediatric wards, primarily transmitted via the fecal-oral route.
Purpose of the Study:
- To describe the characteristics of astrovirus, including its morphology, disease association, transmission, and host range.
- To detail the serotypes, replication, and stability of human astrovirus strains.
- To compare human astrovirus with strains isolated from various animal species.
Main Methods:
- Electron microscopy for viral morphology.
- Clinical observations and epidemiological studies for disease association and transmission.
- Serological studies to identify human and animal strains.
- Tissue culture experiments to assess replication.
- Physicochemical analyses for stability and density.
Main Results:
- Astrovirus confirmed as a cause of gastroenteritis, predominantly in the 2-5 year age group in Britain.
- Widespread animal strains identified (lamb, calf, pig, cat, dog, duck, turkey) with varying pathogenicity.
- Human astrovirus replicates non-productively in human embryo kidney cells, but productively with trypsin.
- Human astrovirus is acid-stable (pH3), heat-stable at 60°C for 5 minutes, and resistant to alcohol inactivation.
- Five distinct human serotypes are described, antigenically different from bovine and ovine strains.
Conclusions:
- Astrovirus is a common cause of mild gastroenteritis in children, with diverse animal reservoirs.
- Understanding its replication and stability is crucial for developing control strategies.
- Further research into human and animal astrovirus strains can elucidate cross-species transmission and disease dynamics.