Astroviruses in poultry

Abstract

Astroviruses are small, round, nonenveloped viruses with star-like morphology and a diameter of 25-35 nm, and their genome constitutes linear, positive-sense ssRNA of about 7 kb of size. Astroviruses are known to cause enteritis in humans, as well as in different animal species, including sheep, cattle, swine, dogs, cats and mice. In poultry, they cause enteritis combined with growth depression and higher mortality, but may also cause other pathological conditions. Duck astrovirus (DAstV) infections trigger hepatitis with a high morbidity and mortality of ducklings. Infections of chickens with avian nephritis virus (ANV) cause diarrhea, growth retardation, kidney damage and gout, resulting in increased mortality. Recently, another member of this group, chicken astrovirus (CAstV), has been described as the etiological factor of “white chicks” condition. Astroviruses have also been detected in domestic geese, guinea fowl, pigeons and different species of wild aquatic birds, and all of them belong to the Astroviridae family, the Avastrovirus genus. Initially, they were further divided into separate species, depending on their host of origin. According to these criteria, six different astroviruses were identified in avian species – in turkeys: turkey astrovirus type 1 (TAstV-1) and type 2 (TAstV-2), in chickens: ANV and chicken astrovirus, and in ducks: DAstV type 1 (DAstV-1) and type 2 (DAstV-2). However, since astroviruses can be transmitted between different species, this classification was replaced with one based on the amino acid structure of viral capsid protein. Currently, astroviruses detected in avian species are classified into three official avastrovirus species: 1, 2, and 3. This review presents data on the replication, pathogenesis, and diagnosis of astroviruses, as well as on the control and prevention of astrovirus infection.