Astroviridae is a family of non-enveloped ssRNA viruses that cause infections in different animals.[1] The family name is derived from the Greek word astron ("star") referring to the star-like appearance of spikes projecting from the surface of these small unenveloped viruses.[2] Astroviruses were initially identified in humans but have since been isolated from other mammals and birds. This family of viruses consists of two genera, Avastrovirus (AAstV) and Mamastrovirus (MAstV).[3] Astroviruses most frequently cause infection of the gastrointestinal tract but in some animals they may result in encephalitis (humans and cattle), hepatitis (avian) and nephritis (avian).[4]
Astroviruses were first identified in humans in 1975 from the stool of children with diarrhea. Human infections are usually self-limiting but may also spread systematically and infect immunocompromised individuals.[5]
The International Committee on Taxonomy of Viruses (ICTV) established Astroviridae as a viral family in 1995.[6] There have been over 50 astroviruses reported, although the ICTV officially recognizes 22 species.[7] The genus Avastrovirus comprises three species: Chicken astrovirus (Avian nephritis virus types 1 - 3), Duck astrovirus (Duck astrovirus C-NGB), and Turkey astrovirus (Turkey astrovirus 1). The genus Mamastrovirus includes Bovine astroviruses 1 and 2, Human astrovirus (types 1-8), Feline astrovirus 1, Porcine astrovirus 1, Mink astrovirus 1 and Ovine astrovirus 1.[7]
Avastroviruses are members of the Astroviridae family that infect birds.[7] Avastrovirus 1-3 are associated with enteric infections in turkeys, ducks, chicken and guinea fowl. In turkey poults 1-3 weeks of age, some symptoms of enteritis include diarrhea, listlessness, liver eating and nervousness. These symptoms are usually mild but in cases of poult enteritis and mortality syndrome (PEMS), which has dehydration, immune dysfunction and anorexia as symptoms, mortality is high.[8] Post mortem examination of the intestines of infected birds show fluid filled intestines. Hyperplasia of enterocytes is also observed in histopathology studies. However, in contrast to other enteric viruses, there isn't villous supply.[4]
Avastrovirus species often infect extraintestinal sites such as the kidney or liver resulting in hepatitis and nephritis.[4] Birds infected by avian nephritis virus typically die within 3 weeks of infection. The viral particles can be detected in fecal matter within 2 days and peak virus shedding occurs 4-5 days after infection.[9] The virus can be found in the kidney, jejunum, spleen, liver and bursa of infected birds. Symptoms of this disease include diarrhea and weight loss. Necropsies show swollen and discolored kidneys and there is evidence of death of the epithelial cells and lymphocytic interstital nephritis.[4] Another extraintestinal avastrovirus is avian hepatitis virus which infects ducks. Hepatitis in ducks caused by this Duck astrovirus (DAstV) is often fatal.[10]
In birds, Avastroviruses are detected by antigen-capture ELISA. In the absence of vaccines, sanitation is the prevalent way to prevent Avastrovirus infections.[4]