A Review of the Strain Diversity and Pathogenesis of Chicken Astrovirus

Abstract

Although a relatively recently emerged virus, identified only in 2004 as a separate species of avian astrovirus, chicken astrovirus (CAstV) has been associated with poor growth of broiler flocks, enteritis and diarrhea and is a candidate pathogen in cases of runting stunting syndrome. More recently CAstV has been implicated in cases of two other diseases of broilers as the sole etiological agent, namely severe kidney disease of young broilers with visceral gout and the “White Chicks” hatchery disease. Examination of the strains of CAstV associated with the two latter diseases reveals they are closely related genetically. This review will discuss the pathogenesis of CAstV in relation to strain diversity and the effects of vertical versus horizontal transmission, virus load, co-infections and age of bird at infection, all factors that may impact upon disease severity.

Isolation of avian nephritis virus from chickens showing enteric disorders

“…From day 3 to 21, the virus was also detected in the bursa, jejunum, and spleen, but no alterations were found (Imada et al, 1979 , 1981 ; Shirai et al, 1991 ), showing that the target organ of this virus is kidneys, but it could be present in other organs, such as gut. Actually, ANV is related to one of the principal causative agents of enteric problems, more specifically those related with RSS (Kang et al, 2012 ; Day and Zsak, 2013 ; Mettifogo et al, 2014 ; Day et al, 2015 ; Smyth, 2017 ; De la Torre et al, 2018 ). The samples used here were from chickens showing signs of enteric diseases that were positive only for ANV after molecular screening, suggesting that the principal agent is involved in the genesis of some enteric problems may be ANV.…”

“…Infected birds are affected from the first day of birth showing early clinical signs of enteric diseases, principally diarrhea; however, chickens of different ages are also affected, whether or not they are showing clinical signs (Pantin-Jackwood et al, 2007 ; Smyth et al, 2009 ; Todd et al, 2010 ; Mettifogo et al, 2014 ; Veen et al, 2017 ; Xue et al, 2017 ; De la Torre et al, 2018 ; Kang et al, 2018 ). In poultry, runting-stunting syndrome ( RSS ) is of great relevance to avian intestinal health, and many viruses are involved (Pantin-Jackwood et al, 2008 ; Day et al, 2015 ; Smyth, 2017 ). The syndrome is also known as infectious stunting syndrome, pale-bird syndrome, malabsorption syndrome, malassimilation, and helicopter disease (Goodwin et al, 1993 ; Kang et al, 2012 , 2018 ; Bulbule et al, 2013 ; Day and Zsak, 2013 ; Nuñez and Ferreira, 2013 ; Smyth, 2017 ), and was first described by Olsen ( 1977 ).…”

“…In poultry, runting-stunting syndrome ( RSS ) is of great relevance to avian intestinal health, and many viruses are involved (Pantin-Jackwood et al, 2008 ; Day et al, 2015 ; Smyth, 2017 ). The syndrome is also known as infectious stunting syndrome, pale-bird syndrome, malabsorption syndrome, malassimilation, and helicopter disease (Goodwin et al, 1993 ; Kang et al, 2012 , 2018 ; Bulbule et al, 2013 ; Day and Zsak, 2013 ; Nuñez and Ferreira, 2013 ; Smyth, 2017 ), and was first described by Olsen ( 1977 ). The syndrome is characterized in animals by dwarfism, poor development, diarrhea, and mortality (Kang et al, 2012 , 2018 ; Day and Zsak, 2013 ; Zsak et al, 2013 ; Domaska-Blicharz et al, 2017 ).…”

“…This polyprotein together with ORF 1a is cleaved into the non-structural proteins required for transcription and viral replication (Marvin, 2017 ). The sequencing of ORF 1b gene is not used for astrovirus genotyping where the capsid gene (ORF2) is used (Todd et al, 2011 ; Smyth et al, 2017 ; Luna et al, 2016 ), but could show similarities or differences between sequences from different serotypes of ANV. Recently, the presence of ANV in chickens, layer hens, and breeders showing signs of enteric diseases was reported in Brazil (Nuñez and Ferreira, 2013 ; Mettifogo et al, 2014 ; Luna et al, 2016 ; De la Torre et al, 2018 ), and many outbreaks of enteric diseases have also been observed (unpublished data).…”

Virus-induced immunosuppression in turkeys (<i>Meleagris gallopavo</i>): A review

“…Etiology of this syndrome is not known exactly, however, many viruses are isolated from affected birds. Reoviruses, Astroviruses, Rotaviruses, Coronaviruses, Enterovirus-like, and Adenoviruses are detected in RSS outbreaks (Simmons et al, 1972;Kouwenhoven et al, 1978;Kisary et al, 1984;McNulty et al, 1984;Songserm et al, 2000;Baxendale and Mebatsion, 2004;Otto et al, 2006;Smyth, 2017). In addition, nutritional and management factors could contribute to RSS in poultry.…”