Objective: Avian astroviruses are several group of viruses causing enteritis, hepatitis and nephritis in a range of avian species. Based on the species they infect and their viral genome characteristics, two turkey astrovirus (TAstV-1 and TAstV-2); three chicken astroviruses (ANV1, ANV2, CAstV) and two duck astrovirus (DAstV-1and DAstV-2) have been identified. Growth retardation and kidney lesions and minor mortality have been reported in chickens infected with avian nephritis virus. One-day-old chicks are the birds most susceptible to disease caused by ANV. Avian nephritis virus type 2 (CAstV-2) is claimed to cause diarrhea and passage of partly digested food in feces of day old SPF chicks. The virus is genetically and immunologically distinct from other avian astroviruses, including Avian nephritis virus 1 (ANV1), also known as CAstV1. ANV1 was detected in Iranian chicken flocks with the history of enteritis, nephrosis and growth retardation in 2011. Not much information is available about ANV2 in the literature. The virus has been detected only in a few countries. This report describes molecular detection and partial nucleotide analysis of two Iranian avian nephritis virus type 2, also known as chicken astrovirus type 2 (CAtv-2) in 2 broiler farm. Material and Methods: Two broiler flocks with the symptoms of diarrhea, poor growth and nephropathy were sampled. RNA from feces was extracted. Three sets of diagnostic primers were designed. RT-PCR assay was performed, and products were sequenced and processed for phylogenetic analysis. Conclusion: All three expected products of 200, 340 and 274 bp were amplified in flock 1. But in spite of several attempts, only a 274 bp product was amplified in flock 2. Sequence data confirmed the presence of two different ty ANV type 2. They had 76% identity and 66% similarity at nucleic acid and amino acid levels, respectively. Other than these differences, both strains showed considerable sequence variation with other ANV2 sequences available in the databases. In phylogenetic analysis, strain 1, along with most American isolates of ANV2, were grouped in a separate cluster. In contrast, strain 2 grouped in another cluster along with the most UK isolates of ANV2. Major differences were also recorded between 2 Iranian strains and other avian astroviruses, including ANV1. These facts reconfirmed that astroviruses are enormously varied in their genome profile. This article is the first report of detection of ANV2 in Iran. It also demonstrated two strains of ANV2 with a considerable differences circulating in the field.

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