engleski

Astroviruses detected by molecular methods in duck flocks in Croatia

Astroviruses are small (27-30 nm), non-enveloped, single-stranded RNA viruses characterized by the typical star-shaped morphology. Avian astroviruses that infect domestic poultry are turkey astrovirus 1 and 2 (TAstV-1 ; 2), chicken astrovirus (CAstV), avian nephritis virus (ANV) and duck astrovirus (DAstV). While DAstV is an etiological agent of fatal hepatitis in ducks, TAstV 1 and 2, CastV and ANV are associated with poult enteritis and mortality syndrome (PEMS) and runting and stunting syndrome in chicken (RSS). In this study, 8 duck flocks from northern Croatia were tested by reverse transcriptase-polymerase chain reaction (RT-PCR) for the presence of avian astroviruses. 30-days old ducklings were collected from 1 flock, while 10-20 dead-in-shells per flock were gathered from 7 duck flocks. From all carcasses the liver and intestines were sampled, while the intestines and kidneys from 30-days old ducklings were taken for the histopathological examination. The specific primers and adjusted RT-PCR reaction conditions were used for each tested virus. ANV was found in 5 (1 flock of 30-day old ducklings and 4 flocks of dead-in-shells) and TAstV-1 in 2 flocks of dead-in-shells. One flock of dead-in shells was positive both to ANV and TAstV-1. No other astroviruses have been found to infect tested ducklings. All positive samples were sequenced. Molecular and phylogenetical analysis of the portion of the ANV polymerase gene showed the greatest similarity of ANV sequences obtained with ANV-1 sequence G-4260 (ABO33998), originated from the USA. The TAstV-1 nucleotide sequences showed 99.5% similarity and were identical in deduced amino-acid composition. Phylogenetic analysis revealed their highest relation with the sequence NC-SEP-A552-05 (DQ324823) originated from USA turkey flock. Histopathological examination of ducklings aged 30 days showed that moderate multifocal periglomerular and interstitial mononuclear cell infiltrates were the most prominent histological lesion in the kidneys. A rather diffuse pericriptal mononuclear cell (lymphocytes) hyperplasia and fibroplasia were found in the duodenum. ANV infection in ducks showed lesions similar to those described in chickens. The severity and significance of ANV and TAstV-1 infection in ducks still need to be investigated.

ducks; astroviruses; avian nephritis virus; turkey astrovirus-1; PCR

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