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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.
Between 2008 and 2011, commercial turkey flocks in Poland were examined for the presence of rotaviruses. Ten faecal swabs from each of 207 turkey flocks (turkeys aged one to 19 weeks) were collected in different regions of the country and tested using a PCR assay that targeted the NSP4 gene. The prevalence of rotavirus was 20.3% in the flocks tested. Phylogenese analysis revealed a clear division into groups dependent on geographical origin of the analysed viruses. All Polish rotaviruses belonged to the Kuropean group. However, they were found to be genetically variable based on the sequence analysis. The most frequently identified rotaviruses belonged to RV-1 subgroup and two of them formed a distinct subgroup of RV-2. Rotaviruses were detected in healthy and enteric turkeys. The observed amino acid changes probably did not affect the group affiliation, nor the pathogenecity of the studied rotavirus strains.
The aim of the study was to compare immunoperoxidase (IP) and Antigen-Capture ELISA (AC-ELISA) tests in detecting infectious bursal disease virus (IBDV) in the Fabricius Bursa (BF) of infected chickens. BFs were collected for 3 days p.i. with IBDVs of low pathogenicity (isolated from a mild form of IBD) as well as very virulent ones (isolated from an acute form of IBD) 1, 3, 6 and 9 days p.i. with vaccinal, low pathogenic and very virulent strains. BFs from broiler chickens suspected of having IBD were also used. BFs were cut into frozen histological sections and, after fixing with formaldehyde, were stained using the IP method. The remainder of BFs was used in AC-ELISA after homogenization and clarification. The sensitivity and specificity of both tests in detecting IBDV antigens were comparable but the amount of viral antigen could be determined only by using the AC-ELISA method. The intensity of reaction and the time during which the viral antigen was detected were strongly correlated with the pathogenicity of the IBDV strain being used. Inoculation with the vaccine strain yielded positive results only on day 6 p.i. and the amount of detectable antigen was very low. Infection with the low pathogenic Polish strain produced more antigens, detectable from days 1 to 6 p.i. The antigen of the very virulent strain was found in the largest amount and could be detected for 9 days beginning on day 1 p.i. The study indicated that the IP method is simple, rapid and less laborious than AC-ELISA. However, AC-ELISA is more useful because it additionally measures the amount of detected antigen in a specimen.
The "in house" PCR method and four commercial PCR kits (designed symbolically as A, B, C, and D) for the detection of Mycoplasma synoviae (MS) in tracheal swabs of infected experimentally SPF chickens were compared. The chickens were inoculated intranasally with 1x10⁴ colour change unit (cfu)/mL of ATCC reference MS strain, and at 4, 7, 14, 28, and 35 d post infection (d.p.i.), the tracheal samples were collected and examined. The methods showed different sensitivities. The commercial test C seemed to be less sensitive (0.5 ng/mL) than the rest of the methods (50 pg/mL). Only the "in house" method and commercial test D detected MS DNA from 7 to 14 d.p.i.; no satisfactory results were obtained with the other kits. Since the methods have shown different sensitivity, their suitability for MS detection seems to be limited.
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