Abstract
In the present study a Blencher duckling flock with 70% recurrent mortality on each reared batch was examined for the cause of mortality. live duckling were showing nervous signs and opisthotonos, sacrificed samples revealed depressed areas on the liver marking the large blood vessels while Hemorrhagic lesion suggestive for DVH were only noticed on liver of dead duckling carcasses. Liver samples were collected for virus isolation trials and for immunofluorescence. Initial virus isolation in embryonated chicken eggs ECE after ultra-filtration through 400 nm membrane filter revealed small size hemorrhagic edematous embryos this lesion was consistent upon a series of ultra-membrane filtration through 200 and 100 nm membrane filters which indicate a Picorna virus. Immunofluorescence examination revealed positive results for duck virus hepatitis (DVH). Clinical samples examined by generic RT-PCR assays followed by partial sequence analysis of the 3D gene revealed that the isolate was characterized as Duck hepatitis A virus resembling the strain (DHV/Duck / Egypt / Al-Gharbia /2014) in the 3D protein gene whom its gene bank accession number was (KP202874). The current study stresses on the value of ultra-membrane filtration through a 100 nm membrane filters as a rapid diagnostic tool For DVH without the need for extra laboratory diagnostic work. Interpretation of sequence results revealed that. The isolated (DVH/EG. Bayoumieh-Sharkia-2015) is a Duck hepatitis type A virus. With 100% resemblance to the strain (DHV/Duck/ Al-Gharbia /2014) Egypt/ in 3D protein gene with gene bank accession number (KP202874) unpublished data. Sequence and phylogenetic analysis indicated that the (DVH/EG. Bayoumieh-Sharkia-2015) isolate is clustered in the DHAV serotype 1 but was distinguishable from the other isolated Egyptian strains with resemblance ranging between 63.1 - 63.8%.
Highlights
Duck virus hepatitis (DVH) is a highly fatal rapidly spreading viral infection of young ducklings, characterized primarily by hepatitis
DHAV-2 isolated in Taiwan by Tseng and Tsai (2007), and DHAV-3 isolated in South Korea by Kim et al (2007), and in China by Fu et al (2009) are two newly described DHV genotypes, belongs to the same proposed Avihepatovirus genus; they can cause high mortality in ducklings
Part of allantoic fluid (AF) from the first passage was filtered through 200 nm filter; another part was filtered through 100 nm filter, these were further used for Embryonated chicken eggs (ECE) inoculation
Summary
Duck virus hepatitis (DVH) is a highly fatal rapidly spreading viral infection of young ducklings, characterized primarily by hepatitis. DHAV-2 and DHAV-3 were first recognized as separate entities because they induced hepatitis in DHAV-1–immune ducklings Asplin (1965), Toth (1969), Haider and Calnek (1979), Calnek (1993), Gough et al (1984) ,Gough et al (1985), Gough and Stuart (1993), Monroe et al (2005), Todd et al (2009), Fu et al (2009) These two viruses are reclassified and named as Duck Astrovirus types 1 and 2, respectively Fu et al (2009)
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