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 ultramembrane 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to the strain (DHV/Duck/ Al-Gharbia /2014) Egypt/ in 3D protein gene with gene bank accession number (KP202874) unpublished data.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%.
In the present study 1317 serum samples obtained from 6 broiler flocks, 2 broiler breeders and 28 commercial layer flocks were examined for HI antibodies of {NDV, IBV 4/91,, AIV (H5N1, H5N2, H5N3, H9, H7) and Adenov (EDS 76 )}. Studying the vaccination protocols in flocks under investigation and their seroconversion had led us to speculate and conclude viral affections in the different localities of Sharkia governorate. Speculating viral affections was a very hard task because the Egyptian market is jammed with a great variety of protective vaccines this was conflicting during result interpretation. Positive immune titers for AIV-H7 in sharkia governorate was detected at June /2014 in (El-salhia, 10 th of Ramadan, El-ibrahemia and Abo-hammed) in commercial layer flocks only. The seropositive samples that exceeded the cutoff values were 63 out of 1317 (4.8%). AIV-H9 high seropositive immune titers was constantly found in examined samples although their protective vaccines were neglected. AIV-H 5 N 3 seropositive results was recorded in a totally non vaccinated flocks against H 5 which reflect virus circulation in the poultry premises. Seropositive titer for IBV-D 274 and EDS 76 was recorded in a totally non vaccinated flocks against such antigens., which refer to their role in the total simultaneous incidence of disease and consequent mortality. From another point of view it should be noted that. Vaccinating chicken flocks following a ready made manuscript of the producing companies without prior evaluation of the maternally derived antibodies (MDA) or evaluating the immune titers before taking the decision of vaccination or even considering the disease situation in the area is possible cause for vaccine failure. Sentinel birds inclusion in poultry patches should be taken seriously to give a mirror for the circulating viral agents in the poultry premises. It worth to mention that a parallel bacteriological work was running during investigation of the causes of increased mortality or dropped egg production. This work revealed the isolation of a resistant bacteria of the (Kebseilla spp).
Serological assays can be used for evaluating immune response post vaccination, they can be also helpful in studying the status of maternally derived antibodies (MDA), and they can also give a diagnostic mirror for viral sero-epidemiology. In the present study comparison between hemagglutination inhibition test (HI) and Enzyme linked immunesorbant assay (ELISA) and their abilities to detect IBV antibodies at different circumstances (post vaccination, infection, and (MDA) was studied. HI test for IBV was performed against two distinct IBV serotypes namely (Mass-41, 4/91). Since they are the major vaccines used commercially in the Egyptian market. ELISA was performed at two dilutions (1/100, 1/ 1000) which is nearly the reciprocal of dilution of (7 and 10) in HI test in a trial to set two points for comparing the obtained results From the two tests. ELISA test showed 100% sensitivity and specificity at dilution 1/100 and showed 80.96%, 95.5 % respectively at 1/1000 dilution. The sensitivity and specificity of HI test were 80.91%, 95% respectively when Mass-41 antigen was used and was 73.91 %, 62 % when 4/91 antigen was used .The difference in sensitivity and specificity with HI reflects it selectivity during serotyping and this picture will necessarily differ if samples were tested against other antigens like (D-274, 1466,…..etc.,) this confirms our point of view for using HI in detecting immunity after IBV vaccination. It became obvious that ELISA result may be misleading as seen during studying MDA in sample (S-20), ELISA reading at 1/100 dilution was 12051±2018 with STDV(6384) and was 2406±754 with STDV(2385) at dilution 1/1000 their Conversion into two base log titer 1/10 will be 14.28±.317 and 14.56±.4 respectively on the other hand the HI titer was 4.5±.166 with STDV(0.5) when Mass -41 antigen was used and it was 2.4±.476 with STDV (1.5) when antigen 4/91 was used, result of ELISA will be conflicting when devising a vaccination protocol for such flock.
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