Abstract
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 (Mass-41, 4/91, and D-274), AIV (H5N1, H5N2, H5N3, H9, H7) and Adenov (EDS76)}. 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, 10th 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-H5N3 seropositive results was recorded in a totally non vaccinated flocks against H5 which reflect virus circulation in the poultry premises. Seropositive titer for IBV-D274 and EDS76 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).
Highlights
Eid (1994) stated that avian viruses causes severe economic losses in poultry beside other identified causative agents (Bacterial, mycotic, intoxication, etc.) and that the outcome of infection is influenced by many factors associated with the host, organisms and environment Bradbury )1984(, Dhillon and Kibenge )1987(, and Gelb )1989).Morrow (2008) stated that demonstration of antibody shows the antigen that a bird has been in contact with at some time in the past., but this does not prove that a clinical disease syndrome is caused by the organism associated with the particular antigen., because vaccinated flocks will have antibody from vaccination., and because natural infection could have occurred earlier
Morrow (2008) stated that., demonstration of antibody through seroservillance shows what a bird has been in contact with at some time in the past., but this does not prove that a clinical syndrome is caused by a certain antigen., because vaccinated flocks will have antibody from vaccination., and natural infection could have occurred earlier and was not associated with this clinical syndrome
During interpretation of serologic data It is usually impossible to differentiate between antibodies that are produced by vaccination or those resulting from field exposure to a given infectious agent
Summary
Morrow (2008) stated that demonstration of antibody shows the antigen that a bird has been in contact with at some time in the past., but this does not prove that a clinical disease syndrome is caused by the organism associated with the particular antigen., because vaccinated flocks will have antibody from vaccination., and because natural infection could have occurred earlier. For this Paired serum samples (taken at the time of clinical disease and in convalescence) will provide a convincing evidence of seroconversion and association of an agent to the clinical signs seen. Comin et al (2013) stated that the serological diagnosis of avian influenza (AI) can be performed using different methods, yet the haemagglutination inhibition (HI) test is considered the ‘gold standard’ for AI antibody subtyping
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