الفهرس 
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Abstract
show that Avian influenza is caused by an orthomyxovirus. It is a single stranded, negative sense RNA virus which has eight segments of its genome surrounded by a lipid envelope. A peculiar characteristic of the virus is that it contains rod-shaped and mushroom-shaped glycoproteins called hemagglutinin and neuraminidase respectively projections on their surface.
There are many serological tests used for diagnosis of avian influenza virus as Immunochromatography test the advantage of this test is high specificity, sensitivity, and stability but it had adisadvantages like The specificity and sensitivity of the immunochromatographic strip are largely dependent on the following factors, the first is the quality of the MAbs used in the strip test, while the second factor is the pretreatment of the sample pad and the conjugate pad is important for enhancing the release speed of the conjugate and for reducing non specificity.
Immunofluorescent antibody (IFA) test the advantage of this test is it performed directly on cells from respiratory specimens and it is rapid test as provide results in less than an hour.The disadvantage of this test is it is restricted to laboratories with immunofluorescent microscopes and it depends on well trained, experienced technologists.
Agar gel immunodiffusion (AGID) test the advantages of this test are: it is a simple and reliable test in chicken and turkey sera, very specific, can be performed in any laboratory with basic equipment, The disadvantages of this test are: it is of limited sensitivity; completely unreliable in waterfowl as these birds do not produce precipitating antibodies, has not been fully validated in other avian species.
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So in the present study we used the haemagglutination test as HA test are reliable, economical and time saving test for initial diagnosis and monitoring of AI outbreaks as both also needs ordinary used chemicals. And we studied the effect of certain factor on the haemagglutination activity of avian influenza virus subtype H5N1 like :
1)effect of RBCS species on the haemagglutination activity,the species were chicken ,duck, geese, quail, turkey, pigeon and sheep RBCS.
2) effect of diluents on the haemagglutination activity, We used two types of diluents like phosphate buffer saline and normal saline.
3) effect of incubation period on the haemagglutination ,We used three incubation period like 20 ,30 ,and 40 minutes.
4) effect of incubation temperature on the haemagglutination activity We used two incubation temperature 25ₒC (room temperature) and 37 ₒC.
Effect of incubation period on HA activity of six avian influenza virus isolates from RBCS of different sources at time intervals 20 minutes showed that the HA titre show significant difference when RBCs from chicken was used than other RBCS from duck, pigeon ,turkey, geese , quail and sheep were used (Table 1) and the best and higher HA titre was when used chicken RBCS.
Six virus isolates were kindly obtained from Dept. of Avian and fish Diseases. The isolates were used for studying factors affecting haemagglutination activity of avian influenza virus subtype H5N1.
The virus isolates inoculated into groups of 9 day old embryonated chicken eggs via allantoic sac using 5 eggs and 0.2ml as an inoculums/egg.Inoculated eggs were incubated at 37 oC for 5 days and candled daily for mortalities.
Death recorded within the first 24 hours post inoculation were excluded and considered as non specific . Dead embryos and survivors that were killed at the end of observation period by chilling for few hours in the refrigerator were examined for gross lesions and their allantoic fluids were harvested.
The presence of haemagglutinating agent was checked by testing harvested fluid by rapid slide haemagglutination test using 10% washed RBCS .And confirmed by rapid test (chromatography test).
Then we checked the Hemagglutination activity of 6 AI virus isolates by using 1 % washed RBCs from different animal species like(chicken, sheep, duck, geese, pigeon, quails and turkey) at three different incubation period (20 , 30 and 40 minutes) ,different incubation temperatures like (25 oC and 37 oC) and with different types of diluents like (normal saline and phosphate buffer saline).We found that these factors affected directly on Hemagglutination activity of AI virus.
The HA titers obtained with two incubation temperatures (25oC and 37oC) used in the present study showed the best incubation temperature was 25oC which gave HA titre higher than37oC.
The HA titer of AI virus obtained by keeping the plates at room temperature ( 25oC) for 20 ,30 and 40 minutes showed significant difference when RBCs from chicken, duck, geese, quail, turkey, sheep and pigeon were used we found the best HA titre obtained from using chicken RBCS incubated for 30 minutes . Also found the HA titre was obtained with PBS was more preferable than using normal saline.
Finally we concluded the factors that gave the higher and accurate HA titre as the following using chicken RBCS incubated at room temperature (25oC) for 30 minutes using phosphate buffer saline as a diluent .