الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Infectious coryza (IC) is an acute highly contagious disease of
chickens caused by Av. paragallinarum. The disease occurs worldwide
and the reasons behind success of survival for this bacterium are that
birds become carriers after recovering from infection. The economic
impact of the disease is attributed to the resultant increase in unthrifty
chickens and significant DROP in egg production (10 to 40%) in layer
flocks and retardation of growth leading to increased number of culls
particularly on multi-aged farms. In developing countries, the outcome of
IC infection is more drastic and economic losses are much higher than
those in developed ones
In our study 120 field samples were collected from different
poultry farms with a complain of rapid onset of clinical symptoms of
nasal discharge, watery eyes, conjunctivitis, lacrimation, swelling of the
sinuses and face, difficulty in breathing, anorexia, and swelling of
wattles. Infected flocks suffered from decreased feed and water
consumption and up-to 40% reduction in egg production in laying flocks.
Through cultivation and biochemical identification, 12 samples
gave positive results for IC of the total examined samples. Going through
molecular diagnosis and confirmation, 9 isolates of these identified
samples proved to be Av. paragallinarum, with an isolation rate of NADdependent
isolates in our study of 7.5%. Molecular serotyping revealed
that, 4 isolates were serovar A isolates, 3 isolates were serovar C, and 2
isolates were serovar B.
The results of the current study further confirmed the co-circulation
of the Av. paragallinarum serotypes A, B and C in Egypt. Moreover, the
study further confirmed the reliability of using both conventional and
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multiplex PCR as a useful tool for fast diagnosis and serotyping of Av.
paragallinarum isolates rather than laborious bacteriological isolation
and identification techniques.
Protection of chicken flocks against IC involves use of both
vaccination and biosecurity. Vaccination is one of the most important
means for controlling IC in chickens, and must be used to minimize the
impact of IC, particularly in endemic areas. Hence, the current study was
designed to prepare and evaluate an inactivated trivalent oil-emulsion
based IC vaccine, using the locally identified Av. paragallinarum isolates
(one serotype of each serovar A, B, and C), and comparing the efficacy of
prepared vaccine with one of the commercially imported and approved
trivalent IC vaccine.
Firstly, the prepared vaccine was subjected to quality control
measures assessment, and was proved to be of acceptable measures
according to the protocols of the Egyptian Veterinary Codex 2009
CLEVB.
Furthermore, this study went through identification and insurance
of the safety and potency of the prepared vaccine. This was done through
4 experiments. This experimental part of the thesis was carried out on
mixed developed baladi breed chickens purchased from layer farm,
recognized to have no history of IC infection for long period. Chickens
were purchased before introduction for IC vaccine regime in farm and
confirmed to be seronegative for IC.
The first experiment of our study was to assess the safety of the
prepared vaccine. Our result demonstrated that both our locally prepared
and the commercial used vaccine are good and of acceptable safety
measures to be used for immunization of chickens.
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The second experiment was designed to assess the efficacy of
vaccine after single dose and challenge subsequently three weeks after.
Our results demonstrated that protection rate in chickens immunized with
the trivalent locally prepared vaccine was 85.7%. It was higher than
protection rate developed in chickens immunized with the trivalent
commercial vaccine (73.8%). Also, it was observed that protection
developed by the local prepared vaccine was clearly prominent
particularly against challenge with serotype B and C. On the level of
serotype, protection rate developed on use of the local prepared vaccine
was 78.57%, 85.71%, and 92.86% against challenge with serotypes A, B,
and C, respectively. While with the imported used vaccine, protection
rate was 85.71%, 64.3%, and 71.43% against challenge with serotypes A,
B, and C serotypes, respectively.
The re-isolation rate was 12% from chickens vaccinated with the
local prepared vaccine and challenged with Av. paragallinarum
serotypes. While in chickens received the imported vaccine and
challenged, re-isolation rate was 21%.
On the other hand, the third experiment of our study, to assess
efficacy of local prepared vaccine for protection against challenge with
locally isolated serotypes of Av. paragallinarum after single and booster
vaccination regimes with 4 weeks interval,
We demonstrated that, the developed protection rate in chickens
vaccinated with the locally prepared vaccine and challenged 3 weeks after
booster dose was 95.2%, while it was 81% in the chickens vaccinated
with the commercial vaccine. The overall protection rate was improved in
third experiment following booster vaccination regime than single dose
vaccination in second experiment. This improvement was obvious with
the local prepared vaccine. As, protection rate elevated to 92.86% against
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challenging with serotypes A and B, and gave complete protection (100
%) against serotype C infection. While, booster dose in commercial
vaccine resulted in slight improvement in protection against A and C
serotypes, as it increased from 85.71% to 92.86% against challenge with
serotype A, and from 71.43% to 78.57% against C serotype. While there
was no improvement against B serotype infection and remained at 64.3%.
Concerning re-isolation trials, the re-isolation rate was 4.8% in
birds vaccinated with local prepared vaccine. While in birds received the
commercial vaccine, re-isolation rate was 16.6%. So, with booster dose
of the local prepared vaccine, the challenging bacteria was re-isolated
from 2 birds instead of 5 birds with single dose vaccination with an
improvement in immune response represented by rapid bacterial
clearance from sinus by 60%. While with the commercial vaccine, the
challenging bacteria was re-isolated from 9 birds after single dose
vaccination and from 7 birds after booster dose vaccination with
decreasing in possibility of colonization and replication of bacteria by
21%.
The fourth experiment of our study was to evaluate
immunogenicity of the local prepared vaccine, and to investigate the
duration of provided protection using ELISA test.
We found that, the level of antibody titers were weekly increased
in vaccinated chickens either with the locally prepared vaccine or the
commercial one, with a prominent higher antibody titer in chicken
vaccinated with the local vaccine.
The average antibody titer of the group vaccinated with local
prepared vaccine was higher than the group vaccinated with commercial
imported vaccine. Moreover, overall mean changes of antibody titer of
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local prepared vaccine is significantly high (P=0.0001) compared to those
of commercial vaccine.
We can conclude that, there were improvement in the protection
and immunity of birds on vaccination with the locally developed vaccine
while the commercial used vaccine did not react with the same efficacy
against challenge with the locally isolated serotype of Av.
paragallinarum. Hence, studies concerned with control IC disease should
be conducted to characterize Av. paragallinarum isolates countrywide for
the production of the corresponding autogenous vaccines.
In conclusion the ability to protect birds through vaccination
confirms the need for well-structured vaccination programs. The present
study highlights the importance of a suitable vaccine formulation that
generates protection throughout the productive life of chickens and the
need for incorporation of local dominant strains in the vaccine.