Elie
K. Barbour, Fouad A. Mastori, Afif M. Abdel Nour, Houssam A. Shaib,
Lina S. Jaber, Ryan H. Yaghi, Alia Sabra, Fawwak T. Sleiman, Rana
K. Sawaya, Aleksandra Niedzwieck, Ihsan T. Tayeb, Zeina G. Kassaify,
Matthias Rath, Steve Harakeh & Kamil E. Barbour |
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Summary
Primary
infection by low pathogenic avian influenza (LPAI) predisposes for
secondary infection by Escherichia coli in poultry, leading
to significant economic losses. Future research in control of this
ailment requires the establishment of a successful controlled challenge
by avian influenza virus (AIV)/E. coli. Six groups of broilers
(6 birds/group) were included for the standardisation of the controlled
challenge by AIV/E. coli. Birds in groups 1, 2, 3, 4 and
5 received an intra-tracheal challenge of 0.5 ml of two haemagglutinating
units of H9N2 virus at 20 days of age. At the age of 23 days, birds
in group 1 received an intra-thoracic (right air sac)-E. coli
challenge equivalent to 1.6 × 109 colony-forming
units (cfu)/0.5 ml/bird, while birds in groups 2, 3, 4 and
5 received E. coli by the same route and in the following
respective decreasing order of viable cells: 1.6 × 106,
1.6 × 105, 1.6 × 104 and 1.6 × 103
cfu. Birds in control group 6 were deprived of H9N2 and E. coli
challenge. Results showed significant early mortality in group 1
that was challenged with the highest number of E. coli, in
comparison
to groups 2-6 (p<0.05); however, the average weight
at 28 days of age was similar in surviving birds of groups 2-6 (p>0.05).
The frequencies of four signs at 2 days and at 5 days post E.
coli challenge (conjunctivitis, diarrhoea, ocular exudates and
rales) in the surviving birds of groups 2-5 were most often higher
than those observed in control group 6 (p<0.05). These four
signs and five gross lesions (abdominal airsacculitis, left thoracic
airsacculitis, pericarditis, right thoracic airsacculitis and tracheitis)
had a decreasing pattern of frequency related to a decrease in the
E. coli count used in the challenge.
Keywords
Avian
influenza, Broiler, Challenge, Escherichia coli, Lebanon,
Standardisation, Virus. |