الفهرس 
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Abstract
The duck breeding become excessively in Egypt and thus become duck industry. This leading to an increase in disease problems and appearance of a new diseases condition as CRD. The aim of this study to investigate a new emerging bacterial disease in ducklings named (ORT) which caused mortality, DROP in egg production, decreased feed consumption rate, negative impact on bird performance and retarded growth.
Sixty ducklings were grouped into 6 groups, each one contained 10 ducklings.
Experimentally infection of different doses of ORT through occulonasal route alone or combined with E. coli through s/c route at neck. Tracheal swabs were taken at 1, 3, 7, 14, 21, 28 DPI for reisolation of ORT and E.coli. The ducklings were bled at 14, 21 and 28 DPI in order to obtain serum samples for antibody response by ELISA test.
The study showed that the dual infection of ORT with E. coli led to 20-30% mortality. Single infection of either ORT or E. coli led to 10 % mortality. The dual infection with ORT and E. coli as lead to severe respiratory manifestations and post mortem lesions thickening wall of airsacs, airsacculitis, trachitis, uni or bi lateral pneumonia .
The histopathology of birds received single infection with ORT showed that Lung: showed congestion, edema, and collapse of the alveoli. Perivascular and interlobular edema and interstitial aggregation of lymphocyte and macrophage were.