Study On The Dynamic Variation In Ducklings By Artificially Infected With Riemerella Anatipestifer

Experimental ducklings artificially infected with Remerella anatipestifer serotype I to establish patholoqical model of Remerella anatipestifer disease and to study the dynamic variation in pathobiology, Dynamic variation about bacterial reproduction, biochemical indicator of blood and immunologic function and so on in ducklings. The result showed that the incubation period of crop injection group was shorter. 12 hours after artificial infection, the duckling appeared with visible clinical symptom. The death peak was 65% and observed between 72 hours to 84 hours after injection, which was lower than trachea injection group. There was no visible clinical symptom showed up until 24 hours after trachea injection, and the death peak, which was 85%, arrived during 36 hours and 72 hours. The pathological characteristics observed as depressed, dipsa and appetite were descended, diarrhea, weak legs, turbid eyes, opisthotomus, swelling head, and arthrophyma. The pathological changes were as follows: swelling and congestion occurred in heart, liver, spleen, lung, kidney and brain, atrophy occurred in thoracic gland and bursa of Fabricius. Parenchyma organs of infected ducklings such as heart, liver and spleen showed fibrins inflammation. And there were congestion and emphysema of lung; congestion of glomcrulus, swelling renal tubule, cellular degeneration and necrosis of cellula epithelialis; congestion of thoracic gland and swelling reticular cell; the number of achroacytes decreased, celluar proliferation of macrophage, and cell degeneration of epithelium mucosae; cellular swelling and granular degeneration of exocrine acinar cells and thickening of envelope, cellulose effusion of pancreas; affection of meningocephalitis in brain; And eosinophlis were present in all organs.In early period, all organs were observed congestion. Cellular swelling and cell degeneration to begin with the increase in infected time. Cell degeneration was gradually aggravated and cell necrosis and karyopycnosis occurred in some organs sach as heart, liver, brain and spllen in crest-time. This was a process in which congestion passes by degrees to swelling and apomorphosis even necrosis. Cop injection group was the same as trachea injection group, but the pathological changes was in advance in some organs sach as heart, liver, spleen, kidney. The TP, GLB, ALB content and AST, Cr activity of the crop injection group and the trachea injection group were higher than control group, while ALT activity appeared with decreasing-increasing trend, and UA activity showed oppositely.Infected ducklings with cop injection and trachea injection, within 6 hours can be detected pathogenic bacteria in heart, liver, spleen, lung, kidney, thoracic gland, bursa of Fabricius, brain and pancreas. On the whole, liver was the highest bacterial number in all organs both groups of experimental ducklings at all times after infecting, while the bacterial number in heart, lung, kidney in trachea injection group and thoracic gland, heart, bursa of Fabricius in crop injection group got lower one by one. The results indicated the liver was the best organs to detective Remerella anatipestifer and isolated pathogenic bacteria, then were heart, lung, kidney and immune organs.The cell immunity of ducklings in both groups was active in the whole period of onset, the activity of cell immunity growth to the peak value at the point of 72h post infectionem, and the time point of 72h post infectionem is also the juncture of the course, so we conjecture that cell immunity was important in the process of resisting the infestation of RA.The weight of the ducklings in the group which infected with RA was significantly lower than the control group, this certify that the digestive organ of the ducklings infected with RA was major injured, thus the appetite of ducklings decrease and even to abolish at the crest-time, the growth and development of ducklings become to stagnate.