Study On The Pathogenesis Of Broiler Tracheal Obstruction

The tracheal obstruction is a serious and comprehensive, epidemic respiratory disease, which occurs widely in the north area of China in recent years. Different scale, different species, different ways of broiler breeding farms have happened with the characteristic of faster onset, treatment difficulties, high mortality, which has brought huge economic losses to the farmers. To lucubrate the tracheal obstruction and provide the theoretical basis for clinical prevention of broiler tracheal obstruction, this paper is going to study pathologic histology, isolation and identification of pathogens, susceptibility test of pathogenic bacteria and analysis microorganism diversity and its relateness of broiler tracheal obstruction in the respiratory system by histopathological observation, biological chemistry, susceptibility test and Miseq high-throughput sequencing method.Histopathological observation. To provide the theoretical basis for the research and clinical prevention of broiler tracheal obstruction, lung and tracheal of natural disease chicken were sampled and pathohistological method was used to study pathological changes. The results showed that hyperemia and hemorrhage were seen in the tracheal ring, many yellowish-white caseous materials blocked the trachea and bronchus, and obstruction easy occurred in the connected place of bronchus and lung. Hyperemia and hemorrhage were seen in the tracheal mucosa and the epithelial cells exfoliated seriously. Hemorrhage and congestion were seen obviously in the lung. Lung bronchiolar was obstructed, and the obstruction materials are mainly epithelial cells, blood cells, fibre and protein. Results showed that a more severe tissue damage occurred in the broiler, accompanied by inflammatory reaction.Isolation and identification of pathogens. In order to determine some of the factors of broiler tracheal obstruction, bacteria was separated and identified from dead chickens’ lungs by culture characteristics and biochemical test. Drug sensitive test was carried out on isolated strain. At the same time, virus is separated and identified by embryonated eggs inculation, hemagglutinin and hemagglutination inhibition test and molecular biology methods. The results showed that 10 typical cases of broiler tracheal obstruction in Liaocheng city have been analysed to isolate the pathogens, separating 10 strains of Escherichia coli, 10 strains of Staphylococcus aureus, 8 strains of H9 subtype of avian influenza virus and 3 strains of newcastle disease virus. Drug sensitive test of Escherichia coli and Staphylococcus aureus reveals that the commonest antiotics come across varying degrees of resistance and it has more serious phenomenon of multidrug resistance. Furthermore, the separating rate of H9 subtype of avian influenza virus and newcastle disease virus reaches 80% and 30%, both coinfection rate is 30%. It showed that broiler tracheal obstruction was caused by a variety of pathogens and mixed infection was serious.Analysis of the bacterial diversity. This study was conducted to analyse the bacteria diversity and its relateness of the broiler tracheal obstruction in the respiratory system. The microorganism of nine samples from the lungs and tracheas of the diseased and healthy broilers were detected by Miseq high-throughput sequencing method. And the category of strain, community composition, species differences and the relationship with the disease were analyzed. The results showed 270 types of microbe bacteria in the samples of lung and trachea were detected, belonging to 13 phylums, 23 classes, 39 orders, 74 families, 140 genera. Bacterial number of sick chicken trachea is higher than the lungs healthy trachea, but bacteria number of most sick chicken lung is less than healthy lungs. The results showed that, there are some species differences among different samples. Region can produce a great influence on bacteria microbial components. The bacterial pathogens causing broiler tracheal obstruction are also different. There are mainly mycoplasma, Escherichia coli, shigella, riemerella, corynebacterium, staphylococcus, ornithobacterium and enterococcus; In addition, a larger proportion of lactococcus and lactobacillus are probiotics.Analysis of the fungal diversity. This experiment was conducted to analyse the fungal diversity and its relateness of the broiler tracheal obstruction in the respiratory system. The results showed 403 species of fungi in the samples of lung and trachea were detected, belonging to 4 phylums, 18 classes, 49 orders, 91 families, 147 genera. Based on the phylum level of classification, fungus of nine samples mainly are ascomycota and basidiomycota. Zygomycota assumes a certain ratio in the healthy lung. Moreover, some category of fungus are difficult to identify. Based on the genus level of classification, dominant genera of fungi mainly are aspergillus, emericella, guehomyces, alternaria, cladosporium, candida, trichosporon and fusarium.