実験的鶏大腸菌症の慢性化病変

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タイトル別名
  • ジッケンテキ ケイ ダイチョウキンショウ ノ マンセイカ ビョウヘン
  • Chronic Lesions of Colibacillosis in Chickens Experimentally Infected with Escherichia coli

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ブロイラーに好発する鶏大腸菌症の慢性化病変についての理解を深めるために，実験的に鶏大腸菌症を作出し，これら病変の経時的変化について病理学的に検索した。供試鶏にはLine-M系白色レグホン種，供試細菌として鶏大腸菌症の野外症例由来の大腸菌株(Y0451株，KB4-1株，Da2株)を使用した。実験1では28日齢および35日齢雛にY0451株を臀部皮膚に掻傷感染させ，実験2ではKB4-1株，実験3ではDa2株をそれぞれ28日齢雛の大腿部に筋肉内接種した。死亡鶏は随時，生残鶏は接種5週後まで1週毎に一定羽数ずつ剖検，諸臓器の病理組織学的検索を行った。また，生残鶏では剖検時に心臓および接種部位からの大腸菌の再分離も試みた。 漿膜炎について，死亡鶏では全ての実験群で主に重度の線維素化膿性ないし化膿性肉芽腫性心膜炎が認められ，肝被膜炎，気嚢炎，腹膜炎などを伴うものが多かった。生残鶏では，接種後1週で心膜炎の発生が認められ，その多くは中等度の線維素化膿性心膜炎を示していた。接種後2週では線維素や壊死組織の肉芽腫による吸収を示す中程度の炎症反応がみられ，病変は慢性化していた。接種後3週から4週では病変は消退し，軽度の心膜炎が多くなり，接種後5週では漿膜炎は認められなかった。接種部位の蜂窩織炎は死亡鶏および生残鶏のほとんどで認められ，接種後3週ないし4週以降では，肉眼的および病理組織学的にも壊死組織は縮小し，軽度の病変を示すものが多くなった。

To obtain a better understanding of the chronic lesions of chicken colibacillosis which commonly occur in broiler chickens, we reproducted colibacillosis experimentally, and investigated the chronological change of lesions pathologically. White leghorn line-M chickens and E. coli strains (Y0451, KB4-1, Da2) isolated from field cases were used for experiments 1 to 3. In experiment 1, 28- and 35-day-old chicks were inoculated with Y0451 strains through an artificial scratch made at gluteal skin region, and in experiment 2 and 3, 28-day-old chicks were inoculated in femoral area intramuscularly with KB-1 strain and Da2 strain, respectively. If the chickens died during experimental period, they were necropsied immediately. Certain number of survived chickens were euthanized and necropsied every week by 5 weeks postinoculation (p.i.). The specimens from main organs were investigated histopathologically. In addition, re-isolation of E.coli from surface of heart and inoculation sites was attempted at necropsy of the survived chickens. In regard to serositis, dead chickens of all groups had predominantly severe fibrinopurulent or suppurative granulomatous pericarditis, and many of them had concurrent perihepatitis, airsacculitis and peritonitis. At 1 week p.i., some survived chickens developed various degrees of pericarditis from mild to severe, many of which showed moderate fibrinopurulent pericarditis. At 2 weeks p.i., the pericarditis showed moderate inflammation reaction with absorption of fibrin and necrotic debris by granulomatous tissue and became chronic. From 3 to 4 weeks p.i., the lesions regressed, and mild pericarditis were often seen. At 5 weeks p.i., no serositis was seen. Most of dead and survived chickens developed cellulitis at inoculation site, and at 3 or 4 weeks p.i., many necrotic tissue decreased in size grossly and showed mild lesions histopathologically.

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