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A Retrospective Study of Chlamydia psittaci and Pigeon Circovirus Infection in Captive Birds
Chlamydia psittaci,pigeon circovirus,Streptopelia orientalis,PCR,IHC,
|Publication Year :||2021|
|Abstract:||鸚鵡披衣菌(Chlamydia psittaci)能夠感染的宿主範圍相當廣泛，其中包含爬蟲類、鳥類、哺乳類以及人類。目前已知有多達460以上的鳥類得以感染鸚鵡披衣菌，其中又以鸚鵡、鴿子以及八哥最為常見。鳥類感染鸚鵡披衣菌稱之為鳥類披衣菌症(avian chlamydiosis)，其臨床症狀不具專一性，而且嚴重程度也有相當大的差異，即可能導致亞臨床性感染或是死亡。在2020年3月起，台北市市立動物園之生態鳥園出現大量鳩鴿科鳥類死亡，經由組織病理學檢查後，大多數鳥類呈現消瘦，並伴隨氣囊混濁與肝臟、脾臟或腎臟腫大。組織病理學結果顯示，全身多處臟器可見組織球性炎症反應且發現有不等量之嗜鹼性針點狀物質位於巨噬細胞的細胞質內，有時在肝細胞和腎小管上皮細胞內亦可見相同物質。此外，可見華氏囊淋巴組織流失，而且偶爾可見嗜酸性葡萄串樣質內包涵體。進行組織化學染色、免疫組織化學染色及實驗室分子檢驗後，最終診斷為鸚鵡披衣菌合併鴿子環狀病毒(pigeon circovirus；PiCV)感染症。根據先前發表文獻可知，PiCV陽性鴿子可能因淋巴組織破壞導致免疫抑制，進而導致C. psittaci感染機率較高。因此，為了進一步了解鸚鵡披衣菌造成此次感染症爆發的可能原因，本研究回溯2018至2020年之鳥類解剖病例，自50例的新鮮肝臟組織與98例的石蠟包埋蠟塊萃取核酸，利用聚合脢連鎖反應(polymerase chain reaction, PCR)或巢式PCR(nested PCR)，檢測C. psittaci 16S rRNA與PiCV cap基因，而C. psittaci陽性病例會再使用免疫組織化學染色進行確認，並且進行基因型分析。根據實驗結果顯示，疾病爆發期間C. psittaci PCR陽性率為93.5%(58/62)，而IHC結果為92.5% (49/53)，其 PiCV PCR陽性率則為80.6%(50/62)。序列分析結果顯示，爆發期間檢測到之C. psittaci屬於基因型B且與CP3菌株有高達99-100%的基因相似性；PiCV核酸序列則與台灣P99/04株有91.2-97.3%的相似性。然而，2018至2020年疾病爆發前之病例均未檢測到C. psittaci核酸，但2018和2019年分別有31.3% (10/32)與10.8%(4/37)以及在爆發後2020 有1.3% (1/79) 病例定序結果為披衣菌目非披衣菌科細菌(non-Chlamydiaceae Chlamydiales；NCC)，而PiCV的陽性率則分別為25% (8/32)與19.4% (7/36)。根據結果可知，2020年之疾病爆發應為單一事件，而且PiCV可能在其中扮演重要角色，但C. psittaci的感染源仍無法確定，仍需未來進一步探討。|
Chlamydia psittaci is well known to be capable of infecting a wide range of hosts, including reptiles, birds, mammals and human. In birds, more than 460 species can be affected by C. psittaci, especially psittacines, pigeons and mynahs. Infection of C. psittaci in birds, namely avian chlamydiosis, can be subclinical infection to lethal with various clinical manifestations. Since March in 2020, there was a lethal outbreak of Columbiformes birds in the aviary in Taipei Zoo. Pathological examination revealed that these birds were usually emaciated with turbid air sacs, hepatomegaly, splenomegaly or renomegaly. Microscopically, histiocytic inflammation was observed in multiple organs, and accompanied with various numbers of basophilic pinpoint intracytoplasmic organisms in the macrophages and occasionally hepatocytes and renal epithelial cells. In addition, eosinophilic botryoid intracytoplasmic inclusions were also found in the macrophages in the bursa of Fabricius. According to the results of histochemistry staining, immunohistochemical (IHC) stain and molecular examinations, concurrent infection of C. psittaci and pigeon circovirus (PiCV) was diagnosed. It has been reported that pigeons infected with PiCV, which may cause damage to lymphoid tissues resulting in immunosuppression, are more susceptible to C. psittaci. To investigate the cause of the disease, a retrospective survey of necropsied bird cases from 2018 to 2020 was performed. Nucleic acid samples were extracted from fifty fresh liver and ninety-nine formalin-fixed paraffin-embedded tissue blocks, and polymerase chain reaction (PCR) or nested PCR was performed to detect the 16S rRNA of C. psittaci and PiCV cap gene. Following, the C. psittaci-positive cases would be furthermore confirmed by IHC staining and subjected to genotyping. The results showed that the positive rates of PCR or nested PCR C. psittaci and PiCV were 93.5%(58/62) and 80.6%(50/62), respectively, and 92.5% (49/53) cases were positive of C. psittaci by IHC staining. The nucleotide sequences of C. psittaci detected in the outbreak belong to the genotype B and have 99-100% identity to the CP3 strain, and those of PiCV share 91.2-97.3% identity with the Taiwan P99/04 strain. However, cases of 2018 [31.3% (10/32)], 2019 [10.8% (4/37)], and 2020 [1.3% (1/79)] were non-Chlamydiaceae Chlamydiales (NCC) instead of C. psittaci. The positive rates of PiCV were 25% (8/32) and 18.9% (7/37), respectively. In summary, the lethal outbreak in 2020 is considered as a single episode, in which PiCV might play an important role. However, the origin of C. psittaci is still not determined and further investigation is needed.
|Appears in Collections:||分子暨比較病理生物學研究所|
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