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Molecular Serotyping of the Porcine Teschoviruses in Endemically Infected Pigs
|Publication Year :||2015|
|Abstract:||豬鐵士古病毒(Porcine Teschovirus, PTV)為Picornaviridae科Teschovirus屬，直徑約為25-30nm、球型、正向單股RNA病毒。目前PTV有13種血清型，各年齡豬隻皆有感受性，臨床症狀以引起神經症狀之腦脊髓灰質炎及下痢為主。台灣在2000年及2004年爆發兩次疫情，現今在豬場呈現普遍的地方性感染。先前檢測出台灣存有五種血清型，分別為PTV-1、-4、-6、-7、-11，最常見的為PTV-7及PTV-6。本研究目的為利用增幅病毒VP1核酸序列進行鑑定台灣目前PTV是否有更多血清型的存在。實驗樣材來自於七個豬場，每場採集3隻淘汰病弱豬及1隻臨床症狀健康豬隻；每頭豬隻收集糞便、迴腸、扁桃、鼠蹊淋巴結、血漿、脾臟、腎臟、膀胱、尿液以及鼻腔拭鏡共10個樣材。首先以增幅5’NTR高度保留區域檢測PTV感染，所有28頭豬隻皆為PTV陽性(100%, 28/28)，其中又以糞便的陽性率最高(96%, 27/28)，其次為迴腸、扁桃、鼻腔試鏡(93%, 26/28)，血漿(86%, 24/28)，鼠蹊淋巴結及尿液(79%, 22/28)，膀胱(64%, 18/28)，脾臟(57%, 16/28)及腎臟(10%, 10/28)。接著利用本研究新設計之引子增幅病毒VP1序列，在217個PTV陽性樣本中有63個成功完成增幅且區分血清型。28頭豬隻皆至少有一種血清型存在，總共檢測出五種PTV血清型，分別為PTV-2、-4、-5、-6、-10，其中又以PTV-10 (57%, 36/63)最為常見，其次為PTV-2 (14/63, 22%)。其中有14頭豬隻有兩種以上血清型存於不同臟器 (14/28, 50%)。本研究再度印證了台灣PTV普遍感染的現象，加上先前的結果，證實台灣目前至少存在8種血清型，分別為PTV-1、-2、-4、-5、-6、-7、-10、-11。值得注意的是在分別來自三個豬場的三頭豬隻尿液亦可檢測出PTV-10，顯示PTV可經尿液排出體外，糞尿混合下加速了病毒傳播速度，證實之前的推論。|
Porcine teschoviruses (PTVs) is a non-enveloped, spherical, positive-sense, single-stranded RNA virus, which belong to genus Teschovirus within the family Picornaviridae. Up to date, PTVs are reclassified into 13 serotypes that are associated with a variety of clinical signs and prominent with polioencephalomyelitis and diarrhea. Two epidemic outbreaks of PTV-1 occurred in Taiwan, one in 2000 and a second in 2004, causing severe economic loss. The enzootic status is now confirmed in swine herds in Taiwan. Previous study has demonstrated at least 5 different serotypes of PTV (PTV-1, -4, -6, -7, -11) existing in Taiwan, and PTV-7 and -6 are the most common serotypes. The aim of this study was to investigate the wider variety of serotypes of PTV by introducing a set of newly designed primer, based on the sequence of VP1 outer capsid gene presented in the feces, plasma, urine, nasal swab, and solid samples in naturally infected piglets. Samples were collected from 7 clinically healthy and 21 culled piglets of 7 different herds. The PTV infections were screened by the published primers to amplify highly conserved 5’NTR region using RT-PCR followed by nested PCR. The PTV detection rate was 100% (28/28) by heads. Out of 217/280 PTV-positive samples the most common detected sample was feces (96%, 27/28), and followed by in decreasing order ileum, tonsil, and nasal swab (93%, 26/28), plasma (86%, 24/28), inguinal LN and urine (both were 79%, 22/28), bladder (64%, 18/28), spleen (57%, 16/28), and kidney (10%, 10/28). VP1 region was successfully amplified, by the newly designed primers, out of 63/217 (29%) pan-PTV nested PCR-positive samples, sequenced, and phylogenetic tree constructed. All 28 piglets had at least one serotype existed, and a total of 5 serotypes of PTV-2, PTV-4, PTV-5, PTV-6, and PTV-10, were identified from 28 piglets. The most common serotype was PTV-10 (36/63, 57%) and the 2nd one was PTV-2 (14/63, 22%). In 14/28 (50%) heads had at least two serotypes identified in the same animals but in different samples. In 2/7 herds, four PTV serotype co-circulated. In conclusion, this study confirms the enzootic and contaminated status of swine herds, combined with previous study at least 8 serotypes of PTV, namely PTV-1、-2、-4、-5、-6、-7、-10、-11 are identified. In particular PTV-10 is found shed in the urine of 3 piglets from 3 separate herds, consistent with the multiple models of PTV pathogenesis. Urine makes solid feces into semisolid slurry thus enhancing the exposure of piglets to PTV.
|Appears in Collections:||分子暨比較病理生物學研究所|
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