臺灣貓隻麻疹病毒偵測與疾病相關性

Abstract

慢性腎病定義為單側或雙側腎臟有結構或功能上的損傷、且持續至少三個月以上，為貓隻最常見的腎病之一，與其他腎臟病變比較，腎小管間質性腎炎為貓隻慢性腎病最主要的特徵。而目前能證明貓慢性腎病因果關係的研究還是十分有限。研究顯示傳染性疾病在慢性腎病可能扮演一種要角色，像是貓免疫不全病毒 (FIV)及貓白血病 (FeLV)。最近在2012年，Woo等人從香港首次從貓隻上分離出貓麻疹病毒 (FmoPV)，且由組織病理學的結果推論貓麻疹病毒的感染與腎小管間質性腎炎相關。2013至2016年間，日本、歐洲及美國等國也陸續發表關於貓麻疹病毒存在的報告，除了腎小管間質性腎炎之外，腎炎及貓下泌尿道疾病也被認為可能與貓麻疹病毒相關。因此，確認臺灣是否也有貓麻疹病毒的感染及找出其致病性是有其必要性。本實驗的研究目的是藉由反轉錄聚合酶鏈反應調查臺灣貓隻是否也有貓麻疹病毒的感染，親源性序列分析用來比較陽性檢體的基因歧異度。此外，受感染貓隻的臨床病理檢驗數據及臨床徵狀也皆記錄下來，並藉由統計分析其與泌尿道疾病之相關性。根據我們的實驗結果，自2014至2016年總共從臺大動物醫院收集339隻貓的尿液檢體，其中有九隻經由反轉錄聚合酶鏈反應放大部分貓麻疹病毒L基因片段，確認為貓麻疹病毒陽性感染 (2.65%)。經由親緣性序列分析發現，陽性序列可分為兩群不同的病毒株，一群與香港病毒株相似，另一群則和日本病毒株較相似。另一方面，我們也利用陽性質體設計出新的引子用在即時定量聚合酶鏈反應。在九隻陽性貓當中發現，統計上貓麻疹病毒感染與泌尿道疾病伴隨輕微升高的腎指數有顯著相關性 (p =0.034)。然而，在感染組與未感染組的比較當中，腎指數 (尿素氮、肌酐酸及尿比重)、慢性腎病及貓下泌尿道疾病並沒有發現顯著關聯。此外，其中一隻感染的貓在兩年後仍能從其尿液偵測到特定的貓麻疹病毒基因片段。有兩隻陽性感染的貓出現目前尚未被報告的神經相關症狀。綜合以上實驗結果，我們證實臺灣貓隻也有貓麻疹病毒感染，而且貓麻疹病毒可能與泌尿道疾病相關，此病毒最長能在兩年後持續在同隻病患的尿液中被偵測到。

Chronic kidney disease (CKD) is the most common renal disease in cats and tubulointerstitial fibrosis is the most common finding. However, the evidence to demonstrate a cause-and-effect etiology of tubulointerstitial fibrosis was limited. Infections might play a causal role in some cases of CKD, like feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV). Recently, Woo et al. (2012) reported the isolation of feline morbillivirus (FmoPV) in domestic cats in Hong Kong and Main China. The histological findings from the infected cats suggested that there might be a correlation between FmoPV infection and tubulointerstitial nephritis (TIN). During 2013-2016, the studies from Japan, Europe and America also demonstrated evidence for the presence of FmoPV in domestic cats. Except TIN, renal inflammation and feline lower urinary tract disease (FLUTD) may also relate to FmoPV infection. Thus, it is essential to confirm the presence of FmoPV in Taiwan and identify its pathogenicity. The aim of this study is to detect FmoPV from urine samples in Taiwan by RT-PCR. Phylogenetic analysis was used to determine sequence divergences. Furthermore, laboratory parameters and clinical signs from the cats suffered from infection were statistically analyzed for the correlation between FmoPV and urinary disease. Based on our results, partial sequence of FmoPV L gene was detected by RT-PCR from 9 out of 339 urine samples (2.65%) of cats brought to National Taiwan University Veterinary Hospital (NTUVH) during 2014-2016. Two different strains of FmoPV similar with the strains from Hong Kong and Japan respectively were found via phylogenetic analysis. Additionally, by using positive plasmid, quantitative PCR was established with new primers designed by our group. Among nine positive cats, urinary disease with mild increased renal index concentration was significantly correlated to FmoPV infected cats (p =0.034). Nevertheless, there was no significant difference of renal values (BUN, Creatinine and urinary specific gravity) of the number of CKD or FLUTD between infected and non-infected cats. Moreover, target viral genomic fragments of FmoPV still could be detected in urine of one positive cat during two years of follow-up. It’s interesting that two virus positive cats had neurological signs and which was never reported. In conclusion, our findings support that the existence of FmoPV infection in Taiwan. Additionally, FmoPV may relate to urinary disease and is still detected from urine of infected cats after two year.