台灣地區吉貝氏焦蟲分子特徵研究

Abstract

犬焦蟲病(canine babesiosis)為一種由Babesia屬的血球內寄生蟲所引起的疾病，病原一般認為為Babesia gibsoni(吉貝氏焦蟲)與Babesia canis，在台灣以吉貝氏焦蟲為多。臨床診斷大多依賴鏡檢，B. gibsoni 與B. canis可由滋養體大小來區分，然而由於潛伏感染期或帶原者體內滋養體數目過少而不易與型態學來區分，或是無明顯臨床症狀而易被忽略。所以已發展岀其他實驗室診斷方法如免疫學方法或是分子生物學方法做診斷。許多報告應用聚合脢鏈反應(Polymerase chain reaction, PCR)的方法來偵測焦蟲的感染，並將所得序列做序列分析而發現各地所分離的焦蟲有序列上的差異，而有學者傾向修正原來的分類。在本研究中應用PCR的方法偵測焦蟲的小次單位核糖體RNA基因(18S rDNA)，並分析其核酸序列，發現台灣地區犬小焦蟲之18S rDNA序列和基因庫上發表之 “Oklahoma分離株” (AF205636)最為接近，相似度達99%。另外也針對我們所得到序列研發岀診斷用巢氏聚合脢鏈反應(nested PCR)診斷技術，以檢出B. gibsoni感染。並使用已發表引子針對台灣地區的大焦蟲做調查，發現其屬於Babesia canis vogeli這個亞種。這是台地區首次針對B. gibsoni以及B. canis所做的分子特徵研究。

Canine babesiosis is an important disease found in domestic dogs with infection of the intra-erythrocytic protozic parasites known as Babesia. Historically, pathogens that caused canine babesiosis have been attributed to either Babesia canis and/or Babesia gibsoni, and both species can be found in Taiwan. Laboratory diagnosis of canine babesiosis is primary based on blood smear. B. gibsoni and B. canis can easily be distinguished by their difference in size. However, due to limited number of parasites presented, it would be difficult to differentiate these two species especially in carriers or latently infected dogs with no obvious clinical signs. There is necessity to develop a more reliable diagnostic technique. We sequenced small subunit ribosomal RNA gene (18S rDNA) of B. gibsoni in Taiwan and compare that with the published sequence in gene bank. The most identical sequence is “Oklahoma” isolate (AF205636). The similarity is 99%. We also developed the diagnostic nested polymerase chain reaction (nested PCR) based on the sequence we found to detect B. gibsoni infection. In addition, samples were examined by published primers for B. canis. B. canis in Taiwan and were proved to be the subspecies B. canis vogeli. This is the first description of molecular characteristics of B. gibsoni in Taiwan.