School of Veterinary and Biomedical Sciences, Murdoch University, South St., Murdoch, Western Australia 6150, Australia.
Vet Parasitol. 2011 Sep 27;181(2-4):91-6. doi: 10.1016/j.vetpar.2011.05.004. Epub 2011 May 10.
An intestinal Eimeria was previously reported as a significant pathogen of Asian seabass (Lates calcarifer) in nurseries in Vietnam. In the present study, both Eimeria and Cryptosporidium were detected by sequence analyses of fragments of the 18S rRNA gene amplified from these Vietnamese L. calcarifer tissues. Based on these analyses, the Eimeria from the Vietnamese L. calcarifer formed clades with the Eimeria detected in L. calcarifer tissues from Australia, but clustered separately from other known Eimeria and Goussia species. The Cryptosporidium detected in L. calcarifer from Vietnam clustered closest with C. parvum and C. hominis. In situ hybridization using DIG-labeled DNA probes generated from 18S PCR products on the Vietnamese L. calcarifer wax block tissues showed that this method could not be used to distinguish between Eimeria and Cryptosporidium, due to the conserved nature of the 18S locus. A previously published study on the morphology of parasite developmental stages and oocysts in the Vietnamese L. calcarifer tissues showed only an intestinal Eimeria infection. The Cryptosporidium could be present at very low levels undetectable by microscopy in intestines, or being ubiquitous, was a possible contaminant from feed or water. While molecular analysis is a very useful tool in the study of disease and identification of aetiological agents, this study reiterates the importance of demonstrating organisms in situ in tissues.
先前有报道称，一种肠道艾美球虫是越南养殖场亚洲海鲈鱼（Lates calcarifer）的重要病原体。在本研究中，通过对从这些越南 L. calcarifer 组织中扩增的 18S rRNA 基因片段进行序列分析，同时检测到了艾美球虫和隐孢子虫。基于这些分析，来自越南 L. calcarifer 的艾美球虫与从澳大利亚 L. calcarifer 组织中检测到的艾美球虫形成了分支，但与其他已知的艾美球虫和 Goussia 种聚类分开。在越南的 L. calcarifer 中检测到的隐孢子虫与 C. parvum 和 C. hominis 聚类最接近。使用从越南 L. calcarifer 蜡块组织的 18S PCR 产物生成的 DIG 标记 DNA 探针进行原位杂交显示，由于 18S 基因座的保守性质，该方法不能用于区分艾美球虫和隐孢子虫。先前对越南 L. calcarifer 组织中寄生虫发育阶段和卵囊形态的研究仅显示存在肠道艾美球虫感染。隐孢子虫可能在肠道中以非常低的水平存在，显微镜无法检测到，或者它可能无处不在，是饲料或水中的一种可能污染物。虽然分子分析是研究疾病和鉴定病因的非常有用的工具，但本研究再次强调了在组织中原位证明生物体的重要性。
