Laboratory of Parasitology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820, Merelbeke, Belgium; Laboratory of Infectious and Parasitic Diseases, Veterinary Research Institute, Hellenic Agricultural Organization - DEMETER, 57001, Thermi, Thessaloniki, Greece.
Laboratory of Parasitology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820, Merelbeke, Belgium.
Exp Parasitol. 2020 Mar;210:107848. doi: 10.1016/j.exppara.2020.107848. Epub 2020 Jan 28.
Marine bivalves are usually cultivated in shallow, estuarine waters where there is a high concentration of nutrients. Many micro-pollutants, including the protozoan parasites Giardia duodenalis and Cryptosporidium spp., which also occur in such environments, may be concentrated in shellfish tissues during their feeding process. Shellfish can thus be considered as vehicles for foodborne infections, as they are usually consumed lightly cooked or raw. Therefore, the main objective of this study was to investigate the presence of both parasites in Mediterranean mussels, Mytilus galloprovincialis that are cultivated in Thermaikos Gulf, North Greece, which is fed by four rivers that are contaminated with both protozoa. Moreover, the occurrence of these protozoa was monitored in treated wastewaters from 3 treatment plants that discharge into the gulf. In order to identify potential sources of contamination and to estimate the risk for human infection, an attempt was made to genotype Giardia and Cryptosporidium in positive samples. Immunofluorescence was used for detection and molecular techniques were used for both detection and genotyping of the parasites. In total, 120 mussel samples, coming from 10 farms, were examined for the presence of both protozoa over the 6-month farming period. None of them were found positive by immunofluorescence microscopy for the presence of parasites. Only in 3 mussel samples, PCR targeting the GP60 gene detected Cryptosporidium spp. DNA, but sequencing was not successful. Thirteen out of 18 monthly samples collected from the 3 wastewater treatment plants, revealed the presence of Giardia duodenalis cysts belonging to sub-assemblage AII, at relatively low counts (up to 11.2 cysts/L). Cryptosporidium oocysts (up to 0.9 oocysts/L) were also detected in 4 out of 8 samples, although sequencing was not successful at any of the target genes. At the studied location and under the sampling conditions described, mussels tested were not found to be harboring Giardia cysts and the presence of Cryptosporidium was found only in few cases (by PCR detection only). Our results suggest that the likelihood that mussels from these locations act as vehicles of human infection for Giardia and Cryptosporidium seems low.
贝类通常在营养物质浓度高的浅海河口水域养殖。许多微污染物，包括原生动物寄生虫贾第虫和隐孢子虫，也存在于这些环境中，在贝类摄食过程中可能会集中在贝类组织中。贝类因此可以被视为食源感染的载体，因为它们通常是轻度烹饪或生吃的。因此，本研究的主要目的是调查在希腊北部的 Thermaikos 湾养殖的贻贝（Mytilus galloprovincialis）中是否存在这两种寄生虫，该湾由四条受原生动物污染的河流供给。此外，还监测了 3 家污水处理厂排放到该湾的处理废水中这些原生动物的发生情况。为了确定潜在的污染来源并估计人类感染的风险，尝试对阳性样本中的贾第虫和隐孢子虫进行基因分型。免疫荧光法用于检测，分子技术用于寄生虫的检测和基因分型。在 6 个月的养殖期间，总共检查了来自 10 个养殖场的 120 个贻贝样本，以确定是否存在这两种原生动物。没有一个样本通过免疫荧光显微镜检测到寄生虫的存在。只有在 3 个贻贝样本中，针对 GP60 基因的 PCR 检测到隐孢子虫属 DNA，但测序不成功。从 3 家污水处理厂采集的 18 个每月样本中，有 13 个样本检测到属于亚类 AII 的十二指肠贾第鞭毛虫囊，数量相对较低（高达 11.2 个囊/L）。在 8 个样本中的 4 个样本中也检测到隐孢子虫卵囊（高达 0.9 个卵囊/L），尽管在任何目标基因上的测序都不成功。在所研究的地点和描述的采样条件下，未发现测试贻贝携带贾第虫囊，仅在少数情况下（仅通过 PCR 检测）发现隐孢子虫的存在。我们的结果表明，这些地点的贻贝作为贾第虫和隐孢子虫人类感染载体的可能性似乎较低。
