Department of Aquatic Animal Health, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran.
Department of Medical Parasitology and Mycology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
BMC Vet Res. 2024 Feb 12;20(1):54. doi: 10.1186/s12917-024-03902-6.
Free-living amoebae (FLA) are capable of inhabiting diverse reservoirs independently, without relying on a host organism, hence their designation as "free-living". The majority of amoebae that infect freshwater or marine fish are amphizoic, or free-living forms that may colonize fish under particular circumstances. Symphysodon aequifasciatus, commonly referred to as the discus, is widely recognized as a popular ornamental fish species. The primary objective of the present study was to determine the presence of pathogenic free-living amoebae (FLA) in samples of discus fish. Fish exhibiting clinical signs, sourced from various fish farms, were transferred to the ornamental fish clinic. The skin, gills, and intestinal mucosa of the fish were collected and subjected to culturing on plates containing a 1% non-nutrient agar medium. The detection of FLA was conducted through morphological, histopathological and molecular methods. The construction of the phylogenetic tree for Acanthamoeba genotypes was achieved using the maximum likelihood approach. The molecular sequence analysis revealed that all cultures that tested positive for FLA were T4 genotype of Acanthamoeba and Acanthamoeba sp. The examination of gill samples using histopathological methods demonstrated the presence of lamellar epithelial hyperplasia, significant fusion of secondary lamellae, and infiltration of inflammatory cells. A multitude of cysts, varying in shape from circular to elliptical, were observed within the gills. The occurrence of interlamellar vesicles and amoeboid organisms could be observed within the epithelial tissue of the gills. In the current study, presence of the Acanthamoeba T4 genotype on the skin and gills of discus fish exhibiting signs of illness in freshwater ornamental fish farms was identified. This observation suggests the potential of a transmission of amoebic infection from ornamental fish to humans, thereby highlighting the need for further investigation into this infection among ornamental fish maintained as pets, as well as individuals who interact with them and their environment.
自由生活的阿米巴虫（FLA）能够独立栖息在各种不同的环境中，而不依赖宿主生物，因此被称为“自由生活”。感染淡水或海水鱼类的大多数阿米巴虫都是两性营养的，或者是自由生活的形式，在特定情况下可能会在鱼类中定植。Symphysodon aequifasciatus，通常被称为圆盘鱼，是一种广泛认可的受欢迎的观赏鱼类。本研究的主要目的是确定圆盘鱼样本中是否存在致病性自由生活的阿米巴虫（FLA）。从不同的鱼养殖场采集出现临床症状的鱼，将其转移到观赏鱼诊所。采集鱼的皮肤、鳃和肠黏膜，并在含有 1%非营养琼脂培养基的平板上进行培养。通过形态学、组织病理学和分子方法检测 FLA。使用最大似然法构建棘阿米巴基因型的系统发育树。分子序列分析显示，所有检测到 FLA 阳性的培养物均为棘阿米巴 T4 基因型和棘阿米巴属。用组织病理学方法检查鳃样本显示，板层上皮增生，二级板层显著融合，并浸润炎症细胞。在鳃中观察到许多形状从圆形到椭圆形的囊泡。在鳃的上皮组织中可以观察到板间囊泡和阿米巴样生物体。在本研究中，在淡水观赏鱼养殖场出现疾病症状的圆盘鱼的皮肤和鳃中发现了棘阿米巴 T4 基因型。这一观察结果表明，从观赏鱼向人类传播阿米巴感染的可能性，因此需要进一步研究作为宠物饲养的观赏鱼以及与它们及其环境互动的个体中的这种感染。
