The farmed red-bellied pacu Piaractus brachypomus is a valuative commercial fish widely exploited in fish farming. Histopathologic alterations in small intestine of this fish were associated with heavy roundworms infection. Of a total of thirty-five fish examined, all were parasitized with a prevalence of 100%, intensity of 290–6403, and mean intensity of infection of 4467.5 parasites per fish. According to the morphological features of whole nematodes examined using light and electronic microscopy, the parasite was identified as Rondonia rondoni Travassos. Rev Vet e Zoot 10, 59–70; 1920. The fish intestinal tissue alterations include fusion of villi, edema, disorganization of epithelial cells, epithelial abrasion, and flaking of the villus at mucosa layer level and submucosa layer with some regions of necrosis and lymphocyte infiltrate. This is the first report of histopathological alterations caused by infection of the atractid nematode R. rondoni in a farmed population of P. brachypomus in the Peruvian Amazon. The study points out the need of improving the strategies of parasitic prevention and control in order to better prevent future disease outbreaks.

养殖的红腹pa鱼Piaractus brachypomus是一种有价值的商业鱼，广泛用于养鱼业。该鱼小肠的组织病理学改变与重round虫感染有关。在检查的总共35条鱼中，所有鱼均被寄生，流行率为100％，强度为290–6403，每条鱼的平均感染强度为4467.5寄生虫。根据使用光学和电子显微镜检查的整个线虫的形态特征，该寄生虫被鉴定为Rondonia rondoniTravassos。Vet e Zoot 10，59-70；1920.鱼的肠组织改变包括绒毛融合，水肿，上皮细胞紊乱，上皮磨损以及绒毛在粘膜层和粘膜下层的剥落，并伴有某些坏死和淋巴细胞浸润。这是秘鲁秘鲁亚马逊河地区养殖的P. brachypomus种群中由白术线虫R. rondoni感染引起的组织病理学改变的首次报道。研究指出，有必要改进寄生虫的预防和控制策略，以更好地预防未来的疾病暴发。