Wanja Daniel W, Mbuthia Paul G, Waruiru Robert M, Bebora Lilly C, Ngowi Helena A
University of Nairobi, College of Agriculture and Veterinary Sciences, Department of Veterinary Pathology, Microbiology and Parasitology, P.O. Box 29053-00625, Kangemi, Nairobi, Kenya.
Animal Health and Industrial Training Institute (AHITI) Kabete, P.O. Box 29040-00625, Kangemi, Nairobi, Kenya.
Vet Med Int. 2020 Jul 30;2020:8821324. doi: 10.1155/2020/8821324. eCollection 2020.
Nile tilapia () is the most cultured and available fish for Kenyan consumers, and therefore, any tilapine disease deprives them the valuable source of protein. Nile tilapia farm was diagnosed with severe concurrent black spot disease and multiple bacteriosis using gross lesions and parasitological, histopathology, and standard bacteriological procedures. A total of 25 fish were sampled and inspected, and all of them had raised, macroscopic 1 mm-sized black spot lesions. The mean intensity of black spots per fish was 728 with an abundance of 2-1740 metacercariae cysts per fish. A high intensity of black spot infestation was observed in the fins (43.9%), skin and underlying muscles (18.3%), and gills (18%). In addition, histopathological data confirmed presence of a metacercaria of spp. as the aetiological agent of black spot disease. Furthermore, a thick fibrous capsule around the metacercaria, black pigment melanomacrophages, and moderate muscle atrophy were observed. The most prevalent bacteria isolated were , , , and . Physicochemical parameters of pond water were temperature (28.2°C), dissolved oxygen (4.2 mgl), pH (8.5), ammonia free nitrogen (15.8 mgl), alkalinity (112 mgl), hardness (68 mgl), nitrites (0.058 mgl), nitrates (58 mgl), and phosphates (0.046 mgl). However, the levels of nitrates, nitrites, alkalinity, and ammonia free nitrogen exceeded the recommended limits. In conclusion, these findings suggest that coinfections by these organisms coupled by water quality-related stress can be associated with low-grade mortality observed in postfingerling tilapia as well as reduced growth. The authors recommended immediate destocking, thorough disinfection, and control of piscivorous birds. Moreover, attention ought to be geared towards prevention of parasitic infestations in fish so as to minimize fish deaths related to secondary bacteriosis. Further experimental studies should be carried out to elucidate the relationship of these pathogens.
尼罗罗非鱼（）是肯尼亚消费者养殖最多且最容易获得的鱼类，因此，任何罗非鱼疾病都会使他们失去宝贵的蛋白质来源。通过肉眼可见的病变以及寄生虫学、组织病理学和标准细菌学程序，对尼罗罗非鱼养殖场进行诊断，发现患有严重的并发黑斑病和多种细菌感染。总共对25条鱼进行了采样和检查，所有鱼都有凸起的、肉眼可见的1毫米大小的黑斑病变。每条鱼黑斑的平均强度为728，每条鱼有2 - 1740个囊蚴囊肿。在鱼鳍（43.9%）、皮肤及皮下肌肉（18.3%）和鳃（18%）中观察到高强度的黑斑感染。此外，组织病理学数据证实存在某种复口吸虫的囊蚴，为黑斑病的病原体。此外，还观察到囊蚴周围有一层厚厚的纤维囊、黑色色素巨噬细胞以及中度肌肉萎缩。分离出的最常见细菌为、、和。池塘水的理化参数为温度（28.2°C）、溶解氧（4.2毫克/升）、pH值（8.5）、无氨氮（15.8毫克/升）、碱度（112毫克/升）、硬度（68毫克/升）、亚硝酸盐（0.058毫克/升）、硝酸盐（58毫克/升）和磷酸盐（0.046毫克/升）。然而，硝酸盐、亚硝酸盐、碱度和无氨氮的水平超过了推荐限值。总之，这些发现表明这些生物体的混合感染以及与水质相关的应激可能与尼罗罗非鱼幼鱼期观察到的低死亡率以及生长减缓有关。作者建议立即清塘、彻底消毒并控制食鱼鸟类。此外应关注预防鱼类寄生虫感染，以尽量减少与继发性细菌感染相关的鱼类死亡。应开展进一步的实验研究以阐明这些病原体之间的关系。
