ResearchArticle Natural Concurrent Infections with Black Spot Disease and Multiple Bacteriosis in Farmed Nile Tilapia in Central Kenya Daniel W. Wanja , 1,2,3 Paul G. Mbuthia, 1 Robert M. Waruiru, 1 Lilly C. Bebora, 1 and Helena A. Ngowi 3 1 University of Nairobi, College of Agriculture and Veterinary Sciences, Department of Veterinary Pathology, Microbiology and Parasitology, P.O. Box 29053-00625, Kangemi, Nairobi, Kenya 2 Animal Health and Industrial Training Institute (AHITI) Kabete, P.O. Box 29040-00625, Kangemi, Nairobi, Kenya 3 SokoineUniversityofAgriculture,CollegeofVeterinaryandMedicalSciences,P.O.Box3000,ChuoKikuu,Morogoro,Tanzania Correspondence should be addressed to Daniel W. Wanja; wanjadanie@gmail.com Received 5 May 2020; Revised 29 June 2020; Accepted 3 July 2020; Published 30 July 2020 Academic Editor: Francesca Mancianti Copyright © 2020 Daniel W. Wanja et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Nile tilapia (Oreochromis niloticus) 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. e 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 Neascus 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. e most prevalent bacteria isolated were Aeromonas, Enterobacter cloacae, Klebsiella pneumoniae, and Micrococcus luteus. Physico- chemical parameters of pond water were temperature (28.2 ° C), dissolved oxygen (4.2 mgl −1 ), pH (8.5), ammonia free nitrogen (15.8mgl −1 ), alkalinity (112mgl −1 ), hardness (68 mgl −1 ), nitrites (0.058 mgl −1 ), nitrates (58 mgl −1 ), and phosphates (0.046 mgl −1 ). 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. e 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. 1. Introduction Nile tilapia (Oreochromis niloticus) is a resilient species, which grows in a diverse range of aquatic environment, enduring extreme limits of dissolved oxygen, temperature, and contaminants [1]. Nile tilapia possesses advantageous characteristics for pisciculture, including ability to grow rapidly [2], excellent feed conversion efficiency [3], high resistance to disease [4], and ability to reproduce in captivity [5]. is justifies the dominance of Nile tilapia in global-scale production. e roughness and/or resilient nature and disease resistance make it an ideal aquatic “zebu”. However, recent epidemics such as tilapia lake virus have threatened the species and consequently have outlined the importance of protecting the species through increased disease sur- veillance [6]. Farmed tilapine fish are exposed to single or multiple pathogens such as parasitic, bacterial, or mixed infections leading to diseases and mortalities [7]. Even though multiple or concurrent infections are common naturally, most studies Hindawi Veterinary Medicine International Volume 2020, Article ID 8821324, 8 pages https://doi.org/10.1155/2020/8821324