Natural co‐infection of cultured Nile tilapiaOreochromis niloticuswithAeromonas hydrophilaandGyrodactylus cichlidarumexperiencing high mortality during summer

Abstract

Aeromonas hydrophila and Gyrodactylus cichlidarum are common pathogens that induce significant economic losses in farm‐reared Nile tilapia. Nowadays, the sudden appearance of fish mortalities was exaggerated due to mixed and multiple infections. During summer 2016, mass mortality among earthen pond‐farmed Nile tilapia was reported. Clinico‐pathological, bacteriological and parasitological examinations have been demonstrated. As well, the water quality parameters were assessed. The clinical and histopathological findings of the moribund and recently dead fish were characterized by generalized septicaemic signs. The water quality parameters were significantly elevated over the permissible levels, whereas there was an elevation in nitrite (0.04 mg/L), un‐ionized ammonia (0.8 mg/L), hydrogen sulphide levels (153.1 mg/L) and organic matter content (3.79 mg/L). A. hydrophila was identified based on phenotypic characterization, API 20E features and the homology of 16S rRNA gene sequence analysis. In addition, PCR data confirmed the presence of aerolysin (aerA) and haemolysin (hly) genes in the identified A. hydrophila isolates. Gene sequencing and phylogenetic analysis based on 16S rRNA sequence confirmed that A. hydrophila H/A (accession No. MN726928) of the present study displayed 98%–99% identity with the 16S rRNA gene of A. hydrophila. Furthermore, the monogenetic trematode, G. cichlidarum was identified in the wet mounts from the skin and gills of the examined fish with a high infestation rate. In this context, it was reported that the synergistic co‐infection of A. hydrophila and G. cichlidarum with deteriorated water quality parameters could induce exaggerated fish mortalities during hot weather.

Co-Infections of Tilapia Lake Virus, Aeromonas hydrophila and Streptococcus agalactiae in Farmed Red Hybrid Tilapia

“…The recent intensification of tilapia rearing leads to the emergence of TiLV infections. On the other hand, A. hydrophila in this study was closer to the Iranian strain and shared similar phenotypic and biochemical characteristics with A. hydrophila isolated from Nile tilapia ( O. niloticus ) from Egypt [ 34 ]. Furthermore, isolates of S. agalactiae in this study were found closer to the Brazilian isolate and have similar characteristics with S. agalactiae isolated from tilapia in Thailand, with the exception of the arginine dihydrolase test [ 35 ].…”

Prevalence, Virulence Gene Distribution and Alarming the Multidrug Resistance of Aeromonas hydrophila Associated with Disease Outbreaks in Freshwater Aquaculture

“…Members of this genus have been the focus of attention because of their potential to act as pathogens on a wide range of hosts not only in fish, amphibians, and reptiles but also in mammals, including humans [8,9]. Among Aeromonas species that cause fish diseases, A. hydrophila has been identified as one of the most dangerous pathogens Antibiotics 2021, 10, 532 2 of 17 causing mortality outbreaks in a diversity of cultured fish species [6,10] and has been responsible for huge economic losses in various countries [11,12].…”

Moringa Oleifera Leaf Extract Repairs the Oxidative Misbalance following Sub-Chronic Exposure to Sodium Fluoride in Nile Tilapia Oreochromis niloticus

“…Nile tilapia, Oreochromis niloticus, is a type of freshwater fish that is commonly used in toxicological investigations [29]. It is characterized by resistance to diseases, fast growth, and easy adaption to commercial diets [30]. Several studies were performed to evaluate the importance of medicinal plants' leaf extracts for detoxification of polluted ecosystems [31][32][33][34][35], promote fish growth [36], and improve resistance against toxicity.…”