Cyathocotylidae spp and motile aeromonads co-infections in farmed Nile tilapia (Oreochromis niloticus) causing mass mortality

Motile aeromonads, and Cyathocotylidaespp.co-infections were identified in farmed Nile tilapia(Oreochromis niloticus) which suffering from mortalities. Moribund fish showed signs of septicemia, skin irritations, and res-piratory distress. A total of 150 O. niloticus specimens showing signs of disease were collected from the affected earthmen ponds and examined. Bacteriological examination of fish samples revealed infections with motile aeromonads species. Phenotypic characteristics and phylogenetic analysis of gyrB gene sequences of aeromonads isolates identified them as Aeromonas hydrophila (12.6%), A.sobria (12.6%), and A. caviae (30.4%). Aeromonads strains harbored some virulence genes: Aer (78.62%); Hyl (60.86%); laf-A (52.17%); and Act (47.82%). The antibiogram of aeromonads showed high resistance against tetracycline (73.9%), and gentamycin (65.2%), while a high sensitivity was noticed to ciprofloxacin (82.6%),and trimethoprim/sulfamethoxazole (60.86%). Parasi-tological examination of fish revealed the presence of Cyathocotylidae spp. encysted metacercaria (EMC). High levels of interleukin 6 (IL-6) and cluster of differentiation 4 (CD4) were noticed in fish with parasitic and bac-terial co-infection compared to those with a single infection or non-infected. Experimentally infected fish with Aeromonas spp. showed septicemic signs similar to that noticed in naturally infected tilapia with variable cu-mulative mortality. The study is one of the earlier reports identifying as Cyathocotylidae spp., and motile aero-monads co-infections, and their link with the exaggerated tilapia mortality which will be of value for incorporating these pathogens in the necessary management strategies to protect fish health.

Automated summary

Motile aeromonads and Cyathocotylidae spp. co-infections were found in farmed Nile tilapia suffering from mortalities. Moribund fish showed signs of septicemia, skin irritations, and respiratory distress. Bacteriological examination revealed infections with Aeromonas hydrophila, A. sobria, and A. caviae, while Cyathocotylidae spp. encysted metacercaria were found in parasitological examination. High levels of interleukin 6 (IL-6) and cluster of differentiation 4 (CD4) were noticed in fish with co-infection. The study provides valuable information for managing these pathogens in order to protect fish health.