Streptococcus, Centrocestus formosanus and Myxobolus tilapiae concurrent infections in farmed Nile tilapia (Oreochromis niloticus)

Alaa Eldin Eissa; Marwa M Attia; Mamdouh Y Elgendy; Gehad A Ismail; Nader M Sabry; Abdelbary Prince; Mahmoud A Mahmoud; Ghada O El-Demerdash; Mohamed Abdelsalam; Hassan I M Derwa

doi:10.1016/j.micpath.2021.105084

Streptococcus, Centrocestus formosanus and Myxobolus tilapiae concurrent infections in farmed Nile tilapia (Oreochromis niloticus)

Microb Pathog. 2021 Sep:158:105084. doi: 10.1016/j.micpath.2021.105084. Epub 2021 Jul 8.

Authors

Affiliations

¹ Department of Aquatic Animal Medicine and Management, Faculty of Veterinary Medicine, Cairo University, 12211, Giza, Egypt. Electronic address: aeissa2005@gmail.com.
² Department of Parasitology, Faculty of Veterinary Medicine, Cairo University, 12211, Giza, Egypt.
³ Department of Hydrobiology, Veterinary Research Division, National Research Centre, 12622, Dokki, Giza, Egypt.
⁴ Agriculture Research Centre, Animal Health Research Institute, Fish Diseases Research Department, Dokki, Giza, Egypt.
⁵ Fish Disease Lab, Aquaculture Division, National Institute of Oceanography and Fishery (NIOF), Egypt.
⁶ Department of Biochemistry and Molecular Biology, Faculty of Veterinary Medicine, Cairo University, 12211, Giza, Egypt.
⁷ Department of Pathology, Faculty of Veterinary Medicine, Cairo University, Giza, 12211, Egypt.
⁸ Agriculture Research Centre, Animal Health Research Institute, Al-Fayoum Provincial Laboratory, Egypt.
⁹ Department of Aquatic Animal Medicine and Management, Faculty of Veterinary Medicine, Cairo University, 12211, Giza, Egypt.
¹⁰ Department of Fish Diseases and Management, Faculty of Veterinary Medicine, Suez Canal University, Ismailia, Egypt.

PMID: 34246747
DOI: 10.1016/j.micpath.2021.105084

Abstract

Stress triggered concurrent microbial/parasitic infections are prevalent in earthen pond based farmed Nile tilapia Oreochromis niloticus. In the current study, a total of thirty five O. niloticus were collected from a commercial fish farm with a history of severe mortalities at Port Said, Egypt. Nile tilapia samples were subjected to bacteriological, parasitological and pathological examinations. Twenty one Enterococcus fecalis and 15 Streptococcus agalactiae isolates were presumptively identified utilizing the semi-automated API 20 Strept test kit. The identities of the retrieved bacteria were confirmed by the sequencing of 16 S rRNA gene. Moribund O. niloticus were found to be heavily infected by one or both of Centrocestus formosanus encysted metacercariae (EMC) and/or Myxobolus tilapiae spores presenting a unique form of synergistic and/or symbiotic relationship. The identities of both parasites were confirmed through morphological and molecular characterization. Variable circulatory, degenerative, necrotic and proliferative changes were also noticed in hematopoietic organs. Interestingly, multiple myxobolus spores and EMC were noticed in some histological sections. It was obvious that the current concurrent bacterial and parasitic infections are triggered by the deleterious effects of some stressing environmental conditions. The unfavorable climatic conditions (high temperature and high relative humidity) recorded at the surge of mortalities are probable predisposing stress factors.

Keywords: Centrocestus formosanus; Concurrent infection; Egypt; Enterococcus faecalis; Myxobolus tilapiae; Nile tilapia; Streptococcus agalactiae.

MeSH terms

Animals
Cichlids*
Fish Diseases*
Myxobolus* / genetics
Spores, Bacterial
Streptococcal Infections* / veterinary
Streptococcus agalactiae