Photobacterium damselae subsp. piscicida Infection, a Persistent Cause of Mortalities in Old Hatchery-reared Gilthead Seabream (Sparus aurata) Broodstocks: Molecular-pathological Evidences and Control Strategy

Arafa, Ahmed; Eissa, Alaa Eldin; Khallaf, Mohamed A.; Ghetas, Hanan A.; Ragab, Reham H; Mansour, Shaimaa M.; Younis, Eman M.; Ali, Samah F.; Ismail, Eman M; Rashwan, Eman H.; Diab, Hassan M.; Hamouda, Awatef H.; Abuelkasem, Suzan S.; Elnakeeb, Mahmoud A.; Abd-Elghany, Mohamed; Ismail, Mona M.; Abdel Hady, Heba A.; Korany, Reda; Younis, Nehal A.

doi:10.21608/ejvs.2025.339899.2526

Photobacterium damselae subsp. piscicida Infection, a Persistent Cause of Mortalities in Old Hatchery-reared Gilthead Seabream (Sparus aurata) Broodstocks: Molecular-pathological Evidences and Control Strategy

Articles in Press

Document Type : Original Article

Authors

¹ Department of Aquatic Animals Medicine and Management, Faculty of Veterinary Medicine, University of Sadat City, Sadat City 32897, Egypt.

² Department of Aquatic Animal Medicine and Management, Faculty of Veterinary Medicine, Cairo University, Giza 11221 Egypt

³ Department of aquatic animal medicine and management faculty of veterinary medicine Cairo university

⁴ Department of Fish Diseases, Ismailia Provincial Lab, Animal Health Research Institute, Agriculture Research Center, Dokki, Egypt.

⁵ Department of Biochemistry, Animal Health Research Institute, Agriculture Research Center, Dokki, Egypt.

⁶ Department of Bacteriology, Animal Health Research Institute, Agriculture Research Center, Dokki, Egypt.

⁷ Department of Veterinary Hygiene and Management, Faculty of Veterinary Medicine, Cairo University, Egypt

⁸ Department of Veterinary Hygiene and Management, Faculty of Veterinary Medicine, Cairo University, Giza 12211 Egypt.

⁹ Department of Animal and Poultry Health & Environment, Faculty of Veterinary Medicine, South Valley University, Qena 83523, Egypt

¹⁰ Department of Fish Health and Diseases, Faculty of Fish and Fisheries Technology, Aswan University, Aswan 81528, Egypt.

¹¹ Department of Nutrition and Food Safety, Faculty of Applied Health Sciences Technology, October 6 University, 6th of October City, Egypt.

¹² Department of Fish Production, Faculty of Agriculture, Al-Azhar University, Nasr City, Cairo 11884, Egypt

¹³ Department of Animal Production, Faculty of Agriculture, Al-Azhar University

¹⁴ Department of Fish Diseases and Management, Faculty of Veterinary Medicine, Suez Canal University, Ismailia, Egypt.

¹⁵ Department of Virology and Serology, Animal Health Research Institute, Alexandria Provincial Laboratory, Alexandria, Egypt

¹⁶ Department of Pathology, Faculty of Veterinary Medicine, Cairo University

¹⁷ Department of Department of Aquatic Animal Medicine, Faculty of Veterinary Medicine, Cairo University, Giza 11221, Egypt

10.21608/ejvs.2025.339899.2526

Abstract

Almost all Egyptian marine hatcheries collect their young Gilthead seabream brood stock from open water at Deeba Triangle or Damietta. Some of these wild broodstock could possibly harbour hidden mild Photobacterium damselae subsp. piscicida infection. In the current study, a total of 20 mortal/moribund 5-7-years old broodstocks were clinically examined and then subjected to microbiological and histopathological examination. Moribund brood stocks were lethargic and anorexic. Externally, broodstocks showed generalized skin darkening, haemorrhages at the base of fins together with pale gills. Internally, the spleen, liver, and kidney were remarkably infiltrated with several whitish various-sized nodules together with an unpleasant odor originating from the abdominal cavity of necropsied brood stocks. Pathology has revealed multiple granulomas together with lymphocytic and inflammatory cell infiltrations through the anterior kidney, spleen and liver tissues together with severe melano-macrophage center (MMC) activation. Bacteria-laden macrophages were also noticeable through stained tissue sections. Photobacterium damselae subsp piscicida was presumptively isolated from the internal organs of moribund and mortal fishes. Initial identification was based on bipolarity staining, API 20 E profile, and antibiotic susceptibility testing. The final identity was confirmed using partial sequencing of 16S rRNA gene. The control strategy was based initially on oral antibiotic therapy (florfenicol) to combat systemic infection and tank water disinfectant (Hydrogen peroxide) to minimize bacterial load followed by an immune-boosting feed additive program utilizing probiotics, B-glucan, nucleotides, vitamin C, organic zinc and selenium. Brood stock tanks' follow-up for 1 month after the initiation of the control strategy has revealed no mortalities among reared broodstocks.

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