Pathological lesions associated with Vibrio infection in Atlantic horse mackerel (Trachurus trachurus L., 1758) from the Western Coast of Tripoli, Libya

Background: Vibrios are aquatic bacteria and ubiquitous in the marine environment causing Vibriosis in humans and aquatic animals. Vibriosis is a significant disease of cultured and wild fish living in marine water, brackish, and freshwater, which causes highly economic losses. Aim: The present study was aimed to address the impact of Vibrios on the health status of Trachurus trachurus inhabiting coastal area of Tripoli. Methods: A total of 100 samples of (Trachurus trachurus) were collected randomly from the Western Coast of Tripoli and Bab Al- Baher market, throughout the period from spring 2019 to summer 2019.All the sampled fish were examined externally and internally to identify any potential lesions. Bacterial isolation from liver and kidney was carried out using the appropriate culture media. Tissue samples were taken from liver, kidney and spleen in 10% neutral buffered formalin for histopathology examination. The tissue sections were stained with Hematoxylin and Eosin (H&E) to assess morphologically and Perl's Prussian blue for the demonstration of ferric iron. Results: On average 69% of the infected fish exhibited at least one pathological lesion. Vibrios were recovered from 90% of the examined fishes. The histopathological changes in the liver were observed as severe congestion of blood vessels, mononuclear cell infiltration surrounding a bile duct, granular degeneration and coagulative necrosis of hepatocytes in the centrilobular area, marked vacuolar degeneration of hepatocytes, activation of melano-macrophages centers (MMCs), multiple cysts of nematode in hepatic tissue (incidental finding). With respect to kidney and spleen, examination of H & E stained tissue sections have severe congestion of blood vessels, vacuolar degeneration of the renal tubular epithelium, severe interstitial mononuclear cell infiltration, and marked activation of melano-macrophages centers (MMCs) in the kidney. Moreover, congestion of blood vessels and marked activation of melano-macrophages (MMCs) were found in the spleen. The melano-macrophage centers (MMCs) of most of the sampled tissues showed a strong positive reaction for ferric iron. Conclusion: The polluted aquatic environment by sewage at Tripoli Coast is an essential factor for triggering the pathogenicity and invasion of Vibrios to vulnerable Atlantic horse mackerel fishes. Also, this study are a preliminary step to give a baseline for further future studies on epidemiology and control of Vibrio infection in Libyan fish. [Open Vet J 2023; 13(3.000): 327-336

Identification and prevalence of Anisakis pegreffii and A. pegreffii × A. Simplex (s.s.) hybrid genotype larvae in Atlantic horse Mackerel (Trachurus trachurus) from some North African Mediterranean coasts

Atlantic horse mackerel is one of the most popular fish for North African consumers. Mackerel constitutes a common host for the Anisakis species of infective larvae (L3). A. pegreffii and A. pegreffii × A. simplex (s.s.) hybrid genotype were identified using PCR-RFLP and entire ITS-DNA sequencing protocol. This research investigated the prevalence and mean intensity of A. pegreffii and its hybrid form in randomly collected mackerel samples throughout spring to summer seasons from the Libyan western coast. Briefly, 55 out of 240 (22.9%) fish samples were confirmed to be infected and the prevalence of A. pegreffii reached 22.08% with mean intensity of infection 29.13 ± 2.43 parasite/fish, while the prevalence of A. pegreffii × A. simplex (s.s.) hybrid genotype was 0.8% with mean intensity of infection 22 ± 0.85 parasite/fish. The prevalence of infection noticeably elevated during the summer season to reach 30.8%. Additionally, female fish samples were heavily infected as the mean intensity of infection was 34.75 ± 1.27 parasite/fish. Furthermore, results indicated that the highest intensity of infection was recorded in older and female mackerel. To sum up, the current study has provided substantial information about the impacts, diversity and epidemiology of A. pegreffii and its hybrid form in North African waters. Keywords: Anisakis pegreffii, Anisakis hybrid genotype, PCR-RFLP, Atlantic horse mackerel, Trachurus trachurus, Liby