The Nasal Epithelium as a Route of Infection and Clinical Signs Changes, in Rainbow Trout (Oncorhynchus mykiss) Fingerlings Infected with Aeromonas spp

Abstract

The genus Aeromonas is a group of bacteria that is widely distributed in water bodies and belongs to the normal intestinal microbiota of aquatic and terrestrial animals. In the present work, rainbow trout fingerlings were experimentally infected by an immersion bath with different Aeromonas species. Subsequently, the behavior of the infected groups was observed and recorded. Infected fingerlings were evaluated by histopathology. The highest percentages of hyperpigmentation (18.88%) and inappetence (47.7%) were observed in fish infected with A. salmonicida, while abnormal swimming (83.33%) was recorded in fish infected with A. bestiarum. In histopathological findings, the highest percentages were observed in the olfactory epithelium (50.0%) for A. lusitana and A. salmonicida (41.1%)-infected fish. While, in the nervous system, the cerebral hemispheres (31.1%) in A. media-infected fish and the oblongata medulla (40.0%) in the A. bestiarum-infected fish presented the highest percentages. Meanwhile, A. salmonicida and A. bestiarum have the highest pathogenicity and virulence based on the histopathological findings in the olfactory epithelium and nervous system. Due to the proximity of the olfactory epithelium with the nervous tissue, it is possible that the infection generated by the Aeromonas species and the histopathological findings in the nervous tissue are reflected in different behavioral changes that suggest differences in the pathogenicity and virulence of the bacteria.

Special Issue on the Histopathology of Aquatic Animals

“…Histomorphometrical methods were further employed in order to show changes on a range of different cells and structures in the mentioned tissues. Gómez de Anda et al [12] exposed rainbow trout (Oncorhynchus mykiss) fingerlings to a bath containing several species of Aeromonas spp. They found several histopathological alterations of nervous tissues (nasal epithelium, telencephalon, and oblongata medulla), which were distinct to the fish infected with A. lusitana and A. salmonicida and with the higher severity grades.…”

Utilizing of black cumin (Nigella sativa) flour to increase the immunity system of tilapia (Oreochromis niloticus) against Aeromonas hydrophila bacteria attack

“…Treatment A experienced the most severe body damage due to the absence of body defenses provided, seen from the number of leukocytes that did not increase so that the immunity system and survival of fish was low. Hyperpigmentation or darkened skin can be caused due to changes in the physiology of fish that experience stress due to bacterial infection, and disruption of the hormonal system resulting in changes in skin color (Gómez et al, 2021). While haemorrhagic or red spots can be due to the nature of Aeromonas hydrophila bacteria that make tissue inflammation and some organs of the fish are damaged and bleeding occurs (Basri et al, 2020).…”