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Bacteriological and pathological investigation of skin wounds in Prussian carp (Carassius gibelio)
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Javad Daghigh Roohi1 *   , Alireza Mirzajani1 , Monireh Faeed1 , Mohaddeseh Ahmadnezhad1 |
| 1-Inland Waters Aquaculture Research Center, Iranian Fisheries Science Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Bandar Anzali, Iran , javad_daghigh@yahoo.com |
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Abstract: (171 Views) |
Introduction: Anzali Wetland, as one of the most important wetlands in the north of the Iran, has many ecological and biodiversity values. Among the fish of Anzali Wetland, the Prussian carp Carassius gibelio (Bloch, 1782) is an alien species for which there is no precise information about when and how it entered to Anzali Wetland.Unfortunately in the past three decades, this non-native and low-value fish has accounted for a significant portion of the catch from Anzali Wetland. In recent years 20 to 30 percent of Prussian carp caught from Anzali Wetland in late winter and early spring, has been showing symptoms such as scale loss, skin ulcers on the trunk and base of the fins, which in some cases were accompanied by bleeding, and exophthalmia. Based on clinical signs, the disease was suspected to bacterial infection.
Material and Methods: In order to investigate the causes of these ulcers, 30 Prussian carp showing clinical signs with an average weight of 250±50 gr were caught and subjected to bacteriological and histopathological examinations from february 2024 to May 2024. After sampling from the wound site and major internal organs such as the liver, spleen, and kidneys, culture was performed on basic and specific media such as BA and TSA. Then, pure cultures were prepared from the various bacteria grown in these media. Finnaly the bacteria were identified by biochemical tests (Macfaddin, 2000; Garrity et al., 2001). For histopathological examination a tissues sample with 5 mm diameter was removed from the wound site and placed in Bowen’s solution. After dehydration and clarification, the tissues were embedded in paraffin. Sections with a thickness of 5-7 µm were prepared using a microtome. The tissue sections stained with hematoxylin-eosin and a coverslip was attached to each tissue slide. The sections were imaged and studied by light microscopy (Roberts, 2001).
Results and Discussion: Based on the results of the initial cultivation and biochemical tests, two bacteria, Aeromonas hydrophila and Pseudomonas aeruginosa, were identified. Both are gram-negative, motile, and opportunistic bacteria. Aeromonas hydrophila can cause bacterial hemorrhagic septicemia in fish. On the other hand Pseudomonas aeruginosa is another waterborne pathogen that has become a major public health concern. In the pathological examination of skin and muscle tissues, extensive destruction was observed in the epidermis and dermis. Also, severe infiltration of leukocytes into the dermis indicates the presence of inflammation in this area. The normal structure of the dermis was damaged and cyst-like structures were observed in it. myofiber necrosis, decomposition of muscle cells and myolysis of muscular tissue were also among the other damages observed in these fish. Diseases caused by these opportunistic bacteria occur under environmental stressors conditions. These bacteria, especially Aeromonas hydrophila, are zoonotic and can be transmitted to humans through the consumption of raw or undercooked fish.
Conclusion: Severe skin lesions in prussian carp can be caused by physical damage from natural predators of these fish in Anzali wetland or escape from gill nets, which can lead to secondary bacterial infections. Bacterial cepticemia caused by Aeromonas hydrophila is one of the most common infectious diseases of Carassius genus. Since these fish are finally included in community food basket, the importance of paying attention to the health of Anzali Wetland is doubled. It is very important and necessary to observe sanitary standards in the disposal of urban, hospital, agricultural, and industrial wastewater, and especially to accelerate the construction of efficient treatment plants for coastal cities in order to prevent of the entry of various pollutants and sewages into the rivers leading to the Anzali Wetland can prevent the occurrence of such diseases in aquatic animals. |
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| Keywords: Aeromonas hydrophila, Pseudomonas aeruginosa, Pathology, Bacterial hemorrhagic septicemia |
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Type of Study: Research |
Subject:
Special
Received: 2025/07/13 | Accepted: 2025/09/23
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