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Health Status of Eels from Open Waters: a Clinical and Histopathological Approach

M. T. Hosain
Department of Aquaculture, Faculty of Fisheries, Bangladesh Agricultural University, Bangladesh.

M. M. Hossain
Faculty of Fisheries, Sylhet Agricultural University, Bangladesh.

M. M. M. Alam
Faculty of Fisheries, Sylhet Agricultural University, Bangladesh.

M. A. Kashem
Faculty of Fisheries, Sylhet Agricultural University, Bangladesh.

M. M. Hassan
Noakhali Integrated Agro Industries Ltd. Noakhali Sadar, Noakhali, Banglladesh.

G. U. Ahmed
Department of Aquaculture, Faculty of Fisheries, Bangladesh Agricultural University, Bangladesh.

Abstract/ Executive Summary:

An experiment was conducted to know the health and disease problems of two freshwater eels, viz. Monopterus cuchia and Mastacembelus armatus which were collected from open waters of Mymensingh region (i.e. Kailla beel and Brahmaputra river) through clinical and histopathological examination. Water quality parameters, clinical and histopathological examinations were carried out on a monthly basis. The average value of temperature and dissolved oxygen (DO) decrease in winter season. During month of December and January, eels were found to be severely affected and characterized by clinical signs of red spots, rough skin and deep ulcers in the ventral and lateral regions of the body. Additionally, there weresevere necrosis in the skin and muscle of eels, presence of melanomacrophage, loss of epidermis, vacuoles, split of dermis and muscle were observed. Histopathological examination of gills were revealed missing of primary and secondary gill lamellae, necrosis, hyperplasia, highly hypertrophied and hemorrhagic gill lamellae. In liver, pyknotic and hyperplasid hepatocytes, necrosis, hemorrhages and vacuoles were evident. Hemorrhages, vacuolation, necrosis, missing and ruptured kidney tubules, pyknosis and presence of fungal granuloma were the major pathological alterations of kidney. The observed signs of diseases in eels could be realted to epizootic ulcerative syndrome (EUS), dactylogyrosis, parasitic and bacterial diseases associated with other opportunistic pathogens.. Our results indicated that the examined eels of Kailla beel river were found to be more severely affected than eels of the Brahmaputra oneduring the colder months of the year (December and January), in comparison to other months of the year.

Keywords: Eel fish, Health and disease, Open water, Histopathology, EUS

Location: Bangladesh Agricultural University campus, Sadar, Mymensingh.

Start Date: 00-08-2012

End Date: 00-01-2013

Program Area: Animal Health and Management

Commodity: Eel

Objectives:

To investigate the health and disease problems of two freshwater eels, viz. Monopterus cuchia and Mastacembelus armatus from open water bodies of Mymensingh through clinical and histopathological measures.

Methodology:

Site profile: The present investigation was conducted for a period of six months from August 2012 to January, 2013 in two open water bodies of Mymensingh namely, Kailla beel and Brahmaputra river. Clinical and histopathological examination: The sampled fishes were clinically examined by naked eye and magnifying glass to record any external signs, injury and other abnormalities. Organs like skin and muscle, gills, liver and kidney were collected with the help of a sharp scalpel and forceps and fixed in 10% buffered formalin for histopathological examination. After at least Kailla beel, situated at Ishwarganj subdistrict, located in between 24°33’ and 24°44’ north latitudes and between 90°28’ and 90°46’ east longitudes and about 30 km south east of Mymensingh district (Banglapedia, 2013), comprised an area of approximately 4000 acres, having average depth 2.5 and 8.0 meter (m) in winter and rainy seasons respectively. The Brahmaputra river, possess average depth of five and 15 m in dry and rainy season respectively, flowing through the East side of the Bangladesh Agricultural University campus, Sadar, Mymensingh, located between 24°38´ and 24°54´ north latitudes and between 90°11´ and 90°30´ east longitudes. Sampling procedure: Live eels and water samples were collected monthly from the study sites and immediately carried to the Fish Disease Laboratory of the Faculty of Fisheries, BAU, Mymensingh. Water quality parameters like temperature, dissolved oxygen (DO) and pH were measured by using HACH’s kit (Model FF-IA). Clinical and histopathological examination: The sampled fishes were clinically examined by naked eye and magnifying glass to record any external signs, injury and other abnormalities. Organs like skin and muscle, gills, liver and kidney were collected with the help of a sharp scalpel and forceps and fixed in 10% buffered formalin for histopathological examination. After at least eight hours of fixation, the samples were trimmed in order to obtain a standard size of 1 cm3 (maximum) and placed in an automatic tissue processor (SHANDON CITADEL 1000) for dehydration, clearing and infiltration. The samples were then embedded, sectioned (5μm thickness) and stained with Haematoxylin and Eosin. Sections were mounted with Canada balsam and covered by cover slips and examined under a compound microscope (Olympus). Photomicrographs of the stained sections were obtained by using a photomicroscope (OLYMPUS, Model CHS, Japan).

Source of Information: Annals of Veterinary and Animal Science Vol.9 (1), 30-37; 2014

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The average value of temperature and dissolved oxygen (DO) decrease in winter season. During month of December and January, eels were found to be severely affected and characterized by clinical signs of red spots, rough skin and deep ulcers in the ventral and lateral regions of the body. Additionally, there were severe necrosis in the skin and muscle of eels, presence of melanomacrophage, loss of epidermis, vacuoles, split of dermis and muscle were observed. Histopathological examination of gills were revealed missing of primary and secondary gill lamellae, necrosis, hyperplasia, highly hypertrophied and hemorrhagic gill lamellae. In liver, pyknotic and hyperplasid hepatocytes, necrosis, hemorrhages and vacuoles were evident. Hemorrhages, vacuolation, necrosis, missing and ruptured kidney tubules, pyknosis and presence of fungal granuloma were the major pathological alterations of kidney. The observed signs of diseases in eels could be realted to epizootic ulcerative syndrome (EUS), dactylogyrosis, parasitic and bacterial diseases associated with other opportunistic pathogens.. Our results indicated that the examined eels of Kailla beel river were found to be more severely affected than eels of the Brahmaputra one during the colder months of the year (December and January), in comparison to other months of the year.

Knowledge Management: Journal