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Histopathological Studies of Experimentally Infected Shing, Heteropneustes Fossilis with Aeromonas Hydrophila Bacteria

M. T. Islam
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

K. Mostafa
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

M. M. Rashid
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Abstract/ Executive Summary:

Heteropneustes fossilis (shing) of 35g body weight were experimentally infected with Aeromonas hydrophila by two different methods: viz. intraperitonial and intramuscular injection. A standard dose of infection (6.4 × 107 CFU/ml) was selected based on predetermined LD50. Each method gave rise to the mortality of shing up to 85%. Clinical signs of fish included injury, hemorrhage and large ulcerative lesions on the body at the injected area. In kidney, liver and intestine pathologically, massive atrophy and focal necrosis were found. Hemorrhage, Vacuolation and atrophy of hepatic sinusoids represented by necrosis of the sinusoidal lining cells, degeneration of hepatic tissue and distribution of bacterial cell all over the tissue were found in liver. Atrophy, hemorrhage, villi missing and missing of epithelium were found in intestine of the experimentally infected shing. Bacterial cells were distributed in the whole hematopoietic tissue including the renal tubules. Tissue abscess characterized by focal necrosis, hemorrhage and Vacuolation were also found in the kidney of the infected shing. But the above symptoms were not found in the organs of the apparently healthy shing species.

Keywords: Aeromonas, Experimental infection, Histopathology, Shing

Location: The Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh, Bangladesh

Start Date: 00-07-2006

End Date: 00-12-2006

Program Area: Animal Health and Management

Commodity: Fish

Objectives:

i. To relate the abundance of A. hydrophila bacteria with the health hazard of shing fish and

ii. To study the histopathological changes in kidney, liver and intestine of shing fish through experimental infection.

Methodology:

The experiment was conducted for a period of six months, from July 2006 to December 2006, in the fish disease laboratory of the Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh.The catfish of average body weight of 35 g were collected from the stock pond of the Faculty. Prior to experiment, all the fish were acclimatized in 12 rectangular glass aquaria for seven days at wet laboratory. Aeromonas hydrophila were purely cultured on TSA agar at 25°C for 48 hours prior to the experiment. An amount of 52 mg of fresh culture of the bacteria was carefully scraped and mixed with 4 ml sterile physiological saline (0.85% NaCl = PS) and desired dilutions were prepared by serial decimal dilution method. From the result of a previous LD₅₀ experiment, one dose higher than the LD50 dose (6.9 × 107 CFU/fish), around 107 CFU/fish was planned as an estimated dose of the pathogen for the present experimental histopathology. Accordingly, for intramuscular (IM) injection, a total of 15 fish were injected intramuscularly with 0.2 ml of a suspension containing 6.9 × 107 CFU/fish of A. hydrophila just below the anterior part of the dorsal fin. For intraperitoneal (IP) injection, same numbers of fish were injected intraperitoneally with the same amount of the same suspension just near the pectoral fin carefully. All the injected fish were released into an aquarium and observed for 15 days. Water recirculation and aeration were continuously maintained and no feed was given to the fish during the experimental periods. The fish were observed every day. Infection was recorded by observation of lesion, clinical appearance and mortality. Moribund fish were attended, waited for their death and immediately after death transferred to the laboratory for histopathological study of liver, intestine and kidney. Collected samples of liver, intestine and kidney were preserved and fixed in 10% neutral buffered formalin. After at least 8 hours of fixation, the samples were trimmed in order to obtain a size of 1 cm³. The samples were then processed in an automatic tissue processor (SHANDON, CITADEL 1000) for dehydration, clearing and infiltration. They were then embedded in paraffin wax and sectioned at 5 μm by a microtome (Leica JUNG RM 2035). The ribbon with the sections was placed on a water bath (Electro thermal, MOUNTING BATH) at a temperature of 40⁰C, which were finally picked up over glass slides. The sections were then stained with haematoxyline and eosin stains and were mounted with Canada balsam. The stained slides were then examined under a compound microscope (Olympus). Photomicrographs of the stained sections were done by using a photomicroscope (OLYMPUS, Model CHS, Japan).

Source of Information: Progress. Agric. 19(1) : 89-96, 2008 ISSN 1017-8139

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

It was evident from the experiment that A. hydrophila caused gradual pathological symptoms which became severe and massive at the moribund stage of the experimental fish. It proved that H. fossilis might be a susceptible fish towards the suspective attack of the ubiquitous bacteria A. hydrophila at least in their intensive culture condition. It was pointed out earlier that suspective EUS like ulcerative syndrome were encountered in the Agro-3 farm of Mymensingh area (Hasan, 2007), from where Aeromonas bacteria could be isolated. So, it may be concluded that shing fish culturists should have been taken sufficient preventive measure so that their culture environment may be excluded with at least such an ubiquitous opportunistic pathogen like A. Hydrophila.

Knowledge Management: Journal