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Incidence of Ulcer Type of Disease in Wild Fishes of Bangladesh

B. Majumder
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

M.G.A. Sarker
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

M.H. Khan
Bangladesh Fisheries Research Institute, Mymensingh 2201

M.B.R. Chowdhury
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Abstract/ Executive Summary:

Disease occurred in wild fish species investigated in different water bodies like canals, ditches, beel, haor, flood plain etc. in 17 districts of Dhaka division. Haemorrhagic lesions were observed on the body surface of affected fishes. Incidence of the disease in the investigated water bodies ranged from 0 to 100%. In total 19 fish species were found to be affected and prevalence of infection ranged from 0.0 to 100.0%. Channa punctatus and Puntius ticto were severely affected in all locations. Percentage of infection in these fishes ranged from 0.0 to 100.0. The highest infection was observed in Netrokona, Kishoreganj, and Mymensingh districts. Bacterial genera isolated from the lesions of these affected fishes were Aeromonas, Pseudomonas, Flavobacterium, Micrococcus, and Staphylococcus. Among these isolates Aeromonas was the dominant. Abundance of Aeromonas in the lesions among the investigated bacteria ranged from 75 to 90%. Five identified Aeromonas lrydrophila were examined for their pathogenicity and were able to infect the experimental fish, silver barb (Puntius gonionotus). The pathogen Aeromonas hydrophila was thus considered to have an association with the outbreak of ulcer type of disease in the investigated fish species.

Keywords: EUS, Aeromonas hydrophila , Ulcer type of disease , Wild fishes

Location: Dhaka division.

Start Date: 00-11-1998

End Date: 00-03-1999

Program Area: Animal Health and Management

Commodity: Diseases

Objectives:

To achieve the prevalence of the gross fish disease occurred in wild fish species in Dhaka division,
To determine the percentage composition of bacteria in the lesions of the affected fishes and
To perform pathogenicity test of some recovered aeromonad isolates suspected as pathogen.

Methodology:

Investigation of the occurrence of fish disease: Investigation of the occurrence of disease in fishes were carried out on the basis of observation and sampling of fish from different waterbodies in 17 districts of Dhaka division of Bangladesh starting from November'98 and continued up to March'99. Fish were sampled randomly from three wild waterbodies (canal, beel, haor, ditches and flood plain) of one randomly selected thana of each district. Gross diagnosis of ulcer type of disease in the investigated fish was based on eye observation on the spot having haemorrhagic lesions on the fish body. A total of 100 fish samples were grossly examined from each waterbody. Total fish species and the infected fishes were counted and percentage of infection was calculated. Collection of fish: Mymensingh, N etrokona, Kishoreganj, Tangail and Jamalpur among 17 districts were selected for collection of severely affected fish for isolation of bacteria. Bacterial isolates were collected from the lesions of body surface of the farmed fish viz., Channa punctatus, C. striatus, Mastacembelus armatus, M. pancalus and Puntius ticto. The samples were brought to the laboratory immediately after collection for bacteriological study. Bacteriological Investigation: Tryptone Soya Agar (TSA) was used for culture and swabs were aseptically taken on the culture plate with a sterile inoculating loop and spreaded. The plates were incubated at 25°C for 36-48 hours. Twenty colonies were randomly separated from this initial culture and individual culture was maintained on TSA slants at 4°C for characterization. Morphological and biochemical characters were studied. Percentage composition of the identified bacteria isolated from the lesions was based on the 20 colonies initially separated. Artificial infection in fish: For pathogenicity test five identified A. hydrophila isolates were tested on silver barb (Puntius gonionotus) of about 15 g in weight. The experimental fish were acclimatized for 3 days in the laboratory condition and checked their health before use in the experiment. Stock suspension of individual bacteria was prepared in sterile tap water taking 18-24 h culture. In a 40L capacity aquarium, 15L of bacterial suspension was prepared in the tap water with the stock suspension in such way that the bacterial dose become 3-5x10⁸CFU/ml. Ten fish were exposed to bacterial suspension in the aquarium under aerated condition at room temperature ranged 27-28°C. After 24 h of exposure 80% of bacterial suspension was exchanged with tap water and from the following day 60% of water was exchanged at every 24 h. Two replications were set up for the same isolate and thus in total 20 fish were used for each bacterial isolate. Experimental period was 2 weeks. For each set of experiment control fish were maintained in the same way without exposure to bacteria. No food was applied during the experimental period. Infection was recorded by observation of lesions, mortality and continued by re-isolation of bacteria from the experimental fish.

Source of Information: Bangladesh J.fish. Res., 5(2), 2001: 163-168

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

In total 19 fish species were found to be affected and prevalence of infection ranged from 0.0 to 100.0%. Channa punctatus and Puntius ticto were severely affected in all locations. Percentage of infection in these fishes ranged from 0.0 to 100.0. The highest infection was observed in Netrokona, Kishoreganj, and Mymensingh districts. Bacterial genera isolated from the lesions of these affected fishes were Aeromonas, Pseudomonas, Flavobacterium, Micrococcus, and Staphylococcus. Among these isolates Aeromonas was the dominant. Abundance of Aeromonas in the lesions among the investigated bacteria ranged from 75 to 90%.

Knowledge Management: Journal