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Pathogenesis of Aeromonas Species in Stinging Catfish Shing (heteropneustes Fossilis) of Bangladesh

Md. Shirajum Monir
Bangladesh Fisheries Research Institute, Head Quarter, Mymensingh-2201, Bangladesh

Yahia Mahmud
Bangladesh Fisheries Research Institute, Head Quarter, Mymensingh-2201, Bangladesh

Md. Alimul Islam
Department of Microbiology and Hygiene, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Nazneen Bagum
Bangladesh Fisheries Research Institute, Freshwater Station, Mymensingh-2201, Bangladesh

Shuvho Chakra Borty
Department of Microbiology and Hygiene, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Tanvir Ahammed
Department of Microbiology and Hygiene, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Abstract/ Executive Summary:

The present experiment was conducted to evaluate the comparative ability of producing infections and causing mortality to inject Shing (Heteropneustes fossilis) with Aeromonas species. Nine Aeromonas isolates (A. hydrophila-3, A. sobria-3 and A. salmonicida-3) were injected to 9 different groups (each group consisting of 10 fish) of healthy Shing. Experimental Shing (H. fossilis) were injected with A. hydrophila, A. sobria and A. salmonicida to groups 1-3, 4-6 and 7-9, respectively while group 10 was injected with sterile phosphate buffered saline (PBS) and served as the control. For pathogenicity test, dose of 6.7 × 106 cfu/fish with each bacterial species were injected intramuscularly and monitored upto two weeks. The highest clinical infections were developed 100% in group 3 whereas only 30% in group 9. At the end of the experiment (after two weeks), the cumulative mortality rate was also recorded highest (90%) in group 3 and lowest (30%) in group 9. However, the development of infection and mortality to the injected Shing fish was associated more severely by Aeromonas hydrophila than A. sobria and A. salmonicida, used in this experiment.

Keywords: Aeromonas species, Bangladesh, Pathogenesis, Stinging catfish.

Location: Fish disease and health management laboratory, Bangladesh Fisheries Research Institute

Start Date: 00-00-2013

End Date: 00-00-2013

Program Area: Animal Health and Management

Commodity: Cat fish

Objectives:

1. To evaluate the comparative pathogenicity of Aeromonas hydrophila, A. sobria and A. salmonicida in stinging catfish Shing (H. fossilis) of Bangladesh.

Methodology:

Experimental fish and set up: Apparently healthy Shing (H. fossilis) weighting 25-30 g, collected from a local fish farm of Mymensingh those were used in this experiment. Prior to the experiment, fish were stocked in aquariums to acclimatize in laboratory conditions from 28 to 30°C for at least 10 days providing adequate feed and better aeration by circulating water. The pathogenicity test was conducted at the Fish disease and health management laboratory of Bangladesh Fisheries Research Institute, Mymensingh. Bacterial cultures and preparation of suspension: Stock cultures of A. hydrophila, A. sobria and A. salmonicida were used in this study those were isolated from different organs of naturally-infected Shing (H. fossilis) of different fish farms from Mymensingh district of Bangladesh. The isolates were cultured on a Typticase Soya Agar (TSA) at 32°C for 24 hours and identity confirmed using different biochemical characteristics prior to the experiment. They were then suspended in sterile phosphate buffered saline (PBS). Pathogenicity experiment: Intramuscular injection method was used for the pathogenicity challenge test to know the efficacy of the pathogens in initiating the infection as well as observe mortality. After acclimatization for 10 days, 25-30 g, juvenile Shing (H. fossilis) were randomly assigned to 10 groups as 10 fish per group. For the intramuscular (IM) injection, one ml insulin syringes (sterile and disposable) were used to inject intramuscularly with 0.1 ml of pre-selected bacterial dose (6.7 × 10⁶ cfu/fish) as follows: groups 1 to 3 - A. hydrophila, groups 4 to 6 - A. sobria, while groups 7 to 9 were infected with A. salmonicida. A negative control group-10 of 10 fish were injected with sterile PBS as above. Each group was then released in separate aquaria and no feed was given to the experimental fishes to ensure that the water was not further contaminated. The temperature, pH and dissolved oxygen, ammonia concentration of the water was kept at acceptable limit during the experiment. The injected fishes were then observed clinical signs, symptoms and mortalities daily up to two weeks. Re-isolation of challenged pathogens: Re-isolation of inoculated bacteria were done by collecting samples from skin lesions, kidney, liver of moribund and freshly dead or sacrificed experimental infected Shing fish and streaked on TSA plates to check the presence and absence of bacterium. Positive bacterial culture was confirmed by the morphological and biochemical characteristics of the re-isolated bacteria were identical with those of the isolates used in the experimental infection. Statistical analysis: The data collected for rates of developing infection and mortality were subjected to descriptive statistics and expressed in percentages.

Source of Information: Trends in Fisheries Research Volume 4, Issue 1, 1-6 (2015) ISSN: 2319–474X (p); 2319–4758 (e)

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

It was confirmed that Aeromonas species used in this experiment those were able to develop infections as well as cause mortality in test stinging catfish Shing. Further researches are necessary to prepare antibody against these bacteria to prepare vaccines and to try vaccination in susceptible to save catfishes against these pathogenic bacteria.

Knowledge Management: Journal