Abstract
The present study was carried out to evaluate the comparative capability of producing infections and causing mortality of the experimental Magur (Clarias batrachus) with motile Aeromonas species. A total of 200 apparently healthy C. batrachus were acclimatized to the laboratory conditions for experimental study. Nine different groups (each group consisting of 20 fish) of healthy C. batrachus was injected with nine motile Aeromonas isolates (A. hydrophila-3, A. sobria-3 and A. caviae-3). Experimental C. batrachus were infected with motile A. hydrophila, A. sobria and A. caviae to groups 1-3, 4-6 and 7-9, respectively while group 10 was injected with sterile physiological saline (0.85% NaCl) and served as the control. The selected motile bacterial species via intramuscularly were injected at the rate of 4.5 × 105 cfu/fish for pathogenicity study on C. batrachus and monitored up to two weeks. The highest clinical infections were noticed 90% in group-3 whereas only 35% in group-8 within the experimental period. After two weeks of the experiment, the cumulative mortality rate was also found highest (60%) in group-3 but lowest (15%) in group-9 while no infection or mortality showed in group-10 (control group). The development of infection and mortality to the injected C. batrachus was associated more severely by Aeromonas hydrophila than A. sobria and A. caviae used in this study. However, the isolates motile Aeromonas species could serve as the primary cause of skin lesions as well as mortality in cultured C. batrachus.
 Asian Australas. J. Food Saf. Secur. 2017, 1 (1), 45-50
Highlights
Among the different air-breathing catfishes, Magur (Clarias batrachus) is very popular and highly valuable fish species in Bangladesh
Motile Aeromonas hydrophila, A. sobria and A. caviae were isolated from infected Shing (Heteropneustes fossilis) showing severe disease symptom of erosions at the bases of fins and tail, hemorrhages and skin lesions on body surface (Monir et al, 2015; Monir et al, 2016)
After day 6 post-infection, severally diffused hemorrhage was observed on fin bases, edge of head and body surface in groups 1, 2, 3 (Figure 1)
Summary
Among the different air-breathing catfishes, Magur (Clarias batrachus) is very popular and highly valuable fish species in Bangladesh. It is recognized for its delicious taste and market value but it is considered as a medicinal fish and traditionally remained a strike among the pregnant & lactating mothers, the elderly and children. It is a very hardy fish that can survive for quite a few hours outside the water due to presence of accessory respiratory organs. C. batrachus was abundantly available in open water of Bangladesh but presently, it is threatened due to over exploitation and various ecological changes in its natural habitat. The appropriate breeding, nursing and rearing technology of fry and fingerlings of C. batrachus had been developed by Bangladesh Fisheries Research
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