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Studies on diseased freshwater prawn Macrobrachium rosenbergii infected with Vibrio vulnificus
1Department Zoology, Faculty of Science, Tanta University, Tanta, Egypt.
Abstract:
The present study was aimed at isolation and characterization of the pathogenic bacterium from diseased freshwater prawn. The effect of the bacterial pathogen on hepatopancreas, gills and exoskeleton was also investigated. Diseased freshwater prawn, Macrobrachium rosenbergii were collected from commercial hatchery in Behera Governorate, Egypt. The diseased prawn showed dark brown focal lesions and necrosis of appendage tips. The causative bacterial pathogen was isolated from haemolymph and hepatopancreas of the diseased prawn. Based on the morphological, biochemical and physiological characteristics, in addition EPI 20E test, the isolated pathogen was characterized as Vibrio vulnificus. Histopathology, hepatopancreas showed haemocytic infiltration in the interstitial sinuses, thickening and ruptures of the basal lamina and necrosis of its tubules. Similarly, the accumulation of haemocytes in the haemocoelic space, swelling, fusion of lamellae and abnormal gill tips. Also, the cuticular layers of the exoskeleton of diseased prawn had a rough or wrinkled surface and were disrupted and separated from the epidermis. The pathogen, V. vulnificus showed different degrees of sensitivity to different antimicrobial agents. It was highly sensitive to each of the antibiotics rifadin, virbamycin, oflaxcin, garamycin, flummox and trimethoprim/sulfamethoxzole) and resistant to nalidixic acid, unasyn, velosef, claforan, negram and amoxicillin. The minimal inhibitory concentration of trimethoprin/sulfamethoxzole for the studied pathogen, V. vulnificus was 0.31/5.93 microg.
Insights
This study isolated Vibrio vulnificus from diseased freshwater prawns, revealing its damaging effects on prawn tissues and identifying effective antimicrobial treatments for this significant aquaculture pathogen.
Area of Science:
- Aquatic animal health
- Bacteriology
- Pathology
Background:
- Freshwater prawns (Macrobrachium rosenbergii) are vital aquaculture species.
- Disease outbreaks can cause significant economic losses in prawn farming.
- Understanding prawn pathogens is crucial for disease management.
Purpose of the Study:
- To isolate and identify the bacterial pathogen responsible for disease in freshwater prawns.
- To investigate the pathological effects of the identified bacterium on prawn tissues.
- To determine the antimicrobial susceptibility of the isolated pathogen.
Main Methods:
- Collection of diseased prawns from a commercial hatchery.
- Isolation and characterization of the causative bacterium using morphological, biochemical, and physiological tests (including EPI 20E).
- Histopathological examination of affected prawn tissues (hepatopancreas, gills, exoskeleton).
- Antimicrobial susceptibility testing and determination of minimal inhibitory concentration (MIC).
Main Results:
- The isolated pathogen was identified as Vibrio vulnificus.
- Histopathology revealed significant damage to the hepatopancreas, gills, and exoskeleton of infected prawns.
- Vibrio vulnificus exhibited high sensitivity to several antibiotics, including trimethoprim/sulfamethoxazole, and resistance to others.
- The minimal inhibitory concentration of trimethoprim/sulfamethoxazole was determined to be 0.31/5.93 µg.
Conclusions:
- Vibrio vulnificus is a pathogenic bacterium affecting freshwater prawns, causing severe tissue damage.
- Effective antimicrobial agents were identified for treating Vibrio vulnificus infections in prawns.
- Findings provide valuable insights for managing bacterial diseases in Macrobrachium rosenbergii aquaculture.
