Homogenized samples of skin, gill and gut of twelve freshwater fishes of four feeding habits were used for bacteriological test. Total bacterial count (TBC), total coliform (TC), faecal coliform (FC), faecal streptococci (FS) and total Vibrio?like colonies were enumerated using serial dilution and spread plate techniques. Variation of bacterial loads among the fishes of various feeding habits was insignificant. The TBC, TC, FC, FS and total Vibrio counts ranged from 1.72 ± 0.68 × 108 to 7.00 ± 3.39 × 108, 2.49 ± 1.72 × 106 to 6.55 ± 3.00 × 106, 1.58 ± 1.29 × 106 to 2.76 ± 1.42 × 106, 4.83 ± 2.09 × 104 to 1.19 ± 0.46 × 105 and 2.06 ± 0.67 × 103 to 3.68 ± 2.02 × 105, respectively among various feeding groups. However, gill and gut had significantly higher density of TBC, TC and FC than that of the skin. High counts of indicator organisms indicate that market fishes of all varieties could be the potential reservoirs in transmission of pathogenic bacteria responsible for diarrhoeal disease.    Key words: Bacterial load; Freshwater fishes; Feeding habit DOI: http://dx.doi.org/10.3329/dujbs.v19i2.8956 DUJBS 2010; 19(2): 145-150

The e¡ects of ¢ngerlings immersion in low-dose benzocaine (15 and 30 mg L À 1 , silver carp and rohu) and quinaldine (100 mL L À1 silver crap and 250 mL L À1 rohu) for 1, 3 and 6 h on stress responses and survival of rohu, Labeo rohita and silver carp, Hypophthalmichthys molitrix ¢ngerlings were evaluated in a transport simulation experiment. Both quinaldine and benzocaine showed low mortalities (0^2%). The total mortality in control (with no anaesthesia) was 30% for rohu and 14% for silver carp. Quinaldine and benzocaine-treated ¢ngerlings had signi¢cantly higher plasma chloride levels than the control in both species. Benzocaine, quinaldine, as well as the control, had an initial elevation of plasma cortisol levels. Benzocaine lost its e¡ectiveness after 3 h exposure while quinaldine persisted throughout the 6 h experimental period. Both sedatives reduced bacterial buildup compared with the control. No post-exposure mortality was observed for any of the transport methods assessed 48 h after the treatment. This study suggests that the use of low-dose benzocaine or quinaldine during transport has positive e¡ect on the survival and health of rohu and silver carp ¢ngerlings.

White Spot Syndrome Virus (WSSV), the etiological agent of White Spot Disease (WSD) is a major impediment for shrimp aquaculture in the worldwide. A critical threshold level of WSSV load in infected shrimp is an important trait for disease manifestation and WSSV transmission in cultured shrimp and subsequently make outbreaks. The present study investigated 120 naturally infected cultured shrimp samples by SYBR Green based qPCR assay for WSD diagnosis and quantification of WSSV load. Among them, 94 samples resulted a variable count of WSSV load ranging from 2.1 × 108 to 2.64 × 1014 copies/g of shrimp tissue. The severity of WSSV infection was assessed based on the established critical threshold load of WSSV in shrimp tissue. Compared to the established critical threshold value of WSSV load in shrimp tissue, our findings showed the horrifying scenario of the severity of WSSV infection in cultured shrimps of Bangladesh that was found to be above the critical limit to initiate an outbreak in the Bangladeshi shrimp aquaculture industry. The latest phylogenetic pattern was altered from the former monophyletic history among WSSVs of Bangladesh due to a variation at 500th nucleotide of VP28 coding gene. Viruses characterized from recent outbreaks in 2015 and 2017 displayed amino acid substitution at position 167 (G→E) on the surface of VP28 protein which has demonstrated the probable replacement of indigenous virus pool. Therefore, it is imperative to take initiative for the management and prevention of WSSV outbreak to sustain shrimp aquaculture in South-West region of Bangladesh.Electronic supplementary materialThe online version of this article (10.1186/s13568-018-0553-z) contains supplementary material, which is available to authorized users.

Outbreaks of Vibrio vulnificus wound infections in Israel were previously attributed to tilapia aquaculture. In this study, V. vulnificus was frequently isolated from coastal but not freshwater aquaculture in Bangladesh. Phylogenetic analyses showed that strains from Bangladesh differed remarkably from isolates commonly recovered elsewhere from fish or oysters and were more closely related to strains of clinical origin.Vibrio vulnificus causes severe wound infections and lifethreatening septicemia (mortality, Ͼ50%), primarily in patients with underlying chronic diseases (10,19,23) and primarily from raw oyster consumption (21). This Gram-negative halophile is readily recovered from oysters (27,35,43) and fish (14) and was initially classified into two biotypes (BTs) based on growth characteristics and serology (5,18,39). Most human isolates are BT1, while BT2 is usually associated with diseased eels (1, 39). An outbreak of wound infections from aquacultured tilapia in Israel (6) revealed a new biotype (BT3). Phenotypic assays do not consistently distinguish biotypes (33), but genetic analyses have helped resolve relationships (20). A 10-locus multilocus sequence typing (MLST) scheme (8, 9) and a similar analysis of 6 loci (13) segregated V. vulnificus strains into two clusters. BT1 strains were in both clusters, while BT2 segregated into a single cluster and BT3 was a genetic mosaic of the two lineages. Significant associations were observed between MLST clusters and strain origin: most clinical strains (BT1) were in one cluster, and the other cluster was comprised mostly of environmental strains (some BT1 and all BT2). Clinical isolates were also associated with a unique genomic island (13).The relationship between genetic lineages and virulence has not been determined, and confirmed virulence genes are universally present in V. vulnificus strains from both clinical and environmental origins (19,23). However, segregation of several polymorphic alleles agreed with the MLST analysis and correlated genotype with either clinical or environmental strain origin. Alleles include 16S rRNA loci (15, 26, 42), a virulence-correlated gene (vcg) locus (31, 41, 42), and repetitive sequence in the CPS operon (12). DiversiLab repetitive extrageneic palindromic (rep-PCR) analysis also confirmed these genetic distinctions and showed greater diversity among clinical strains (12).Wound infections associated with tilapia in Israel implicated aquaculture as a potential source of V. vulnificus in human disease (6,40). Tilapia aquaculture is increasing rapidly, as shown by a 2.8-fold increase in tons produced from 1998 to 2007 (Food and Agriculture Organization; http://www.fao.org /fishery/statistics/en). Therefore, presence of V. vulnificus in tilapia aquaculture was examined in Bangladesh, a region that supports both coastal and freshwater sources of industrial-scale aquaculture. V. vulnificus strains were recovered from market fish, netted fish, and water samples, and the phylogenetic relationship among strains was examined relativ...

No abstract