Observations on the Occurrence of Bacterial Gill Disease and Amoeba Gill Infestation in Rainbow Trout Cultured in a Water Recirculation System

Abstract

Spontaneous outbreaks of bacterial gill disease (BGD) occurred in 17-44-g rainbow trout Oncorhynchus mykiss after they were placed in a water recirculation system. In each of five groups stocked from September 1991 through July 1992, BGD occurred within 6-8 d after stocking. In each instance, BGD was followed by a secondary amoeba infestation. The spontaneous BGD outbreaks did not occur among previously stocked groups that had recovered from earlier BGD disease outbreaks. Examination of gill tissue by Gram stain and indirect fluorescent antibody technique showed increased numbers of filamentous bacteria associated with BGD after the rainbow trout were stocked into the system. Bacterial numbers decreased after a 1-h treatment with chloramine-T at concentrations of 9-15 mg/L but increased within 2 d after treatment Although the chloramine-T treatments controlled mortality related to BGD, the amoeba infestation persisted. Histological examination of gills showed some focal hyperplasia before the rainbow trout were placed into the recirculation system, but hyperplasia became more extensive and lamellar fusion and mild telangiectasis developed within a week after placement in the system. The density at which the fingerling rainbow trout were stocked and the suspended solids present in tank water may have contributed to the BGD outbreaks. Exposure of juvenile rainbow trout to tank water from the recirculation system before they were placed into the system did not afford them protection against BGD after stocking.

Water-borne diclofenac affects kidney and gill integrity and selected immune parameters in brown trout (Salmo trutta f. fario)

“…Causative factors for telangiectasis are diverse and include parasite infestation, inappropriate sampling techniques and sublethal ammonia intoxication (Bullock et al, 1994;Goodwin, 1999;Herman and Meade, 1985;Powell et al, 2004;Redner and Stickney, 1979). In the present study, the specific cause and mechanism underlying the prevalence of telangiectasis in diclofenac-exposed fish could not be revealed.…”

Do stocking densities affect the gut microbiota of gibel carp Carassius auratus gibelio cultured in ponds?

“…From each pond, genomic DNA from the bacterial communities of feed and the allochthonous and autochthonous fish gut microbiota were extracted as described by previous study [16,17]. Amplification of the 16S V3 region and DGGE analysis were carried as described previously [17].…”

“…Cluster analysis was based on the unweighted pair group method using the arithmetic mean algorithm (UPGMA) as previously described by Liu et al [17]. Similarity coefficients (C s ) < 0.60 is regarded as significant difference, 0.60 ≤ C s < 0.80 as marginal difference, and C s ≥ 0.80 as similar.…”

“…The DNA fragments were excised and amplified using the primers without the GC clamp for sequencing [17]. After removing the unreliable sequences at the 3' and 5' ends, all sequences were subjected to similarity searches with the BLAST program [19].…”

Effects of bacteria on the growth of an amoeba infecting the gills of turbot

“…These effects of amoebae on bacterial density are of interest because pathogenic bacteria are a frequent cause of severe outbreaks of gill disease in fish cultivation (Munday et al 1990). Additionally, in some cases gill disease may be caused by amoebae, whether alone or in mixed infections with bacteria (Bullock et al 1994). Finally, free-living amoebae are increasingly recognized to serve as vehicles of dispersal for various bacterial pathogens and as hosts for a variety of obligate bacterial endocytobionts (Horn et al 2000).…”