Disease Problems in Cultured Marine Fish in the Mediterranean.

A bacteriological survey of gilthead sea bream Sparus aurata from different fish farms and culture systems on the Spanish Mediterranean coast was conducted. Three different studies were performed. Study A included hatchery-reared larvae; Study B, periodic examination of randomly sampled growing fish; and Study C, growing fish sampled only during mortality/morbidity events. In Studies B and C, sea cages, earth ponds and indoor tanks were surveyed, and in both cases diseased (showing clinical signs) and non-diseased fish were included. In Study A, a shift from Vibrio spp. (30 d after hatching) to oxidative species (60 d after hatching) was detected, and no mortality events were registered. The percentage of fish yielding bacterial growth were similar in Studies B and C, reaching 57.4 and 61.3%, respectively. A statistically significant relationship between the bacterial carriage and the type of facility was only found in Study B, showing that fish from sea cages had a higher bacterial occurrence than fish from other facilities. A statistically significant relationship between bacterial carriage and signs of disease was found, although the pattern differed in each study. Thus, in Study B only 36.2% of fish yielding abundant bacterial growth were diseased, versus 68.0% in Study C. In total, 25.0% of the fish examined were diseased. Bacterial species composition was similar in asymptomatic and diseased fish, except for a group of V. ichthyoenteri-like isolates that occurred almost exclusively in asymptomatic fish. Dominant bacterial species were V. harveyi and V. splendidus, followed by V. ichthyoenteri-like isolates, Photobacterium damselae ssp. damselae and V. fisheri. Non-fermenters were less frequent but, among them, unidentified halophilic Cytophaga-Flavobacterium isolates and Pseudoalteromonas haloplanktis were the most abundant. An association of individual species with disease was not clear, which suggests the involvement of mixed infections. KEY WORDS: Sparus aurata · Vibrio harveyi · Vibrio splendidus · Photobacterium damsela · Pseudoalteromonas haloplanktis · Vibrio ichthyoenteri · Mediterranean aquaculture Resale or republication not permitted without written consent of the publisherDis Aquat Org 54: [119][120][121][122][123][124][125][126] 2003 Baptista et al. 1999). These species have been recovered from moribund or recently dead fish showing clinical signs. However, studies on the bacterial flora present in asymptomatic fish are scarce.Several studies have been conducted along the Spanish Mediterranean coast to identify the main bacterial groups present in water and bivalves (Ortigosa et al. 1994a,b, Arias et al. 1999. Some of these bacteria exhibit clear seasonal variation, as Vibrio harveyi dominated with temperatures above 20°C and V. splendidus dominated at temperatures below 20°C (Arias et al. 1999). These and other bacterial species showing seasonal occurrence have been reported as opportunistic pathogens for sea bass and sea bream (Balebona 1998b).In the present study, bacterial car...

Section: Introductionmentioning

confidence: 99%

Carriage of potentially fish-pathogenic bacteria in Sparus aurata cultured in Mediterranean fish farms

Pujalte¹,

Sitjà‐Bobadilla²,

Álvarez-Pellitero³

et al. 2003

“…Caligid copepods are among the most problematic parasites in cultured marine species, including Mediterranean sea bass and sea bream (Paperna 1980, Rodgers & Furones 1998. Other examples are Lepeophtheirus salmonis and C. elongatus, which cause severe problems in Scottish, Irish and Norwegian salmon farming (Pike & Wodsworth 2000).…”

Section: Discussionmentioning

confidence: 99%

Parasites of wild sea bass Dicentrarchus labrax from Norway

Sterud¹

2002

Thirteen wild sea bass from the Oslo fjord in south-eastern Norway were examined for parasites. Nineteen species were found, comprising 5 protozoans, 1 monogenean, 8 digeneans, 1 cestode, 2 nematodes and 2 crustaceans. Based on the similarity to the parasitic fauna of Mediterranean sea bass, it is predicted that sea bass farmers in Northern Europe will experience the same parasite problems as sea bass farmers in warmer regions. KEY WORDS: Aquaculture · Fish farming · Parasitic diseases Resale or republication not permitted without written consent of the publisherDis Aquat Org 48: [209][210][211][212] 2002 RESULTSA total of 19 parasite species were found in the 13 examined sea bass (Table 1). The 5 protozoans found in fresh mucosal smears from the skin and gills of the fish were not identified to species level. Preservation was considered impractical, due to the low numbers of each organism (exemplified by the finding of a single trichodinid ciliate).The most common parasites were diplectanid monogeneans, occurring at 100% prevalence. On the basis of morphological characters of the squamodisc and the penis, all were designated Diplectanum aequans. They were commonly aggregated in small clusters of 2 to 4 individuals on the gill filaments. The attachment sites were commonly whitish, thickened and apparently necrotic when observed by light microscopy. Scanning electron microscopy showed loss of lamellae in such filaments (Figs. 1 to 3).The trematodes were the dominating parasite group with 8 (possibly 9) species present. One unidentified species was present as metacercariae in the skin and fins, and the rest were present as adults in the gastrointestinal tract. With few exceptions, all species were present in low numbers and no signs of a pathological effect of the infections were seen.The 2 nematode species and the cestode were all found as larval or immature stages. The 2 crustaceans were found on fish caught in June. DISCUSSIONAquaculture conditions, concentrating many hosts within a limited space, favour parasites with direct life cycles. In marine fish this has been shown to apply to Ichthyobodo necator (Urawa et al. 1998), trichodinid ciliates (Moksness et al. 1989, Moksness 1990, Lom 1995, Nilsen 1995 and scuticociliates (Cheung et al. 1980, Dragesco et al. 1995, Cawthorn et al. 1996, Messick & Small 1996, Munday et al. 1997, Sterud et al. 2000. Although protozoans were found at very low intensities in the present study, their potential as serious skin and gill parasites in farmed sea bass should thus not be underestimated.Two diplectanid monogeneans are commonly found on sea bass in the Mediterranean: Diplectanum aequans and D. laubieri (González-Lanza et al. 1991 Table 1 comprised 2 morphs based on differences in size and number of eggs in the uterus. B. baeri and B. labracis, which are both parasites of sea bass, are not distinguished by these features but primarily by their site specificity (Maillard 1976). Unfortunately the digeneans were sampled without paying sufficient attention to thei...

“…Recently, several lethal viruses, such as frog iridovirus RGV (Rana grylio virus), penaeid shrimp baculovirus MBV (Penaeus monodon baculovirus), reptile virus TSV (Trionyx sinesis virus), mandarin fish SCSV (Siniperca chuatsi spherical virus), rhabdovirus SCRV and baculovirus SCBV, have been identified and isolated from diseased R. grylio (Zhang et al 1996a(Zhang et al , 1999b, from diseased Penaeus orientalis Kishinouxe (Jiang et al 1995, Zhang et al 1998, from diseased soft-shelled turtle Trionyx sinensis (Zhang et al , 1999a and from diseased mandarin fish S. chuatsi (Zhang et al 1996b, Zhang & Li 1999. These various species of viruses have also been demonstrated to be associated with serious disease outbreaks in a number of aquaculture animals in other parts of the world (Wolf 1988, Ahne et al 1997, Lightner & Redman 1998, Munday & Owens 1998, Nakajima et al 1998, Rodgers & Furones 1998, Sohn & Park 1998.…”

Section: Introductionmentioning

confidence: 99%

Isolation of a lethal rhabdovirus from the cultured Chinese sucker Myxocyprinus asiaticus

Zhang

Li²,

Gui

2000

A rhabdovirus was found to be associated with a lethal hemorrhagic disease in the cultured Chinese sucker Myxocyprinus asiaticus Bleeker. The rhabdovirus was amplified and isolated from the infected GCO (grass carp ovary) cells. In ultrathin sections of liver cells from the diseased fish, the virus particles exhibited the characteristic bacilliform morphology, and budded through vesicle membranes of the infected cells. The isolated rhabdovirus particles were found to have a bacilliform morphology with 2 rounded ends rather than a typical flat base. The virus particles were measured and ranged in size from 150 to 200 nm in length and 50 to 60 nm in diameter. Most other characteristics, including their size, extensive virus infectivity to fish cell lines, strong cytopathogenic effects, stability at high temperatures, vesicle formation in infected cells, structure protein electrophoretic patterns and the presence of an RNA genome, very closely resembled those of other fish rhabdoviruses. At present it is not known if this is a novel virus species or if it is an isolate of a known fish rhabdovirus. Until a confirmed identification can be made, we will temporarily refer to this virus as Chinese sucker rhabdovirus (CSRV). KEY WORDS: Rhabdovirus · Myxocyprinus asiaticus · Fish viral disease · Electron microscopy · Chinese sucker rhabdovirus (CSRV) Resale or republication not permitted without written consent of the publisherDis Aquat Org 42: [1][2][3][4][5][6][7][8][9] 2000 that the disease might be related to viral infection. We therefore collected diseased fish showing typical symptoms and made an attempt to isolate the virus. Through a series of observations and analysis, a rhabdovirus was identified as the pathogen associated with the disease of sucker fish. Here, we report the isolation process of the rhabdovirus. MATERIALS AND METHODSProcessing of diseased fish samples. A total of 35 diseased juveniles were collected from the diseased population cultured in one pond. These juveniles, weighing about 5 to 10 g, were used to prepare tissue extracts. Liver, spleen, kidney and muscle were sampled from the diseased fish. The samples were ground in a mortar and diluted 1:10 in phosphate buffered saline (PBS) containing antibiotics (100 IU penicillin ml -1 , 100 µg streptomycin ml -1 ). The extract was stored overnight at -20°C. Then, the supernatant was collected by centrifugation at 2000 × g, and filtered through a 300 to 450 nm filter membrane. The filtered supernatant was used as the viral isolate for infecting cell lines, and stored at -80 or -20°C.Cell lines to be used. A total of 8 cell lines, including GCK (grass carp kidney), FHM (fathead minnow), CAB (Carassius auratus blastula embryos), CLC (leucocytes of common carp), EPC (epithelioma papulosum cyprini), GCO (grass carp ovaries), GCF (grass carp fins), and GRO (Gobiocypris rarus ovary), were used for viral sensitivity tests (Zhang 1997). The cells were grown in TC 199 medium with 10% fetal bovine serum and antibiotics (100 IU penicillin ml ...