This chapter focuses on the main marine pathogens (bacteria, fungi oomycetes, virus and parasites) that impact the production of coldwater fish in marine and brackish water. The main viral diseases that have been reported to cause problems to cage culture in marine or brackish water, their clinical signs, diagnosis, treatment and control are presented: infectious haematopoietic necrosis (IHN), infectious pancreas necrosis (IPN), infections with salmonid alphaviruses (SAV), infectious salmon anaemia (ISA), viral haemorrhagic septicaemia (VHS), cardiomyopathy syndrome (CMS), heart and skeletal muscle inflammation (HSMI) and viral encephalopathy and retinopathy (VER). Infections with the following bacterial species are also discussed: Vibrio, Francisella, Piscirickettsia, Aeromonas, Pseudomonas, Tenacibaculum, Mycobacterium, Yersinia and Branchiomonas cysticola. Fungal diseases discussed include Exophiala and Aphanomyces invadans. Protistan and metazoan parasites, their diagnosis, clinical signs, treatment, control and impact on fish production are also discussed.

Infectious pancreatic necrosis (IPN) is a contagious viral disease of fish that causes economic losses in aquaculture worldwide. In Finland, IPN virus (IPNV) has been isolated since 1987 from adult fish showing no signs of clinical disease at fish farms located in the coastal areas of the Baltic Sea. The inland area of Finland, however, remained free of IPN until 2012, when fish on several rainbow trout farms were diagnosed IPNV-positive. The fish mortalities detected at the farms were low, but clinical signs and histopathological changes typical for IPNV infection were seen in juvenile salmonids. IPNV was isolated at high water temperatures up to 22°C. In 2013 and 2014, IPNV detections continued at inland farms, indicating that infections have spread. The aim of this study was to describe the epidemiology of the outbreak and to characterise the Finnish inland IPNV isolates using histopathological, immunohistochemical and genetic approaches. In order to determine the epidemiological origin of the inland IPNV infections, the partial viral capsid protein (VP2) gene sequences of the inland IPNV isolates were compared with the sequences of the isolates from the coastal farms. Based on the genetic analysis, the inland isolates belong to IPNV Genogroup 2 (Serotype A3/Ab), and the origin of the isolates appears to be one or several coastal fish farms.

Thirty-one isolates of Saprolegnia sp., most originating from infected salmon or trout, were characterised genetically and physiologically. The majority (6 of 31) of the isolates from several widely separated geographical locations was found to be genetically almost identical as assessed by RAPD-PCR. The remaining isolates belonged to 3 different groups with 1 to 3 representatives each. It is suggested that the first group of isolates represents a virulent form of the organism that has been widely spread by clonal propagation. The ability to repeated zoospore emergence, as an alternative to direct germination, seems to characterise specific Saprolegnia genotypes that may have adapted to certain hosts.KEY WORDS: Saprolegnia · Saprolegniosis · Fish disease · Random amplification of polymorphic DNA RAPD · Repeated zoospore emergence Resale or republication not permitted without written consent of the publisherDis Aquat Org 53: [47][48][49][50][51][52][53] 2003 guished the fish lesion isolates from the water isolates, and Beakes (1983) was able to identify S. parasitica from S. diclina. Variation in esterase isoenzyme patterns (Beakes & Ford 1983) and differences in radial growth rate (Willoughby & Copland 1984, Hatai et al. 1990) have been used for determining distinct groups of fish lesion isolates. Restriction fragment length polymorphisms (RFLPs) are useful for classification of Saprolegnia and could distinguish S. parasitica from S. diclina (Molina et al. 1995). Also, random amplification of polymorphic DNA polymerase chain reaction (RAPD-PCR;Welsh & McClelland 1990, Williams et al. 1990) has been applied for analysis of the fish pathogenic Saprolegnia genome (Diéguez-Uribeondo et al. 1996, Bangyeekhun et al. 2001). This latter method provides a sensitive and rapid assay for the assessment of genetic distance between different isolates.In the present study, we applied the RAPD-PCR technique and the presence or absence of repeated zoospore emergence to characterise Saprolegnia sp. isolates obtained from Finland and Sweden to investigate the epidemiology of the saprolegniosis in this region. We found that the majority of the isolates belonged to a single genetically defined group that probably has been widely spread by clonal propagation. MATERIALS AND METHODSSaprolegnia strains. Thirty-one isolates of Saprolegnia spp. were isolated from infected tissue of the brown trout Salmo trutta m. lacustris, trout S. trutta, whitefish Coregonus lavaretus, rainbow trout Oncorhynchus mykiss, brook trout Salvelinus fontinalis, landlocked salmon Salmo salar m. sebago, salmon S. salar, noble crayfish Astacus astacus, and pond water from 6 different locations in Finland and 1 location in Sweden. The isolates from Finland are designated FinX, where X is the isolation number and the isolates from Sweden are designated Swe203 and Swe239 (see Table 1). The following reference isolates were used for comparison: S. parasitica (Spt) isolated from freshwater crayfish Astacus leptodactylus (Söderhäll et al. 1991), S. parasit...

BackgroundOccurrence of blood and meat inclusions is an internal egg quality defect. Mass candling reveals most of the spots, but because brown eggshell hampers selection in brown chicken lines it has not been possible to eliminate the defect by selection. Estimated frequency of blood and meat inclusions in brown layers is about 18% whereas it is 0.5% in white egg layers. Several factors are known to increase the incidence of this fault: genetic background, low level of vitamin A and/or D, stress or infections, for instance. To study the genetic background of the defect, a mapping population of 1599 F2 hens from a cross of White Rock and Rhode Island Red lines was set up.ResultsOur histopathological analyses show that blood spots consist of mainly erythrocytes and that meat spots are accumulations of necrotic material. Linkage analysis of 27 chromosomes with 162 microsatellite markers revealed one significant quantitative trait locus (QTL) affecting blood spot and meat spot frequency. We sequenced a fragment of a candidate gene within the region, ZO-2, coding for a tight junction protein. Nine polymorphisms were detected and two of them were included in fine-mapping and association analysis. Fine-mapping defined the QTL result. To further verify the QTL, association analyses were carried out in two independent commercial breeding lines with the marker MCW241 and surrounding SNPs. Association was found mainly in a 0.8 Mb-wide chromosomal area on GGAZ.ConclusionsThere was good agreement between the location of the QTL region on chromosome Z and the association results in the commercial breeds analyzed. Variations found in tight junction protein ZO-2 and microRNA gga-mir-1556 may predispose egg layers to blood and meat spot defects. This paper describes the first results of detailed QTL analyses of the blood and meat spots trait(s) in chickens.

The goal of this review was to describe in some detail the Nordic aquaculture industries in order to illuminate the similarities and differences. Information that was gathered for each country includes aquaculture history, aquaculture acts and regulations, production and production systems, environmental concerns, organic aquaculture and outlook for the future. The information will be useful for risk assessments, design of risk‐based surveillance programs and for construction of comparative risk profiles for endemic and exotic diseases affecting aquaculture in the Nordic countries. Aquaculture in the Nordic countries has a long history; beginning in the 1850s when hatcheries for restocking of salmon and trout were established in Norway. Nowadays, Atlantic salmon is the dominant cultured species in Norway and the Faroe Islands, whereas rainbow trout dominate in Denmark, Finland, and Sweden. Arctic char and cod are most important in Iceland. Other important cultured species include eel and blue mussels. There is much diversity in Nordic aquaculture industries in terms of production, farmed species, and production systems. Although the vast majority of the Nordic aquaculture production is for human consumption, significant numbers of fish are grown for restocking of rivers, lakes, or other bodies of freshwater or seawater.