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13 Alphaviruses in Salmonids

Woo, P.T.K.; Cipriano, R.C. CABI PDF

13

Alphaviruses in Salmonids

Marius Karlsen1* and Renate Johansen2

1

PHARMAQ AS, Oslo, Norway; 2PHARMAQ Analytiq, Bergen, Norway

13.1  Introduction

Alphavirus is a genus of RNA viruses belonging to the family Togaviridae. Most known alphaviruses are mosquito borne and cause diseases in terrestrial hosts such as birds, rodents and larger mammals, including humans (Strauss and Strauss, 1994).

Infections may lead to diverse symptoms, such as rashes, gastrointestinal problems, arthritis/muscular inflammation and encephalitis (Kuhn, 2007; Steele and Twenhafel, 2010). Salmon pancreas disease virus, which is commonly named Salmonid alphavirus and abbreviated SAV (Weston et  al., 2002), is the only known alphavirus that has fish as a natural host (Powers et al., 2001). SAV is distantly related to other members of the genus, but it still causes pathology that may resemble some of that seen in mammals (McLoughlin and Graham, 2007; Biacchesi et al., 2016). The first isolation of SAV in cell culture was reported in 1995 from marine farmed

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21 Renibacterium salmoninarum

Woo, P.T.K.; Cipriano, R.C. CABI PDF

2

  1

  enibacterium salmoninarum

R

Diane G. Elliott*

US Geological Survey, Western Fisheries Research Center,

Seattle, Washington, USA

21.1  Introduction

Since the initial description of bacterial kidney disease (BKD) in wild Atlantic salmon (Salmo salar) in

Scotland in the early 1930s (Smith, 1964), considerable effort has been expended to better understand and control this serious disease, and several comprehensive reviews have been written about

BKD and its causative agent, Renibacterium salmoninarum (Fryer and Sanders, 1981; Austin and

Austin, 1987; Elliott et  al., 1989; Evelyn, 1993;

Evenden et  al., 1993; Fryer and Lannan, 1993;

Pascho et al., 2002; Wiens, 2011).

The geographic range of BKD encompasses both freshwater and marine habitats nearly worldwide where wild or cultured salmonids occur, including countries in North America, South America, Europe and Asia (Wiens, 2011; Kristmundsson et al., 2016).

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11 Viral Encephalopathy and Retinopathy

Woo, P.T.K.; Cipriano, R.C. CABI PDF

11

Viral Encephalopathy and Retinopathy

Anna Toffan*

OIE Reference Centre for Viral Encephalopathy and Retinopathy,

Istituto Zooprofilattico Sperimentale delle Venezie, Legnaro (Padova), Italy

11.1  Introduction

Viral encephalopathy and retinopathy (VER), also known as viral nervous necrosis (VNN) is a severe neuropathological disease caused by RNA viruses of the genus Betanodavirus (Family: Nodaviridae).

This infectious agent, detected in the late 1980s, spread worldwide, became endemic and came to represent a major limiting factor for mariculture in several countries. The disease has recently been included among the most significant viral pathogens of finfish, given the expanding host range and the lack of properly effective prophylactic measures

(Rigos and Katharios, 2009; Walker and Winton,

2010; Shetty et al., 2012).

11.2  The Infectious Agents

The causative agent of the disease is a small

(25–30 nm diameter), spherical, non-enveloped virion, with a bi-segmented genome made of two singlestranded positive-sense RNA molecules. The name

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6 Infectious Salmon Anaemia

Woo, P.T.K.; Cipriano, R.C. CABI PDF

6

Infectious Salmon Anaemia

Knut Falk* and Maria Aamelfot

The Norwegian Veterinary Institute, Oslo, Norway

6.1  Introduction

Infectious salmon anaemia (ISA) is a significant infectious viral disease of farmed Atlantic salmon,

Salmo salar L., that was first reported in Norway during 1984 (Thorud and Djupvik, 1988).

Outbreaks of ISA have an impact on the economy of the Atlantic salmon aquaculture industry, and this has led to the implementation of large-scale biosecurity measures. Outbreaks have now been reported in most Atlantic salmon farming areas, including the east coast of Canada and the USA,

Scotland, Norway, the Faroe Islands and Chile

(Rimstad et al., 2011). In Chile and the Faroe

Islands, the disease caused major economic setbacks and left the entire industry with an uncertain future (Mardones et al., 2009; Christiansen et al.,

2011) in a manner similar to that in Norway in and after 1989 (Håstein et al., 1999; Rimstad et al.,

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18 Mycobacterium spp.

Woo, P.T.K.; Cipriano, R.C. CABI PDF

18

Mycobacterium spp.

David T. Gauthier1* and Martha W. Rhodes2

1

Department of Biological Sciences, Old Dominion University, Norfolk, Virginia,

USA; 2Department of Aquatic Health Sciences, Virginia Institute of Marine

­Science, The College of William and Mary, Gloucester Point, Virginia, USA

18.1  Introduction

18.1.1  Mycobacterium spp.

Members of the genus Mycobacterium (Order

Actinomycetales, Family Mycobacteriaceae) are aerobic to microaerophilic, non-motile, rod-shaped bacteria that stain Gram positive and acid fast.

Excepting non-culturable species (e.g. M. leprae), mycobacteria are frequently grouped by the phenotypic characters of growth rate and pigmentation

(Runyon, 1959). Runyon Groups I–III are fastidious and take more than 5 days to produce colonies on solid media. Group I mycobacteria are photochromogenic, producing yellow–orange pigment (Fig. 18.1) on exposure to light, and include species such as

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