Epidemiological characteristics of infectious hematopoietic necrosis virus (IHNV): a review

Veterinary Research, Jun 2016

Infectious hematopoietic necrosis virus (IHNV, Rhabdoviridae), is the causative agent of infectious hematopoietic necrosis (IHN), a disease notifiable to the World Organisation for Animal Health, and various countries and trading areas (including the European Union). IHNV is an economically important pathogen causing clinical disease and mortalities in a wide variety of salmonid species, including the main salmonid species produced in aquaculture, Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss). We reviewed the scientific literature on IHNV on a range of topics, including geographic distribution; host range; conditions required for infection and clinical disease; minimum infectious dose; subclinical infection; shedding of virus by infected fish; transmission via eggs; diagnostic tests; pathogen load and survival of IHNV in host tissues. This information is required for a range of purposes including import risk assessments; parameterisation of disease models; for surveillance planning; and evaluation of the chances of eradication of the pathogen to name just a few. The review focuses on issues that are of relevance for the European context, but many of the data summarised have relevance to IHN globally. Examples for application of the information is presented and data gaps highlighted.

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Epidemiological characteristics of infectious hematopoietic necrosis virus (IHNV): a review

Dixon et al. Vet Res Epidemiological characteristics of infectious hematopoietic necrosis virus (IHNV ): a review Peter Dixon 0 Richard Paley 0 Raul Alegria‑Moran 1 Birgit Oidtmann 0 0 Centre for Environment, Fisheries and Aquaculture Science , Weymouth, Dorset , UK 1 Faculty of Veterinary and Animal Sciences, University of Chile , Santiago de Chile , Chile Infectious hematopoietic necrosis virus (IHNV, Rhabdoviridae), is the causative agent of infectious hematopoietic necrosis (IHN), a disease notifiable to the World Organisation for Animal Health, and various countries and trading areas (including the European Union). IHNV is an economically important pathogen causing clinical disease and mortalities in a wide variety of salmonid species, including the main salmonid species produced in aquaculture, Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss). We reviewed the scientific literature on IHNV on a range of topics, including geographic distribution; host range; conditions required for infection and clinical disease; minimum infectious dose; subclinical infection; shedding of virus by infected fish; transmission via eggs; diagnostic tests; pathogen load and survival of IHNV in host tissues. This information is required for a range of purposes including import risk assessments; parameterisation of disease models; for surveillance planning; and evaluation of the chances of eradication of the pathogen to name just a few. The review focuses on issues that are of relevance for the European context, but many of the data summarised have relevance to IHN globally. Examples for application of the information is presented and data gaps highlighted. 1 Introduction Infectious hematopoietic necrosis virus (IHNV) is an economically important pathogen causing clinical disease (Figure  1) and mortalities in a wide variety of salmonid species, including the main salmonid species produced in aquaculture, Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss). In 2013, the worldwide production of all farmed salmonids exceeded three million tonnes, with a value of $17.5 billion [ 1 ]. Salmonid production, particularly Atlantic salmon, increased dramatically from 299  000 tonnes in 1990 to 1.9 million tonnes in 2010, at an average annual rate near 10% [ 2 ]. Infectious diseases are one of the main constraints to further expansion of aquaculture production [ 3 ]. Two epizootics of IHNV in Canada (from 1992 to 1996 and 2001 to 2003) caused a combined estimated economic loss to the salmon industry of CDN$40 million in inventory representing CDN$200 million in lost sales [4]. Infection of fish with IHNV is notifiable to the World Organisation for Animal Health, and various countries and trading areas (like the European Union) have particular legislation in place for the control of the disease. Initially identified in western North America, the pathogen spread to Europe and Asia [5, 6]. Data on the characteristics of a given pathogen are relevant for several purposes. In the epidemiological context such data are required for the preparation of import risk assessments (e.g. to evaluate the risk of introducing a given pathogen to support animal health policy with regards to trade and biosecurity); the parameterisation of disease models (e.g. to predict disease spread in the case of an introduction of the pathogen); to evaluate the chances of eradication of the pathogen; for surveillance planning (e.g. following a disease outbreak or to demonstrate freedom from disease) to name just a few. The review focuses on issues that are of relevance for the European context, but many of the data summarised have relevance to IHN globally. The scope of the review covers characteristics of the pathogen, the hosts and the likelihood of detection, all of which provide information towards the likelihood of pathogen transfer and establishment. It is often relevant to understand some details of the studies referred to in order to evaluate the information provided and use it for risk assessments. For this reason, we provided information on the context and/or methods of the referenced papers. This makes this review a relatively detailed document; however, this was done with the view to provide a reference document that allows scientists to refer to the summarised (but not too summarised) information without necessarily having to refer to all the original sources. An overview of the interaction between the various epidemiological factors covered in this review and their impact on disease control is presented in Figure 2. 2 Aetiological agent, agent strains The causative agent of IHN, IHNV, is classified in the family Rhabdoviridae, and is one of three rhabdoviruses of finfish listed by the OIE (World Organisation for Animal Health). The IHNV virion is bullet shaped (Figure 3) and contains a single stranded, non-segmented, negative sense RNA genome of approximately 11  000 bases which encodes six proteins (...truncated)


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Peter Dixon, Richard Paley, Raul Alegria-Moran, Birgit Oidtmann. Epidemiological characteristics of infectious hematopoietic necrosis virus (IHNV): a review, Veterinary Research, 2016, pp. 63, 47, DOI: 10.1186/s13567-016-0341-1