Area management strategies for disease control in aquaculture: Perspectives on infectious salmon anemia (ISA) spread from two continents
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1
USDA APHIS VS, United States
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2
Sernapesca, Chile
The coordination of production and biosecurity practices across neighboring farms in a geographically, or hydrographically, defined region is an important disease prevention and control strategy in aquaculture. Here termed area management, this fairly rigid organizational structure requires buy-in and coordination at many levels, both within and between companies, as well as among local, national and, at times, international governments. Area management in aquaculture perhaps stood its most prominent test in its widespread adoption in response to outbreaks of infectious salmon anemia (ISA) internationally. Successes in ISA virus (ISAV) control have since been attributed to the area separation achieved through synchronized stocking, fallowing, movement restrictions, and fomite or pest control. Area management, however, is costly; often demanding extra biosecurity, lengthy or inconveniently timed fallows, and localized equipment, personnel, and services. It is also inefficient, generating redundancies in workforce and infrastructure, and periodic lapses or surplus of product that may not sync with market demand. Yet high in both cost and potential impact, few epidemiologic studies have examined the utility of area management methods directly.
ISA upended Atlantic salmon production in the east coast of the United States in 2001/2002. Adoption of area management practices in Maine, and harmonization of the same with New Brunswick across the international border, is generally credited with the fairly rapid resolution of the outbreak. The importance of waterborne spread of virus in and between salmon farming areas in Maine and New Brunswick was demonstrated in retrospective analysis, and similar analyses suggested also the importance of fallows. However, data on additional area management tenets lacked volume, variability or controls for empirical analysis. More recently, Chile’s National Fisheries and Aquaculture Service implemented area management practices in response to their 2007 emergence of ISAV. Longitudinal data collected throughout this outbreak allowed the evaluation of the impact of additional area management tenets on virus control. In Chile, retrospective analysis identified hydrographic linkages, shared ports, and fish transfers from areas with recent occurrence of ISAV as the strongest predictors of virus spread between areas, providing support for their strong relevance to area management success.
We compare patterns across continents, and discuss observations and questions that could impact future disease control strategies. For example, in Chile, hydrographic linkages were most predictive of disease spread prior to national adoption of enhanced biosecurity and fallowing regulations, suggesting that viral load can impact spread dynamics. As another example, results varied by ISAV type (generally categorized HPR0 for non-virulent genotypes, and HPRv otherwise). In both countries, HPR0 arose late in the study period, so few HPRv events were available by which to explore the hypothesis of HPR0 as progenitor of outbreaks. However, spatiotemporal patterns in the occurrence of both types suggest a parallel or possibly reversed means of spread. In Chile, the occurrence of HPR0 could be predicted in part by the distribution of HPRv events almost 3 years prior. Finally, we highlight the importance of ongoing efforts to improve data precision, breadth and consistency in field settings; and the importance for continued HPR0 study, both to specify its diagnostic test accuracy and define its role in HPRv outbreaks. These and related efforts will serve to better inform efficient and effective area management strategies.
Keywords:
Isav,
Infectious salmon anemia,
zone,
Aquatic Organisms,
Epidemiology
Conference:
AquaEpi I - 2016, Oslo, Norway, 20 Sep - 22 Sep, 2016.
Presentation Type:
Oral
Topic:
Aquatic Animal Epidemiology
Citation:
Gustafson
L and
Lara Fica
M
(2016). Area management strategies for disease control in aquaculture: Perspectives on infectious salmon anemia (ISA) spread from two continents.
Front. Vet. Sci.
Conference Abstract:
AquaEpi I - 2016.
doi: 10.3389/conf.FVETS.2016.02.00031
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Received:
26 May 2016;
Published Online:
14 Sep 2016.
*
Correspondence:
Dr. Lori Gustafson, USDA APHIS VS, Fort Collins, United States, lori.l.gustafson@usda.gov