Effects of different strategies for lice control, a simulation experiment.
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1
Norwegian Veterinary Insitute, Norway
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2
Vesterålen fiskehelsetjeneste AS, Norway
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3
Inaq, Norway
To simulate different strategies for lice control, a model for the development of lice infestations was produced based on weekly historical data from 2012 to 2015. Count data for PAAM (pre adult and adult male stages of lice) and AF (adult female lice) together with information of medical treatment and production data was available from 75 farms in the Lofoten, Vestrålen and Tysfjord area in the north of Norway. Based on an infection-pressure model developed in Kristoffersen et al. 2014 the influence of reproduction both internally and externally (from neighboring farms) was calculated and used in the historical model. The prospective infection-pressure is calculated depending on the total number of AF on farms and water temperatures. Three historical models for PAAM level abundance was generated, depending on the level of PAAM the previous week, and additionally a separate model for AF. The explanatory variables tested for the PAAM models was PAAM level previous week, internal and external infection pressure this week, fish weight this week, farm size this week, distance to nearest slaughterhouse with holding cages and seasonal effects. For the AF model the explanatory variables tested was PAAM and AF levels previous week, fish weight this week, farm size this week and seasonal effects. Data counted the week after medical treatment were not used when developing the historical models.
The models were then used to simulate PAAM and AF levels as well as time for medical treatments and corresponding infection-pressures on each farm each week on the production data from 2012 to 2015 given different strategic actions followed for lice control. In these simulations the effect of medical treatment was assumed to be 85% lice mortality on both PAAM and AF. The strategies tested were: 1) different regulatory lice limits 2) use of 10 meter deep skirts as a preventive barrier against external infection pressure. Results from 1000 simulation of each strategy showed that lower regulatory lice limits induced higher levels of treatments in the production area. The simulation results also showed that use of skirt in only 28% of the farms (which where those planning to use skirt in 2016) reduced the amount of medical treatments in the area with 25%, irrespectively of the regulatory lice limits.
References
Kristoffersen, A. B., Jimenez, D., Viljugrein, H., Grøntvedt, R., Stien, A., Jansen, P. a. (2014). Large scale modelling of salmon lice (Lepeophtheirus salmonis) infection pressure based on lice monitoring data from Norwegian salmonid farms. Epidemics, 9, 31–39
Keywords:
Sealice,
Simulations,
Effect of regulatory lice limits,
Skirts against lice,
Infection pressue
Conference:
AquaEpi I - 2016, Oslo, Norway, 20 Sep - 22 Sep, 2016.
Presentation Type:
Oral
Topic:
Aquatic Animal Epidemiology
Citation:
Kristoffersen
AB,
Andreassen
KB,
Jansen
PA and
Grøntvedt
RN
(2016). Effects of different strategies for lice control, a simulation experiment..
Front. Vet. Sci.
Conference Abstract:
AquaEpi I - 2016.
doi: 10.3389/conf.FVETS.2016.02.00026
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Received:
16 Aug 2016;
Published Online:
14 Sep 2016.
*
Correspondence:
Dr. Anja B Kristoffersen, Norwegian Veterinary Insitute, Oslo, Norway, anja.kristoffersen@vetinst.no