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A spatial simulation model for the dispersal of the bluetongue vector Culicoides brevitarsis in Australia.

Kelso JK, Milne GJ - PLoS ONE (2014)

Bottom Line: Data from midge trapping programmes were used to qualitatively validate the resulting simulation model.This extended model could then be used as a platform for addressing the effectiveness of spatially targeted vaccination strategies or animal movement bans as BTV spread mitigation measures, or the impact of climate change on the risk and extent of outbreaks.These questions involving incursive Culicoides spread cannot be simply addressed with non-spatial models.

View Article: PubMed Central - PubMed

Affiliation: School of Computer Science and Software Engineering, University of Western Australia, Crawley, Western Australia, Australia.

ABSTRACT

Background: The spread of Bluetongue virus (BTV) among ruminants is caused by movement of infected host animals or by movement of infected Culicoides midges, the vector of BTV. Biologically plausible models of Culicoides dispersal are necessary for predicting the spread of BTV and are important for planning control and eradication strategies.

Methods: A spatially-explicit simulation model which captures the two underlying population mechanisms, population dynamics and movement, was developed using extensive data from a trapping program for C. brevitarsis on the east coast of Australia. A realistic midge flight sub-model was developed and the annual incursion and population establishment of C. brevitarsis was simulated. Data from the literature was used to parameterise the model.

Results: The model was shown to reproduce the spread of C. brevitarsis southwards along the east Australian coastline in spring, from an endemic population to the north. Such incursions were shown to be reliant on wind-dispersal; Culicoides midge active flight on its own was not capable of achieving known rates of southern spread, nor was re-emergence of southern populations due to overwintering larvae. Data from midge trapping programmes were used to qualitatively validate the resulting simulation model.

Conclusions: The model described in this paper is intended to form the vector component of an extended model that will also include BTV transmission. A model of midge movement and population dynamics has been developed in sufficient detail such that the extended model may be used to evaluate the timing and extent of BTV outbreaks. This extended model could then be used as a platform for addressing the effectiveness of spatially targeted vaccination strategies or animal movement bans as BTV spread mitigation measures, or the impact of climate change on the risk and extent of outbreaks. These questions involving incursive Culicoides spread cannot be simply addressed with non-spatial models.

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Schematic overview of the simulation model components.The dynamic state variables (population densities) are shown in black type. The processes midge movement modelling midge movement are shown in purple; processes modelling midge population dynamics are shown in green.
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pone-0104646-g001: Schematic overview of the simulation model components.The dynamic state variables (population densities) are shown in black type. The processes midge movement modelling midge movement are shown in purple; processes modelling midge population dynamics are shown in green.

Mentions: This conceptual automata theoretic model is implemented in software and the dynamics of the midge population (involving population growth and decline) together with vector movement is realized by discrete event simulation [32]. The landscape cell automata state data and the transition functions are used by the simulation algorithm to update the state of each automaton at an appropriate discrete time step, capturing the dynamic behaviour of the physical system being modelled. An outline of the simulation algorithm is given in Text S1. The specific dynamic processes that determine Culicoides spread, namely the changing weather, insect population dynamics, and insect movement between cells may be treated as sub-models which are combined together to produce the overall simulation system. These sub-models are depicted schematically in Figure 1 where 4 discrete cells are pictured for illustrative purposes, and are described in detail in subsequent sections.


A spatial simulation model for the dispersal of the bluetongue vector Culicoides brevitarsis in Australia.

Kelso JK, Milne GJ - PLoS ONE (2014)

Schematic overview of the simulation model components.The dynamic state variables (population densities) are shown in black type. The processes midge movement modelling midge movement are shown in purple; processes modelling midge population dynamics are shown in green.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126746&req=5

pone-0104646-g001: Schematic overview of the simulation model components.The dynamic state variables (population densities) are shown in black type. The processes midge movement modelling midge movement are shown in purple; processes modelling midge population dynamics are shown in green.
Mentions: This conceptual automata theoretic model is implemented in software and the dynamics of the midge population (involving population growth and decline) together with vector movement is realized by discrete event simulation [32]. The landscape cell automata state data and the transition functions are used by the simulation algorithm to update the state of each automaton at an appropriate discrete time step, capturing the dynamic behaviour of the physical system being modelled. An outline of the simulation algorithm is given in Text S1. The specific dynamic processes that determine Culicoides spread, namely the changing weather, insect population dynamics, and insect movement between cells may be treated as sub-models which are combined together to produce the overall simulation system. These sub-models are depicted schematically in Figure 1 where 4 discrete cells are pictured for illustrative purposes, and are described in detail in subsequent sections.

Bottom Line: Data from midge trapping programmes were used to qualitatively validate the resulting simulation model.This extended model could then be used as a platform for addressing the effectiveness of spatially targeted vaccination strategies or animal movement bans as BTV spread mitigation measures, or the impact of climate change on the risk and extent of outbreaks.These questions involving incursive Culicoides spread cannot be simply addressed with non-spatial models.

View Article: PubMed Central - PubMed

Affiliation: School of Computer Science and Software Engineering, University of Western Australia, Crawley, Western Australia, Australia.

ABSTRACT

Background: The spread of Bluetongue virus (BTV) among ruminants is caused by movement of infected host animals or by movement of infected Culicoides midges, the vector of BTV. Biologically plausible models of Culicoides dispersal are necessary for predicting the spread of BTV and are important for planning control and eradication strategies.

Methods: A spatially-explicit simulation model which captures the two underlying population mechanisms, population dynamics and movement, was developed using extensive data from a trapping program for C. brevitarsis on the east coast of Australia. A realistic midge flight sub-model was developed and the annual incursion and population establishment of C. brevitarsis was simulated. Data from the literature was used to parameterise the model.

Results: The model was shown to reproduce the spread of C. brevitarsis southwards along the east Australian coastline in spring, from an endemic population to the north. Such incursions were shown to be reliant on wind-dispersal; Culicoides midge active flight on its own was not capable of achieving known rates of southern spread, nor was re-emergence of southern populations due to overwintering larvae. Data from midge trapping programmes were used to qualitatively validate the resulting simulation model.

Conclusions: The model described in this paper is intended to form the vector component of an extended model that will also include BTV transmission. A model of midge movement and population dynamics has been developed in sufficient detail such that the extended model may be used to evaluate the timing and extent of BTV outbreaks. This extended model could then be used as a platform for addressing the effectiveness of spatially targeted vaccination strategies or animal movement bans as BTV spread mitigation measures, or the impact of climate change on the risk and extent of outbreaks. These questions involving incursive Culicoides spread cannot be simply addressed with non-spatial models.

Show MeSH
Related in: MedlinePlus