Influence of season and meteorological parameters on flight activity of Culicoides biting midges

Abstract

Summary1. Culicoides biting midges are vectors of internationally important arboviruses including bluetongue virus (BTV). The ecological constraints imposed by the small body size of these insects strongly influence the epidemiology of the diseases they can carry. Bluetongue virus recently emerged in northern Europe, and atmospheric dispersion models have subsequently been employed to simulate vector movement (and hence likely spread of BTV). The data underlying such models, however, have hitherto either been obtained from small-scale studies or from outside the northwestern Palaearctic. 2. The effects of seasonality and local meteorological conditions upon the daily presence and abundance of Culicoides vectors were examined using 2760 samples collected across a network of 12 different habitat types in England during 2008. Over 50 000 individuals were estimated to be in the samples with males constituting 62% of the total collection, allowing straightforward comparison between potential vector species in terms of their activity rates and seasonality. Culicoides abundance was linked to livestock density and land use. Farm-associated Culicoides species were recorded at all sites including species thought to be restricted to this ecosystem by larval habitat, suggesting a greater potential for dispersal over land than previously thought. 3. Synthesis and applications. The model developed has already been applied in a functional dispersion model to predict disease risk from wind-borne infected Culicoides incursion into the UK and elsewhere. The study has expounded the long-distance dispersal potential of Culicoides, essential for future prediction of the incursion and spread of Culicoides-borne pathogens. It has additionally contributed to the understanding of the ecology of highly dispersive insect vectors.

A new algorithm quantifies the roles of wind and midge flight activity in the bluetongue epizootic in northwest Europe

“…Key among these, and for which we require further information to improve our model's predictions, are midge responses to environmental variables (topography and weather) [18,47,48], flight properties (survival at different flight height, flight behaviour at different wind speeds), seasonality [48] and population parameters (reproductive status, age and local population density) [21].…”

A first estimation of Culicoides imicola and Culicoides obsoletus/Culicoides scoticus seasonality and abundance in Europe

“…Great Britain (Sanders et al 2011) In 2008, a study was done in 12 sites; samples were collected once every 24 h from 31 March to 16…”

The impact of temperature changes on vector-borne disease transmission: Culicoides midges and bluetongue virus

“…This model accounts for both day-to-day variation in temperature and individual-level (stochastic) variation between vectors and allows us to calculate Ĉ (t) for each day included in a times series of daily temperatures. -An existing statistical model for UK midge flight activity which includes temperature and day of the year as predictor variables [46]. We use the flight activity as a proxy for the (stochastic) number of bites experienced per infected cattle per day.…”

“…As mentioned above, mechanistic modelling of the midge population dynamics, and therefore estimating the rate at which susceptible midges bite infectious livestock, is not currently feasible due to fundamental knowledge gaps [23]. We model the biting rate of susceptible midges using a statistical model for daily flight activity of midges already extant in the literature as a proxy for biting rate per livestock host [46]. The Sanders et al [46] model was chosen because it was parametrized using captures of midges in the UK to make daily predictions of flight activity with temperature as a predictor; therefore, it agrees with both the location of this study and the daily time scale of the model developed here, and is informed by temperature.…”

“…We model the biting rate of susceptible midges using a statistical model for daily flight activity of midges already extant in the literature as a proxy for biting rate per livestock host [46]. The Sanders et al [46] model was chosen because it was parametrized using captures of midges in the UK to make daily predictions of flight activity with temperature as a predictor; therefore, it agrees with both the location of this study and the daily time scale of the model developed here, and is informed by temperature. We find the pattern of temperature that gives the maximum possible Ĉ and show that the maximizing pattern implies significantly more day-to-future transmission risk than any constant temperature.…”