Local dispersal of palaearctic Culicoides biting midges estimated by mark-release-recapture

Abstract

BackgroundFarm to farm movement of Culicoides midges is believed to play a critical role in the spread of bluetongue (BT), Schmallenberg and other midge-borne diseases. To help understand and predict the spread of diseases carried by midges, there is a need to determine their dispersal patterns, and to identify factors contributing to the direction taken and distance travelled.MethodsThe dispersal of Obsoletus Group members was studied on 19 farms around Bala, north Wales. Field-collected Culicoides were trapped in a black-light (OVI) trap and self-marked in the collecting vessel, using micronized fluorescent dust. Culicoides were released at a central farm and OVI traps set on 18 surrounding farms, at distances of 1 to 4 km. The study was repeated using six colours of fluorescent dust over an 18 day period.ResultsAn estimated 61,062 (95% CI = 56,298-65,830) marked Culicoides were released during the study and 12 (0.02%) Culicoides were recaptured. Of the females recaptured, six were C. obsoletus/scoticus, two C. dewulfi, two C. pulicaris and one C. festivipennis. The male was C. obsoletus. Recaptures occurred 1–2.5 km from the release site, with greatest numbers at 2.5 km. Most recaptures were 2 nights post-release; none were more than 3 nights post-release. Two females were recovered at 1.5 km on the night of release and one male at 1 km two nights post-release. The mean distance travelled (MDT) for males was 1 km, females was 2.21 km, and all recaptured Culicoides was 2.15 km. Recaptures were made both downwind and upwind of the prevailing wind direction during the trapping periods, highlighting possible passive and active dispersal of Culicoides between farms.ConclusionsThis is the first study to demonstrate farm to farm movement of the main Palaearctic BT vector species, the Obsoletus Group. Such movement has disease control implications in terms of the vectoral movement of disease between farms. The results suggest that Culicoides control measures applied at an infected farm (trapping or killing Culicoides) will reduce risk of spread to neighbouring farms by lessening the number of Culicoides dispersing from that farm, as well as reducing transmission at the source farm itself.

Quantification of within‐ and between‐farm dispersal of Culicoides biting midges using an immunomarking technique

“…Since collection may not occur at the night during which dispersal occurred, only the first trapping session can be used to confirm upwind or downwind flight of individuals, and here we present evidence for upwind flight and downwind flight of individual Culicoides to distances greater than 1 km in a 24 h period. Whilst Kluiters, Swales & Baylis () suggest upwind and downwind flight from the release point occurred in their study, the wind speed and direction used data were at too low a resolution (24 h average) to test this hypothesis given the likely influence of the local topographic complexity on wind direction (Whiteman & Doran ). Here, all replicates took place under favourable conditions for Culicoides flight, with light winds (<3 ms −1 ) (Fig.…”

“…In previous studies, the low number of individuals recaptured (40 in total) at all distances obscures the estimation of local movement of the majority of Culicoides individuals (Kirkeby et al . ; Kluiters, Swales & Baylis ). Using the SNV transformation of ELISA data did not affect the maximum dispersal distance of marked Culicoides .…”

“…Culicoides collected overnight in light‐suction traps prior to marking (Kirkeby et al . ; Kluiters, Swales & Baylis ), are visibly dehydrated, experience significant mortality and often exhibit inhibited host‐feeding behaviour (Venter et al . ).…”

Assessing the potential for Bluetongue virus 8 to spread and vaccination strategies in Scotland

“…Introduction to new areas through simulated livestock movements often results in little BT spread due to the few areas that are suitable for BT spread. A recent study has shown that over a time period of up to three nights midges are found 1–2.5 km from their release site28. However, the dispersal of midges over time scales greater than two weeks that comprise the EIP of BTv in the midge has not been directly measured and as a result we used kernels derived from the spatial and temporal distribution of observed cases.…”

Analysis of the Spatial Organization of Pastures as a Contact Network, Implications for Potential Disease Spread and Biosecurity in Livestock, France, 2010

“…By the end of 2009, BTV-8 had spread to most countries in western and central Europe, including the United Kingdom, Denmark, Norway, Sweden, Czech Republic, Hungary, Austria, Italy, Luxembourg, Spain, and France [10–13]. This example clearly shows the ability of a vector-borne disease to form an epidemic wave that travels at a continental scale, and the velocity of this wave has been related to the local density of pastures [14], because Culicoides vectors can only fly over relatively small distances (< 3 km) [15]. More generally, whatever the transmission mechanism (direct, indirect, vector-borne), the spatial organization of pastures strongly constraints the risk of contagion between animals located on these pastures [16,17].…”