Cracking the problem: using egg whites to predict bluetongue outbreaks

• Autores: C.J. Sanders, L.E. Harrup, L.A. Tugwell, V.A. Brugman, M. England, S. Carpenter
• Localización: Veterinary Record, ISSN-e 2042-7670, Vol. 180, Nº. 10, 2017, págs. 1-2
• Idioma: inglés
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• Resumen

  • Culicoides biting midges are vectors of arboviruses such as bluetongue virus, which causes a potentially fatal disease in sheep, cattle and other ruminants. Quantification of the range and probability of Culicoides dispersal is essential to inform policy responses during outbreaks. A variety of methods have been used to quantify Culicoides dispersal at a local scale, including capture-mark-recapture (CMR) using fluorescent dusts; however, a key assumption of CMR studies is that the marking process does not effect the survival and behaviour of the insect. An alternative technique that addresses some of the limitations of CMR is the use of protein-based immunomarking, which allows the marking of insects without needing to collect them. This study used an ovalbumin (protein in egg white) immunomarking technique to quantify the within- and between-farm dispersal of Culicoides in southern England.

    A mixed sheep and beef cattle farm in southern England was sprayed with liquid egg white solution so that insects were exposed to the immunomarker when they passed through the area (habitat immunomarking). Insects were then collected for three or four days after treatment at 14 trap locations during two trial replicates completed in 2013; and 24 trap locations during three trial replicates in 2015, where some of the traps extended out from the egg-marked area to a maximum distance of 3876 m. An ovalbumin-specific ELISA was used to detect ovalbumin-positive Culicoides.

    Both within- and between-farm dispersal of Culicoides was observed. Of the 9058 Culicoides collected over 22 nights of trapping, 600 ovalbumin-positive Culicoides, of 12 species including those implicated as arbovirus vectors, were collected with a maximum dispersal distance of 3125 m. Analysis of this data with information collected from on-site weather stations indicated that midges had flown upwind and downwind towards the traps, and that a significant number are actively moving between farms.

    The authors conclude that the use of this novel immunomarking technique will enable improved, data-driven modelling of the spread of Culicoides-borne arboviruses which could inform the policy response to incursions and outbreaks.