Long-term shifts in the seasonal abundance of adult Culicoides biting midges and their impact on potential arbovirus outbreaks.

Christopher J Sanders,Simon Carpenter,Marion England,Beth Purse,Chris R Shortall,Laura Burgin,Simon Gubbins,Richard Harrington,Juan Corley

doi:10.1111/1365-2664.13415

Abstract

Surveillance of adult Culicoides biting midge flight activity is used as an applied ecological method to guide the management of arbovirus incursions on livestock production in Europe and Australia.To date the impact of changes in the phenology of adult vector activity on arbovirus transmission has not been defined. We investigated this at two sites in the UK, identifying 150,000 Culicoides biting midges taken from 2867 collections over a nearly 40 year timescale.Whilst we recorded no change in seasonal activity at one site, shifts in first adult appearance and last adult appearance increased the seasonal activity period of Culicoides species at the other site by 40 days over the time period.Lengthening of the adult activity season was driven by an increase in abundance of Culicoides and correlated with local increases in temperature and precipitation. This diversity in responses poses significant challenges for predicting future transmission and overwintering risk. Policy implications. Our analysis not only shows a dramatic and consistent increase in the adult active period of Culicoides biting midges, but also that this varies significantly between sites. This suggests broad‐scale analyses alone are insufficient to understand the potential impacts of changes in climate on arbovirus vector populations. Understanding the impact of climate change on adult Culicoides seasonality and transmission of arboviruses requires the context of changes in a range of other local ecological drivers.

Highlights

Arthropod‐borne viruses include some of the most important emerging and re‐emerging pathogens of humans, livestock, and wildlife worldwide (Gould, Pettersson, Higgs, Charrel, & Lamballerie, 2017; Liang, Gao, & Gould, 2015; Weaver & Reisen, 2010)
This study demonstrates that significant changes in the first and last date of appearance of adult Culicoides in the UK have occurred in response to climate drivers over 40 years, but that these changes are heterogeneous across sites
While conducted at a single‐country scale and at a logistically restricted number of sites, this is the first time that changes in adult phenology have been directly related to climate parameters at this time scale for this vector group and for vectors of medical and veterinary pathogens as a whole

Summary

| INTRODUCTION

Arthropod‐borne viruses (arboviruses) include some of the most important emerging and re‐emerging pathogens of humans, livestock, and wildlife worldwide (Gould, Pettersson, Higgs, Charrel, & Lamballerie, 2017; Liang, Gao, & Gould, 2015; Weaver & Reisen, 2010). The Rothamsted suction‐traps have been previously used to monitor Culicoides activity (Fassotte et al, 2008) and describe spatial and seasonal patterns of Culicoides flight in relation to meteorological conditions over a single season (Sanders et al, 2011) These collections provide a unique opportunity to examine the seasonal dynamics and abundance of adult vectors over the period of time relevant to that at which global climate has been changing. We use this resource to describe changes in the seasonality and abundance of Culicoides vectors of BTV in the Palearctic, at two sites over a period spanning nearly 40 years and investigate the role of local climate conditions and assess the likely impact of these changes on the transmission of arboviruses

| MATERIALS AND METHODS

| Statistical methods

Findings

| DISCUSSION