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

1. 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.
2. 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.
3. Whilst no change in seasonal activity was recorded 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.
4. 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 response poses significant challenges for predicting future transmission and overwintering risk.
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