Mechanistic model for predicting the seasonal abundance of Culicoides biting midges and the impacts of insecticide control

A - Papers appearing in refereed journals

White, S. M., Sanders, C. J., Shortall, C. R. and Purse, B. V. 2017. Mechanistic model for predicting the seasonal abundance of Culicoides biting midges and the impacts of insecticide control. Parasites & Vectors. 10 (1), p. 162.

AuthorsWhite, S. M., Sanders, C. J., Shortall, C. R. and Purse, B. V.
Abstract

Background
Understanding seasonal patterns of abundance of insect vectors is important for optimisation of control strategies of vector-borne diseases. Environmental drivers such as temperature, humidity and photoperiod influence vector abundance, but it is not generally known how these drivers combine to affect seasonal population dynamics.

Methods
In this paper, we derive and analyse a novel mechanistic stage-structured simulation model for Culicoides biting midges-the principle vectors of bluetongue and Schmallenberg viruses which cause mortality and morbidity in livestock and impact trade. We model variable life-history traits as functional forms that are dependent on environmental drivers, including air temperature, soil temperature and photoperiod. The model is fitted to Obsoletus group adult suction-trap data sampled daily at five locations throughout the UK for 2008.

Results
The model predicts population dynamics that closely resemble UK field observations, including the characteristic biannual peaks of adult abundance. Using the model, we then investigate the effects of insecticide control, showing that control strategies focussing on the autumn peak of adult midge abundance have the highest impact in terms of population reduction in the autumn and averaged over the year. Conversely, control during the spring peak of adult abundance leads to adverse increases in adult abundance in the autumn peak.

Conclusions
The mechanisms of the biannual peaks of adult abundance, which are important features of midge seasonality in northern Europe and are key determinants of the risk of establishment and spread of midge-borne diseases, have been hypothesised over for many years. Our model suggests that the peaks correspond to two generations per year (bivoltine) are largely determined by pre-adult development. Furthermore, control strategies should focus on reducing the autumn peak since the immature stages are released from density-dependence regulation. We conclude that more extensive modelling of Culicoides biting midge populations in different geographical contexts will help to optimise control strategies and predictions of disease outbreaks.

KeywordsBluetongue; Deltamethrin; Obsoletus group; Schmallenberg; Seasonality; Vector-borne disease
Year of Publication2017
JournalParasites & Vectors
Journal citation10 (1), p. 162
Digital Object Identifier (DOI)doi:10.1186/s13071-017-2097-5
PubMed ID28347327
PubMed Central IDPMC5369195
Open accessPublished as ‘gold’ (paid) open access
FunderBiotechnology and Biological Sciences Research Council
Funder project or codeThe Rothamsted Insect Survey [2012-2017]
Publisher's version
Output statusPublished
Publication dates
Online27 Mar 2017
Publication process dates
Accepted20 Mar 2017
PublisherBioMed Central
Biomed Central Ltd
Copyright licenseCC BY
ISSN1756-3305

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