Temperature Dependence of the Extrinsic Incubation Period of Orbiviruses in Culicoides Biting Midges

Abstract

BackgroundThe rate at which viruses replicate and disseminate in competent arthropod vectors is limited by the temperature of their environment, and this can be an important determinant of geographical and seasonal limits to their transmission by arthropods in temperate regions.Methodology/Principal FindingsHere, we present a novel statistical methodology for estimating the relationship between temperature and the extrinsic incubation period (EIP) and apply it to both published and novel data on virus replication for three internationally important orbiviruses (African horse sickness virus (AHSV), bluetongue virus (BTV) and epizootic haemorrhagic disease virus (EHDV)) in their Culicoides vectors. Our analyses show that there can be differences in vector competence for different orbiviruses in the same vector species and for the same orbivirus in different vector species. Both the rate of virus replication (approximately 0.017-0.021 per degree-day) and the minimum temperature required for replication (11-13°C), however, were generally consistent for different orbiviruses and across different Culicoides vector species. The estimates obtained in the present study suggest that previous publications have underestimated the replication rate and threshold temperature because the statistical methods they used included an implicit assumption that all negative vectors were infected.Conclusions/SignificanceRobust estimates of the temperature dependence of arbovirus replication are essential for building accurate models of transmission and for informing policy decisions about seasonal relaxations to movement restrictions. The methodology developed in this study provides the required robustness and is superior to methods used previously. Importantly, the methods are generic and can readily be applied to other arbovirus-vector systems, as long as the assumptions described in the text are valid.

Schmallenberg virus: State of Art

“…In terms of virus replication, SBV is predicted by the model to have a lower threshold temperature for replication (12.3 °C) and to replicate at a faster rate above the threshold (0.03 per day-degree) ( Table 7.1) than has been reported for any strain of BTV (Carpenter et. al., 2011).…”

Generation of virus like particles for epizootic hemorrhagic disease virus

“…As positive controls, EHDV-6 infected cell lysate and purified CLPs were run next to the samples. Arthropod-borne viruses in countries where they were not formerly present can be caused either through the movement of animals by trade, shifting of the geographical range of vectors driven by global warming, or possibly by the introduction/movement of even small numbers of infected adult vectors (Carpenter et al, 2011). The reported co-circulation of BTV and EHDV in several countries during 2011 and 2012, indicates that both viruses can be present simultaneously within the same host and vector populations Toye et al, 2013;Viarouge et al, 2014).…”

The impact of temperature changes on vector-borne disease transmission: Culicoides midges and bluetongue virus

“…where V is the vector competence (the product of the probabilities per bite of transmission from host to vector and vector to host) which we point estimate as V ¼ 0.045 [34,39]. Using the above definition ofĈðt j T t ,T tþ1 , .…”