Orbivirus epidemiology in a changing climate

Authors: Hudson, Amy; McGregor, Bethany; Shults, Phillip; ENGLAND, MARION - Pirbright Laboratory; SILBERNEGAL, CONSTANCE - Animal And Plant Health Inspection Service (APHIS); MAYO, CHRISTIE - Colorado State University; CARPENTER, MOLLY - Colorado State University; SHERMAN, TYLER - Colorado State University; Cohnstaedt, Lee

Submitted to: Journal of Medical Entomology
Publication Type: Review Article
Publication Acceptance Date: 7/3/2023
Publication Date: 10/20/2023
Citation: Hudson, A.R., Mcgregor, B.L., Shults, P.T., England, M., Silbernegal, C., Mayo, C., Carpenter, M., Sherman, T., Cohnstaedt, L.W. 2023. Orbivirus epidemiology in a changing climate. Journal of Medical Entomology. 60(6):1221-1229. https://doi.org/10.1093/jme/tjad098.
DOI: https://doi.org/10.1093/jme/tjad098

Interpretive Summary: Orbiviruses are viruses that impact health of wildlife and domestic animals worldwide. Bluetongue (BT), epizootic hemorrhagic disease (EHD), and African horse sickness (AHS) are animal diseases transmitted when biting midges pass the viruses between animals. The viruses, insect vectors, hosts, and environment determine how the viruses are spread and this dynamic is being altered by global climate change. Warmer temperatures and climate hypervariability alter the biting insects ability to transmit virus as well as their life history traits such as life time and activity during each life stage, dispersal within and between locations, range expansion of geographic distributions, and transmission period duration (earlier spring onset and later fall transmission). If virus transmission intensity is associated with weather anomalies such as droughts and wind speeds, there may be changes in the number of outbreaks and periods between outbreaks for some regions. Traditionally, viruses were defined by serotypes but this type of characterization may not be sufficient to capture all the genetic variation in the virus populations leading to a misunderstanding of the virulence or how damaging a virus may be to animal hosts. Additionally, this information can help to update the criteria used to monitor the distribution of virulence factors and genotypes. As the climate changes, Orbivirus epidemiology is being altered as is seen with recent outbreaks of BT, EHD, and AHS outside of endemic areas, and requires interdisciplinary teams and approaches to assess and mitigate future outbreak threats.

Technical Abstract: Orbiviruses are of significant importance to the health of wildlife and domestic animals worldwide; those transmitted by biting midges (Culicoides) include bluetongue virus (BTV), epizootic hemorrhagic disease virus (EHDV), and African horse sickness virus (AHSV). The viruses, insect vectors, and hosts are impacted by global climate change in established orbivirus epidemiology. Warmer temperatures have been shown to alter the vector competence and extrinsic incubation period of certain biting midge species, dispersal within and between patches, range expansion of geographic distribution of vector species, and transmission period duration (earlier spring onset and later fall transmission). If transmission intensity is associated with weather anomalies such as droughts and wind speeds, there may be changes in the number of outbreaks and periods between outbreaks for some regions. Warmer temperatures impact the viral genome by facilitating reassortment and through the emergence of novel viral mutations. Therefore, viral characterizations based on historic serotyping alone are insufficient to understand the changes at the segment and nucleotide level. Molecular methods in addition to antigenic characterization are needed to reveal and understand mutations at the nucleotide level and their contribution to virulence. Additionally, this information can help to update the criteria used to monitor the distribution of virulence factors and genotypes. As the climate changes, Orbivirus epidemiology is inextricably altered as is seen with recent outbreaks of BT, EHD, and AHS outside of endemic areas, and requires interdisciplinary teams and approaches to assess and mitigate future outbreak threats.