Culicoides-borne Orbivirus epidemiology in a changing climate.

Research Overview

• This study examines how global climate change is expected to affect the epidemiology of Orbiviruses transmitted by biting midges (Culicoides), including their impact on disease spread and outbreak patterns in wildlife and domestic animals.

Introduction to Orbiviruses and their Importance

• Orbiviruses are viral pathogens that affect both domestic animals and wildlife worldwide.
• Key Orbiviruses transmitted by Culicoides biting midges include:
• Bluetongue virus (BTV)
• Epizootic hemorrhagic disease virus (EHDV)
• African horse sickness virus (AHSV)
• These viruses have significant health and economic impacts due to their effects on livestock and important wildlife species.

Role of Climate Change in Orbivirus Epidemiology

• Global climate change influences the three main components of Orbivirus transmission: the viruses, the insect vector populations (Culicoides), and the host animals.
• Specific impacts of climate change include:
• Altered vector competence: The ability of biting midges to acquire, maintain, and transmit viruses may be affected by temperature and environmental conditions.
• Changes in extrinsic incubation period (EIP): This is the time taken for the virus to develop within the insect vector before it becomes infectious. Warmer temperatures generally shorten the EIP, potentially increasing transmission rates.
• Vector dispersal dynamics: Climate-driven changes, such as wind patterns and drought, can alter both local movement and long-distance spread of midge populations.
• Range expansion: Warmer climates may allow Culicoides species to inhabit and establish in previously unsuitable geographic areas, raising the risk of Orbivirus transmission in these new regions.
• Extended transmission periods: Earlier onset of spring and delayed arrival of fall may lengthen the time frame during which transmission can occur annually.

Influence of Weather Anomalies on Outbreak Patterns

• Weather events like droughts and changes in wind speed can influence the number and frequency of Orbivirus outbreaks.
• Variability in outbreak intervals may result due to climate anomalies that affect vector survival, abundance, and host-vector interactions.

Impact of Climate Change on Viral Evolution

• Warmer temperatures and environmental changes may promote viral genome changes by:
• Facilitating reassortment: The exchange of genetic material between different virus strains during co-infections can lead to new virus variants.
• Emergence of novel mutations: Changing environmental pressures may select for viral mutations that alter virus behavior, virulence, or transmission characteristics.

Observed Changes and Future Implications

• Recent outbreaks of bluetongue, epizootic hemorrhagic disease, and African horse sickness outside their historically endemic areas demonstrate the practical effects of climate-linked epidemiological shifts.
• The projected ongoing climate change necessitates comprehensive, interdisciplinary research approaches combining climatology, entomology, virology, and veterinary science.
• Understanding these dynamics is vital to develop strategies for assessing risks and mitigating future Orbivirus outbreak threats in vulnerable regions.