Culicoides midge abundance across years: Modeling inter-annual variation for an avian feeder and a candidate vector of hemorrhagic diseases in farmed wildlife

Authors: BENN, JAMIE - University Of Florida; ORANGE, JEREMY - University Of Florida; GOMEZ, JUAN PABLO - Universidad Del Norte; DINH, EMILY, - Michigan Department Of Health And Human Services; McGregor, Bethany; BLOSSER, ERIK - Sutter-Yuba Mosquito & Vector Control District; BURKETT-CADENA, NATHAN - University Of Florida; WISELY, SAMANTHA - University Of Florida; BLACKBURN, JASON - University Of Florida

Submitted to: Viruses
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/2024
Publication Date: 5/11/2024
Citation: Benn, J.S., Orange, J.P., Gomez, J., Dinh, E.T., Mcgregor, B.L., Blosser, E., Burkett-Cadena, N.D., Wisely, S.M., Blackburn, J.K. 2024. Culicoides midge abundance across years: Modeling inter-annual variation for an avian feeder and a candidate vector of hemorrhagic diseases in farmed wildlife. Viruses. 16(5):766.

Interpretive Summary: Epizootic hemorrhagic disease virus (EHDV) and bluetongue virus (BTV) are viruses of worldwide veterinary concern that are transmitted by Culicoides biting midges. Many species of biting midge can transmit these viruses, but different species likely transmit the viruses across different regions, potentially with varying habitat preferences depending on their life stage. We performed the following study to investigate this and found that two species of Culicoides biting midges, C. haematopotus and C. stellifer, prefer different geographic areas of a wildlife ranch in the Florida panhandle. We also found differences in preferred habitats between midges that were about to lay eggs compared to those that had already laid eggs. Until best management practices for the vectors of EHDV and BTV are identified, learning more about the habitat preferences of biting midges can help understand how these viruses are spread across a ranch and allow us to manage animals in a way that avoids areas of high risk for disease transmission.

Technical Abstract: Epizootic hemorrhagic disease virus (EHDV) and bluetongue virus (BTV) are orbiviruses that cause hemorrhagic disease (HD) with significant economic and population health impacts on domestic livestock and wildlife. In the United States, white-tailed deer (Odocoileus virginianus) are particularly susceptible to these viruses and are a frequent blood meal host for various species of Culicoides biting midges (Diptera: Ceratopogonidae) that transmit orbiviruses. The species of Culicoides that transmit EHDV and BTV vary between regions, and larval habitats can differ widely between vector species. Understanding how midges are distributed across landscapes can inform HD virus transmission risk on a local scale, allowing for improved animal management plans to avoid suspected high-risk areas or target these areas for insecticide control. We used occupancy modeling to estimate the abundance of gravid (egg-laden) and parous (most likely to transmit the virus) females of two putative vector species, C. stellifer and C. venustus, and one species, C. haematopotus, that was not considered a putative vector. We developed a universal model to determine habitat preferences, then mapped a predicted weekly midge abundance during the HD transmission seasons in 2015 (July–October) and 2016 (May–October) in Florida. We found differences in habitat preferences and spatial distribution between the parous and gravid states for C. haematopotus and C. stellifer. Gravid midges preferred areas close to water on the border of well and poorly drained soil. They also preferred mixed bottomland hardwood habitats, whereas parous midges appeared less selective of habitat. If C. stellifer is confirmed as an EHDV vector in this region, the distinct spatial and abundance patterns between species and physiological states suggest that the HD risk is non-random across the study area.