Epizootic hemorrhagic disease virus oral infection affects midge reproduction and is vertically transmitted to offspring in Culicoides sonorensis

Authors: ERRAM, DINESH - Louisiana State University; McGregor, Bethany; ACEVEDO, CAROLINA - Minaris Regenerative Medicine; ALTO, BARRY - University Of Florida; BURKETT-CADENA, NATHAN - University Of Florida

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/30/2025
Publication Date: 5/8/2025
Citation: Erram, D., McGregor, B.L., Acevedo, C., Alto, B.W., Burkett-Cadena, N. 2025. Epizootic hemorrhagic disease virus oral infection affects midge reproduction and is vertically transmitted to offspring in Culicoides sonorensis. Scientific Reports. 15. Article 16078. https://doi.org/10.1038/s41598-025-00849-y.
DOI: https://doi.org/10.1038/s41598-025-00849-y

Interpretive Summary: Epizootic hemorrhagic disease virus (EHDV) is a virus spread by biting midges to animals such as white-tailed deer, which can lead to economic losses and ecological impacts. In this study, we looked at whether EHDV infection caused changes in survival or reproduction in infected midges. We also looked at whether EHDV could be passed from female midges to their offspring. Culicoides sonorensis midges (a known EHDV vector species) were fed blood containing EHDV and then several metrics associated with survival and reproduction were measured. Overall, we found that EHDV infection had no major impact on survival of the infected adult females, but it did affect egg hatch rates and larval survival of her offspring. We also found that female midges were able to spread EHDV to their offspring, although there is more work needed to confirm that this is happening in nature. These findings greatly improve our understanding of the relationship between midges and EHDV in North America.

Technical Abstract: Epizootic hemorrhagic disease virus (EHDV: Reoviridae: Orbivirus) is a Culicoides-borne pathogen that affects a variety of ruminants, causing significant economic losses and/or ecological impacts in animal agriculture and wildlife populations worldwide. In this study, we examined the effect of EHDV serotype-2 oral infection on the survival and reproduction of Culicoides sonorensis Wirth and Jones (a confirmed vector of EHDV in North America), and the potential vertical transmission of EHDV-2 in this midge species. Culicoides sonorensis females were fed on defibrinated bovine blood with EHDV-2 (5.5 log10 PFU/ml) or without EHDV-2 (control). Adult survival/longevity, oviposition rates, number of eggs deposited, egg hatch rates, larval survival, larval stage duration, eclosion rates, and sex-ratios of the progeny were recorded and compared between the two groups. In addition, the progeny (eggs and F1 adults) of the EHDV-2 infected females were processed for viral detection through RT-qPCR and plaque assays. Survival/longevity of the blood-fed adults, oviposition rates, number of eggs deposited, larval stage duration, eclosion rates, and sex-ratios were not significantly different between the two groups. However, egg hatch rates were significantly lower in the EHDV-2 infected group (35.8 ± 5.2%) than the uninfected group (74.5 ± 6.8%), but larval survival rates were higher in the EHDV-2 infected group (59.8 ± 4.9%) compared to the control group (34.1 ± 6.5%). EHDV-2 was detected in the eggs (3.4%, 1/29 females tested, Cq value 22.1) and F1 adult progeny (1.7%, 1/58 adults tested, Cq value 23.5) of the orally exposed females through RT-qPCR as well as plaque assays. Our findings suggest that EHDV-2 infection has no major impact on C. sonorensis survival/longevity or oviposition but has a significant negative effect on midge fecundity/fertility. Our study also provides evidence for the vertical transmission of EHDV-2 in C. sonorensis. However, salivary transmission of EHDV-2 from the vertically infected progeny and its significance in the epidemiology of hemorrhagic disease are currently unknown and remain to be examined in further studies. Overall, these findings collectively indicate that Orbivirus infection can negatively affect vector reproduction and that vertical transmission is a probable mechanism of overwintering of EHDV in North America.