An Embryonated Egg Transmission Model for Epizootic Hemorrhagic Disease Virus

Area of Science:

• Veterinary Virology
• Arthropod-borne Viruses
• Infectious Disease Transmission

Background:

• Epizootic hemorrhagic disease virus (EHDV) is a significant orbivirus affecting ruminants, particularly white-tailed deer in North America.
• EHDV is transmitted by biting midges of the genus *Culicoides*.
• Embryonated chicken eggs (ECE) have emerged as a model for studying vector competence of *Culicoides* for other orbiviruses.

Purpose of the Study:

• To evaluate the applicability of the embryonated chicken egg (ECE) model for assessing vector competence of *Culicoides* species for North American Epizootic Hemorrhagic Disease Virus (EHDV) serotypes.
• To determine if ECEs can support EHDV replication and subsequent transmission to vectors.
• To assess the completion of the EHDV transmission cycle using the ECE model.

Main Methods:

• Infection of embryonated chicken eggs (ECEs) with North American EHDV serotypes (EHDV-1, -2, and -6).
• Exposure of *Culicoides sonorensis* midges to EHDV-infected ECEs to assess transmission.
• Exposure of naive ECEs to EHDV-infected *C. sonorensis* to evaluate the completion of the transmission cycle.

Main Results:

• All three North American EHDV serotypes replicated within ECEs.
• EHDV was successfully transmitted from infected ECEs to *Culicoides sonorensis*.
• The complete transmission cycle, from infected *C. sonorensis* to uninfected ECEs, was achieved for EHDV-1 and EHDV-2.

Conclusions:

• The embryonated chicken egg (ECE) model is suitable for studying the vector competence of *Culicoides* species for North American Epizootic Hemorrhagic Disease Virus (EHDV).
• The ECE model facilitates research into EHDV transmission dynamics and the development of control strategies.
• This study validates a novel approach for investigating orbivirus-vector interactions.