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Title: Potential for Transovarial Transmission of Vesicular Stomatitis Virus in the biting midge, Culicoides sonorensis

item Drolet, Barbara
item Stuart, Melissa

Submitted to: American Society for Virology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/4/2007
Publication Date: 6/15/2007
Citation: Drolet, B.S., Stuart, M.A., Langner, K. 2007. Potential for Transovarial Transmission of Vesicular Stomatitis Virus in the biting midge, Culicoides sonorensis. American Society for Virology Meeting. Corvallis, OR. July 13-18, 2007.

Interpretive Summary:

Technical Abstract: Vesicular stomatitis virus (VSV) is an insect transmitted rhabdovirus which causes economically devastating disease in cattle and horses in the western U.S. Important insect vectors identified thus far include Lutzomyia shannoni sand flies, Simulium vittatum black flies, and Culicoides sonorensis biting midges. Outbreak years occur sporadically and reflect insect feeding seasonality with new clinical cases beginning in late summer and ending shortly after the first hard frost in the fall. For the past 25 years, however, the majority of outbreaks have recurred for two or even three years in a row (’82-’83, ’95, ’97-’98, ’04-’06). It is unknown whether this “overwintering” of the virus occurs in persistently infected livestock, in some as yet determined wild animal population, or in overwintering insect larvae infected by vertical or transovarial transmission (TOT). Although anecdotal field evidence suggests that TOT by competent vectors may play a role in VSV epidemiology, it has only been demonstrated in sand flies. By immunohistochemistry and in situ hybridization, we have shown that VSV readily infects and replicates in the eggs and ovarial tissues of Culicoides midges. Additionally, cell lines derived from embryos of Culicoides are susceptible to VSV, resulting in a persistent, productive infection with little to no cytopathology. This suggests virus infection in adult females may not be harmful to their developing eggs, increasing the likelihood that healthy, infected progeny would result. To determine the potential for TOT in Culicoides midges, females were infected per os with VSV and allowed to complete one or more oviposition cycles. Developmental stages of the F1 progeny were examined for viral infection by real time PCR and virus isolation. Preliminary results suggest that VSV is transovarially transmitted in Culicoides sonorensis biting midges. There are currently no VSV outbreak control recommendations to address possibly infected overwintering stages of VSV transmission vectors. Implications for the control of disease outbreaks, with regards to TOT, will be discussed.