Virological and serological responses of sheep and cattle to experimental Schmallenberg virus infection

Authors: ENDALEW, ABAINEH - Kansas State University; MOROZOV, IGOR - Kansas State University; DAVIS, ANNE - Kansas State University; GAUDREAULT, NATASHA - Kansas State University; WERNIKE, KERSTIN - Friedrich-Loeffler-institut; BAWA, BHUPINDER - Abbvie; RUDER, MARK - University Of Georgia; Drolet, Barbara; McVey, David; SHIVANNA, VINAY - Kansas State University; MA, WENJUN - Kansas State University; FABURAY, BONTO - Kansas State University; Wilson, William - Bill; RICHT, JUERGEN - Kansas State University

Submitted to: Vector-Borne and Zoonotic Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2018
Publication Date: 8/23/2018
Citation: Endalew, A., Morozov, I., Davis, A.S., Gaudreault, N.N., Wernike, K., Bawa, B., Ruder, M.G., Drolet, B.S., McVey, D.S., Shivanna, V., Ma, W., Faburay, B., Wilson, W.C., Richt, J.A. 2018. Virological and serological responses of sheep and cattle to experimental Schmallenberg virus infection. Vector-Borne and Zoonotic Diseases. 18:697-703. https://doi.org/10.1089/vbz.2018.2297.
DOI: https://doi.org/10.1089/vbz.2018.2297

Interpretive Summary: Schmallenberg virus (SBV) emerged in Germany in late 2011 and was mostly associated with a mild transient disease of sheep and cattle. SBV is transmitted by biting midges and causes abortions, stillbirths and congenital defects in naïve pregnant ruminants. Two separate studies were conducted with a primary objective of developing an experimental infection model to understand responses of sheep and cattle to infection. The secondary objective was to produce biological reagents for use in future vaccine and diagnostics research. These studies were carried out using the following infectious inocula: (i) infectious serum (ii) cell culture-grown virus, and (iii) infectious lamb brain homogenate. Isolation of the virus post-infection was only from all cattle inoculated with infectious serum and one sheep inoculated with cell culture-derived virus. Antibodies to the virus were detected in both species. No specific clinical lesions were observed in either study. In conclusion, these studies highlighted the differences in two host species responses to infection.

Technical Abstract: Schmallenberg virus (SBV) is an orthobunyavirus in the Simbu serogroup that emerged in Germany in late 2011 and was mostly associated with a mild transient disease of sheep and cattle. SBV is transmitted by biting midges (Culicoides species) and causes abortions, stillbirths and congenital defects in naïve pregnant ruminants. Two separate studies were conducted with a primary objective of better understanding the virological and serological responses of sheep and cattle to different SBV isolates after experimental infection. The second objective was to produce immunoreagents and challenge materials for use in future vaccine and diagnostics research. These studies were carried out using the following infectious inocula: (i) infectious serum (ii) cell culture-grown virus, and (iii) infectious lamb brain homogenate. The responses were assessed in both species throughout the course of the experiment. SBV RNA in serum (RNAemia) was detected as early as 2 (in sheep) and 3 (in cattle) days post-infection (dpi) and peaked on 3 and 4 dpi in cattle and sheep, respectively. Cattle had higher levels of RNAemia compared to sheep. Experimental infection with infectious serum resulted in the highest level of RNAemia in both species followed by cell culture-grown virus. A delayed, low level RNAemia was detected in cattle inoculated with infectious sheep brain. Isolation of SBV was only possible from 4 dpi sera from all cattle inoculated with infectious serum and one sheep inoculated with cell culture-derived virus. SBV neutralizing antibodies were first detected on 14 dpi in both species. No specific gross and microscopic lesions were observed in either study. In conclusion, these studies highlighted not only the difference in viremia and anti-SBV antibody level against the different SBV isolates, but also the extent of the response in the two host species.