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Title: GRASSHOPPERS CAN SERVE AS RESERVOIRS AND VECTORS OF VESICULAR STOMATITIS VIRUS

Author
item NUNAMAKER, RICHARD - USDA, ARS, RETIRED
item LOCKWOOD, J - UNIV OF WYO, ENTOM
item Stith, Charles
item Campbell, Corey
item Drolet, Barbara
item Wilson, William - Bill
item White, David
item Letchworth, Geoffrey

Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2003
Publication Date: 11/1/2003
Citation: Nunamaker, R.A., Lockwood, J.A., Stith, C.E., Campbell, C.L., Drolet, B.S., Wilson, W.C., White, D.M., Letchworth III, G.J. 2003. Grasshoppers can serve as reservoirs and vectors of vesicular stomatitis virus. Journal of Medical Entomology. 40:957-963.

Interpretive Summary: Vesicular stomatitis (VS) is an economically devastating disease of livestock in the Americas. Despite strong circumstantial evidence for the role of insects in the VS disease cycle, no biting insect model explains the field evidence. Based on the space-and-time association of grasshopper outbreaks and VS disease cycles, we investigated the potential role of these insects as vectors and reservoirs of the disease. The critical steps in the grasshopper-cow transmission cycle were demonstrated, including: 1) 62% of grasshoppers (Melanoplus sanguinipes) fed vesicular stomatitis virus (VSV) became infected, with titers reaching 40,000-times the inoculative dose, 2) 40% of grasshoppers that cannibalized VSV-infected grasshopper cadavers became infected, amplifying virus up to 1000 fold, 3) 1 of 3 cattle consuming VSV-infected grasshopper cadavers contracted typical VS and shed virus in saliva, and 4) 15% of grasshoppers became infected when fed saliva from this infected cow. The ecological conditions and biological processes necessary for these transmissions to occur are present throughout much of the Americas.

Technical Abstract: Vesicular stomatitis (VS) is an economically devastating disease of livestock in the Americas. Despite strong circumstantial evidence for the role of arthropods in epizootics, no hematophagous vector explains the field evidence. Based on the spatiotemporal association of grasshopper outbreaks and VS epizootics, we investigated the potential role of these insects as vectors and reservoirs of the disease. The critical steps in the grasshopper-bovine transmission cycle were demonstrated, including: 1) 62% of grasshoppers (Melanoplus sanguinipes) fed vesicular stomatitis virus (VSV) from cell culture became infected, with titers reaching 40,000-times the inoculative dose, 2) 40% of grasshoppers that cannibalized VSV-infected grasshopper cadavers became infected, amplifying virus up to 1000 fold, 3) 1 of 3 cattle consuming VSV-infected grasshopper cadavers contracted typical VS and shed virus in saliva, and 4) 15% of grasshoppers became infected when fed saliva from this infected cow. The ecological conditions and biological processes necessary for these transmissions to occur are present throughout much of the Americas. Field studies will be required to show these findings are relevant to the natural epidemiology of VSV.