Experimental Infection of Eastern Gray Squirrels (Sciurus carolinensis) with West Nile Virus

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Experimental Infection of Eastern Gray Squirrels (Sciurus carolinensis) with West Nile Virus

Andrés Gómez^*, Laura D. Kramer, Alan P. Dupuis, II, A. Marm Kilpatrick, Lauren J. Davis, Matthew J. Jones, Peter Daszak, AND A. Alonso Aguirre
Columbia University, New York, New York; Wadsworth Center, NewYork State Department of Health, Albany, New York; The Consortiumfor Conservation Medicine, New York, New York; Department ofEcology and Evolutionary Biology, University of California,Santa Cruz, California; Wildlife Trust, New York, New York

Eastern gray squirrels (Sciurus carolinensis) have shown highWest Nile virus (WNV) seroprevalence, and WNV infection hasbeen suggested as a cause of morbidity and mortality in thisspecies. We experimentally infected nine eastern gray squirrelswith WNV to determine the clinical effects of infection andto assess their potential role as amplifying hosts. We observedno morbidity or mortality attributable to WNV infection, butlesions were apparent in several organs. We detected mean viremiasof 10^5.1 and 10^4.8 plaque-forming units (PFU)/mL on days 3 and4 post-infection (DPI) and estimated that ~2.1% of Culex pipiensfeeding on squirrels during 1–5 DPI would become infectious.Thus, S. carolinensis are unlikely to be important amplifyinghosts and may instead dampen the intensity of transmission inmost host communities. The low viremias and lack of mortalityobserved in S. carolinensis suggest that they may be usefulas sentinels of spillover from the enzootic amplification cycle.

Received March 10, 2008. Accepted for publication June 2, 2008.

Acknowledgments: We thank K. Platt, J. Root, and the staff atthe Wildlife Center of Virginia for kindly sharing their restraintand husbandry protocols with us. We also thank M. Behr for invaluableassistance with tissue processing and microscopic pathology.We are grateful to R. Waniewski, F. Blaisdell, K. Bernard, A.Jones, R. Smith, and the animal care staff at the WadsworthCenter for advice and logistical support. Two anonymous reviewersprovided comments that improved an original version of thismanuscript.

Financial support: This work was funded by NIAID contract #NO1-AI-25490,NSF grant EF-0622391 as part of the joint NSF-NIH Ecology ofInfectious Disease program, a Columbia University Graduate Schoolof Arts and Sciences Faculty Fellowship, and the Whitley Fundfor Nature.

^* Address correspondence to Andrés Gómez, Departmentof Ecology, Evolution and Environmental Biology, Columbia University,1200 Amsterdam Avenue, MC 5557, New York, NY 10027. E-mail:ag2112{at}caa.columbia.edu

Authors’ addresses: Andrés Gómez, Departmentof Ecology, Evolution and Environmental Biology, Columbia University,1200 Amsterdam Avenue, MC 5557, New York, NY 10027, Tel: 212-854-9987,E-mail: ag2112{at}caa.columbia.edu Laura D. Kramer, Alan P. DupuisII, Lauren J. Davis, and Matthew J. Jones, Griffin Laboratory,Wadsworth Center, New York State Department of Health, 5668State Farm Road, Guilderland, NY 12084, Tel: 518 869-4500, E-mails:ldk02{at}health.state.ny.us, apd05{at}health.state.ny.us, ljd03{at}health.state.ny.us,and mjj05{at}health.state.ny.us. A. Marm Kilpatrick, Departmentof Ecology and Evolutionary Biology, University of California,A308 Earth and Marine Sciences, Santa Cruz, CA 95064, Tel: 845596 7474, E-mail: marm{at}biology.ucsc.edu. Peter Daszak, The Consortiumfor Conservation Medicine, 460 West 34th Street, 17th Floor,New York, NY 10001, Tel: 212-380-4473, E-mail: daszak{at}conservationmedicine.org.A. Alonso Aguirre, Wildlife Trust, 460 West 34th Street, 17thFloor, New York, NY 10001, Tel: 212-380-4460, E-mail: aguirre{at}wildlifetrust.org.

Reprint requests: Andrés Gómez, Department ofEcology, Evolution and Environmental Biology, Columbia University,1200 Amsterdam Avenue, MC 5557, New York, NY 10027, Tel: 212-854-9987,E-mail: ag2112{at}caa.columbia.edu.