Eastern Cottontail Rabbits (Sylvilagus floridanus) Develop West Nile Virus Viremias Sufficient for Infecting Select Mosquito Species

Abstract

The potential of the eastern cottontail rabbit (CTR; Sylvilagus floridanus) to contribute to an enzootic West Nile virus (WNV) cycle was demonstrated by characterizing the WNV viremia profile of 15 CTRs and demonstrating that mosquitoes could become infected by feeding on these CTRs. Eight CTRs were infected with a titer of 10^5.0 cell-infectious dose 50% endpoints (CID₅₀s) of WNV (NY99-Crow) by needle and seven CTRs by bite of one or more WNV-infected mosquitoes. There were no marked differences between the WNV viremia profiles of CTRs infected by either method. West Nile virus was detected in serums of all CTRs by 24 h p.i. The daily mean titers of all 15 CTRs on days 1–4 p.i. were 10^4.1±0.4, 10^4.7±0.3, 10^4.1±0.6, and 10^3.7±0.6 respectively, declining to 10^1.2±0.1 CID₅₀s/ml of serum by day 6 p.i. No virus was detected in the blood of any CTR on day 7 p.i. The average duration of WNV titers of ≥10^4.3 and 10^5.0 were 11.5 ± 5.5 and 21 ± 6.0%, respectively. These rates increased to 20.5 ± 6.4% and 25.0 ± 3.0% when CTR serum titers were >10^5.0 CID₅₀s/mL. Neither Aedes aegypti (L.) nor Aedes albopictus (Skuse) were infected by feeding on CTRs with titers of 10^5.0 CID₅₀s/ml. None of the CTRs infected by mosquito bite or by needle showed any symptoms of WNV disease. Vector Borne Zoonotic Dis. 5, 342–350.