Experimental Studies of Rio Grande Virus in Rodent Hosts

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  • Vector-Borne Diseases Division, Center for Infectious Diseases, Centers for Disease Control, Public Health Service, U.S. Department of Health and Human Services, Post Office Box 2087, Fort Collins, Colorado 80522
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Rio Grande (RG) virus, a new member of the Phlebotomus fever serogroup, was inoculated into wild wood rats (Neotoma micropus) and laboratory-reared cotton rats (Sigmodon hispidus) to determine if these potential hosts could be experimentally infected. Nine of 14 (64%) wood rats became viremic, with titers of circulating virus ranging from 102.3 to 105.3 plaque-forming units (PFU)/ml and a geometric mean titer of 103.7 PFU/ml. Virus was not detected in urine specimens from inoculated wood rats but was found in a single saliva specimen. RG virus was detected in the blood of 1 of 12 (8%) cotton rats. Neutralizing (N) antibody developed in 8 of 9 inoculated wood rats which survived for 30 days post-inoculation and in 11 of 12 cotton rats. N antibody was still detectable in 4 of 7 wood rats which survived for 1 year, and all 7 were resistant to rechallenge with the virus, as were 3 wood rats with naturally-acquired antibody. High mortality (36%) occurred in inoculated wood rats; whereas low mortality (8%) occurred in cotton rats. The specific cause of death of the rats was not determined. Modes of transmission of the virus in nature are discussed.