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
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.