Modoc Viral Infections in the Deer Mouse Peromyscus maniculatus

The pathogenesis of Modoc virus and its mechanism of transmission were investigated in Peromyscus maniculatus gambeli (deer mouse) as a model to understand the natural history of this virus. Animals were readily infected by the intranasal or subcutaneous route of inoculation. Virus could be detected by direct isolation techniques in many organs and body fluids during the first 7 to 9 days after intranasal inoculation. Increases in viral titers were detectable first in lungs and then the spleen, salivary-submaxillary glands, and lymph nodes. Viremias were low titered and ephemeral. Virus was recovered from urine and throat swabs 4 to 6 days and 4 to 7 days after inoculation, respectively. Serum dilution neutralization, hemagglutination inhibition, or complement fixation antibodies were detected in sera of some animals 13 days after infection and in all animals after 20 days. Antibodies persisted for the 168-day period of observation. Persistent viral infection was demonstrable by in vitro culturing of lungs or pooled lungs, salivary glands, and kidneys from 14 of 69 mice that were sacrificed from 1 to 6 months after intranasal inoculation. Attempts to demonstrate horizontal or vertical transmission of Modoc virus among mice were generally unsuccessful. Female deer mice infected with virus before mating passed maternal antibodies to their young.