Experimental oral and nasal transmission of rabies virus in mice

Weanling female white Swiss mice were exposed to challenge virus standard rabies virus and street virus isolates from various domestic and wild animals. Virus was given free choice as suspension or as infected mouse brain by stomach tube, by single injection of suspension into the oral cavity of unanesthetized mice, by repeated injection into the oral cavity of anesthetized mice and by single application to the external nares of anesthetized mice. Challenge virus standard virus in mouse brain suspension and a suspension of skunk salivary glands infected with street virus (titers greater than or equal to 10(6)MICLD50/0.03 ml) consistently produced high rates of infection in mice exposed intranasally, low to high rates of infection in mice exposed by forced feeding and other artificial methods of oral exposure and very low rates of infection when given free choice. Street virus isolates passaged intracerebrally in mice had titers less than or equal to 10(4.5) MICLD50/0.03 ml and rarely caused rabies in mice exposed orally or nasally by any method. The results indicate that with the isolates used, virus of high titer (greater than or equal to 10(6)MICLD50/0.03 ml) is required to consistently produce infection in mice by the nasal route and that the mucosa of the nasal cavity probably is the chief route of infection even after oral administration.