Efficient induction of persistent and prenatal parvovirus infection in rats

Parvoviruses are prevalent and disruptive infectious agents of laboratory rats. Risks to rat-based research from infection are increased by the persistence of virus in immune rats; and by prenatal transmission of infection. The mechanisms leading to viral persistence and prenatal infection are poorly understood and have been difficult to study for lack of reliable and humane induction methods. We report here protocols for inducing persistent and prenatal infection without causing clinical disease using the UMass strain of rat virus (RV), a common rat parvovirus. Infant rats inoculated by the oronasal route at 6 days of age had greater than 90% prevalence of persistent infection. RV-UMass also induced intrauterine infection in pregnant rats inoculated by the oronasal route. Inoculation of dams at gestation day 9 frequently caused severe disease in the fetuses whereas inoculation at gestation day 12 caused primarily asymptomatic fetal infection that persisted post partum. RV-UMass infection facilitates study of parvoviral-host interactions that are relevant to laboratory rats and which also may improve understanding of persistent and prenatal human parvovirus infection.