The mechanism of transovarial transmission of San Angelo (SA) virus in Aedes albopictus was investigated. A mosquito line with SA virus filial infection rates of almost 100% was developed by selection. Results of crosses and back-crosses between this transovarial transmission-efficient line and noninfected mosquitoes indicated that SA virus was transmitted in Ae. albopictus by maternal inheritance. The infection status of the male parent was of no consequence; the virus was passed from generation to generation through the females. Transovarially infected mosquitoes contained less virus than insects infected by inoculation. The behavior of SA virus in Ae. albopictus was similar to that of sigma virus in Drosophila melanogaster, suggesting that some females in the transovarial transmission-efficient line had developed a chronic infection of their germinal cells (oogonia). Serial transovarial passage of SA virus in Ae. albopictus did not alter its plaque morphology, infectivity for mosquitoes, or pathogenicity for vertebrates. Transovarially infected mosquitoes transmitted the virus by bite to mice.
Present address: Yale Arbovirus Research Unit, Department of Epidemiology and Public Health, Yale University School of Medicine, 60 College Street, New Haven, Connecticut 06510.