Abstract. Three populations of Aedes dorsalis were selected which transmitted California encephalitis (CE) virus vertically to over 90% of their progeny. Infected progeny in these subpopulations transmitted virus at similar rates through five generations; females from the last generation transmitted virus by bite to suckling mice. These high rates of vertical transmission appeared to be due to the development of a stabilized infection with CE virus rather than to genetic selection for a more efficient transmitter or for a mutant strain of virus. In contrast, female Ae. dorsalis and Aedes melanimon infected by intrathoracic inoculation developed nonstabilized infections and transmitted virus vertically to approximately 20% of their progeny. The existence of stabilized infections of CE virus in vector populations and its implications for the natural history of CE virus and on the Fine and LeDuc model are discussed.
Present address: Department of Arboviral Entomology, U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, Maryland 21701.