CHARACTERIZATION OF MODULATION OF WESTERN EQUINE ENCEPHALOMYELITIS VIRUS BY CULEX TARSALIS (DIPTERA, CULICIDAE) MAINTAINED AT 32-DEGREES-C FOLLOWING PARENTERAL INFECTION

Two lines of Culex tarsalis Coquillett genetically selected for low; o r high western equine encephalomyelitis (WEE) virus production (low vi ral producer [LVP] or high viral producer [HVP], respectively) modulat ed WEE (i.e., decreased the concentration of virus to <10(4) plaque-fo rming units after intrathoracic inoculation). The LVP line modulated W EE more than HVP, and modulation was most pronounced at 32 degrees C. At 15 degrees C, viral replication to high titers occurred in both lin es. When infected LVP were transferred to 15 degrees C after id extrin sic incubation at 32 degrees C, replication of WEE to high titers did not occur, Mosquitoes transferred ed from 15 degrees C after replicati on to high titers occurred. to 32 degrees C did significantly modulate WEE titer. Incubation at 32 degrees C prior to infection had no effec t on the degree or timing of WEE modulation in both LVP and HVP lines, Most LW infected following feeding on a high dose of WEE had salivary gland infection barriers. Viral modulation by Cs. tarsalis was an alp havirus phenomenon, and was not restricted to WEE.