The vector competence of Culex (Melanoconion) taeniopus was examined in the laboratory for “enzootic” allopatric and “epizootic” strains of Venezuelan equine encephalomyelitis viruses of hemagglutination inhibition subtypes I, II, III, and IV. Following bloodmeals from viremic hamsters, and extrinsic incubation of 20–22 days, mosquitoes were allowed to refeed for transmission attempts. Infection rates never exceeded 50% with oral doses of <104 chick embryo cell culture plaque forming units (CECPFU), and approached 100% only after ingestion of ≥105.5 PFU. Transmission was achieved for some “epizootic” subtype IABC and “enzootic” subtype ID strains after bloodmeals containing ≥103.4 CECPFU; subtypes II, III, and IV were never transmitted despite oral doses up to 105.0 CECPFU. These data contrast sharply with those reported previously for sympatric “enzootic” subtype IE Middle American Venezuelan encephalitis viruses.
Address reprint requests to: E. W. Cupp, Department of Entomology, Cornell University, Ithaca, New York 14853.