Fig. 6.

Enzootic and epizootic/epidemic transmission cycles of Venezuelan equine encephalitis virus (VEEV). The enzootic transmission cycle of VEEV is maintained among rodents and other vertebrates (e.g., cotton rats, spiny rats, bats, and opossums) as reservoirs and mosquitoes in the subgenus Culex (Melanoconion) as primary vectors. In contrast, epizootic VEEV strains are transmitted by several mosquito vectors (e.g., Aedes and Psorophora spp.) to susceptible amplification hosts, horses. During epizootic or epidemic cycles, horses are efficient amplification hosts with high titered viremia for mosquito transmission.