Systematic Veterinary Virology

VENEZUELAN EQUINE ENCEPHALITIS

• VEE occurs as an epizootics in horses. VEE virus variants I-D to I-F and subtypes II through VI of VEE virus are associated with a rodent-mosquito transmission, in which human beings and horses are only incidentally get affected.
• Many species of mosquitoes under the genera Aedes, Anopheles, Culex, Deinocerites, Mansonia, and Psorophora and other hematophagous insects are involved in the explosive outbreaks.
• Horses are the most important amplifiers of VEE virus during epizootics due to the extremely high viraemias that they develop and the large numbers of hematophagous insects that can feed on an animal of such size. Human beings do not have a significant role in the maintenance and amplification of VEE virus.
• After inoculation by the vector, the virus travels via the lymphatics to lymph nodes and replicates in macrophages and neutrophils, resulting in lymphopenia, leukopenia, and fever. Subsequent replication occurs in other organs and is associated with viremia.