4. 4
VEE - Subtypes
• 6 Subtypes (I, II, III, IV, V, VI)
– Subtype I – five varieties:
• IAB, IC, ID, IE, IF
• Epizootic strains / Enzootic strains
5. 5
VEE – Epizootic Strains
• Subtype I, variants AB or C
• (Subtype I, variants D or E?)
– Equine virulent
• High viremia in horses
– Equine epizootics precede human epidemics
– Produce disease in humans
– Inapparent infections in other domestic and wild
animals
7. 7
VEE – Enzootic Strains
• Subtype I, variants D, E, F
• Subtypes II, III, IV, V, VI
– Subtype II virus present in US (Florida)
• Not usually equine virulent
• Sporadic disease in humans
9. 9
Epizootic VEE History
• 1920 first described in Venezuela
• 1935-1950 – Sporadic outbreaks of epizootic
form in South America
• 1967-1971 – Epizootic form moved northern
South America to Texas
– 1971 Eradication/Control program in US
– 1972 “Last” isolation in Mexico
– 1973 “Last” isolation in Venezuela
10. 10
Epizootic VEE History (cont…)
• 1973-1992 No reports of epizootic form of VEE
– epizootic form considered eradicated
• 1992 Outbreak in Venezuela
• 1993-2000 Outbreaks in several South American
and Central American countries
• 2001 Outbreak in Colombia