Systematic Veterinary Virology

VENEZUELAN EQUINE ENCEPHALITIS

• VEE virus infection may be expressed as
• Subclinical with no signs.
• Moderate and characterized primarily by anorexia, high fever, and depression.
• Severe but non-fatal, and characterized by anorexia, high fever, stupor, weakness, staggering, blindness, and, occasionally, permanent neurologic sequelae or
• Fatal, with the same clinical signs. In general, two forms of the disease exist:
• The fulminating form in which signs of generalized, acute, febrile disease predominate and
• The encephalitic form in which the more impressive signs of central nervous system (CNS) involvement usually dominate.
• An incubation period of 0.5 to 5 days precedes a rise in body temperature to 39-41°C (103-105°F), which is accompanied by a hard, rapid pulse and depression.
• The onset of VEE virus infection is characterised with fever, inappetence, and mild excitability, which progresses to depression, weakness, and ataxia followed by signs of encephalitis such as muscle spasms, chewing movements, incoordination, and convulsions.
• Early encephalitic signs include loss of both cutaneous neck reflexes and visual responsiveness; diarrhoea and colic may also develop.
• Some animals may stand quietly in their surroundings whereas others may wander aimlessly or press their heads against solid objects. A braced stance or circling may occur late in the disease.
• A characteristic paddling motion of the limbs may be observed with lateral recumbency. The course of the disease may be rapid with death ensuing within hours after the observation of the first clinical manifestations of encephalitis.