Chapter 7 - Murray Valley Encephalitis Virus

Abstract

Murray Valley encephalitis virus (MVEV) is a mosquito-borne encephalitic flavivirus. Culex mosquitoes are the major vectors of MVEV. Waterfowl, particularly herons and egrets, are the major reservoir hosts. Major outbreaks of MVEV-related encephalitis in humans occurred in 1917–18 and in the 1950s in Australia and Papua New Guinea. MVEV incidence is greater in seasons with heavy rainfall and flooding. Human infection is rare and often asymptomatic but may result in life-threatening neurological diseases, including encephalitis, cognitive impairment, seizures, hypotonia, and quadriplegia. Among those with encephalitis, approximately 50% of the survivors develop chronic neurological sequelae. Aboriginal children are especially vulnerable. While current treatment of severe cases involves supportive therapy in intensive care units, development of an effective drug targeting the MVEV serine protease is well underway. A licensed vaccine for Japanese encephalitis virus cross-protects against lethal challenge with MVEV. Care must be taken, however, to avoid antibody-dependent enhancement of disease.