NAME: Eastern equine encephalitis virus, Western equine encephalitis virus
SYNONYM OR CROSS REFERENCE: Eastern equine encephalomyelitis, Western equine encephalomyelitis, EEE, WEE, arbovirus
CHARACTERISTICS: 60 - 70 nm diameter, posititive ssRNA, enveloped; Togaviridae, Genus Alphavirus
PATHOGENICITY: Acute inflammatory disease of short duration involving brain, spinal cord, and meninges; EEE mild cases often occur as febrile headache or aseptic meningitis; severe infections are marked by acute onset, headache, high fever, meningeal signs, stupor, disorientation, coma, tremors, occasional spastic convulsions and paralysis; up to 60% case fatality rate; WEE infections are asymptomatic or present as mild, nonspecific illness, mortality rate is about 3%
EPIDEMIOLOGY: EEE in eastern and north central USA and Canada, scattered areas of Central and South America and in Caribbean; WEE in western and central USA, Canada and parts of South America (Argentina); cases occur in temperate latitudes in summer and early fall, and are limited to areas and years of high temperature and many mosquitoes
HOST RANGE: Humans, horses, other animals, birds
INFECTIOUS DOSE: Unknown
MODE OF TRANSMISSION: By the bite of infective mosquitoes
INCUBATION PERIOD: Usually 5 to 15 days
COMMUNICABILITY: Not directly transmitted from person-to-person; virus is usually not demonstrated in blood or CSF of humans after onset of disease; viremia in birds lasts 2 to 5 days; mosquitoes are infective for life, possible vertical transmission (female to egg); viremia in horses rarely present in high titres for long periods
RESERVOIR: Humans and horses are uncommon sources of mosquito infection; virus overwinters possibly in birds, other animals (rodents, bats, reptiles, amphibians), surviving mosquito eggs or adults (true reservoir unknown)
ZOONOSIS: Yes, from infected animals / birds via mosquitoes
VECTORS: EEE - Culiseta melanura ( USA
and Canada) (bird to bird)
- Aedes, Coquillettidia spp. (bird or animal to
humans)
WEE - Culex tarsalis (Western USA and Canada) (major
epidemic vector)
- found in at least 5 genera of mosquitoes
DRUG SUSCEPTIBILITY: N/A
SUSCEPTIBILITY TO DISINFECTANTS: Susceptible to disinfectants - 1% sodium hypochlorite, 2% glutaraldehyde, formaldehyde, 70% ethanol
PHYSICAL INACTIVATION: Sensitive to moist and dry heat, drying
SURVIVAL OUTSIDE HOST: Does not survive outside of host
SURVEILLANCE: Monitor for symptoms of arthropod-borne viral fever; serological identification and antibody titre, PCR, ELISA
FIRST AID/TREATMENT: No specific treatment
IMMUNIZATION: Investigational vaccines available and recommended for personnel who work directly and regularly with EEE and WEE in laboratory
PROPHYLAXIS: WEE immune globulin (human) available but efficacy of product has not been established
LABORATORY-ACQUIRED INFECTIONS: EEE - 4 reported cases; WEE - 7 reported cases with 2 deaths (associated with egg cultures, suckling mice and aerosols - broken lyophilized material)
SOURCES/SPECIMENS: Blood, CSF, central nervous system and other tissues, infected arthropods
PRIMARY HAZARDS: Accidental parenteral inoculation, contact with broken skin or mucous membranes, bites of infected laboratory arthropods, infectious aerosols
SPECIAL HAZARDS: Infection of newly hatched chickens is especially hazardous
CONTAINMENT REQUIREMENTS: Biosafety level 3 practices, safety equipment, and facilities for activities with potentially infectious clinical materials and arthropods, for manipulations of infected tissue cultures, embryonated eggs and rodents and for infection of newly hatched chickens
PROTECTIVE CLOTHING: Laboratory coat; gloves and gown with tight wrists and tie in back should be worn while working with infectious materials
OTHER PRECAUTIONS: Vaccination of personnel working directly and regularly with EEE and WEE
SPILLS: Allow aerosols to settle; wearing protective clothing, gently cover spill with paper towel and apply 1% sodium hypochlorite, starting at perimeter and working towards the centre; allow sufficient contact time before clean up (30 min)
DISPOSAL: Decontaminate before disposal; steam sterilization, incineration
STORAGE: In sealed containers that are appropriately labelled (in locked level 3 facility)
Date prepared: January, 2001
Prepared by: Office of Laboratory Security, PHAC
Although the information, opinions and recommendations contained in this Material Safety Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.
Copyright ©
Health Canada, 2001