MATERIAL SAFETY DATA SHEET - INFECTIOUS SUBSTANCES

SECTION I - INFECTIOUS AGENT

NAME: St. Louis encephalitis

SYNONYM OR CROSS REFERENCE: SEV, SELV, Mosquito-borne encephalitis, arbovirus, viral encephalitis

CHARACTERISTICS: Family Flaviviridae (formerly Togaviridae), Flavivirus genus; 40-50 nm diameter, enveloped, positive sense ssRNA; Member of Japanese encephalitis (JE) antigenic complex

SECTION II - HEALTH HAZARD

PATHOGENICITY: Acute inflammatory disease of short duration involving brain, spinal cord and meninges; most infections are asymptomatic; severe infections marked by acute onset, headache, high fever, nausea, myalgia, and malaise, followed by meningeal signs, stupor, coma, convulsions and paralysis; children may develop urinary tract symptoms; severity increases with age, over 60 has the highest rate of acute encephalitis; fatality rate of 2-22%; HIV infection may be a risk factor; 30-50% of severe cases have prolonged convalescence.

EPIDEMIOLOGY: St. Louis encephalitis occurs in Northern, Southern and Central America; cases occur in temperate latitudes in summer and early fall and are commonly limited to areas and years of high temperature and many mosquitoes

HOST RANGE: Humans, wild birds, other mammals

INFECTIOUS DOSE: Unknown

MODE OF TRANSMISSION: By bite of infective mosquitoes

INCUBATION PERIOD: Usually 4-21 days

COMMUNICABILITY: Not directly transmitted from person to person; virus is not demonstrated in blood of human after onset of disease; viremia in birds 2-5 days; mosquitoes are infective for life

SECTION III - DISSEMINATION

RESERVOIR: Most likely birds; Overwinters possibly in birds, rodents, bats, reptiles, amphibians or surviving mosquito eggs or adults

ZOONOSIS: Yes, from infected animals via mosquitoes; infected animals are asymptomatic

VECTORS: Mosquitoes - Culex spp.
- C. pipiens, C. tarsalis, C, quinquefasciatus, C. nigripalpus

SECTION IV - VIABILITY

DRUG SUSCEPTIBILITY: N/A

SUSCEPTIBILITY TO DISINFECTANTS: Susceptible to disinfectants - 1% sodium hypochlorite, 2% glutaraldehyde, 3-8% formaldehyde, alcohol, iodine, phenol iodophors and organic solvents/detergents

PHYSICAL INACTIVATION: Inactivated by heat; reduced by 50% in 10 min at 50^o C, completely inactivated in 30 min at 56^o C; sensitive to UV and gamma irradiation

SURVIVAL OUTSIDE HOST: Stable in aerosol form for up to 6 hrs at room temperature

SECTION V - MEDICAL

SURVEILLANCE: Monitor for symptoms of arthropod-borne viral fever; serological identification and antibody titire

FIRST AID/TREATMENT: No specific treatment; supportive care

IMMUNIZATION: None

PROPHYLAXIS: None

SECTION VI - LABORATORY HAZARDS

LABORATORY-ACQUIRED INFECTIONS: At least 1 reported infection

SOURCES/SPECIMENS: Blood, CSF, urine and exudates

PRIMARY HAZARDS: Exposure to aerosols of infectious solutions and animal bedding, accidental parenteral inoculation, broken skin contact

SPECIAL HAZARDS: None

SECTION VII - RECOMMENDED PRECAUTIONS

CONTAINMENT REQUIREMENTS: Biosafety level 3 practices, containment equipment and facilities for activities using potentially infectious clinical materials and infected tissue culture, animals or arthropods

PROTECTIVE CLOTHING: Laboratory coat; gloves and gown with ties in back and tight wrists when working with agent

OTHER PRECAUTIONS: None

SECTION VIII - HANDLING INFORMATION

SPILLS: Allow aerosols to settle; wearing protective clothing, gently cover spill with paper towels and apply 1% sodium hypochlorite, starting at perimeter and working towards the centre; allow sufficient contact time before clean up

DISPOSAL: Decontaminate before disposal; steam sterilization, incineration

STORAGE: In sealed containers that are appropriately labelled (in a locked level 3 facility)

SECTION IX - MISCELLANEOUS INFORMATION

Date prepared: March, 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

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