MURRAY VALLEY ENCEPHALITIS

PATHOGEN SAFETY DATA SHEET - INFECTIOUS SUBSTANCES

SECTION I - INFECTIOUS AGENT

NAME: Murray Valley encephalitis

SYNONYM OR CROSS REFERENCE: MVE, Australian X disease, Australian encephalitis, mosquito-borne encephalitis, viral encephalitis, arbovirus

CHARACTERISTICS: This virus is part of the Flavivirus genus and is an enveloped, spherical, positive-strand RNA virus^(1,2,3). It has an icosahedral nucleocapsid and is between 40-70 nm in diameter^(3,4).

SECTION II – HAZARD IDENTIFICATION

PATHOGENICITY/TOXICITY: Lasting usually 2 weeks, the disease is characterized by a rapid onset of 2-5 days of fever, headache, myalgia, malaise, anorexia and nausea before neurological complications occur^(1,5,6). CNS complications involve the brain, brain stem and spinal cord and include photophobia, numbness, stiff neck, encephalitis, paralysis (including respiratory paralysis), meningismus, spastic quadriplegia, coma and seizures^(1,3,5,6,7). The disease can be life threatening and is more severe and common in children and aboriginal populations⁽⁴⁾. 20 % of patients die and 50 % are left with lasting psychological and neurological complications such as cerebellar and extrapyramidal movement disorders, and cranial palsies^(1,3,6).

EPIDEMIOLOGY: The MVE virus is present in Australia and New Guinea. The last major outbreak occurred in Australia in 1974 (58 cases with 13 deaths)⁽¹⁾. From 2001- 2006, two clinical cases were reported each year in Australia; however, most cases are asymptomatic with one clinical case for every 500-1000 infections⁽¹⁾. The disease usually occurs from February to April⁽⁶⁾.

HOST RANGE: Humans, mosquitoes, herons, pelicans, cattle, horses, some marsupials, monkeys, sheep, feral pigs, mice and hamsters have been shown to contain the infectious agent^(1,4,5,6,8).

INFECTIOUS DOSE: Unknown.

MODE OF TRANSMISSION: The disease is spread through the bite of infectious mosquitoes.^(2,6). Aerosol transmission may be possible, as Flaviviruses have been shown to be spread through aerosols.

INCUBATION PERIOD: The incubation period is between 5 and 28 days⁽¹⁾.

COMMUNICABILITY: The virus is not directly transmitted from person-to-person and most arboviruses produce low levels of viraemia that are very hard to detect^(3,9,10). In chickens viraemia can last between 12-48h⁽⁹⁾.

SECTION III - DISSEMINATION

RESERVOIR: Water birds such as herons and pelicans (particularly the night heron Nycticorax caledonicus ) are the main reservoir for this virus; however, cattle, horses, and feral pigs may also act as reservoirs^(1,4,5,6,8).

ZOONOSIS: Yes, from infected animals via mosquitoes. Infected animals can carry the disease without any clinical manifestations and transmit it to mosquitoes during a blood meal⁽⁶⁾.

VECTORS: The Culex (particularly Culex annulirostris ) and Aedes mosquitoes are vectors for the disease^(1,6).

SECTION IV – STABILITY AND VIABILITY

DRUG SUSCEPTIBILITY: None known

SUSCEPTIBILITY TO DISINFECTANTS: Susceptible to 1 % sodium hypochlorite, 2 % glutaraldehyde, 4 % formaldehyde, 70 % ethanol or propanol, 2-5 % phenol compounds, 2 % peracetic acid, 0.16 % iodine and 3-6 % hydrogen peroxide⁽¹¹⁾.

PHYSICAL INACTIVATION: Inactivated by heat with a 50 % reduction in 10 min at 50^o C and complete inactivation in 30 min at 56^o C⁽⁵⁾. The infectious agent can also be inactivated by UV and gamma irradiation^(5,12).

SURVIVAL OUTSIDE HOST: Not known.

SECTION V – FIRST AID / MEDICAL

SURVEILLANCE: Monitor for symptoms. Confirm with PCR, serology or ELISA^(3,5,6).

Note: All diagnostic methods are not necessarily available in all countries.

FIRST AID/TREATMENT: No specific treatment is available; however, intensive supportive care may be required to treat symptoms^(4,6).

IMMUNIZATION: None^(4,6).

PROPHYLAXIS: Avoid mosquito bites and use insect repellent⁽⁷⁾.

SECTION VI - LABORATORY HAZARDS

LABORATORY-ACQUIRED INFECTIONS: There have been 3 cases of laboratory- acquired infections reported by SALS⁽¹⁰⁾.

SOURCES/SPECIMENS: Blood, urine, exudates and CSF contain the infectious agent⁽¹⁰⁾.

PRIMARY HAZARDS: Exposure to infectious aerosols, accidental parenteral inoculation and contact with broken skin are the primary hazards when working with this agent^(2,10).

SPECIAL HAZARDS: None.

SECTION VII – EXPOSURE CONTROLS / PERSONAL PROTECTION

RISK GROUP CLASSIFICATION: Risk group 3⁽¹³⁾.

CONTAINMENT REQUIREMENTS: Containment Level 3 facilities, equipment, and operational practices for work involving infectious or potentially infectious materials, tissue cultures, animals, or arthropods.

PROTECTIVE CLOTHING: Personnel entering the laboratory should remove street clothing and jewellery, and change into dedicated laboratory clothing and shoes, or don full coverage protective clothing (i.e., completely covering all street clothing). Additional protection may be worn over laboratory clothing when infectious materials are directly handled, such as solid-front gowns with tight fitting wrists, gloves, and respiratory protection. Eye protection must be used where there is a known or potential risk of exposure to splashes⁽¹⁴⁾.

OTHER PRECAUTIONS: All activities with infectious material should be conducted in a biological safety cabinet (BSC) or other appropriate primary containment device in combination with personal protective equipment. Centrifugation of infected materials must be carried out in closed containers placed in sealed safety cups, or in rotors that are loaded or unloaded in a biological safety cabinet. The use of needles, syringes, and other sharp objects should be strictly limited. Open wounds, cuts, scratches, and grazes should be covered with waterproof dressings. Additional precautions should be considered with work involving animals or large scale activities⁽¹⁴⁾.

SECTION VIII - HANDLING AND STORAGE

SPILLS: Allow aerosols to settle and, wearing protective clothing, gently cover spill with paper towels and apply appropriate disinfectant, starting at the perimeter and working towards the centre. Allow sufficient contact time before clean up (30 min)⁽¹⁴⁾.

DISPOSAL: Decontaminate all materials before disposal by steam sterilization or incineration⁽¹⁴⁾.

STORAGE: The infectious agent should be stored in a sealed and identified container in a level 3 containment laboratory⁽¹⁴⁾.

SECTION IX – REGULATORY AND OTHER INFORMATION

REGULATORY INFORMATION: The import, transport, and use of pathogens in Canada is regulated under many regulatory bodies, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment Canada, and Transport Canada. Users are responsible for ensuring they are compliant with all relevant acts, regulations, guidelines, and standards.

UPDATED: September 2010

PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada.

Although the information, opinions and recommendations contained in this Pathogen 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 ©
Public Health Agency of Canada, 2010
Canada

REFERENCES:

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3. Murray, P. R., Baron, E. J., Jorgensen, J. H., Landry, M. L., & Pfaller, M. A. (Eds.). (2007). Manual of Clinical Microbiology (9th ed.). Washington: ASM Press.
    
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8. Solomon, T., & Mallewa, M. (2001). Dengue and other emerging flaviviruses. The Journal of Infection, 42 (2), 104-115. doi:10.1053/jinf.2001.0802
    
9. Kay, B. H., Young, P. L., Hall, R. A., & Fanning, I. D. (1985). Experimental Infection with Murray Valley Encephalitis Virus. Pigs, Cattle, Sheep, Dogs, Rabbits, Macropods and Chickens. Australian Journal of Experimental Biology and Medical Science, 63
    
10. Fleming, D. O., Richardson, J. H., Tulis, J. J., & Vesley, D. (Eds.). (1995). Laboratory Safety Principles and Practices (2nd ed.). Washington: American Society for Microbiology.
     
11. Collins, C. H., & Kennedy, D. A. (Eds.). (1983). Laboratory-acquired Infections (4th ed.). Oxford: Butterworth-Heinermann.
     
12. Block, S. S. (Ed.). (2001). Disinfection, Sterilization, and Preservation (5th ed.). Philidelphia: Lippincott Williams & Wilkins.
     
13. Human pathogens and toxins act. S.C. 2009, c. 24, Second Session, Fortieth Parliament, 57-58 Elizabeth II, 2009. (2009).
     
14. Public Health Agency of Canada. (2004). In Best M., Graham M. L., Leitner R., Ouellette M. and Ugwu K. (Eds.), Laboratory Biosafety Guidelines (3rd ed.). Canada: Public Health Agency of Canada.