Pathogen Safety Data Sheet - Venezuelan Equine Encephalomyelitis (VEE)

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SECTION I: DISEASE / INFECTIOUS AGENT

SYNONYM / CROSS REFERENCE: Venezuelan encephalitis, Venezuelan equine encephalitis ⁽¹⁾ VEE ⁽²⁾

ETIOLOGY / TAXONOMY:
Family: Togaviridae ⁽¹⁾
Genus: Alphavirus ⁽¹⁾
Species: VEE virus

ORGANISM CHARACTERISTICS:

• Single stranded enveloped RNA virus ^(1,3)
• 70 nm diameter ⁽³⁾
• Six subtypes (I to VI); subtype I has five antigenic variants ^(1,2)
• Variants I-AB and I-C are highly virulent for equines and are responsible for epizootics/epidemics ^(1,2)
• Variants I-D, I-E, I-F, and subtypes II, III, IV, V, and VI are the enzootic strains that are not pathogenic for equines ^(1,2)

SURVEILLANCE:

Venezuelan equine encephalomyelitis is a reportable disease in Canada. Animal owners, veterinarians and laboratories are required to immediately report the presence of an animal that is contaminated or suspected of being contaminated to a CFIA district veterinarian. Control or eradication measures will be applied immediately (http://laws.justice.gc.ca/en/H-3.3/fulltoc.html).

DISTRIBUTION:

• The status of VEE in Canada is non-indigenous
• Endemic in South and Central America and Trinidad ^(1,4)
• Enzootic subtypes are found in Florida, the Rocky Mountains and northern plains of the United States ⁽⁴⁾
• Epizootic VEE is foreign to the United States and Canada

SECTION II: ANIMAL HEALTH HAZARD AND EPIDEMIOLOGY

CLINICAL DISEASE / PATHOGENESIS:

1) Clinical signs: ⁽⁴⁾

• Septicaemic disease ^(3,5)

  Humans:

  • Acute, mild systemic illness (flu-like)
  • Fever, generalized malaise, severe headache, photophobia and myalgia, particularly in the legs and lumbosacral region; symptoms last for 24 to 72 hours
  • May be followed by a cough, sore throat, nausea, vomiting and diarrhea
  • Disease lasts 1 to 2 weeks
  • In pregnant women, VEE can affect the fetus; fetal encephalitis, placental damage, abortion, or severe congenital neurological anomalies may be seen
  • Encephalitis may develop, usually in 4% of children and less than 1% of adults infected
  • In mild cases, symptoms may include lethargy, somnolence, or mild confusion
  • Severe infections are characterized by seizures, ataxia, paralysis or coma.

  Animals:

  • Enzootic subtypes usually infect horses subclinically.
  • Epizootic subtypes can cause asymptomatic infections or two clinical syndromes:
    1. Febrile prodrome followed by neurological signs and sometimes diarrhea and colic; death can occur within hours after the onset of neurological signs. Clinical signs may include fever, anorexia, head pressing, depression, wandering, tripping, ataxia, weakness, blindness and convulsions. Animals that recover may have permanent neurological signs.
    2. Acute febrile disease without neurological signs; fever, weakness, depression, anorexia, colic, diarrhea
  • Case fatality rate is 80%

2) Infectious dose: Unknown

3) Incubation period: One to six days ^(3,4,5)

SOURCE / MODE OF TRANSMISSION / COMMUNICABILITY:

• Transmission can occur by exposure to aerosolized infective material ⁽⁵⁾
• Infected humans and horses are infectious to mosquitos for up to 72 hours; infected mosquitos transmit virus throughout life ⁽⁶⁾

Enzootic Cycle:

• Continuous cycle between rodents and mosquitoes, mainly Culex species ⁽⁵⁾
• Bite of infected mosquito to non-infected, susceptible animals ⁽¹⁾
• Possible transmission to humans via infected mosquito vector ⁽¹⁾

Epizootic Cycle:

• Horses are the most important amplifier due to large production of viraemias and large numbers of hematophagous insects that feed on an animal of such size ⁽⁵⁾
• High viremic titer in a single equid infected with epidemic strain is enough to infect several thousand mosquitoes in a day; these titers last for four or five days in an infected horse ⁽¹⁾
• Mosquitos of the genera Aedes, Anopheles, Culex, Deinocerites, Mansonia, and Psorphora are efficient vectors ⁽⁵⁾
• Mosquitos transmit the infection from a viremic equine to a susceptible equine, human, or other vertebrate ⁽¹⁾

VECTORS:

• Mosquitos: Aedes, Anopheles, Cules, Deinocerites, Haemogogus, Mansonia, Psorphora, Sabethes ^(1,3)

HOST RANGE:⁽⁵⁾

• Variety of laboratory animals
• Domestic animals such as cattle, swine and dogs do not become ill or spread the disease
• Humans
• Equidae

ZOONOTIC POTENTIAL:

• VEE can be transmitted to humans from horses via a mosquito vector ⁽⁵⁾
• There is no evidence that the disease can be transmitted directly from a horse to a human, nor from a human to a human ⁽⁶⁾

RESERVOIR:

• Reservoir between outbreaks was unknown until it was recently demonstrated that epidemic VEE virus arises by mutation of endemic strains ⁽⁷⁾
• Rodents are reservoirs for enzootic strains ⁽³⁾
• Birds act as reservoirs of the III-B variant of the enzootic strain ⁽¹⁾
• Horses, mosquitos and humans are reservoirs of disease for the epizootic subtypes ⁽³⁾

Section III: DIAGNOSIS

NECROPSY / HISTOPATHOLOGY FINDINGS:

• Lesions in central nervous system vary from no lesions to extensive necrosis with hemorrhage ⁽⁵⁾
• Necrotic foci are sometimes seen in the pancreas, liver and heart of horses ⁽⁴⁾
• Typical brain lesion is severe inflammation of the grey matter; neuronal degeneration, infiltration by inflammatory cells, gliosis, perivascular cuffing and hemorrhages ⁽⁴⁾

SAMPLE SUBMISSION:

• Whole blood
• Serum
• Fixed and fresh tissues
• Whole horse brain

All samples should be transported at 4°C.

For more information regarding the type of samples necessary for Venezuelan Equine Encephalomyelitis diagnosis, please contact the National Centre for Foreign Animal Disease:

Diagnostic Co-ordinator National Centre for Foreign Animal Disease 1015 Arlington Street Winnipeg, Manitoba R3E 3M4 Telephone : 204-789-2012 Fax: 204-789-2038

Associate Diagnostic Co-ordinator National Centre for Foreign Animal Disease 1015 Arlington Street Winnipeg, Manitoba R3E 3M4 Telephone: 204-789-2113 Fax: 204-789-2143

LABORATORY DIAGNOSIS:^(2,4)

Virus identification:

• Virus neutralization
• Complement fixation
• Haemagglutination inhibition
• Plaque reduction neutralization (PRN)

Identification of epizootic variants:

• Differential PRN test
• Nucleic acid sequencing

Serological tests:

• IgM capture ELISA
• Haemagglutination inhibition test
• Complement fixation test

DRUG SUSCEPTIBILITY:

• Attenuated virus vaccine, strain TC-83, and an inactivated virus preparation made from that strain ⁽²⁾
• VEE TC-84 effective in horses and guinea pigs to maintain survival following an immunity challenge with VEE ⁽⁸⁾

DIFFERENTIAL DIAGNOSIS:^(5,7)

The following diseases may show clinical similarity to VEE:

• Eastern equine encephalomyelitis, Western equine encephalomyelitis
• West Nile virus infection
• African Horse sickness
• Rabies
• Borna disease - Europe
• Japanese encephalitis - Asia
• Hepatic encephalopathy
• Botulism
• Yellow star thistle poisoning
• Neurologic forms of equine herpesvirus-1
• Fumonisins poisoning
• Liver failure

SECTION IV: DECONTAMINATION PROCEDURES

<>Select a registered disinfectant with a drug identification number (DIN). Use according to label directions for concentration and contact time. Consider organic load and temperature. It is recommended that laboratories evaluate the effectiveness of the disinfectant using a validated method (eg. Quantitative Carrier Test). See table 1 to help select a registered disinfectant for use against VEE virus.

Table 1: Active ingredients considered to be effective against VEE virus.

PHYSICAL INACTIVATION:

• Inactivated by moist and dry heat, as well as drying ^(3,4)

SURVIVAL OUTSIDE OF HOST:⁽³⁾

• Virus is stable in dried blood or exudates ⁽³⁾
• Disappears from infected tissues within a few hours of death ⁽⁷⁾

SECTION V: LABORATORY HAZARDS FOR HUMANS

LABORATORY-ACQUIRED INFECTIONS:

• Eight cases of VEE reported in 1943 were caused by the inhalation of dust from mouse cages containing infected suckling mice ⁽¹⁰⁾
• Four cases associated with blending egg cultures; two people affected worked elsewhere in the building, thus an airborne transmission occurred ⁽¹¹⁾
• Ampules containing dried virus were dropped and broken in a hallway; 24 people who worked on the same floor, and 1 above and 1 below were infected ⁽¹¹⁾
• Majority of lab-acquired infections occurred prior to the use of a BSC and other routine protocols

BIOSAFETY PRECAUTIONS :

• Avoid exposure to aerosols of infectious solutions and animal’s bedding, accidental parenteral inoculation, broken skin contact; be aware that the virus is stable in blood and exudates ⁽³⁾
• It is recommended that all personnel working with VEE, infected animals or entering rooms where these agents or infected animals are present, are vaccinated ⁽³⁾
• Infective VEE viruses or their antigens prepared from infected tissue or cell cultures must never be handled by personnel who do not possess demonstrable immunity in the form of neutralizing antibody ⁽²⁾.

SECTION VI: PHYSICAL AND OPERATIONAL REQUIREMENTS

CONTAINMENT REQUIREMENTS:

All physical containment and operational practices for containment level 3, as per the Containment Standards for Veterinary Facilities must be met. In addition, respiratory protection must be used when performing aerosol-prone procedures. The Standards can be accessed at : http://www.inspection.gc.ca/english/sci/lab/convet/convete.shtml.

PERSONAL PROTECTIVE EQUIPMENT :
Laboratory:

• Primary layer of protective clothing should include dedicated laboratory clothing (e.g. scrubs and headwear) and laboratory dedicated footwear.
• Secondary layer of protective clothing (e.g. solid-front gowns with tight-fitting wrists, 2 pairs of gloves) should be worn over laboratory clothing when directly handling infectious materials.
• Adequate respiratory protection should be worn when directly handling infectious material outside BSC.
• A shower is required on exit.

Post Mortem

• Primary layer of protective clothing should include dedicated laboratory clothing (e.g. scrubs and headwear) and laboratory dedicated footwear.
• Secondary layer of protective clothing (e.g. solid-front gowns with tight-fitting wrists, 2 pairs of gloves) should be worn over laboratory clothing when directly handling infectious materials.
• Cut resistant gloves, adequate respiratory protection, steel toed/steel shanked rubber boots.
• A shower is required on exit.

HANDLING INFORMATION :
Spills in laboratory:
Spill protocol must be in place and include the following scenarios:

• Spills inside the Biological Safety Cabinet (BSC)
• Spills outside the BSC
• Spills while performing aerosol generating procedures
• Also consider entry and exit procedure modifications if necessary, appropriate PPE, disinfection of spill and surroundings including contact time, flow (pattern) of the clean up and disposal of contaminated materials.

Refer to Table 1 for disinfectant selection.

STORAGE: All cultures and infected material should be stored in leakproof, sealed containers that are accurately labeled and clearly identified as a biohazard risk. The access to infectious material should be controlled at all times. Records must be kept to describe the use, inventory and disposal of infectious material.

DISPOSAL: Decontaminate all infectious material prior to disposal. Use steam sterilization, incineration or chemical disinfection.

REFERENCES:

1. Acha, P.D. and Szyfres, B. Zoonoses and Communicable Diseases Common to Man and Animals. Third Edition. Volume II. Chlamydioses, Rickettsioses, and Viroses. Scientific and Technical Publication No. 580. Pan American Health Organization. 2003. Pages 333-45.
2. Manual of Diagnostic Testshttp://active.inspection.gc.ca/tech/extsite.asp?url= and Vaccines for Terrestrial Animals, OIE World Organisation for Animal Health. Venezuelan Equine Encephalomyelitis, updated 2004/07/23. http://www.oie.int/eng/normes/mmanual/A_00090.htm.
3. Publhttp://active.inspection.gc.ca/tech/extsite.asp?url=ic Health Agency of Canada. Material Safety Data Sheet, Infectious Substances. Venezuelan equine encephalitis virus. Updated 2001/09/25. http://www.phac-aspc.gc.ca/msds-ftss/msds162e.html.
4. The Center for Food Security and Public Health. Venezuelan Equine Encephalomyelitis Fact Sheet - PDF (140 kb). Jan, 2004. http://www.cfsph.iastate.edu/Factsheets/pdfs/easter_wester_
   venezuelan_equine_encephalomyelitis.pdf
5. Buisch W.W, Hyde J.L. & C.A. Mebus. Foreign Animal Diseases. Sixth Edition. United States Animal Health Association. 1998. Pages 406-14.
6. Chin, J. Control of Communicable Diseases Manual. 17^th Edition. American Public Health Association. 2000. Pages 45-7.
7. Radostits OM, Gay CC, Blood DC, and KW Hinchcliff. Veterinary Medicine, A Textbook of the Diseases of Cattle, Sheep, Pigs, Goats and Horses. Ninth Edition. W.B. Saunders Company Ltd. 2000. Pages 1289-96.
8. Foster NM, Barber TL, Walter TE. Venezuelan equine encephalomyelitis virus: concentration, partial purification, inactivation and immunogenicity. Comp Immonol Microbiol Infect Dis. 1983; 6(1): 31-7.
9. Australian Veterinary Emergency Plan. Operational Procedures Manual: Decontamination. 2000. Page 50.
10. Lennette EH, Koprowski H. Human infection with Venezuelanm equine encephalomyelitis virus. A report of eight cases of infection acquired in the laboratory. Journal of the American Medical Association. 1943; 123: 1088-95.
11. Collins C.H. Laboratory Acquired Infections. Third Edition. Butterworth-Heinemann Ltd. Oxford. 1993. Page 38.

LAST UPDATED (DATE): 2005/11/28

PREPARED BY: The Biohazard Containment and Safety Unit, CFIA

Disclaimer: Although the information and recommendations in this Pathogen Safety Data Sheet are compiled from reliable sources, there is no guarantee, warranty or any assurance that the information and recommendations are correct, accurate, sufficient, reliable or current and the Canadian Food Inspection Agency shall not be responsible for any loss or damage resulting from or in connection with the use of or reliance upon the information and recommendations.

The user assumes all risks and responsibility for and shall be liable for the use of and any reliance on the information and recommendations and the results thereof and any loss or damage resulting therefrom.

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