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PATHOGEN SAFETY DATA SHEET

Rift Valley Fever

SECTION I: DISEASE / INFECTIOUS AGENT

DEFINITION: Rift Valley Fever ( Enzootic hepatitis ) is an acute mosquito-borne viral disease affecting mainly ruminants and humans. In animals Rift Valley Fever (RVF) causes abortions and high mortality in young. In humans RVF causes severe influenza-like syndrome.

ETIOLOGY / TAXONOMY : Virus
Family: Bunyaviridae
Genus: Phlebovirus
Species: Rift Valley Fever Virus

ORGANISM CHARACTERISTICS:

• It is a three-segmented, single-stranded RNA genome virus with spherical virions.

SURVEILLANCE :
Rift Valley Fever is a reportable disease in Canada. Animal owners, veterinarians and laboratories are required to immediately report the presence of an animal that is infected or suspected of being infected 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 Rift Valley Fever in Canada is non-indigenous.
• Primarily African countries but in 2000, RVF was confirmed in Saudi Arabia and Yemen.⁽¹⁾
• RVF occurs in cycles associated with periods of high rainfall, and high mosquito populations

SECTION II: ANIMAL HEALTH HAZARD AND EPIDEMIOLOGY

CLINICAL DISEASE / PATHOGENESIS:
1) Clinical signs: Young animals- Most severe in lambs and calves; “peracute stage” – sudden death or severely weakened and collapse when forced to move; “acute stage” – after a 12 hour incubation period there is a sudden onset of high fever ( 40-42°C ), incoordination with loss of appetite, rapid pulse, vomition, mucopurulent nasal discharge followed by collapse and death within 36 hours in 95-100% of affected one week old lambs, 40 - 60 % death rate in older lambs and 10 - 70% death rate in young calves. ⁽²⁾

Adult sheep- “Sub-acute stage” – high temperature (40-41°C ), unsteady gait, bloody diarrhea, mucopurulent nasal discharge, vomiting, and jaundice.⁽³⁾ Abortion amongst infected pregnant ewes is almost 100% . Goats exhibit similar signs as sheep, but less severe. Adult cattle show a decrease in milk production, abortion, excessive salivation, anorexia, muscle weakness and occasional cases with fetid diarrhea. Mortality is less than 10 %. ⁽³⁾

Humans- There are 4 clinical syndromes associated with RVF ⁽⁴⁾

Mild form: Sudden fever, rigor, headache, retro-orbital pain, severe muscular pain, cloudy conjunctiva, vomiting and loss of appetite.
Ocular form: Less common, presents initially as a fever, diminishing of visual acuity between 7 and 20 days after onset. Macular, paramacular or extramacular retinal lesions are seen, often bilaterally. Edema, hemorrhage and vasculitis are frequently observed and approximately 50% of patients suffer permanent loss of central vision.
Meningoencephalitic RVF: Starts with acute fever for 5-10 days followed by hallucination, disorientation and vertigo. Long-term neurological complications have been reported in some patients, although the mortality rate is low.
Hemorrhagic RVF: Acute fever of 2-4 days duration followed by jaundice and hemorrhage, in the following3-6 days either death occurs or the patient begins to recover slowly.

2) Infectious dose: Not known

3) Incubation period: 1-6 days (5); 12-36 hours for lambs ⁽⁶⁾

4) Adult mortality: Sheep 20-30%, cattle 10%⁽²⁾

SOURCE / MODE OF TRANSMISSION / COMMUNICABILITY:

• Predominantly a vector-borne disease – Aedes, Anopheles, culex, Eretmapodites, Masonia are competent vectors
• Aedes mosquitoes are the reservoir host ⁽⁵⁾
• Man is infected through aerosols from infected animals, contact with infected tissues, aborted fetuses, consuming raw milk and improper laboratory procedures
• Windborne dispersal of infected vectors and infected livestock and people movement are a means of spreading RVF

VECTORS:

• Mosquitoes species act as competent biological vectors
• Aedes lineatopinnis mosquito acts as viral reservoir
• In North America Aedes, Culex and Anopheles mosquitoes have been found to be capable vectors ⁽⁷⁾
• Mechanical vectors such as midges and biting flies play a significant role during major epidemics

HOST RANGE :

• Primarily ruminants – with sheep (lambs) being highly susceptible, followed by goats
• Cattle, camels, several species of rodents, buffaloes, antelope, wildebeest, horses, donkeys, cats, dogs, monkeys, horses, and birds are also affected ⁽⁷⁾
• Humans are very susceptible

ZOONOTIC POTENTIAL :

• Rift Valley Fever Virus is a major zoonotic concern
• Nasal discharge, blood, vaginal secretions following abortions, as well as direct exposure to mosquitoes are sources of infection
• Consumption of meat and raw milk from viremic cattle and sheep
• Aerosols from infected animals as well as poor laboratory procedures present potential infection sources

RESERVOIR :

• The virus is dormant in the eggs of the mosquito Aedes lineatopennis in dry soil of grassland depressions. With adequate rainfall, the infected mosquitoes develop and infect ruminants. The virus can be spread by many mosquito species.

Section III: DIAGNOSIS

NECROPSY / HISTOPATHOLOGY FINDINGS:

• Hepatic lesions are similar in all species (vary only with age). The most severe lesions are seen in aborted fetuses and new born lambs ⁽⁶⁾. Liver is moderately to severely enlarged, soft, friable with irregular congested patches. Numerous gray-white necrotic foci are invariably present.
• Cutaneous haemorrhage, petechial or ecchymotic haemorrhage on parietal and visceral serosa
• Haemorrhage and edema of wall of gallbladder and mucosa of abomasum are common.
• Intestinal contents are often dark chocolate-brown – with some cases of haemorrhagic enteritis
• In all animals the spleen and peripheral lymph nodes are enlarged and edematous and may have petechiae
• In man – RVF is associated with influenza-like syndrome, with some instances of ocular lesions, encephalitis and hepatitis

SAMPLE SUBMISSION:

• Whole blood – 20 ml – from febrile animals ( in EDTA coagulant or heparin )
• Serum – 10ml – from both acute febrile and convalescent animals
• Fresh tissue samples from recently dead animals and aborted fetuses (spleen and liver, kidney, lymph nodes, heart, brain)
• Fixed tissues (spleen and liver ) collected in 10 % buffered formalin

All samples should be transported at 4°C using ice packs
If shipping delay is greater than 24 hours – fresh tissue and serology samples should be frozen at minus 20° C and shipped with ice packs

For more information regarding the type of samples necessary for Rift Valley Fever diagnosis, please contact the National Centre for Foreign Animal Disease:

LABORATORY DIAGNOSIS:
Identification of the agent ⁽⁵⁾

• Virus isolation:

Serological tests:

All tests with the exception of the neutralization tests can be performed with inactivated antigens to promote laboratory safety.

RT-PCR Reverse Transcriptase - Polymerase Chain Reaction – RVF antigen demonstration
IHC Immuno-Histo-Chemistry for virus antigen detection in tissue

DRUG SUSCEPTIBILITY :

• No specific treatment
• Vaccination: Attenuated vaccine:– one inoculation with resultant 3 year immunity - may cause abortions in ewes or teratogenesis, or prolonged gestation
• Inactivated vaccine: – requires two inoculations and repeat on an annual basis and is expensive to produce
• For humans only inactivated s are used – primarily for laboratory staff and Field veterinarians

DIFFERENTIAL DIAGNOSIS :
The following diseases may show clinical similarity to Rift Valley Fever.⁽⁵⁾

• Bluetongue
• Wesselsbron disease
• Enterotoxemia of sheep
• Ephemeral fever
• Brucellosis
• Vibriosis
• Trichomonosis
• Nairobi sheep disease
• Heartwater
• Ovine enzootic abortion
• Toxic plants
• Bacterial septicaemias
• Rinderpest and Peste des petits ruminants

In humans the clinical signs are diverse, and a differential diagnosis should include the following: ⁽⁴⁾

• Malaria
• Brucellosis
• Lassa Fever
• Ebola Fever
• Marburg virus disease
• Congo-Crimean hemorrhagic fever
• Dengue fever
• Dengue hemorrhagic fever

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 Rift Valley Fever virus.

Table 1: Active ingredients considered to be effective against Rift Valley Fever.

• Note: Alkalis should not be used ⁽⁸⁾

PHYSICAL INACTIVATION:

SURVIVAL OUTSIDE OF HOST :

• RVF virus is inactivated by lipid solvents, detergents and low pH
• Virus survives in neutral or alkaline pH in presence of protein (serum ) – up to 4 months at 4ºC ⁽³⁾
• Specimens stored below 0ºC will remain infective for 8 years
• Virus remains dormant in Aedes genus mosquito eggs for years; when eggs hatch after rainfall mosquito harbours virus ⁽⁷⁾
• Blood may remain infective for up to 4 months at 25ºC ⁽⁸⁾ so particular care must be used when decontaminating bloody surfaces

Section V: LABORATORY HAZARDS FOR HUMANS

LABORATORY-ACQUIRED INFECTIONS :

• May occur through aerosols from handling infected tissues and aborted fetuses
• According to Newsom (1976) this virus seems to have caused infections in every laboratory where it has been studied. Pike (1976) records 28 infections and SALS (1980) 47 ⁽⁷⁾

BIOSAFETY PRECAUTIONS:

• Special precautions must be taken to prevent inhalation of aerosols (eg handling infected animals and contact with the virus in the laboratory). Care should also be taken when slaughtering infected animals. The virus may infect humans through skin abrasions, cuts, and skin punctures ⁽¹⁾

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. The Standards can be accessed at : http://www.inspection.gc.ca/english/sci/lab/convet/convete.shtml.

PERSONAL PROTECTIVE EQUIPMENT :
Laboratory:

• Dedicated laboratory clothing (e.g. scrubs and headwear) and dedicated laboratory 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
• Respiratory protection should be worn when directly handling infectious material outside BSC
• A shower is required on exit

Post Mortem:

• 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
• Respiratory protection should be worn when performing the post mortem and sample collection procedures
• 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. World Health Organization, Rift Valley Fever factsheet: http://www.who.int/mediacentre/factsheets/fs207/en/print.html
2. Radostits, O.M.; Gay, Clive C.; Blood, Douglas C.; Hinchcliff, Kenneth W. Veterinary Medicine. A textbook of the Diseases of Cattle, Sheep, Pigs, Goats and Horses. 9^th Edition. 2003
3. Geering, W. A. Exotic Diseases of Animals for Austalian Veterinarians. 1995
4. Australian Veterinary Emergency Plan. Disease Strategies Manual: Rift valley Fever, online at: http://www.animalhealthaustralia.com.au/shadomx/apps/fms/fmsdownload.cfm?file_uuid=2B29ABF1-CBE5-D8F1-C8C5-F5CA4780DBD8&siteName=aahc
5. OIE, Rift Valley Fever factsheet: http://www.oie.int/eng/maladies/fiches/a_A080.htm
6. Merck Veterinary Manual, Rift Valley Fever sheet: http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/55800.htm&word=rift%2cvalley%2cfever
7. Foreign Animal Diseases, United States Animal Health Association 1998
8. Australian Veterinary Emergency Plan. Operational Procedures Manual: Decontamination, online at: http://www.animalhealthaustralia.com.au/shadomx/apps/fms/fmsdownload.cfm?file_uuid=2B50B4BD-E62D-ECF1-C6AB-FA21B96A0ED7&siteName=aahc
9. Collins, C.H. Laboratory Aquired Infections. 3^rd Edition.1993

LAST UPDATED: 2005/10/14

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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