Pathogen Safety Data Sheet - Pseudorabies

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SECTION I: DISEASE / INFECTIOUS AGENT

SYNONYM / CROSS REFERENCE: Aujeszky’s Disease, Mad Itch ⁽¹⁾

ETIOLOGY / TAXONOMY:
Family: Herpesviridae⁽¹⁾
Subfamily: Alphaherpesvirinae⁽¹⁾
Genus: Varicellovirus⁽²⁾
Species: Porcine herpesvirus-1, AD virus ⁽¹⁾

ORGANISM CHARACTERISTICS:

• AD virus is a large lipid-containing virus ⁽³⁾.
• AD virus is an enveloped double-stranded DNA virus ⁽²⁾.
• There is only one serotype, but strains vary in pathogenicity, minimum infective dose and tissue tropisms ⁽³⁾.
• Virus is more thermostable than other herpesviruses

SURVEILLANCE:

Pseudorabies 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 Pseudorabies in Canada is non-indigenous ⁽³⁾.
• Pseudorabies can be found in most of Europe, Mexico, Cuba, Brazil, Venezuela, New Zealand, Samoa, Southeast Asia, and parts of the United States ⁽⁴⁾.
• Outbreak in Bolivia (September 2006) resulted in 25 deaths out of 40 reported cases ⁽⁷⁾.

SECTION II: ANIMAL HEALTH HAZARD AND EPIDEMIOLOGY

CLINICAL DISEASE / PATHOGENESIS:

Pseudorabies is a viral disease that causes encephalomyelitis and respiratory infections primarily in swine ⁽³⁾

1) Clinical signs: ^(3,4)
Pigs:
Newborn Pigs:

• Death occurs within hours of the onset of sickness in pigs less than 2 weeks old, prostration is often the only sign.
• Slightly older piglets show fever and variable signs of loss of appetite, vomiting, depression with central nervous system (CNS) and respiratory involvement.
• The CNS signs consist of incoordination, abnormal "goose-stepping" gait, drowsiness, muscular twitching, convulsions, involuntary eye movements and paralysis.
• Deaths occur up to one week after the onset of signs, but may be seen as early as 24 hours after onset of disease.
• Pruritis is rare in pigs
• Mortality ranges from 20% to 100%

Weaner Pigs:

• Clinical signs are the same as for Newborn pigs, but respiratory signs may be more prominent.
• Respiratory symptoms include coughing, sneezing, dyspnea and conjunctivitis.
• Mortality ranges from 5% to 10%

Grower and finisher pigs:

• Respiratory disease is the most common clinical sign and resemble the aforementioned symptoms.

Adults:

• Infection is often mild or inapparent.
• Virus can cross the placenta; if sows are infected earlier than the 13th day of pregnancy, may result in embryonic reabsorption. Later stages of pregnancy result in abortion, mummified fetuses, stillbirths or the birth of weak, trembling pigs.

Cattle and Sheep:

• Disease is almost invariably fatal within a few days.
• Most striking clinical sign is intense pruritis of a patch of skin, innervated by one or more spinal nerves; this leads to licking, rubbing or gnawing so severe it can result in self-mutilation.
• Animals become progressively weaker and prostrate.
• Other symptoms include convulsions, bellowing, teeth grinding, pharyngeal paralysis, rapid shallow breathing and cardiac irregularities.
• Death usually occurs two days after onset of clinical signs

Dogs and Cats:

• The clinical signs are similar to ruminant; including intense pruritis and self-mutilation.
• Paralysis of pharynx leads to profuse salvation, resembling rabies.
• Animals may emit plaintive whimpers and howls
• Clonic convulsions are common
• Death within 24-48 hours in dogs, often more rapidly in cats

Rodents:

• Disease is fatal.

2) Infectious dose: Unknown

3) Incubation period:

• One week in pigs ⁽⁴⁾
• Can be as short as 2-4 days in sucking pigs and 3-6 days in finishers ⁽³⁾

SOURCE / MODE OF TRANSMISSION / COMMUNICABILITY:

• The most important method of infection is via oral and nasal secretions ⁽³⁾.
• Virus can be recovered from oral and nasal secretions, milk, tonsillar epithelium, vaginal, uterine and preputial excretions
• Spread principally by nose-to-nose contact ⁽³⁾
• Infection may occur from contaminated feed
• Aerosol transmission from projection of discharges during sneezing ⁽¹⁾ and windborne spread ⁽³⁾
• Fomites such as contaminated drinking water and feed and veterinary instruments can spread disease ⁽¹⁾
• Via semen or vaginal secretions, by placental infection, or via colostrum or in milk ⁽³⁾
• Pigs excrete virus oronasally during the 2-4 weeks following primary infection ⁽¹⁾
• Latent carriers excrete the virus intermittently for up to one year during times when the animal is stressed ⁽¹⁾.

VECTORS:

• No insect vectors and no reliable reports to suggest that mechanical transmission occurs via a vector ⁽¹⁾

HOST RANGE: ^(1,3,4)

• Pigs are the only known natural host for disease
• Can infect sheep, goats, rodents, mink, foxes, deer and rabbits
• Dogs and cats may be infected by contact with infected pigs
• Cattle, sheep and goats tend to be dead end hosts
• Horses are rarely infected

ZOONOTIC POTENTIAL:

• Pseudorabies is not transmissible to humans ^(3,4)..

RESERVOIR:

• Pigs are the reservoir host for infection ⁽³⁾
• Rats and wildlife may have some role as reservoirs but this requires further study ⁽³⁾
• Latent infected pigs can excrete the disease intermittently, when stressed ^(1,3)

Section III: DIAGNOSIS

NECROPSY / HISTOPATHOLOGY FINDINGS:

Pigs:

• Post mortem lesions are often minimal or absent ^(3,4)
• Many may have a serous or fibrinonecrotic rhinitis; can only be visible if head is split and nasal cavity opened ⁽⁴⁾
• May be purulent inflammation of the nasal lining, pharyngitis, tonsillitis and areas of edema, congestion or consolidation in the lungs ^(3,4)
• Lymph nodes may be congested and contain some petechial hemorrhages ^(3,4)
• Liver and spleen may have necrotic foci in affected animals and aborted fetuses ^(3,4)
• Typically, a diffuse, nonsuppurative meningoencephalitis is found upon examination of both white and grey matter ⁽⁴⁾
• A marked mononuclear perivascular cuffing and neuronal necrosis may be seen ⁽⁴⁾
• Pulmonary edema and interstitial pneumonia are common
• Necrotic foci in tonsils, liver, kidneys, spleen and associated lymph nodes is common

All other species:

• Only nervous system lesions are found in the spinal cord; areas of edema, congestion and hemorrhage ^(3,4)
• Lesions are usually found in the portion of the spinal cord that innervates the area or pruritis ^(3,4)
• CNS lesions similar to those in pigs, but milder, are often found ^(3,4)

SAMPLE SUBMISSION:

• Whole blood 10ml each from acute and convalescent animals
• Serum
• Fixed and fresh tissues
• One half brain (fresh) sectioned longitudinally
• Skin and subcutaneous tissues from pruritic areas
• Pigs- lung, spleen, tonsils
• Nasal swabs submitted in transport media
• One half brain, cervical, thoracic and lumbar segments of spinal cord fixed in 10% buffered formalin
• Tonsil, mesenteric lymph nodes, spleen, lung, liver and kidney sections fixed in 10% formalin

All samples should be transported at 4°C.

For more information regarding the type of samples necessary for Pseudorabies 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:

• Virus neutralization/ serum neutralization (SN) ^{(1, 3, 4,5)}
• Enzyme-linked immunosorbent assay (ELISA) ^{(1, 4, 5)}
• Virus isolation
• Polymerase chain reaction (PCR) ^(4,5)

DRUG SUSCEPTIBILITY:

• No treatment is available ⁽¹⁾
• No form of vaccination is currently used in Canada
• Vaccination is used to reduce clinical disease when outbreaks occur or when the disease is endemic in the herd ⁽¹⁾
• Attenuated vaccines are considered better than inactivated or killed vaccines ⁽³⁾
• Gene-deleted vaccines have been genetically engineered to remove some non-essential glycoprotein genes and the absence of these surface proteins (eg. gG, gE, gC) makes them useful as negative immunological markers ^(1,3)

DIFFERENTIAL DIAGNOSIS:

The following diseases may show clinical similarity to Pseudorabies:

• Porcine polioencephalomyelitis ⁽⁴⁾
• Classical and African swine fever ^(3,4)
• Hemagglutinating encephalomyelitis infection ^(1,3,4)
• Streptococcal meningoencephalitis ^(3,4)
• Swine influenza ⁽⁴⁾
• Salt poisoning ⁽⁴⁾
• Hypoglycemia ^(3,4)
• Organic arsenic or mercury poisoning ^(3,4)
• Congenital tremor ⁽⁴⁾
• Enterovirus encephalomyelitis (Teschen disease) ⁽³⁾
• Encephalomyocarditis (EMC) ⁽³⁾
• Other diseases causing abortion ^(3,4)

Other species:

• Rabies ^(3,4)
• Scrapie ^(3,4)
• Bovine spongiform encephalopathy (BSE) ⁽³⁾
• Conditions causing signs of persistant itching ⁽³⁾

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 Herpesviridae.

Table 1: Active ingredients considered to be effective against Herpesviridae.

PHYSICAL INACTIVATION:

• Inactivated by sunlight/ ultraviolet light ⁽⁴⁾
• Rapidly inactivated at 37°C, in sunlight and dry conditions ⁽³⁾
• Stable between pH 5-9 ⁽³⁾

SURVIVAL OUTSIDE OF HOST:⁽³⁾

• Survives for extended periods under winter conditions below 4°C
• Remains infective in contaminated straw, bedding and feeding troughs for 10-30 days at 24°C or for up to 46 days at -20°C
• On fomites for 2-7 days
• In effluent for up to 3 days
• In drinking water for 7 hours (unchlorinated)

SECTION V: LABORATORY HAZARDS FOR HUMANS

LABORATORY-ACQUIRED INFECTIONS:

• None

BIOSAFETY PRECAUTIONS :

• None

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. 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.
2. Murray PR, Barron EJ, Pfaller MA, Tenover FC, and RH Yolken. Manual of Clinical Microbiology. Seventh Edition. American Society for Microbiology. 1999. Page 840.
3. Australian Veterinary Emergency Plan, 1996. Disease Strategy, Aujeszky’s Disease: http://www.animalhealthaustralia.com.au/fms/Animal%20Health%20Australia/AUSVETPLAN/aujfinal.pdf
4. The Center for Food Security and Public Health. Aujeszky’s Disease Fact Sheet - PDF (100 kb). Jun 3, 2003. http://www.cfsph.iastate.edu/Factsheets/pdfs/aujeszkys_disease.pdf.
5. Manual of Diagnostic Tests and Vaccines for Terrestrial Animals, OIE World Organisation for Animal Health. Aujeszky’s Disease updated 2004/07/23. http://www.oie.int/eng/normes/mmanual/A_00041.htm.
6. Australian Veterinary Emergency Plan. Operational Procedures Manual: Decontamination. 2000. Page 50.
7. OIE. Disease Information: http://www.oie.int/eng/info/hebdo/a_dsum.htm.

LAST UPDATED (DATE): 2005/11/07

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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