RABIES AND OTHER LYSSAVIRUS INFECTIONS

Last updated: 25 July 2007

1. Reason for surveillance

• To identify cases and their risk factors, and

• To prevent disease in people exposed to infectious animals.

2. Case definition

Lyssavirus - Australian Bat Lyssavirus (ABL)
A confirmed case requires laboratory evidence.

Laboratory evidence

• Isolation of Australian bat lyssavirus confirmed by sequence analysis, or

• Detection of ABL viral RNA in clinical material.

Clinical evidence
Not applicable.

Epidemiological evidence
Not applicable.

Lyssavirus - Rabies
A confirmed case requires laboratory evidence.

Laboratory evidence

• Isolation of rabies virus confirmed by sequence analysis, or

• Detection of rabies viral RNA in clinical material.

Clinical evidence
Not applicable.

Epidemiological evidence
Not applicable.

Lyssavirus - Unspecified
A confirmed case requires:

• Laboratory evidence, and

• Clinical evidence.

Laboratory evidence

• Positive fluorescent antibody test result for lyssaviral antigen on fresh brain smears, or

• Specific immunostaining for lyssaviral antigen on formalin fixed paraffin sections of central nervous system tissue, or

• Presence of antibody to serotype 1 lyssavirus in the CSF, or

• Detection of lyssavirus-specific RNA (other than to ABL or rabies) in clinical material.

Clinical evidence
Acute encephalomyelitis with or without altered sensorium or focal neurological signs.

Epidemiological evidence
Not applicable.

Factors to be considered in case identification
The Australian Animal Health Laboratory at Geelong in Victoria is the reference laboratory for diagnosis of human and animal infection.

3. Notification criteria and procedure

Rabies and other lyssavirus infections are to be notified by:

• Hospital CEOs on clinical diagnosis (ideal reporting by telephone within 1 hour of diagnosis)

• Laboratories on diagnosis (ideal reporting by telephone within 1 hour of diagnosis).

Only confirmed cases should be entered onto NDD.

The diagnosis "Lyssavirus - Unspecified", should only be entered where there is insufficient evidence to meet a case definition for Australian bat lyssavirus or rabies.

Note that rabies is subject to the Commonwealth Quarantine Act (1908).

4. The disease

Infectious agents
Viruses of the genus Lyssavirus.

Mode of transmission
Rabies and other lyssavirus infections are typically transmitted by the virus-laden saliva of a rabid animal introduced via a bite or scratch. They are theoretically communicable from person-to-person via saliva. Transmission from contaminated corneal transplantation has been reported.

Timeline
The typical incubation period is 3 to 8 weeks, but can range from 9 days to 7 years depending on the severity and site of the wound.

Clinical presentation
The usual clinical presentation of rabies is a non-specific prodrome of fever, headache, malaise, anorexia, nausea and vomiting for 1 to 4 days followed by signs of apprehension, hydrophobia, encephalitis and brain stem dysfunction. Excess salivation and difficulty swallowing produces the traditional picture of frothing at the mouth. The disease is inevitably fatal. Death from respiratory paralysis generally occurs within 2 to 6 days of onset.

Only 2 cases of Australian lyssavirus have ever been identified, so the clinical presentation of infection is less certain, although it is thought to be similar to rabies.

5. Managing single notifications

Response times
Investigation
On same day of notification of a confirmed case begin follow-up investigation and notify the Communicable Diseases Branch.

Data entry
Within 1 working day of notification enter confirmed cases on NDD.

Within 3 working days of a report of a person requiring post-exposure treatment, fax the Rabies/Lyssavirus Post-Exposure Treatment form to the Communicable Diseases Branch, NSW Health (fax 02-93919189).

Response procedure
The response to a notification will normally be carried out in collaboration with the case's health carers. But regardless of who does the follow-up, PHU staff should ensure that action has been taken to:

• Confirm the onset date and symptoms of the illness

• Confirm results of relevant pathology tests, or recommend the tests be done

• Find out if the case or relevant care-giver has been told what the diagnosis is before beginning the interview

• Seek the doctor's permission to contact the case or relevant care-giver

• Review case management.

Case management

Investigation and treatment
Determine animal contacts, both overseas and in Australia. Animals suspected of being infected should be isolated from other animals and humans pending veterinary investigation. If the animal is killed, the head, with minimal damage, should be submitted to the local Regional Veterinary Laboratory for testing.

Education
The case or relevant caregiver and contacts should be informed about the nature of the infection and the mode of transmission.

Isolation and restriction
The case should be isolated using Contact Precautions, and Standard Precautions are to be used for handling any body fluids for the duration of the illness. Treatment is supportive.

Environmental evaluation
None usually required.

Contact management

Identification of contacts
Contacts include persons who are exposed to the saliva or neurological tissue of an infectious person.

Contacts also include persons who have been bitten or scratched by potentially infected animals:

• In countries where rabies has been reported

• By a bat anywhere in the world.

Investigation and treatment
Post exposure treatment (PET)
Where a person is exposed to a potentially infected animal, the wound should be washed thoroughly as soon as possible with soap and water. Proper cleansing of the wound is the single most effective measure for reducing the transmission of classic rabies virus.

For people with no previous vaccination against rabies, post-exposure treatment consists of 5 doses of 1ml of rabies vaccine given as deep subcutaneous or intramuscular injection, on days 0, 3, 7, 14 and 30, and a dose of HRIG, unless previous vaccination has been received. Vaccine should be given in the deltoid area, as rabies neutralising antibody titres may be reduced after administration in other sites. In children, administration into the anterolateral aspect of the thigh is also acceptable. Vaccine should not be administered by the intradermal route.

For people who have been previously vaccinated against rabies, PET consists of a total of 2 doses of rabies vaccine (1.0ml each) at day 0 and day 3. If previous vaccination history is uncertain or was given intradermally, a complete PET course (5 doses and HRIG) should be given.

Rabies immunoglobulin should be given as a single dose at the same time as the first dose of the post-exposure vaccination course. Where the site permits, as much as the dose as feasible should be infiltrated into the wound and any remainder given intramuscularly. It should not be given at the same site as the vaccine. The dose is 20 International Units per kilogram body mass. If rabies immunoglobulin is administered in the buttock, care should be taken to ensure that the dose is given intramuscularly, and not into adipose tissue. If vaccination has been commenced 7 days before, rabies immunoglobulin should not be administered.

PET is expensive and HRIG occasionally in short supply, and sometimes associated with adverse reactions. Therefore recommendation for its use requires careful consideration.

Timing of PET
For bat exposures in Australia, PET should be arranged immediately (including urgent after hours ordering /delivery) if:

• The person was bitten on the head or neck by the bat, or

• There were multiple bites or severe local trauma due to bites, or

• The bat appeared to behave abnormally, or

• The bite was unprovoked (for example the person made no attempt to handle the bat).

PET may be delayed for up to 48 hours if the exposed person:
Was previously immunised against rabies with a complete three dose pre-exposure course of rabies vaccination (days 0, 7 and 21 or 28), or

• Was only scratched by the bat, or

• Reported that the exposure did not occur recently (within the previous few weeks), or

• Was bitten by the bat, and

• the bite was single/minor and provoked, and

• the bite was not on the head or neck, and

• the bat was not behaving abnormally.

An animal can be considered not infected with a lyssavirus (rabies or ABL) if its brain is examined for lyssavirus by the Queensland Scientific Services or CSIRO's Australian Animal Health Laboratory (AAHL) and found to be negative on DFAT and PCR. In this situation PET need not be commenced or if already commenced, may be terminated.

For persons bitten by animals in countries where rabies has been reported (see the World Health Organization website for epidemiological details of world-wide rabies occurrence in humans and animals by country: http://who.int/rabies/resources/en/ and http://gamapserver.who.int/mapLibrary/), exposed persons should commence PET (HRIG and 5 doses of vaccine) without delay.

For people exposed overseas to a potentially rabid dog or cat more than 10 days before, if the dog or cat is known to have remained healthy for 10 days after the exposure, then it can be considered not able to transmit rabies, and PET need not be commenced. Where the exposure occurred less that 10 days before, then PET should be administered unless rabies can be excluded in the animal.

Where doubts exist about the accuracy of rabies surveillance in a particular area, for example Bali, exposure by bite or inoculation of a mucous membrane with saliva from an animal that appears to be acting abnormally should be considered a risk for rabies.

Note that bat bite or scratch exposures in any country should be considered to pose a risk of lyssavirus infection.

Obtaining PET
PHUs should arrange for delivery of PET to the exposed person's elected doctor based on the above assessment. PET is supplied free of charge by NSW Health (via the NSW Vaccine Centre). Pre-exposure vaccination (PEV) is not the responsibility of the PHU and is not funded by NSW Health. Persons requiring PEV should be referred to their local doctor who can order it through a pharmacy.

To order PET, the PHU should fax a copy of the NSW Health PHU Order Form to the NSW Vaccine Centre (fax 1800 041 528). When ordering after hours, obtain the name, address, telephone and opening hours of the practice to which the vaccine will be delivered, and calculate the required amount of RIG required (20 IU per kg body mass for all ages) before calling the NSW Vaccine Centre's on call person. For example, a 70 kg person requires 70 kg x 20 IU=1400 IU. RIG is supplied at a concentration of 150 IU/mL, therefore a 70 kg person requires 1400/150= 9.3mL. RIG is supplied in 2mL and 10mL vials, therefore either 1 x 10 mL vial or 5 x 2mL vials (10mL) should be ordered for this person (and the dose would be 9.3 mL).

After arranging PET, the PHU should write to the doctor to confirm that delivery has been arranged, asking the doctor to report to the PHU if there are problems in completing the course of vaccine, and recommending that the doctor ensures that details of the administration (including batch numbers) be kept on the patient's medical record (see model letter attached).

Testing the animal
Bats that have bitten or scratched a person should be sent for testing if they can be secured and euthanised without putting further people at risk. Tests are performed by the CSIRO's Australian Animal Health Laboratory (AAHL), Geelong. AAHL advises that results for immunofluorescence and PCR testing on brain tissue can be made available within one working day of sample receipt. Where necessary a weekend service can be arranged if considered urgent.

PHU staff should facilitate the testing. To test the bat, the exposed person should be advised to take the bat to a veterinarian, who can euthanise it and send it to the nearest Regional Veterinary Laboratory (RVL). RVLs in NSW are located at:

• Menangle (near Camden): Elizabeth Macarthur Agricultural Institute, Woodbridge Road, Menangle

• Wollongbar (near Lismore): Wollongbar Agricultural Institute, Bruxner Highway, Wollongbar

• Orange: Orange Agricultural Institute, Forest Road, Orange.

Specimens should be refrigerated (not frozen) and marked "Urgent - human exposure". The cost of euthanasia and transport to the RVL ideally will be borne by either the exposed person or the veterinarian. The laboratory will then send the specimens to AAHL for testing at the aboratory's expense. Where veterinarians require advice about specimen submission, and are unable to contact an RVL, they should call the Animal Disease Watch Hotline.

AAHL may also accept bats specimens directly but prefer the above procedure.

PET should commence as soon as possible after the exposure for severe bites as described above, but can be delayed for up to 48 hours for minor exposures (as above) while awaiting bat test results. PET can be withheld or ceased if the bat test result is negative. PHU staff should facilitate the testing of the bat and provision of PET to the exposed person's nominated doctor.

Bats can be sent live if secured appropriately or dead at 4 degrees, not frozen, and marked "Urgent - human exposure" directly to AAHL.

Australian Animal Health Laboratory, 5 Portarlington Rd, East Geelong , VIC 3219, Australia, Phone: 61 3 5227 5000 Fax: 61 3 5227 5555

Education
Advise susceptible contacts (or parents/guardians) of the risk of infection. Handling of bats should be discouraged. If bat handling is a necessary part of a person's work, the person should be trained in bat handling, wear protective clothing and be fully immunised against rabies. Every effort should be made to prevent scratches and bites.

PHUs should consider the value of media releases at strategic times (e.g., before at birthing season) to remind the public about the importance of the above.

Isolation and restriction
None

6. Managing special situations

Domestic animal exposed to a bat
From time-to-time, pet owners report that their pet has caught or been exposed to a bat. Available data (i.e., the absence of reported lyssavirus infection in terrestrial animals in Australia) suggests that the risk to the pet is very low. Veterinary authorities do not recommend post exposure treatment for animals in Australia.

If the pet owner has undue anxiety about their exposure, then testing of the bat can be arranged. Should the bat test positive, the owner should be counselled about the low level of risk. The Senior Field Veterinary Officer should be notified immediately of any positive test results.

There is only a remote possibility that the animal may become infected with ABL if the bat was infected. This should be carefully explained to the owner, and the owner made aware of the importance of keeping it under close observation for 3 months. During this time, should the animal develop any illness, it must be taken to the vet immediately for evaluation for possible ABL infection.

Sample letter

[PHU letterhead]
[Date]
[Dr's name and address]
[Dr's fax no.]

Dear Dr [dr's surname]

Post-exposure treatment for rabies or Australian bat lyssavirus infection for [patient name], dob:

I am writing to confirm that staff of the ZZZ Public Health Unit have arranged the delivery of [X number of] doses of Rabies Vaccine and/or [Y number of] mls of Human Rabies Immunoglobulin to the following address for post-exposure treatment of your above-name patient.

[space for practice address]

Your patient should receive, as soon as possible, D mls (E IU) of Rabies Immunoglobulin (based on your estimate of the patient's weight of F kg).

He/She should/did receive a dose of Rabies Vaccine on [date]; you should arrange for subsequent doses to be given on days [A, B, C etc] from the date of the first dose.

When you record details of the administration of the vaccine and/or immunoglobulin in the patient record, please also record the batch number.

If you have any problems in arranging follow up of this patient for the necessary doses of Rabies vaccine, please do not hesitate to contact the Public Health Unit (bh: ah: ) for assistance.

Yours sincerely
[name]
Director

encl. [usually sent with info about vaccine etc]