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rabies

rabies

introduction

  • rabies is a zoonotic disease caused by human exposure to saliva or nerve tissue of an animal infected with rabies virus or other lyssaviruses.
  • Lyssaviruses are single-stranded RNA viruses in the family Rhabdoviridae, genus Lyssavirus. There are 12 known species within the genus Lyssavirus, including the classical rabies virus and other closely related lyssaviruses.
  • the clinical disease caused by classical rabies virus and other lyssaviruses is indistinguishable
  • human exposure can occur via a scratch or bite that has broken the skin, or via direct contact with the mucosal surface of a person, such as nose, eye or mouth.
  • most human cases of rabies occur after animal bites – cases after animal scratches, the licking by animals of open wounds or contact of animal saliva with intact mucous membranes are very rare.1)
  • incubation period is usually 3 to 8 weeks but can be 1 week to years
  • risk of rabies is higher, and the incubation period shorter, after severe and multiple wounds proximate to the central nervous system (such as on the head and neck) and in richly innervated sites (such as the fingers).
  • rabies is almost invariably fatal.

reducing risk and pre-exposure prophylaxis

  • contact with bats should be avoided anywhere in the world, including Australia.
  • travellers to endemic regions should be advised about pre-travel (i.e. pre-exposure) rabies vaccination (or, if appropriate, booster doses), and on what to do should they be either bitten or scratched by an animal while abroad such as immediate and thorough washing of all bite wounds and scratches with soap and water, and the application of a virucidal preparation such as povidone-iodine solution after the washing, are important measures in the prevention of rabies.
  • travellers to endemic areas should:
    • not allow young children to feed, pat or play with animals. The height of young children makes bites to the face and head more likely
    • avoid contact with stray dogs or cats. Remain vigilant when walking, running or cycling
    • not carry food, and not feed or pat monkeys, even in popular areas around temples or markets where travellers may be encouraged to interact with the monkeys. In particular, avoid focusing attention on monkeys carrying their young, as they may feel threatened and bite suddenly.
  • in the case of PEP commenced overseas, every traveller should be advised to request a PEP certificate from the vaccination centre and to obtain or record the following information (preferably in English):
    • the contact details for the clinic attended (telephone and email address)
    • the batch and source of RIG used (Note: equine RIG rather than human RIG may be used in some countries)
    • the volume of RIG administered
    • the type of cell culture vaccine used
    • the vaccine batch number
    • the number of vials used
    • the route of vaccine administration
    • the date of RIG and/or vaccine administration.

post-exposure prophylaxis (PEP) for those who have not had full rabies vaccine course

  • patients are best referred to a hospital which have supplies of rabies vaccine - in Melbourne the hospitals are RMH, MMC or the Alfred
  • other Victorian hospitals will need to contact DHS M-F business hours and vaccine gets delivered the following business day - not really very useful or expedient for the patient

  • commence course of rabies vaccine ASAP
    • 4 dose course (plus a 5th dose if immunocompromised)
    • there are two inactivated rabies cell culture-derived vaccines available in Australia:
      • Mérieux Inactivated Rabies Vaccine
      • Rabipur Inactivated Rabies Virus Vaccine (CSL)
    • dose: 1.0ml im in the deltoid (never in the buttocks as failure has been reported) for both adults and children
    • 1st dose of vaccine is given as soon as practicable (day 0), and subsequent doses are given on days 3, 7 and 14; deviations of a few days from this schedule are probably unimportant
    • immunocompromised patients should be given a 5th dose on day 28
  • PLUS give rabies specific immunoglobulin (HRIG) as soon as possible
    • can be given up to 7 days following 1st dose of rabies vaccine
    • the dose of HRIG is based on body mass and should be infiltrated in and around all wounds, using as much of the calculated HRIG dose as possible.
    • wounds to fingers and hands may be small, particularly following exposures to bats, and infiltration of HRIG into these wounds is likely to be both technically difficult and painful for the recipient. However, due to the extensive nerve supply to these sites it is important that as much of the calculated dose of HRIG as possible should be infiltrated into finger and hand wounds using either a 25 or 26 gauge needle.
    • to avoid the development of a compartment syndrome, the HRIG should be infiltrated very gently, and should not cause the adjacent finger tissue to go frankly pale or white.
    • it may be necessary to give a digital block using a local anaesthetic
    • the remainder of the HRIG dose should be administered intramuscularly at a site away from the injection site of rabies vaccine.

post-exposure prophylaxis for those who have had the full rabies vaccine course

  • only require 2 booster doses of the vaccine
  • 1st dose of vaccine is given as soon as practicable (day 0), and subsequent dose is given on day 3
  • MUST NOT be given the immunoglobulin as this may interfere with the antibody response!

post-exposure Mx of contact with Australian bats

  • Mx is as for rabies exposure above
  • no stock of Rabies Immunoglobulin is kept at any Western Health campus.
  • in the event of presentation of a potentially exposed person the on call Infectious Diseases Unit Consultant must be contacted.
  • post-exposure treatment should be considered in the following scenarios
    • person bitten or scratched by bats in Australia
    • person bitten or scratched by any animal in a country with endemic rabies
  • contact public health authorities for advice - must be made in consultation with the Health Protection Communicable Disease Prevention and Control Unit Department of Health. 1300 651 160 (BH) or 1300 790 733 (AH).
  • if post-exposure prophylaxis is indicated, the Department of Health will arrange for rapid delivery of vaccine and immunoglobulin as required
  • cleanse wound thoroughly with soap & water then povidone iodine
  • human diploid cell vaccine 1.0ml im deltoid - days 0, 3
  • if not vaccinated prior, then also give:
    • human rabies immune globulin 20IU/kg into wound and remainder into gluteal region
    • human diploid cell vaccine 1.0ml im deltoid - days 7, 14, (28) in addition to days 0 & 3.

clinical features

prodromal phase

  • lasts up to 10 days
  • non-specific symptoms such as anorexia, cough, fever, headache, myalgia, nausea, sore throat, tiredness and vomiting
  • paraesthesiae and/or fasciculations at or near the site of the wound may be present

encephalitic phase

  • signs of nervous system involvement include aerophobia, hydrophobia, bizarre behaviour, disorientation and hyperactivity.
  • signs of autonomic instability such as hypersalivation, hyperthermia and hyperventilation may occur.
  • neurological status of the patient deteriorates over a period of up to 12 days
  • patient either dies abruptly from cardiac or respiratory arrest, or lapses into a coma.

epidemiology

classical rabies virus

  • ~50,000 human deaths worldwide per annum, half of which are in India
  • occurs in land dwelling (terrestrial) mammals and is present throughout much of Africa, Asia, the Americas and Europe, where the virus is maintained in certain species of mammals, particularly dogs.
  • in countries where rabies vaccination of domestic animals is widespread (North America and Europe), wild animals such as raccoons and foxes are important reservoirs.
  • Australia, New Zealand, Japan, Papua New Guinea and Pacific island nations are currently free of rabies in terrestrial mammals.

Australian bat lyssavirus (ABLV)

  • first reported in bats in 1996
  • two cases of fatal encephalitis caused by ABLV have been reported in Australians, one in 1996 and the other in 1998

European bat lyssaviruses

  • Four human deaths from European bat lyssavirus variants have been reported in Europe.
rabies.txt · Last modified: 2018/02/28 04:00 by gary1