The Australian Immunisation Handbook 10th Edition 2013

4.16 RABIES AND OTHER LYSSAVIRUSES (INCLUDING
AUSTRALIAN BAT LYSSAVIRUS)
4.16.1 Virology
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 such as
the Australian bat lyssavirus (ABLV) and European bat lyssaviruses. 1
4.16.2 Clinical features
Rabies is a zoonotic disease caused by human exposure to saliva or nerve
tissue of an animal infected with rabies virus or other lyssaviruses. As the
clinical disease caused by classical rabies virus and other lyssaviruses is
indistinguishable, the term ‘rabies’ refers to disease caused by any of the known
lyssavirus species. 2-5 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. Aerosol
transmission has never been well documented in the natural environment. 6 There
has been transmission of rabies virus reported following tissue transplantation
from donors who died with undiagnosed rabies. 7 Transmission of rabies virus to
humans through unpasteurised milk may be possible; however, rare reports of
transmission via this route have not been confirmed. 8
Once a person is infected, the incubation period of rabies is usually 3 to 8 weeks,
but can range from as short as a week to, on rare occasions, several years. The
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. Typically, in the prodromal phase of rabies,
which lasts up to 10 days, the patient may experience non-specific symptoms
such as anorexia, cough, fever, headache, myalgia, nausea, sore throat, tiredness
and vomiting. 9 Paraesthesiae and/or fasciculations at or near the site of the
wound may be present at this stage. Anxiety, agitation and apprehension may
also occur. Most rabies patients present with the furious or encephalitic form. 10
In the encephalitic phase, objective 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. 10 The neurological status of the patient deteriorates
over a period of up to 12 days, and the patient either dies abruptly from cardiac
or respiratory arrest, or lapses into a coma.
PART 4 VACCINE-PREVENTABLE DISEASES 353
4.16 RABIES AND OTHER
LYSSAVIRUSES (INCLUDING
AUSTRALIAN BAT LYSSAVIRUS)