- rapidly progressive, acute infectious disease of the central nervous system (CNS) in humans and animal
- infection normally transmitted from animal vectors
- encephalitic and paralytic forms that progress to death
RABIES
- single-strand RNA virus
- nonsegmented, negative-sense (antisense) genome that consists of 11,932 nucleotides
- encodes 5 proteins: nucleocapsid protein, phosphoprotein, matrix protein, glycoprotein, and a large polymerase protein.
Rabies
Transmission of Rabies
Bite of an infected animal
Location where human disease of rabies is usually associated with transmission from bats
North America
incubation period of rabies
20-90 days, but in rare cases is either as short as a few days or >1 year.
- most characteristic pathologic finding in rabies
- are not observed in all cases of rabies
Negri bodies
has led to the concept that neuronal dysfunction—rather than neuronal death—is responsible for clinical disease in rabies
lack of prominent degenerative neuronal changes
GENERAL CLINICAL MANIFESTATIONS OF RABIES
atypical encephalitis with relative preservation of
consciousness
Clinical Stages of Rabies
- 20-90 days
- NO Ssx
Incubation period
Clinical Stages of Rabies
- 2-10 days
- Fever, malaise, anorexia, nausea, vomiting; paresthesias, pain, or pruritus at the wound site
Prodrome
Acute Neurologic Disease
- 2-7 days
- Anxiety,
- agitation,
- hyperactivity,
- bizarre behavior,
- hallucinations,
- autonomic dysfunction,
- hydrophobia
Encephalitic (80%)
Acute Neurologic Disease
- 2-10 days
- Flaccid paralysis in limb(s) progressing to quadriparesis
with facial paralysis
Paralytic (20%)
Acute Neurologic Disease
Coma, death Duration
0-14 days
- distinguished by earty brainstem involvement,
= results in the classic features of hydrophobia and aerophobia - Autonomic dysfunction is common and may result in hypersalivation, gooseflesh, cardiac arrhythmia, and priapism.
- episodes of hyperexcitability are typically followed by periods of complete lucidity that become shorter as the disease progresses
- These symptoms are probably due to dysfunction of infected brainstem neurons that normally inhibit inspiratory neurons near the nucteus ambiguus, resulting in exaggerated defense reflexes that protect the respiratory tract.
ENCEPHALITIC RABIES
- About 20% of patients have
= muscle weakness predominates and cardinal features of encephalitic rabies (hyperexcitability, hydrophobia, and aerophobia) are lacking. - early and prominent flaccid muscle weakness, often beginning in the bitten extremity and spreading to produce quadriparesis and facial weakness
PARALYTIC RABIES
LAB INVESTIGATION
- ANIMAL TESTING
- LUMBAR PUNCTURE
- SKIN BIOPSY
- BLOOD TEST
- HEAD MRI or CT Scan
Diagnostically useful specimens
- serum,
- CSF,
- fresh saliva,
- skin biopsy samples from the neck, and brain tissue (rarely obtained before death).
tests never exclude a diagnosis of rabies, and tests may need to be repeated after an interval for diagnostic confirmation
Negative antemortem rabies-specific laboratory tests
In a previously unimmunized patient, ___ to rabies virus
are diagnostic.
serum neutralizing antibodies
The presence of rabies virus-specific neutralizing antibodies in the CSF suggests ___, regardless of immunization status.
rabies encephalitis
A diagnosis of rabies is ___ in patients who recover from their illness without developing serum neutralizing antibodies to rabies virus
questionable
- Detection of rabies virus RNA by RT-PCR is highly sensitive and specific.
- can detect virus in fresh saliva samples, skin biopsy specimens, CSF, and brain tissues
- RT-PCR with genetic sequencing can distinguish among rabies virus variants, permitting identification of the probable source of an infection
RT-PCR AMPLIFICATION
- highly sensitive and specific for the detection of rabies virus antigen in tissues;
- the test can be performed quickly and applied to skin biopsy and brain tissue samples
- In skin biopsy samples, rabies virus antigen may be detected in cutaneous nerves at the base of hair follicles.
DIRECT FLUORESCENT ANTIBODY TESTING
treatment for rabies
- no established treatment
- ## Aggressive management with supportive care in critical care units has resulted in the survival of more than 15 patients with rabies.
