Rabies

A82.9

*Notifiable condition (Inform state veterinarian or local veterinary official)

• Description
• Diagnostic criteria
• General and supportive measures
• Medicine treatment to prevent infection
• Referral

DESCRIPTION

A viral infection of the central nervous system following transmission of the rabies virus from the saliva of affected animals through bites or contamination of mucosa or skin lesions.
Incubation period 2–8 weeks.

DIAGNOSTIC CRITERIA

Clinical

• Signs and symptoms may begin with:
  • fever,
  • headache,
  • nausea,
  • diarrhoea,
  • irritability.
• Early signs include paraesthesia or itching at site of bite in ⅓ of cases.
• The acute neurologic phase interspersed with lucid periods manifests with:
  • agitation,
  • mania,
  • hyperactivity,
  • hallucinations.
• Seizures may be precipitated by auditory or tactile stimuli.
• Hypersalivation, hydrophobia or aerophobia may occur.
• Death is usually due to cardio-respiratory failure.

Investigations

• Virus specific fluorescent antigen in brain tissue confirms diagnosis in animals.
• Preserve brain tissue of the dead animal.

GENERAL AND SUPPORTIVE MEASURES

• Symptomatic and supportive treatment.
• Prompt cleansing of the bite wound.
• Do not suture puncture wounds.
• Seek advice.

Post exposure prophylaxis

Caution
Start post exposure prophylaxis immediately.
Do not wait for confirmatory laboratory tests in the animal.

Post exposure prophylaxis may be lifesaving and should always be given if there is a reasonable suspicion that the animal may have been rabid.
The decision to give post exposure prophylaxis is based on the risk of rabies transmission, the species and behaviour of the animal and the nature of the bite. Diagnosis is largely clinical.

MEDICINE TREATMENT TO PREVENT INFECTION

Treatment depends on the risk category.

Wound treatment

Local wound care:
Flush wound thoroughly and clean with soap and water or sodium chloride 0.9% or chlorhexidine 0.05%.

• Povidone iodine 10%, topical.

For penetrating wounds:

• Tetanus toxoid (TT), IM, 0.5 mL.

Pre-emptive antibiotic only if hand is bitten or for extensive wounds or human bites. Data does not support the use of antibiotics in minor animal bites.

• Amoxicillin/clavulanic acid, oral, 30mg/kg/dose of amoxicillin component 8 hourly.

Rabies Vaccine

Must be given for category 2 and 3 bites.
Vaccine is administered on days 0, 3, 7, 14. Vaccine is ideally given as soon as possible after exposure, but should still be given if patient presents some time after the exposure. An additional dose on day 28 may be appropriate for immune compromised patients.
If vaccine administration is delayed > 48 hours, a double dose should be given initially.
Rabies vaccine is given IM but never in the buttock . Give into deltoid muscle in older children & adolescents and antero-lateral aspect of thigh in infants.

Rabies Immunoglobulin (RIG)

Must be given for all category 3 exposures.
In HIV infected children also give for category 2 exposures.
Give rabies vaccine first.
Immunoglobulin must be given as soon as possible after exposure, but may be administered up to 7 days after the first vaccine is given.
Do not give RIG if the patient has previously received pre- or post-exposure prophylaxis.

• Rabies immunoglobulin (RIG),
  • Human RIG: 20 IU/kg
    • Infiltrate as much as anatomically feasible around wound Administer remaining immunoglobulin into deltoid muscle opposite to vaccine administration site.
    • If multiple wounds, dilute in sodium chloride 0.9% to 2–3 times so that all wounds are infiltrated.
    • Do not exceed maximum dose as antibody production to the vaccine is inhibited.
    • If unavailable, do not delay active immunisation.

REFERRAL

• Where prophylactic treatment is not immediately available.
• All cases of human clinical rabies for appropriate palliative care.