Code Ready
Log inSign up free

Level 2 of 6Must-remember

Rabies: post-exposure prophylaxis and established disease

Assess, manage and stay safe — enough on its own

The card — assess, manage, caution

Assessment— look, ask, measure

  • Decide first which of two diseases you have: a rabies exposure is an asymptomatic person bitten, scratched or licked by a potentially rabid mammal — a preventable event and a therapeutic emergency — while established rabies is a symptomatic patient with encephalitis or ascending paralysis, a diagnostic and palliative problem; treating the first with the tempo appropriate to the second is the central error in this field.
  • Take the exposure history in detail: the species, whether the attack was provoked or unprovoked, whether the animal was roaming, bit several people, was unusually aggressive or unusually docile, was drooling and unable to swallow, had hindlimb paralysis, or died within days — and whether it can be observed or has escaped.
  • Know which animals matter: dogs cause about 99% of human rabies (more than 90% of cases and 99% of deaths in low- and middle-income countries); cats are a genuine and under-recognised risk assessed exactly as for a dog; any direct contact with a bat is a high-risk exposure and a bat bite may leave no visible mark; foxes, skunks, jackals, mongooses, raccoons and wolves are established sylvatic reservoirs; non-human primates are a documented source; cattle, goats, horses, pigs and camels can transmit; rodents, rabbits, hares, birds, reptiles and fish are not implicated.
  • Establish whether saliva or neural tissue reached a break in the skin or a mucous membrane — saliva on broken or excoriated skin, saliva contaminating mouth, eye or genitalia, and handling or skinning a rabid carcass or nervous tissue with any break in the skin are the exposures most often missed; contact with intact skin, and handling clothing or bedding, are not exposures.
  • Grade the exposure by WHO category: I — touching or feeding animals, licks on intact skin (no exposure); II — nibbling of uncovered skin, minor scratches or abrasions without bleeding (vaccine, no immunoglobulin); III — single or multiple transdermal bites or scratches, licks on broken skin, contamination of mucous membranes with saliva, or any direct contact with a bat (immunoglobulin and vaccine).
  • When in doubt, treat as Category III: where it is uncertain whether skin was broken, the cost of over-treating is a course of vaccine and the cost of under-treating is a death; where the biting animal has escaped it must be considered rabid and prophylaxis initiated unless there is no endemic rabies in the area; and in a severely immunosuppressed patient Category II is managed as Category III.
  • Note the anatomy of the bite, because it predicts risk: the percentage of rabid bites leading to clinical disease ranges from about 10% for bites on the legs to 80% for bites on the head, richly innervated sites carrying the highest risk and shortest incubation.
  • Look for the danger features in the exposed patient: bites to head, face, neck, hands or genitalia; multiple or deep wounds; any bat contact, including an unrousable adult or small child found in a room with a bat whether or not a wound is visible; an animal that died or became ill within ten days; a wound over a joint or tendon; a scalp bite in a small child where skull penetration is possible; a neck bite with expanding haematoma or stridor; and immunosuppression.
  • Ask about previous rabies vaccination and document it: a documented complete previous course changes the regimen entirely (two boosters, no immunoglobulin), while undocumented or partial prior vaccination is treated as unvaccinated.
  • In the symptomatic patient look for the prodrome: two to ten days of fever, malaise, headache, anorexia, nausea and anxiety, with the one specific clue in the whole disease — paraesthesiae, pain or pruritus at or near the site of the exposure, in 50–80% of patients — so ask every encephalitic or weak patient about odd sensation, pain or itching anywhere, then inspect the site.
  • Recognise encephalitic (furious) rabies, about 80% of cases: anxiety and agitation about ten days after the prodrome begins, then hallucinations and bizarre behaviour with delirium alternating with periods of calm; hyperexcitability precipitated by auditory or visual stimuli such as a slammed door, a torch in the eyes or a draught; hydrophobia in about 50% — extremely painful pharyngeal and laryngeal spasm on attempting to drink; and aerophobia, considered pathognomonic — the same spasm provoked by a current of air across the face.
  • Recognise paralytic (dumb) rabies, about 20% of cases: symmetrical ascending flaccid paralysis closely resembling Guillain–Barré syndrome, often beginning in the bitten limb, with areflexia, sphincter disturbance and eventual bulbar and respiratory involvement, consciousness preserved until late — hyperexcitability, hydrophobia and aerophobia are lacking, and it is characteristically recognised only at autopsy.
  • Look for autonomic overactivity in established disease: hypersalivation, diaphoresis, pupillary dilatation and labile blood pressure, with hyper-reflexia and spasticity, followed by convulsions, progressive coma, respiratory paralysis and arrhythmias; death usually occurs 10–14 days after symptom onset without intensive support.
  • Remember the incubation period is long: usually 20–90 days, ranging from a few weeks to several years and averaging one to three months, rarely as short as a few days or longer than a year, with bites on the head, face and neck incubating more quickly — so patients present late and casually with a healed wound and a vague memory of a dog three weeks ago.
  • Suspect rabies on the clinical presentation with or without a history of exposure: children may say nothing about a bite sustained while playing so ask the parents separately, older patients are labelled delirium from sepsis or dementia or, in the paralytic form, stroke, and bat-variant illness may begin with focal neuropathic pain, myoclonus, hemiparesis or ataxia with no exposure history at all.
  • Understand that no laboratory test tells you whether a patient needs prophylaxis — the decision is clinical and epidemiological, and in high-risk exposures and areas where canine rabies is endemic prophylaxis is initiated without waiting for laboratory results.

Management— do this, in order

  • Wash the wound first: copious irrigation with soap and running water for a full 15 minutes, timed. The virus has a lipid envelope and soap is a lipid solvent, so mechanical removal during the extraneural replication phase prevents disease; a quaternary ammonium detergent is preferred where available and povidone-iodine is an accepted virucidal agent applied after, not instead of, the wash.
  • Irrigate deep punctures under pressure with sterile 0.9% sodium chloride, because a canine tooth creates a narrow entry over a deep contaminated cavity that surface washing does not reach; excise devitalised tissue conservatively, leaving extensive excision on the face, hand or over a joint to a surgeon.
  • Do not suture the wound — closure traps virus and bacteria in an anaerobic space and drives inoculum along tissue planes; where closure of a large facial wound is unavoidable it follows full irrigation and infiltration of immunoglobulin, with the loosest apposition and drainage.
  • Elevate and immobilise the injured part, particularly the hand, and give analgesia first if pain prevents adequate washing: paracetamol 1 g orally or intravenously (child 15 mg/kg), with morphine 2.5–5 mg intravenously titrated in an adult (0.1 mg/kg in a child) if needed.Doctor / Nurse
  • Give rabies immunoglobulin for every Category III exposure in a previously unvaccinated patient, and for any category in the severely immunosuppressed: human rabies immunoglobulin (HRIG) 20 IU/kg body weight as a single total dose, or purified equine rabies immunoglobulin (ERIG) 40 IU/kg, on day 0, weighing the patient rather than estimating.Doctor / Nurse
  • Infiltrate as much of the dose as possible into and around the wound, including into the depths of the track, using a fine needle in multiple small passes with aspiration, giving any unusable remainder intramuscularly at a site distant from the vaccine; where the volume is insufficient for multiple wounds, dilute two- to threefold in sterile 0.9% sodium chloride — dilute, do not exceed the dose.Doctor / Nurse
  • Infiltrate fingertips, eyelids, pinna and genitalia in small aliquots only, since a large volume in a closed compartment can cause compartment syndrome; observe 30–60 minutes after equine product and have adrenaline to hand, remembering that skin testing does not reliably predict anaphylaxis and is not a reason to withhold it.Doctor / Nurse
  • Give the vaccine on the day of presentation: one full dose intramuscularly on days 0, 3, 7 and 14 (Essen regimen) in the previously unvaccinated; Davidson's gives days 0, 3, 7 and 21, and WHO accepts the final dose between day 14 and day 28 — a late fourth dose is far better than an omitted one.
  • Give intramuscular vaccine into the deltoid in adults and children aged two and over, and into the anterolateral thigh under two; it must never be given into the gluteal muscle, where deposition into fat reduces immunogenicity and failures have been documented.
  • The vaccine dose is not weight-based — a neonate receives the same full dose as a 100 kg adult; only immunoglobulin is dosed by weight.
  • In a documented, complete previous course give two booster doses on days 0 and 3, with no immunoglobulin, wound washing remaining mandatory; treat undocumented or partial prior vaccination as unvaccinated with a full course plus immunoglobulin if Category III.
  • In severe immunosuppression (advanced HIV, transplantation, high-dose corticosteroid, chemotherapy) give five doses — days 0, 3, 7, 14 and 28 — plus immunoglobulin for any exposure category, and check neutralising antibody at 2–4 weeks (a titre of at least 0.5 IU/mL is conventionally adequate).Doctor / Nurse
  • Cover the bacterial infection of the bite: co-amoxiclav 875/125 mg orally 12-hourly in adults, or 45 mg/kg/day of the amoxicillin component in two divided doses in children to a maximum of 875 mg of that component per dose; intravenously, ampicillin/sulbactam 3.0 g IV 6-hourly, or ceftriaxone 2 g IV once daily plus metronidazole 500 mg 8-hourly; in penicillin allergy clindamycin or metronidazole plus either co-trimoxazole one double-strength tablet twice daily or ciprofloxacin 500 mg twice daily — prophylaxis is usually given for 3–5 days.Doctor / Nurse
  • Treat every bite as a tetanus-prone wound: give a booster if primary immunisation was completed but none received in the past five years, and immunise plus give tetanus immune globulin to those who have not completed primary immunisation; for human bites assess hepatitis B and HIV risk as well.
  • When immunoglobulin is unavailable, give the vaccine now — its absence never justifies delay; arrange immunoglobulin, still permissible up to day 7, and intensify wound treatment, which is then the only other barrier.
  • Rescue the deviations: treat a late presentation in full as if the bite were today; resume and complete an interrupted course rather than restarting it; and if vaccine was given gluteally, repeat it in the deltoid and recount the schedule from that day.
  • In established rabies, palliate: a quiet darkened single room; gown, gloves, eye protection and mask with strict sharps discipline because saliva is infectious; intravenous access early with everything given parenterally, since swallowing provokes agonising spasm; diazepam 5–10 mg IV slowly repeated as required or midazolam 2–5 mg IV, morphine 2.5–5 mg IV titrated to comfort, and chlorpromazine 25–50 mg IM for agitation watching the blood pressure — in a uniformly fatal disease under-sedation is the error.Doctor / Nurse
  • Treat the treatable alternatives empirically even when you are sure it is rabies: aciclovir 10 mg/kg intravenously 8-hourly, renally adjusted, for possible herpes simplex encephalitis, and antibiotics for possible bacterial meningitis; and give full prophylaxis to every contact with a Category II or III exposure to the patient's saliva.Doctor / Nurse

Caution— what harms

  • Never suture a bite wound — closure traps virus and bacteria in an anaerobic space and drives inoculum along tissue planes.
  • Never give rabies vaccine into the gluteal muscle: deposition into fat reduces immunogenicity and documented prophylaxis failures have followed; if it has happened, repeat in the deltoid and recount the schedule from that day.
  • Never exceed the calculated immunoglobulin dose (HRIG 20 IU/kg, ERIG 40 IU/kg) — excess immunoglobulin suppresses the patient's own response to the vaccine; dilute two- to threefold in sterile 0.9% sodium chloride if the volume will not cover the wounds.
  • Never give immunoglobulin to a person with a documented complete previous course — it blunts the anamnestic response — and never give it beyond day 7 after the first vaccine dose, because active antibody production has begun and passive antibody would interfere.
  • Never give vaccine and immunoglobulin at the same site or with the same syringe.
  • Never wait for a laboratory result before starting prophylaxis — no test tells you whether a patient needs it, and negative antemortem rabies-specific tests never exclude rabies and may need repeating after an interval.
  • There is no interval after which prophylaxis becomes pointless in an asymptomatic person, and there are no contraindications — not pregnancy, breastfeeding, infancy, minor febrile illness or immunosuppression, the last being a reason to give more rather than less; even a serious adverse reaction to a previous dose is a matter for discussion, since the risk of rabies development should be carefully considered before deciding to discontinue.
  • Start prophylaxis and stop it only for exoneration, never withhold it pending information: the only circumstances in which a started course is stopped are a negative laboratory test on the animal's brain, or a dog or cat healthy at the time of the bite and still well ten days later — rabies virus enters a dog's salivary glands only 5–7 days before the animal dies.
  • Beware the drugs that cause failure: chloroquine and hydroxychloroquine reduce the response to intradermal vaccine, so use the intramuscular route; corticosteroids blunt the antibody response and should be avoided during a course unless essential.
  • Vaccine and immunoglobulin given after symptom onset do not alter outcome and are not indicated for the patient — once virus is inside the axon it is sequestered from circulating antibody — though they are urgently indicated for exposed contacts.
  • Do not attempt oral fluids or medication in a patient with hydrophobia, since swallowing provokes agonising spasm; secure intravenous access early and give everything parenterally.
  • Perform the aerophobia or hydrophobia provocation test once only, never for demonstration: fanned air or an offered cup of water is diagnostically decisive but agonising.
  • Do not be reassured by a healed wound, a missing bite history or an animal that looks well: the incubation period is usually 20–90 days and may exceed a year, the exposure may never have been reported (a child bitten while playing may say nothing), and a bat bite may leave no visible mark.
  • Do not offer the Milwaukee protocol as standard care: therapeutic coma with ketamine and midazolam plus antiviral agents is genuinely contested, attempts to reproduce the original result have overwhelmingly failed, and it should not displace early palliation; ribavirin, interferon and amantadine have no demonstrated benefit.

Refer / escalate

Refer urgently for surgical assessment where extensive excision is needed on the face, hand or over a joint, for a scalp bite in a small child, a neck bite with expanding haematoma or stridor, or a wound over a joint or tendon; escalate immediately for any patient with suspected established rabies (hydrophobia, aerophobia, hypersalivation with inability to swallow, agitation alternating with lucidity, paraesthesiae at an old healed wound, unexplained encephalitis from an endemic area, or ascending paralysis with fever and early sphincter involvement) for barrier precautions, palliation and identification of contacts.

PreviousNext

Read the full lesson free

Create a free account to unlock every page, the level exams, and progress tracking.

Sign up freeLog in