Rabies
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Direct answer
Category III exposure — a transdermal bite or scratch, or saliva on broken mucosa — demands the full post-exposure package: immediate washing of the wound with soap and running water for a full 15 minutes, infiltration of rabies immunoglobulin into and around the wound, and the vaccine series, because rabies is virtually 100 per cent fatal once symptoms begin and fully preventable before them. The agent is a bullet-shaped Lyssavirus of the rhabdovirus family whose Negri bodies — eosinophilic cytoplasmic inclusions in the cerebellar Purkinje cells and hippocampal pyramidal neurons — remain the classic post-mortem finding, with ante-mortem diagnosis resting on nuchal skin biopsy, saliva polymerase chain reaction and corneal impressions. India carries an estimated 18,000–20,000 rabies deaths a year, roughly a third of the global toll, mostly from dog bites — the burden the National Action Plan for Dog Mediated Rabies Elimination by 2030 aims to end.
What you must remember
- Exposure categories: I (touching, licks on intact skin — no prophylaxis), II (nibbling of uncovered skin, minor scratches without bleeding — vaccine alone), III (transdermal bites, scratches with bleeding, licks on broken skin or mucosa — vaccine plus rabies immunoglobulin).
- Wound care is the first drug: soap and running water for 15 minutes, then povidone-iodine; avoid suturing if possible.
- Rabies immunoglobulin: infiltrate as much as possible into the wound, the remainder intramuscularly at a distant site; never exceed the calculated dose, and omit it entirely in previously vaccinated persons, who need only two booster doses.
- Indian regimens: intradermal updated Thai Red Cross — two sites on days 0, 7 and 21 at 0.1 millilitre per site, the regimen national guidelines prefer for cost and dose-sparing; or the intramuscular Essen five-dose series on days 0, 3, 7, 14 and 28 (or the four-dose Zagreb 2-1-1 schedule).
- Bites on head, neck, hands and genitalia carry the highest risk of short incubation — immunoglobulin and vaccine start the same day.
- Diagnosis: ante-mortem polymerase chain reaction on saliva, nuchal skin biopsy and corneal impressions; post-mortem direct fluorescent antibody test on brain, with Negri bodies the histological marker.
- The ten-day observation rule applies only to confined, observable dogs and cats: if the animal stays healthy ten days after the bite, prophylaxis can stop — begin it meanwhile.
- Pre-exposure prophylaxis (days 0 and 7) belongs to veterinarians, animal handlers and laboratory staff; the public system provides vaccine and immunoglobulin free in most states.
A category III bite, minute by minute
A child is bitten on the cheek by a stray dog — category III on a richly innervated site close to the brain. Wash with soap under running water for a full 15 minutes, then povidone-iodine; mechanical removal of virus at the wound is the single most effective intervention, and it is free. Do not suture primarily. Calculate equine or human rabies immunoglobulin (40 and 20 units per kilogram), infiltrate every drop possible into the cheek wound — diluting with saline for large wounds rather than leaving tissue untouched — and give the remainder intramuscularly at a distant site. Then the vaccine: two-site intradermal doses on days 0, 7 and 21, in the deltoid, never gluteal. If the dog stays healthy for ten days the series stops, otherwise it runs.
Where students slip
Category mismatches cost the first mark: a lick on broken skin is category III, and examinees treat it as II, omitting immunoglobulin. The second error is route trivia — gluteal injection and immunoglobulin given in the same limb as vaccine are both wrong, and stems quietly include them. Third, the previously-vaccinated person needs no immunoglobulin, just days 0 and 3 boosters, a detail repeatedly tested. Fourth, hydrophobia and aerophobia describe furious rabies, but the paralytic form lacks them, so ascending flaccid weakness after a forgotten dog bite is still rabies until excluded; and the ten-day observation rule applies only to confined, observable dogs and cats — Indian guidance starts prophylaxis regardless.
Frequently asked questions
What constitutes a category III rabies exposure?
Transdermal bites or scratches, licks on broken skin or mucous membranes — all requiring wound washing, rabies immunoglobulin infiltration and the full vaccine series.
How should the wound be managed first?
Wash with soap and running water for 15 minutes, apply povidone-iodine, avoid primary suturing — mechanical cleaning removes far more virus than any later step.
Which vaccine regimens are used in Indian practice?
Post-exposure: the intradermal updated Thai Red Cross regimen (0.1 millilitre at two sites on days 0, 7 and 21) or the intramuscular Essen course on days 0, 3, 7, 14 and 28; pre-exposure prophylaxis covers days 0 and 7 for high-risk groups.
How is rabies confirmed ante-mortem and post-mortem?
Ante-mortem: polymerase chain reaction on saliva, nuchal skin biopsy and corneal impressions. Post-mortem: direct fluorescent antibody on brain smear, with Negri bodies in Purkinje and hippocampal neurons.
What does a previously vaccinated bite victim need?
Wound care plus two booster doses on days 0 and 3 — no rabies immunoglobulin, because existing antibody responds immediately.