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What is Rabies Antiserum?
Rabies antiserum refers to a sterile solution containing antibodies against rabies virus. It is prepared from the blood serum of animals immunized with rabies vaccines. Rabies antiserum contains rabies virus neutralizing antibodies and helps prevent rabies infection in humans when administered promptly after potential rabies exposure.
How Does Rabies Antiserum Work?
Rabies antiserum works by providing passive immunization against rabies virus. When a potentially rabid animal bites a person, the saliva containing rabies virus enters the wound. If administered quickly after exposure, rabies antiserum neutralizes the rabies virus present at the wound site before it gets a chance to spread in the body. The rabies virus neutralizing antibodies in the antiserum bind to the rabies virus and prevent it from infecting cells in the human body. This helps prevent the onset of rabies illness.
Source and Production of Rabies Antiserum
Rabies antiserum is usually produced in horses or donkeys by immunizing them against rabies virus through multiple injections of purified, inactivated rabies vaccines over weeks or months. The hyperimmune blood serum is then collected from these immunized animals containing high levels of rabies virus neutralizing antibodies. The blood serum undergoes purification, sterilization and safety testing before it is approved for human use as rabies antiserum. Equine rabies immunoglobulin is the most widely used and available type of rabies antiserum globally.
Recommended Usage of Rabies Antiserum
Rabies antiserum is recommended for post-exposure prophylaxis against rabies as per the guidelines of World Health Organization (WHO). It should be administered at the earliest possible after a potential rabies exposure along with rabies vaccines. For category II exposure like nip or superficial scratch by a potentially rabid animal, only antiserum along with the first dose of rabies vaccine is sufficient. For category III exposure involving broken skin and wounds by potentially rabid animals, both antiserum and full regimen of 5 doses of rabies vaccine on days 0, 3, 7, 14 and 30 are recommended. Antiserum provides immediate protection until the body develops its own immune response to rabies vaccination.
Quantity of Rabies Antiserum Required
The recommended dosage of rabies antiserum for passive immunization depends on the category of exposure and body weight of the exposed person. For category II exposure involving a scratch or superficial bite by a potential rabid animal, 20 IU/kg of body weight of antiserum is administered on days 0 at and around the wound site. For category III exposures involving deep wounds or bites, 40 IU/kg of antiserum should be administered on day 0, also around the wound site. Children require higher dose of antiserum per kg of body weight compared to adults.
Administration of Rabies Antiserum
The rabies antiserum is usually administered through injection around the wound site or by infiltration into and around the wound using tuberculin or other small gauge syringes. Multiple injections are given around the wound edges to achieve thorough infiltration of antibodies. Care should be taken not to inject directly into major blood vessels. The antiserum also gets rapidly distributed to other body sites through systemic absorption after local infiltration around bite or scratch wounds. Rapid administration at or near the wound site maximizes the effectiveness of antiserum.
Side Effects and Precautions of Rabies Antiserum
Rabies antiserum is generally safe and well-tolerated. Minor reactions like pain, swelling or tenderness at the injection site may occur. Allergic reactions to horse or donkey proteins in equine rabies immunoglobulin is rare but possible. Anaphylactic shock is an extremely rare but potentially life-threatening complication. As antiserum contains heterologous animal proteins, it is not advised in persons with known hypersensitivity to equines. Rabies antiserum should be administered only under proper medical supervision. Overdose can potentially suppress active immunity developed by subsequent vaccination. Hence, recommended antiserum dosage should be strictly followed.
Significance of Timely Administration of Rabies Antiserum
Rabies antiserum provides immediate active and passive immunity against rabies and prevents the virus from establishing infection when administered promptly after potential exposure. With the rabies virus multiplying rapidly at the wound site early on, timely administration of antiserum within hours or maximum days ensures maximum effectiveness. Any delay in antiserum administration can potentially allow the rabies virus to spread systemically before antibodies can neutralize it, rendering post-exposure prophylaxis ineffective in preventing clinical rabies. Hence, for an optimal outcome after a rabies exposure, rabies antiserum should be administered at the earliest under medical guidance as per WHO guidelines. Timely administration of antiserum along with vaccination series forms the mainstay for effective post-exposure prophylaxis and prevention of rabies deaths worldwide.
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1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile
