What is Rabies Antiserum?
Rabies antiserum refers to the antibody-rich serum obtained from animals that have been immunized against rabies virus. It contains high concentration of rabies virus neutralizing antibodies. This serum is administered to people who have been exposed to rabies virus through dog/animal bites or scratches to boost their immune system against rabies infection.
How does Rabies Antiserum Work?
When a person is exposed to rabies virus through infected animal bite, the virus enters the body through the wound and starts multiplying at the site of exposure. It then travels through the peripheral nerves to the central nervous system and brain. Rabies antiserum works by providing passive immunity against rabies virus. The rabies neutralizing antibodies present in the serum bind to the rabies virus particles in the exposed site and bloodstream and prevent them from multiplying and spreading further in the body through nerves. This provides immediate short term protection to the exposed person until their own active immunity develops through vaccination.
Post Exposure Prophylaxis (PEP) Treatment Protocol
As per the World Health Organization (WHO) guidelines, the standard post exposure prophylaxis (PEP) treatment against rabies consists of immediate thorough washing and flushing of the wound along with rabies vaccine administration along with rabies immunoglobulin/antiserum.
For category III exposures which include single or multiple transdermal bites or scratches, contamination of mucous membrane with saliva (licks) or bat bites, rabies immunoglobulin 20IU/kg body weight is administered around the wound infiltrating as much of the serum volume as possible at different sites along with the first dose of rabies vaccine on day 0.
Additional doses of rabies vaccine are given on days 3, 7, 14 and 30 for complete vaccination. Rabies immunoglobulin provides immediate virus neutralizing antibody levels for a short period of around 10-14 days until the active immunity develops in the body through vaccination by day 14. This prevents rabies virus from multiplying at the exposed site until vaccination takes effect.
Sources of Rabies Antiserum
Traditionally, equine (horse) rabies immunoglobulin was used as rabies antiserum for PEP treatment. However, due to high cost, limited availability and adverse reactions like serum sickness associated with equine IgG, it is now replaced by human or monoclonal antibody-based products.
Some commonly used antiserum products include:
– Human Rabies Immunoglobulin (HRIG): Derived from plasma of immunized human donors, it has minimal adverse reactions but limited availability.
– Equine Rabies Immunoglobulin (ERIG): Produced from immunized horses, it has greater availability than HRIG but higher risk of adverse reactions.
– Purified Chicken Embryo Cell Vaccine (PCECV) Rabies Immunoglobulin: Developed from immunized hens, this has minimal adverse reactions and acceptable efficacy.
– Monoclonal antibody products like Rabies Monoclonal Antibody (RMAb): Genetically engineered monoclonal antibodies against rabies virus have high efficacy and safety.
Administration and Precautions
Rabies antiserum needs to be infiltrated around the wound site through multiple deep injections within 24 hours of exposure as delays reduce its effectiveness. Clinical monitoring is necessary as allergic reactions may rarely occur. Those with prior equine hypersensitivity must get HRIG/RMAb. Full PEP course with vaccine must be completed even after antiserum administration for protection.
Role of Rabies Antiserum in Saving Lives
Rabies antiserum plays a crucial role in breaking the chain of rabies virus transmission and preventing fatal rabies disease in humans following exposure. By providing immediate virus-neutralizing antibody levels even before active immunity develops, it helps “buy time” for the exposed person until vaccination takes effect.
Timely administration of adequate doses of rabies antiserum along with vaccine as per PEP protocol has proven effective in preventing rabies in over 99% of cases if completed properly. This life-saving biological has contributed immensely in controlling urban rabies spread globally by preventing human deaths through rapid post-bite immunization. Improved antiserum products and wider availability is further strengthening rabies elimination efforts worldwide.
Future Prospects
Though rabies antiserum is an indispensable component of PEP, its use faces certain limitations like high production cost, limited shelf life, restricted local availability and rare adverse reactions. Research is ongoing on newer approaches like alternative routes of administration for antiserum through intradermal or intramuscular routes instead of traditional infiltration method which may improve accessibility in resource-limited settings.
Development of long-acting monoclonal antibody products are promising future prospects for replacing conventional antiserum which can do away with multiple infiltration doses requirement and extend passive immunity duration beyond two weeks. With continuous improvements in rabies control measures including newer PEP tools, the goal of eliminating human deaths due to dog-mediated rabies globally seems increasingly achievable in the coming decades.
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1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile