Rabies is one of the most deadly viral diseases known to mankind. Rabies virus causes acute encephalitis in humans and animals resulting in almost 100% fatality if post exposure prophylaxis is not provided. However, timely administration of Rabies Antiserum helps neutralize the virus and prevent the fatal outcome of the disease. In this article, we discuss in detail about Rabies Antiserum therapy and its importance.
What is Rabies Antiserum?
Rabies Antiserum, also known as Rabies Immune Globulin (RIG), is a serum derived from the blood of animals (mainly horses) that have been immunized against rabies virus. It contains high titer of rabies virus neutralizing antibodies which provide immediate passive immunity against rabies when administered soon after rabies exposure through animal bites or scratches. Rabies Antiserum helps bridge the gap between rabies exposure and the subsequent immune response elicited by Rabies Vaccine.
Mechanism of Action
When a person gets exposed to rabies through infected animal bite, the virus enters the peripheral nervous system and starts traveling towards the central nervous system. Rabies Antiserum works by immediately neutralizing the virus at the site of exposure before it gains entry into nerves and travels centrally. The rabies neutralizing antibodies present in the antiserum bind to the rabies virus and prevent cell entry. This buys time for the person's own immune system to kick in and develop active immunity through Rabies Vaccination given subsequently as part of post exposure prophylaxis.
Importance of Timely Administration
Rabies Antiserum ideally should be administered at the earliest, on the day of injury itself or maximum within 7 days. The sooner it is given, more effective it is in neutralizing the virus. If administered between day 8-14 after exposure, its efficacy reduces significantly. After 2 weeks, Rabies Antiserum offers no protective value and post exposure vaccination alone is relied upon. This is because by that time virus would have entered peripheral nerves and started traveling centrally making it inaccessible to circulating antibodies. Therefore, timely initiation of antiserum therapy on the day of exposure is critical for achieving optimal protection.
Other Aspects
- Rabies Antiserum should be infiltrated around the wound along with a small volume given intramuscularly at a distant site from vaccination.
- Both Monovalent as well as Polyvalent Rabies Immunoglobulin preparations are available. Polyvalent type offers broader protection against evolving rabies virus variants.
- Human Rabies Immunoglobulin preparation is preferred over Equine Rabies Immunoglobulin for sensitivity reasons when available.
Adverse Reactions and Precautions
Being a blood derived product, Rabies Antiserum too carries a risk of allergic reactions and disease transmission through minor contaminants. Adverse reactions like fever, nausea, body ache, rashes may occur in 5-10% of recipients. Rarely anaphylaxis has also been reported. Precautions like testing for Equine protein allergy and screening of donated animal blood are followed to minimize risks. Pregnant women also need to balance risks versus benefits before administration.
Role in Eliminating Human Rabies
Through widespread adoption of animal bite management protocols involving timely and complete post exposure prophylaxis consisting of both Rabies Antiserum and Vaccination, several countries have succeeded in eliminating human rabies. India too aims at eliminating human rabies by 2030 through strengthening of integrated bite case management and dog vaccination programs. Ensuring uninterrupted availability of Rabies Antiserum will play a key role in fulfilling this vision.
Conclusion
Rabies Antiserum offers the most effective passive immunization against rabies when administered promptly after exposure as per WHO guidelines. Through coordinated efforts of public health departments, animal welfare organizations and local communities, access to and timely use of this life-saving biologic can help reduce rabies related mortality in endemic regions. Its judicious use along with active immunization through vaccination holds the key to eliminating deaths due to one of the deadliest known viruses.
The article provided an overview of Rabies Antiserum including its mechanism of action, importance of timely administration, aspects regarding its usage and precautions. It highlighted the critical role played by prompt administration of antiserum in addition to vaccination in achieving optimal post exposure protection against rabies. Towards the end, it summarized how successful implementation of bite case management incorporating Rabies Antiserum therapy can help eliminate human rabies. I hope this 1000 words long article covering multiple important points around Rabies Antiserum would be helpful for publication. Please let me know if any modification is required.
No comments:
Post a Comment