Pre-exposure prophylaxis for rabies is worth a shot 

Thiruvananthapuram The death of a 19-year-old college student at Palakkad due to rabies, even after she had been administered the immunoglobulin serum and full vaccination as per schedule, has created much anxiety among the public. This year, Kerala has already reported 14 rabies deaths.

“A series of activities at the human, animal and environmental levels need to go hand in hand for effective rabies prevention. Human rabies will continue to be perpetuated if we focus only on vaccination after exposure and yet fail to address issues in the field. These include intensive surveillance of human and animal rabies, anti-rabies vaccination for animals, control of animal population and rabies education in a more coherent manner,” says T. S. Anish, Additional Professor of Community Medicine, Government Medical College, Manjeri.

Timely vaccination after the animal bite is a successful strategy to prevent rabies. But focusing only on the treatment of people after the bite is not enough, because delays in vaccination or partial vaccination can be dangerous in a disease which is almost 100% fatal

PrEP recommended

Pre-exposure prophylaxis (PrEP) or rabies vaccination administered ahead, to protect a person from getting rabies from possible animal bites, is a strategy normally recommended for those whose occupation frequently puts them at risk of animal bites, like veterinarians or animal handlers.

However, in a rabies-endemic State, where a practical solution seems to evade the control of stray dog population and people are quite lax about the annual rabies vaccination for pets, the background risk of a random canine bite turning out to be fatal can be reduced if some attention is paid to pre-exposure prophylaxis, says Dr. Anish.

PrEP simplifies the rabies post-exposure treatment and it may protect in cases of unrecognised rabies exposure or if treatment after the animal bite is delayed. PrEP is recommended especially for those who own pets or regularly handle pets.

Rabies virus is a neurotropic virus which targets neurons as part of their infectious cycle. When a person sustains an animal bite, the virus in the wound site attaches itself to the exposed peripheral neurons or nerve fibres at the wound site and thus enters the nervous system. To successfully infect the host (human), the virus must move from the nerve endings to the nerve cell body where it replicates.

The incubation period of the virus is variable and it can take anywhere from 7-14 days for the vaccination to develop antibodies to a level that it can kill the virus. Which is why immunoglobulin serum is administered to the wound site as soon as possible to neutralise the virus, followed by vaccination at 0-3-7-14-28 days

“If the wounds are deep, more nerve fibres are exposed, which means that the virus enters the nervous system faster. Very often, people are quite lax about seeking medical care immediately or there could be unanticipated delays in getting treatment. If you have received PrEP, antibodies against rabies are already in your body to fight the virus. A booster shot after the bite would be enough to prevent rabies,” points out Dr. Anish

Wash the wound

The first thing to do after an animal bite is washing the wound with soap and water because it will wash off about 70% of the virus particles. Immediate washing of the wound is more effective than delayed vaccination.

About 60 % of the animal bites which result in human rabies and death are caused by domestic dogs. Children often get accidental bites while playing with pet dogs and they might fail to inform parents on time. The incubation period of the rabies virus is typically 2-3 months but may vary from one week to even one year. PrEP thus protects children in cases of unrecognised rabies exposure

Faulty injection technique is also a rare possibility in cases of suspected “vaccine failure”. While Intradermal Rabies Vaccination (IDRV) is a successful strategy, some level of technical skill is required to administer the vaccine into the inner layers of the skin. If the vaccine is misinjected into the subcutaneous tissue, the vaccine will not elicit sufficient immunogenicity.

Incidence of rabies can be impacted only if the circulating rabies virus in the community can be reduced. The focus thus shifts to the One Health model wherein the human, animal and environmental components require equal attention

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Printable version | Jul 2, 2022 5:53:36 pm |