Rabies: What it is and why it matters to me?

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John Tiong Jeh Lung
MPharm, PhD, RPh

Lau Hui Ling
MPharm, PhD, RPh

In recent days, a number of rabies cases have been reported in Malaysia. The last canine rabies outbreak in the country was in 2015, which ended after mass vaccination and controversial culling of potentially infected animals. Despite multiple dog bite cases during that period, no cases of human rabies were reported. Although not a new disease, it is often lesser known compared to dengue and leptospirosis.

What is rabies?

Rabies is a contagious viral infection caused by Lyssavirus. While all mammals (including humans) are susceptible to rabies; dogs, foxes, wolves, skunks, racoons and bats are known to also act as ‘reservoir hosts’ where they remain as a source for transmission to other mammals.

Most of the rabies in human is transmitted through the bites or scratches of infected animals, while human to human transmission via saliva remains rare and has not been conclusively proven. Annually, the disease causes between 50,000 to 100,000 deaths worldwide (highest prevalence in Asia followed by Africa) with children under the age of 15 accounting for approximately 40% of the total number of people being bitten by infected animals.

Unvaccinated domestic pets such as dogs and cats can acquire the virus from infected reservoir hosts when they are outdoors unsupervised. Since the virus is typically found in high concentration in saliva, the disease can be transmitted to pet owners if the saliva comes into contact with wounds or mucous membranes. However, it is worth noting that the virus cannot enter your body through intact skin therefore, touching or licking on intact skin by animals will not spread the disease. Moreover, not all rabid animal bites will result in disease transmission since the viral load in the saliva of infected animals varies largely depending on species and viral strain.

Once it enters the host, the virus begins to reproduce itself in the muscles and is not easily detected during this replication phase, thus resulting in an ‘incubation period’ which ranges between days to months (typically 1-3 months). Early symptoms which are not specific to rabies occur during this period and can be easily mistaken for other conditions:

  • fever
  • headache
  • tiredness
  • pain, burning or tingling sensation at the site of the bite or infected wound

After this incubation period, the virus begins to concentrate in the salivary glands and the nerves including the central nervous system (the spinal cord and brains) leading to inflammation and the appearance of neurological symptoms which include:

  • anxiety
  • confusion
  • insomnia
  • hallucination
  • nightmares
  • irritability
  • phobias (fear of water, light, air)
  • difficulty in swallowing
  • paralysis
  • difficulty in swallowing
  • increased salivation

As the disease progresses, the patient may fall into coma, where heart and lung failures ensue. The disease is almost always deadly if treatment (such as the post-bite vaccination and/or anti-rabies immunoglobulin) is not given in a timely manner. The mortality rate is approximately 99.9% if not treated before the appearance of clinical symptoms. As a rule of thumb, always seek immediate medical attention as soon as possible if you have been bitten or have had wounds exposed to the saliva of potentially rabid animals even if you are asymptomatic.

What should I do?

  • If you suspect that you are bitten or scratched by an infected animal, wash the wound with soap and water or other useful detergents for a minimum of 15 minutes, followed by application with povidone-iodine or 70% ethanol. Seek medical attention IMMEDIATELY Post-exposure treatment is most effective when initiated soon after exposure.
  • Vaccinate your pets to break the human transmission. According to the World Health Organization, rabies is 100% vaccine-preventable which revolves around mass vaccination of animals especially dogs.
  • Watch out for signs and symptoms of infection in pets which include aggression, restlessness, apprehension, paralysis, seizures, foaming at the mouth, especially if there was prior contact with rabid or wild animals. If you suspect that your pet could be rabid; ensure it is confined (if it is safe to do so) and notify local authorities.
  • Avoid stray cats or dogs particularly in geographical area known for rabies cases.
  • Avoid handling or feeding wild animals especially the ones behaving erratically or are violent.
  • If there are bats around your housing area, seal cracks and gaps to prevent the bats from entering your home.

Together, we can nip the disease in the bud!

References:

  1. Hemachudha al. (2013) Human rabies: neuropathogenesis, diagnosis, and management. Lancet Neurol 12(5): 498-513.
  2. Leung, A., Davies, HD., & Hon, KL. (2007) Rabies: epidemiology, pathogenesis, and prophylaxis. Adv Ther 24(6): 1340-1347.
  3. Nigg, A., & Walker, PL. (2009) Overview, prevention, and treatment of rabies. Pharmacotherapy 29(10): 1182-1195.
  4. http://www.who.int/mediacentre/factsheets/fs099/en/
  5. Rupprecht, C. (1996). Medical Microbiology 4th Edition. Rhabdoviruses: Rabies Virus. S. Baron. Texas, University of Texas Medical Branch at Galveston.
  6. Disease Control Division, Ministry of Health Malaysia. Interim guideline for human rabies prevention & control in Malaysia.

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