What you need to know about Rabies

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There is nothing scarier than contracting an infection that has no cure.

Yes!!!

It is super scary that sometimes such diseases can be preventable but due to some constraints we often don’t take the necessary precautions.

This blogpost will educate you properly about Rabies

INTRODUCTION

  • Rabies is derived from a Latin word “rabere” which means madness
  • It is an acute, progressive viral encephalomyelitis that principally affects carnivores and bats, although any mammal can be affected.
  • Disease is fatal once clinical signs appears
  • Rabies is present on all continents except Antarctica

HISTORY

  • 2300 BC

            Dog owners in Babylon fined heavily for deaths caused by their dogs biting people

  • Early 16th Century

            Bats spread the disease among cattle and humans in Central America

  • 19th Century

            Rabies was considered a scourge for its prevalence

  • 1885

            Rabies vaccine was developed by Louis Pasteur and Emile Roux.

AETIOLOGY

  • Rabies is caused by Lyssaviruses in the family Rhabdovirus

PATHOPHYSIOLOGY

  • After the rabies virus enters through the break in skin or bite, it replicates in the muscle thereby infecting the muscle spindle. It then infects the nerve that innervate the spindle.
  • It continues with centripetal spread of virus via peripheral nerves to the CNS.
  • Proliferation within the CNS and centrifugal spread via peripheral nerves to many tissues.
  • The highest concentration of the virus is in the saliva where it undergoes replication in the salivary gland

RABIES IN DOGS

  • Transmission

            Introduction of virus-laden saliva into tissues, usually by the bite of a rabid animal

            Although much less likely, virus from saliva, salivary glands or brain can cause infection by entering the body through fresh wounds or intact mucous membranes

  • Incubation period in dogs

            21 – 80 days post exposure

CLINICAL SIGNS

The clinical course may be divided into three general phases which are:

  1. Prodromal period: lasts for about 1-3 days, animals show only vague non-specific signs which intensify rapidly
  2. Furious period: “Mad-dog syndrome”, the animal is irritable and aggressive with the slightest provocation. Attacks indiscriminately. Dog may chew the wire and frame of their cage.
  3. Paralytic period: manifest as ataxia and paralysis of the throat and masseter muscles, often with profuse salivation and inability to swallow. Coma and death follow.

PREVENTION AND CONTROL

  1. Notification of suspected cases and euthanasia of dogs with clinical signs and dogs bitten by a suspected rabid animal
  2. Reduction of contact rates between susceptible dogs by leash laws, dog movement control and quarantine
  3. Mass immunization of dogs by campaigns and by continuing vaccination of young dogs
  4. Stray dog control and euthanasia of unvaccinated dogs.

MYTHS ABOUT RABIES

  • Rabies is rare
  • Rabies is not widespread
  • Nothing can be done to make impact towards rabies elimination.

RABIES IN MAN

  • Rabies is a vector-borne disease with high mortality in unvaccinated humans
  • The route of infection is usually by a bite or scratch from a rabid animal (dog)
  • Transmission can rarely occur between human-human but few cases have been recorded through transplant surgery
  • Incubation period is 2-3 months or 1week to 1year

CLINICAL SIGNS

There are basically two forms of the disease

  1. Furious Form: hyperactivity, excitable behavior, hydrophobia and sometimes aerophobia, death occurs after a few days due to cardio-respiratory arrest
  2. Paralytic Form: muscles gradually become paralyzed starting at the site of the bite. Coma slowly develops and eventually death occurs

DIAGNOSIS

  • History of animal exposure and typical neurologic clinical signs
  • Laboratory diagnosis

            Gold standard: Postmortem demonstration of viral antigens in CNS by Direct Fluorescent Antibody Test (D-FAT)

TREATMENT

Post exposure prophylaxis (PEP) is the immediate treatment of a bite victim and this includes:

  • Extensive washing and local treatment of the wound with soap and water, detergent, povidone iodine as soon as possible after exposure, for a minimum of 15 minutes
  • One dose of human rabies immunoglobin (HRIG) and four doses of vaccination over a 14-day period

PROGNOSIS

  • In unvaccinated humans, rabies is almost always fatal after neurological symptoms have developed. Vaccination after exposure, PEP, is highly successful in preventing the disease if administered promptly within 6 days of infection.
  • If there is significant delay the treatment still has a chance of success.

PREVENTION AND CONTROL

  • Vaccination of dogs, cats, domestic pets
  • Control of stray dogs and cats
  • Awareness on rabies
  • Preventive immunization in people

KEY FACTS

  • Rabies is a vaccine-preventable viral disease which occurs in more than 150 countries and territories
  • Infection causes tens of thousands of deaths every year, mainly in Asia and Africa
  • Dogs are the main source of human rabies deaths, contributing up to 99% of all rabies transmissions to humans.
  • Immediate, thorough wound washing with soap and water after contact with a suspect rabid animal is crucial and can save lives
  • Rabies elimination is feasible through vaccination of dogs and prevention of dog bites.
  • WHO, OIE, FAO and the GARC have established a global “United Against Rabies” collaboration to provide a common strategy to achieve “Zero human rabies deaths by 2030”.

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REFERENCES

  • Charles E. Rupprecht, VMD, MS, PhD Chief Rabies Program; Division of High Consequence Pathogens and Pathology National Center for Emerging and Zoonotic Infectious Diseases Centers for Disease Control and Prevention
  • World Health Organization News Room Fact- Sheets Detail Rabies.