Diagnosis of Rabies

Treatment for rabies should be administered if there is any reasonable ground for suspicion. An accurate diagnosis is not always possible. In the event that the exposure is not detected it would be too late when the eventual appearance of symptoms confirms the presence of rabies. Vaccines for rabies are therefore administered if there is even a possibility of exposure, not just if there is definite contamination. Doctors will typically make enquiries to ascertain and measure the risks before deciding on the course of action:

  • Was the bite from a domestic animal? If so, was the animal behaving in an unusual manner?
  • Was the bite from an animal prone to rabies? These may include mice, hamsters, rats or wild animals like raccoons and skunks.
  • Was the animal vaccinated? Most domesticated animals are given rabies vaccines.
  • Was there any exposure to saliva near a scratch, wound or mucus membrane?
  • Is rabies prevalent in the region where the bite occurred?

Based on the answers to these questions, the doctor will decide if rabies treatment is necessary. The doctor may also consult with public health officials in the area. If the animal that bit the individual is caught, it can be examined for symptoms of rabies. If the animal has been killed, its brain or other tissues can be tested for the rabies virus. The diagnosis of rabies is most likely to be made in case these tests are positive. If treatment is administered within 48 hours of exposure, the success rate is found to be as high as a hundred percent.

The tests for Rabies include:

  • Direct Fluorescent Antibody (DFA) Test: This is a quick test which checks for the rabies virus protein. It is done by obtaining a sample of tissue from the area which has been exposed to infected material.
  • Polymerase Chain Reaction (PCR) Assay: This test checks for genetic material of the rabies virus proteins. This test is quite accurate and may be done on the tissues, saliva or cerebrospinal fluid.

Frequently asked questions
  1. Wolfgang Haupt, Rabies – risk of exposure and current trends in prevention of human cases, Vaccine, Volume 17, Issues 13–14, January 1999, Pages 1742-1749, ISSN 0264-410X, 10.1016/S0264-410X(98)00447-2.
  2. George M. Baer, 1 - The History of Rabies, In: Alan C. Jackson and William H. Wunner, Editor(s), Rabies (Second Edition), Academic Press, Oxford, 2007, Pages 1-22,I, ISBN 9780123693662, 10.1016/B978-012369366-2/50003-8.