Felis ISSN 2398-2950

Rabies antibody assay

Synonym(s): Rabies blood test

Contributor(s): Paul Burr, Julien Bazelle


  • The Rabies antibody assay measures the level of neutralizing antibodies to rabies virus in all species.
  • There are 2 test systems recognized by the Office International des Epizooties (OIE):
    • FAVN (Fluorescent Antibody Virus Neutralization Test) and
    • RFFIT (Rapid Fluorescent Focus Inhibition Test), although both tests are based on similar principles.
  • Results are compared to an international standard serum and quoted in International Units/ml. A test titer of greater or equal to 0.5 IU/ml is considered to show protective levels of immunity to classical rabies virus.


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  • For both FAVN and RFFIT tests serial dilutions of the sample are incubated with an infectious dose of rabies virus.
  • Cells susceptible to the virus are subsequently added and after a further incubation period the presence or absence of virus in the culture determined using a rabies specific fluorescently tagged antibody.
  • Results for test samples are calculated in comparison to an international reference serum diluted to 0.5 IU/ml.


  • Samples must be sent to an EU recognized laboratory for this test.
  • Lists of recognized laboratories are available on DEFRA, EU and other country websites.



  • Virus neutralization tests are considered to be the best available tests for determining immunity as they demonstrate a clear biological effect on the virus. The International threshold of 0.5 IU/ml is set to ensure confidence that animals or people with antibodies at or above this level are definitely protected against classical rabies. It is possible that some individuals with lower titers may also have protective levels of immunity. There is some evidence that patients previously vaccinated but with a negative titer can retain an immunological memory (Derbyshire, 1984).

Result Data

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Further Reading


Refereed papers

  • Recent references from VetMed Resource and PubMed.
  • Mansfield K L, Burr P D, Snodgrass D R, Sayers R, Fooks A R (2004) Factors affecting the serological response of dogs and cats to rabies vaccination. Vet Rec154, 423-426 PubMed.
  • Cliquet F, Aubert M, Sagne L (1998) Development of a fluorescent antibody virus neutralisation test (FAVN test) for the quantitation of rabies-neutralising antibody. J Immunol Meth 212, 79-87 PubMed.
  • Derbyshire J B, Mathews K A (1984) Rabies antibody titres in vaccinated dogs. Can Vet J 25(10), 383-385 PubMed.


Recognized blood testing laboratories