Etiology
Rabies is neurotropic rhabdovirus that causes fatal infection in dogs, cats and humans. Usually infection is transmitted by inoculation with saliva by means of a bite. The virus then spreads into the CNS via peripheral nerves. Once the brain is infected, the virus spreads out through peripheral nerves to the salivary glands among other targets – at this point, the animal can transmit rabies.
Signalment
Any dog, cat, horse, cow, HUMAN
Clinical Signs
Two syndromes are described:
Furious syndrome (forebrain signs)
Paralytic syndrome (lower motor neuron signs ascending from the site of the bite).
Once neurologic signs are present, progression is rapid, and most animals will be dead within several days. Rabies should be considered as a differential diagnosis in any animal with acute onset, rapidly progressive neurologic disease especially if there is a poor vaccination history or exposure to other rabid animals.
Diagnostic Tests
Key point: Definitive diagnosis can only be achieved postmortem, and requires fluorescent antibody staining of brain tissue to demonstrate rabies antigen. A serum RFFIT (Rapid fluorescent foci inhibition test) can be performed to evaluate for evidence of previous vaccination however it should NOT be used to make a diagnosis of active rabies infection. Due to the neurotropic nature of rabies it can remain undetected by the immune system and therefore cause a negative (false negative) RFFIT antibiotic result.
Further reading
If you're interested in reading about a real case of Rabies virus infection please check out this article. https://doi.org/10.5326/0390547 I saw this case a number of years ago, but the disease hasn't changed much in 20 years! Furthermore, a rabies positive bat was identified on a sidewalk in Dane county just this week. Although fewer Rabies positive bats have apparently been identified this year (so far) the virus is still around and therefore still something we should be talking about!
Thanks for reading! Rabies virus infection is something I think about daily, given the cases that I see, and is one of the more daunting diseases we are faced with. Please reach out if you have any questions!
Other good resources:
The Wisconsin Rabies Algorithm: (for exposure or sick animals) https://www.dhs.wisconsin.gov/rabies/algorithm/algorithmcategories.htm
Illinois Rabies information: https://www.ilga.gov/commission/jcar/admincode/008/00800030sections.html