References:
- Global Infectious Diseases and Epidemiology Online Network: Infectious Diseases of the Philippines, 2013 eBook Edition, ISBN 978-1-61755-582-4, by Stephen Berger. Accessed here.
| Agent | VIRUS - RNA. Rhabdoviridae, Mononegavirales, Lyssavirus: Rabies virus. Other human Lyssaviruses = Mokola, Duvenhage, European Bat (EBL) |
| Reservoir | Dog Fox Skunk Jackal Wolf Cat Raccoon Mongoose Bat Rarely rodents or rabbits |
| Vector | None |
| Vehicle | Saliva Bite Transplants Air (bar aerosol) |
| Incubation Period | 1 to 3 months (As early or late as 4 days to 19 years) |
| Diagnostic Tests | Viral culture & direct immunofluorescence of saliva, CSF, corneal smears Serology Nucleic acid amplification |
| Typical Adult Therapy | Strict isolation; supportive. The Milwaukee protocol (prolonged deep sedation and support) has been successful in some cases. See Vaccines module for pre- and post-exposure schedules |
| Typical Pediatric Therapy | As for adult |
| Vaccines | Rabies Rabies immune globulin |
| Clinical Hints | Follows animal bite (rarely lick) - often after months: agitation, confusion, seizures, painful spasms of respiratory muscles, progressive paralysis, coma and death; case-fatality rate > 99% |
| Synonyms | Aravan, Australian bat lyssavirus, Ballina, BBLV, Bokeloh bat lyssavirus, Duvenhage, EBL, European bat Lyssavirus, Hondsdolheid, Hydrophobia, Ikoma lyssavirus, Irkut, Khujand, Lyssa, Mokola, Pteropus lyssavirus, Rabia, Rage, Raiva, Saint Hubert’s disease, Shimoni bat virus, Tollwut, West Caucasian bat, Wutkrankheit |
WHO Case Definition for Surveillance
An acute neurological syndrome (encephalitis) dominated by forms of hyperactivity (furious rabies) or paralytic syndromes (dumb rabies) that progresses towards coma and death, usually by respiratory failure, within 7 to 10 days after the first symptom if no intensive care is instituted.
- Bites or scratches from a suspected animal can usually be traced back in the patient medical history.
- The incubation period may vary from days to years 1 but usually falls between 30 and 90 days.
Laboratory criteria for diagnosis: one or more of the following
- Detection of rabies viral antigens by direct fluorescent antibody (FA) in clinical specimens, preferably brain tissue (collected post mortem)
- Detection by FA on skin or corneal smear (collected ante mortem)
- FA positive after inoculation of brain tissue, saliva or CSF in cell culture, in mice or in suckling mice
- Detectable rabies-neutralizing antibody titer in the CSF of an unvaccinated person
- Identification of viral antigens by PCR on fixed tissue collected post mortem or in a clinical specimen (brain tissue or skin, cornea or saliva)
- Isolation of rabies virus from clinical specimens and confirmation of rabies viral antigens by direct fluorescent antibody testing
Case classification
- Rabies:
- Suspected: A case that is compatible with the clinical description.
- Probable: A suspected case plus history of contact with suspected rabid animal.
- Confirmed: A suspected case that is laboratory-confirmed.
- Rabies exposure:
- Possibly exposed: A person who had close contact (usually a bite or scratch) with a rabies-susceptible animal in (or originating from) a rabies-infected area.
- Exposed: A person who had a close contact (usually a bite or scratch) with a laboratory-confirmed rabid animal.
The initial symptoms of rabies are often limited to low grade fever and pain or paresthesia at the site of inoculation.
- Progressive encephalitis then ensues.
- “Furious rabies” is characterized by hyperactivity, fluctuating level of consciousness, aerophobia and hydrophobia.
- Bizarre behavior and lack of focal neurological signs are typical.
- Hydrophobia may manifest as ‘jerky’ inspiratory spasms progressing to opisthotonus, generalized seizures or cardiorespiratory arrest.
- Similar reactions may be elicited by fanning the patient (“aerophobia).
- Paralytic (“dumb”) rabies is characterized by progressive flaccid paralysis, with fasciculation and pain in the affected muscles.
- Minor sensory disturbances may be present. Such patients may survive for as long as one month, ultimately dying of bulbar and respiratory paralysis.
- Rare instances of survival have been documented.
- In Africa, rabies is often mis-diagnosed as cerebral malaria.