CASES/YEAR
60 (US); 55,000 (Global)
INCUBATION
Usually 3 weeks to 2 months (range of a few days to several years); [CCDM] Several weeks to several months; [CDC Travel]
INITIAL SYMPTOMS
2-10 day prodrome of fever, headache, malaise, nausea/vomiting, and paresthesias/pain at the bite site followed by delirium or paralysis; [Guerrant, p. 527]
PRECAUTIONS
Standard; "Person to person transmission rare; transmission via corneal, tissue and organ transplants has been reported. If patient has bitten another individual or saliva has contaminated an open wound or mucous membrane, wash exposed area thoroughly and administer postexposure prophylaxis." [CDC 2007 Guideline for Isolation Precautions]
COMMENTS
FINDINGS:
Patients may have paresthesias and pain, and later weakness, at the site of the bite wound. The two forms of rabies are "furious" and "paralytic." The symptomatic phase lasts for 2-14 days, followed by coma and then death about 18 days after the onset of symptoms. Patients with furious rabies have increased salivation and sweating. Cardiac arrhythmias and myocarditis may precipitate congestive heart failure.
DIFFERENTIAL DIAGNOSIS:
Opisthotonus is observed in patients with both rabies and tetanus, but rabies patients lack the persistent rigidity caused by tetanus toxin. [Guerrant, p. 529] In the differential diagnoses with paralytic rabies are Guillain-Barre syndrome, poliomyelitis, and transverse myelitis. [PPID, p. 2134]
FURIOUS RABIES & PARALYTIC RABIES
About 80% of cases are furious rabies. The other 20% are paralytic rabies, which affects the spinal cord and causes ascending flaccid paralysis. Patients with paralytic rabies do not have hydrophobia, hyperactivity, or seizures. [PPID, p. 2133, Table 163.4] Leg weakness and cranial nerve palsies are symptoms of paralytic rabies. [Cohen, p. 1461] The ascending paralysis in paralytic rabies is similar to Guillain-Barre syndrome. [ID, p. 1434]
EPIDEMIOLOGY:
Animals infected include wild and domestic Canidae: dogs, foxes, coyotes, wolves, and jackals; also bats, skunks, raccoons, mongooses, cats, and other mammals. Rarely infected are rabbits, squirrels, chipmunks, rats, mice, and opossums. Thought to occur very rarely: 1.) After saliva contact with a break in the skin or mucous membranes; 2.) Airborne transmission in bat caves or in the laboratory; [CCDM, p. 499] ". . . rabies transmission to laboratory personnel has been reported in vaccine production and research facilities after exposure to high-titered infectious aerosols. Theoretically, rabies may be transmitted to health care personnel from exposures (bite and nonbite) to saliva from infected patients, but no cases have been documented after these types of exposures." [Guidelines for Infection Control in Health Care Personnel. CDC. 1998] "During 1990--2000, a total of 24 (75%) of 32 U.S. human rabies cases were caused by bat-associated rabies virus variants. In 22 (92%) of these cases, no documentation of a bite existed; however, this does not mean that a typical bite exposure did not take place. Instead, such a history was not uncovered during presentation or case investigation." [MMWR. January 23, 2004 / 53(02);33-35] Dog rabies in the US was brought under control in the 1950s. The few cases per year in the US are now caused mostly by bats. Canine rabies is endemic in the developing world. [Cecil, p. 2466] Cases of skunk, fox, and raccoon rabies occur in specific localities of the US. [Harrison ID, p. 944]
PREVENTION:
See "Rabies Postexposure Prophylaxis." [Merck Manual, p. 1855] Immunizations should be offered to long-term travelers in endemic areas and to others in high-risk jobs. [CCDM, p. 501] Previously vaccinated patients should not receive rabies immune globulin (RIG). [Harrison ID, p. 948] The major reservoirs are carnivores and bats. All mammals (mainly terrestrial carnivores & bats) are thought to be susceptible to infection. "Bat bites anywhere in the world are a cause of concern and an indication for prophylaxis." [CDC Travel, p. 316]
DIAGNOSTIC
"A combination of tests for detection of rabies specific antibodies, antigens, and nucleic acids is needed for conclusive antemortem diagnosis." [CCDM]
SCOPE
Most of the estimated 55,000 deaths/year occur in Asia and Africa; Only 9 cases were reported in Latin America in 2012; In 2000-2012, there were 30 deaths in the US with almost all bat-associated infections; [CCDM, p. 498]
SIGNS & SYMPTOMS
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>fatigue, weakness
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>fever
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E dysphagia
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G nausea, vomiting
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N confusion, delirium
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N headache
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N lethargy
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N muscle weakness
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N opisthotonus
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N paresthesia
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N seizure
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N stiff neck
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*cranial neuropathy
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*encephalitis
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*myocarditis
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*paralysis
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*stupor, coma
ENTRY
Inhalation, Skin or Mucous Membranes (Includes Conjunctiva), Animal Bite
RESERVOIR
Cattle, Goats and Sheep, Cats, Dogs, Horses, Rabbits, Rodents, Swine, Wild Animals
RISK FACTORS
- Fail to complete immunizations
- Handle dog or cat (bite or scratch)
- Handle infected skunk, raccoon, bat, fox, or other carnivore (bite)
- Travel to endemic area
- Work in a medical or research lab
TREATMENT
"Although one patient has survived with the use of therapeutic coma without vaccination, subsequent reports of patients treated in similar fashion have been associated with a fatal outcome." [Cecil, p. 2467] "There is no established treatment for rabies." [Harrison ID, p. 947]
REFERENCES FOR CASES/YEAR
1. (US) Published in MMWR 2011 = 6; Use correction factor of 10 for reported diseases: 6 X 10 = 60;
2. (Global) 55,000 deaths per year; 15 million patients treated with post-exposure vaccination/yr; [Fact sheets from WHO 2013]