- From ProMED-mail
Source: Morbidity and Mortality
Weekly Report, Fri 14 Nov 2003 /52(45);1102-1103
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- Rabies is an acute, progressive, incurable viral encephalitis,
caused by the bite of an infected animal. In March 2003, a previously healthy
man aged 25 years from northern Virginia died from a diagnosed illness
of meningoencephalitis of unknown etiology after a 3-week illness. Histopathologic
review of central nervous system tissues at CDC revealed viral inclusions
suggestive of Negri bodies, and subsequent tests confirmed a diagnosis
of rabies. Genetic sequencing identified a rabies virus variant associated
with raccoons, but how the patient became infected remains unknown. This
report summarizes the investigation of the first documented case of human
rabies associated with a raccoon rabies virus variant in the United States
and highlights the importance of continued education in the prevention
and diagnosis of rabies.
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- In February 2003, the patient visited his physician with
head and body aches, nausea, abdominal pain, chills, fever of 99 to 100
degrees F (37.2 to 37.7 degrees C), dry cough, and listlessness. Upon retrospective
questioning, his wife reported that he had showed mild personality changes
during the previous days. 6 days later, the patient awoke disoriented with
unsteady gait and slurred speech. He was evaluated in a local emergency
department and admitted to the hospital. Physical examination revealed
mild ataxia and confusion. Laboratory values were substantial for decreased
sodium. A lumbar puncture revealed a white blood cell count of 24/microL
(normal: 0 to 5 cells/microL), a red blood cell count of 10/microL (normal:
0 to 5 cells/microL), a glucose concentration of 58 mg/dL (normal: 40 to
70 mg/dL), and a protein concentration of 81 mg/dL (normal: 15 to 45 mg/dL).
An electroencephalogram demonstrated generalized slowing. Magnetic resonance
imaging of the brain was interpreted with a high T2 signal in the hypothalamus
and bilateral mesial temporal lobes.
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- The patient remained febrile and hyponatremic (range:
119 to 125 mmol/L) with declining mental status. On the 5th day of hospitalization,
the patient was intubated, and twitching on his right side was noted. On
day 6, he was unresponsive and had near-constant myoclonic activity. On
the 11th day, a computerized tomography scan of the head showed sulcal
effacement and diffuse cerebral edema. The patient remained comatose and
intermittently febrile. Despite aggressive critical care management, the
patient died on the 14th hospital day.
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- At autopsy, histopathologic evaluation showed severe
meningoencephalitis involving the cortex and white matter of the cerebral
hemispheres, deep gray nuclei, cerebellum, and spinal cord. Brain tissue
submitted to a research laboratory was positive by polymerase chain reaction
(PCR) for _Naegleria_.
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- The possibility of rabies was discussed briefly during
hospitalization but was discarded from further consideration on the basis
of a review of the history and clinical signs and symptoms. A brain biopsy
was planned but was canceled because of hemodynamic instability. Initial
microscopic examination of brain tissue did not detect any inclusions suggestive
of viral infection.
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- Tissues were forwarded to CDC for pathologic evaluation
for _Naegleria_. Immunohistochemical (IHC) assays for various amoebae,
including _Naegleria fowleri_, were negative. However, abundant intracytoplasmic
inclusions of neurons in several areas of the brain suggested a diagnosis
of rabies. The diagnosis was confirmed by IHC stains for rabies virus.
Further testing, including both indirect and direct fluorescent antibody
tests and reverse transcriptase-PCR of fixed brain tissue, supported the
diagnosis of rabies. Nucleotide sequence analysis and antigenic typing
with monoclonal antibodies on frozen brain tissue indicated that the specific
etiologic agent was a southeastern raccoon rabies virus variant. Genetic
sequence analysis indicated 100 percent homology with a raccoon rabies
virus variant from Virginia.
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- Approximately 125 family members and friends and 173
health-care workers were questioned retrospectively about direct unprotected
exposures to the patient's secretions and tissues. After detailed investigation,
5 family members and 3 hospital employees received post-exposure prophylaxis
for potential exposure to patient secretions.
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- The patient was an office worker who for the previous
6 years had lived, worked, and recreated in areas in which raccoon rabies
was endemic. However, extensive interviews with family, friends, and co-workers
revealed that he had no specific exposure to terrestrial animals likely
to be infected with the raccoon rabies virus variant. The patient did not
spend much time outdoors, but the potential existed for encountering a
rabid mammal while camping or in a trash can, wood pile, or other outdoor
environment.
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- MMWR Editorial Note ------------------- Approximately
7000 to 9000 cases of animal rabies are diagnosed annually in the United
States (1). This report describes the 1st documented case of human rabies
associated with a raccoon rabies virus variant. Of the 37 human rabies
cases reported in the United States since 1990, no history of suspicious
animal bite exposure was documented for 28 of the 30 cases presumed to
be acquired in the United States. With the isolation of raccoon rabies
virus from this patient, human cases have been associated with all of the
major reservoirs and vectors of the disease in the United States, including
dogs, cats, bats, foxes, skunks, coyotes, and bobcats. Human rabies cases
without a definitive history of animal exposure are associated commonly
with bat rabies viruses (2). Challenges to implicating an animal source
readily can include failure to seek medical care for perceived minor lesions,
non-recognition of the actual exposure event, communication (i.e., language)
barriers, and recall bias from memory loss or impaired speech in encephalitic
patients. Incubation periods range typically from 1 to 3 months after exposure
but in rare cases can exceed 1 year in duration, further complicating collection
of an adequate history.
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- During the late 1970s, rabid raccoons were identified
in Virginia and West Virginia after probable translocation of infected
animals from the southeastern United States. Raccoon rabies spread throughout
the region, with approximately 50 000 rabid raccoons diagnosed to date.
During 2003, Tennessee became the 20th affected state, and the enzootic
area now stretches from eastern Canada to Florida (3).
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- Rabies should be considered in the differential diagnosis
of any acute, rapidly progressive encephalitis, regardless of documented
history of animal bite. Prompt ante- or postmortem diagnosis is necessary
for accurate reporting of human rabies to public health officials and implementation
of appropriate infection-control measures, including prompt administration
of prophylaxis to exposed persons.
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- The Advisory Committee on Immunization Practices publishes
guidelines for human rabies prevention (4), and recommendations have been
published for the management of suspected cases (5). Human rabies post-exposure
prophylaxis is effective when administered promptly and properly. Human-to-human
transmission is a concern, but no cases among health-care workers exposed
to a rabies patient have been reported (6,7). In the case described in
this report, careful risk assessment based on identifiable contact with
the patient's secretions limited the number of persons receiving prophylaxis.
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- Emergency medicine physicians, infectious-disease consultants,
and state and national public health officials can provide advice on rabies
prophylaxis for complicated or unusual exposure scenarios to prevent this
fatal disease and aid in its diagnosis.
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- References:
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- (1)Krebs JW, Noll HR, Rupprecht CE, Childs JE. Rabies
surveillance in the United States during 2001. J Am Vet Med Assoc 2002;221:1690--701.
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- (2) Messenger SL, Smith JS, Rupprecht CE. Emerging epidemiology
of bat-associated cryptic cases of rabies in the United States. Clin Infect
Dis 2002;35:738--47.
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- (3) Guerra MA, Curns AT, Rupprecht CE, Hanlon CA, Krebs
JW, Childs JE. Skunk and raccoon rabies in the eastern United States: temporal
and spatial analysis. Emerg Infect Dis 2003;9:1143--50.
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- (4) CDC. Human rabies prevention---United States, 1999.
Recommendations of the Advisory Committee on Immunization Practices (ACIP).
MMWR 1999;48 (No. RR-1).
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- (5) Jackson AC, Warrell MJ, Rupprecht CE, et al. Management
of rabies in humans. Clin Infect Dis 2003;36:60--3.
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- (6)Helmick CG, Tauxe RV, Vernon AA. Is there a risk to
contacts of patients with rabies? Rev Infect Dis 1987;9:511--8.
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- (7) Noah DL, Drenzek CL, Smith JS, et al. Epidemiology
of human rabies in the United States, 1980 to 1996. Ann Intern Med 1998;128:922--30.
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