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21
An elderly man and his wife were staying at a motel in
northeast Texas. While sleeping, the husband was awakened
when he felt something on his left arm. He observed that it was
a bat, and he subsequently removed it and disposed of it. The
wife immediately examined him and saw no bite wounds. The
couple felt that no harm had occurred and did not feel medical
attention was necessary.
Two months later, the man reported feeling a sharp pain on
the left side of his face with a severe, stabbing pain in his left ear.
During the next several days, he became anorexic, developed
malaise, and seemed lethargic. He visited his primary-care
physician because of the continual burning pain in his left ear
that radiated to his chest. When queried about possible animal
exposure, he did not recall or mention the bat incident. The
patient had a temperature of 37.2°C (99.0°F) with a blood
pressure of 170/100 mm Hg (reference range, 120/80 mm Hg).
A dental examination and cardiac evaluation revealed nothing
abnormal. Pain medication was prescribed, and he was asked to
return for more outpatient diagnostic tests. The next day, while
feeling dizzy and disoriented, his evaluation as an outpatient
included a computed tomographic scan and a laryngeal
examination. The scan revealed left frontal and sphenoid
sinusitis, and the laryngeal examination revealed left vocal cord
paralysis. Antibiotics, along with antianxiety medications and
thiamine, were prescribed. However, by evening, the man had
become increasingly agitated and confused.
Five days later, the man was admitted to the hospital for
further evaluation of continuing symptoms related to anxiety,
confusion, paralysis of the left vocal cord, fever, sinusitis, rash,
and possible alcohol withdrawal. He appeared wide-eyed,
agitated, and tremulous, but he was deemed to be mentally
coherent. A light maculopapular rash was found on his back,
chest, and arms; his temperature was 37.8°C (100.1°F). He was
treated empirically with additional antibiotics and
benzodiazepines. During the next 2 days, his fever increased to
39.8°C (103.6°F); his rash persisted; and he developed ocular
motor paralysis, myoclonic tremors, and the inability to
swallow his saliva. Laboratory Results describe the findings of
analysis of fluid drawn by lumbar puncture and analysis of
serum. An electroencephalogram showed mild bilateral
cerebral dysfunction. Previous medications were discontinued,
and ofloxacin (an antiinflammatory) and vancomycin (an
antibiotic) were administered.
Three days after admission, the patient’s blood pressure
dropped dramatically to 70/40 mm Hg; he developed
respiratory distress with a partial pressure of carbon dioxide in
arterial blood (pCO2) of 90.3 mm Hg (reference range, 35-48
mm Hg); and he became semicomatose. Medication for
hypotension was administered, and he was placed on a
mechanical ventilator. The next day, the patient’s wife
remembered the bat exposure, which had occurred
approximately 2 months before hospitalization. This prompted
rabies to be suspected in the differential diagnosis. A sample of
the patient’s serum was sent to a commercial laboratory for
evaluation for rabies virus–neutralizing antibodies, and the
patient was placed in isolation. The antemortem serum sample
sent to the commercial laboratory the next day did not reveal
rabies virus–neutralizing antibodies. Over the next several days,
he became comatose, with flaccid paralysis of the extremities.
Five days later, his brain stem reflexes were absent, ventilator
support was removed, and the patient died.1,2
MICROBIOLOGY NO. MB-4 2004
RODNEY E. ROHDE, MS, SV (ASCP)
Assistant Professor, Southwest Texas State University, Clinical
Laboratory Science Department, San Marcos, Texas
PAMELA J. WILSON, RVT, MED, CHES
Program Specialist, Texas Department of Health, Zoonosis
Control Division, Austin, Texas
BONNY S. MAYES, MA
Adjunct Professor of Biology, Austin Community College,
Riverside Campus, Austin, Texas
ERNEST OERTLI, DVM, PHD
Program Director, Oral Rabies Vaccination Program, Zoonosis
Control Division, Austin, Texas
JEAN S. SMITH, MS
Rabies Microbiologist, Centers for Disease Control and
Prevention, Rabies Section, Atlanta, Georgia
TECHSAMPLE ©American Society for Clinical Pathology
Questions to be Considered:
1. When should a diagnosis of rabies be considered in the
differential diagnosis of a patient?
2. What type of samples from a human should be collected
during the early stages of a differential diagnosis of rabies,
and why is the integrity of these samples so critical to the
diagnosis of rabies?
3. What are some of the tests (antemortem and postmortem)
available for diagnosis of a suspected rabies case?
4. Why is it critical, if possible, to test a specimen from the
suspected biting animal by the direct fluorescent antibody
test or other experimental diagnostic tests?
5. What are some benefits of sending suspected rabies
isolates to reference laboratories for virus variant
characterization?
22
TECHSAMPLE MICROBIOLOGY NO. MB-4 2004 ©American Society for Clinical Pathology
Laboratory Results.
Test Patient Result Reference Range
Lumbar puncture
Peripheral WBC, /µL (×109/L) 11,000 (11.0) 4000-10,000 (4.0-10.0)
CSF protein, mg/dL 67 <45
CSF WBC, /µL 17 (48% lymphocytes, 24% neutrophils, <5
17% mononuclear cells)
CSF glucose, mg/dL (mmol/L) 84 (4.7) 50-80 (2.8-4.4)
CSF RBC, /µL 12 0
Serum
Glucose, mg/dL (mmol/L) 150 (8.3) 70-110 (3.9-6.1)
Transmission of rabies occurs when saliva containing
rabies virus is introduced into an opening in the skin, usually
via the bite or scratch of a rabid animal. Although rare,
transmission can also occur through contamination of mucous
membranes.
In the United States, rabies in humans is quite rare; just 32
deaths due to indigenously acquired rabies have occurred since
1980. Of these, 29 (90%) have been attributed to bat-associated
variants of the virus, although a bat bite was documented in
only 2 cases. Some type of encounter with a bat occurred in
approximately 45% of the cases (Table). These cases represent
various bat histories: a bat bite, direct contact with bats with
multiple opportunities to be bitten, and possible direct contact
with a bat.3-7 In approximately 21% of the cases, there was no
known exposure, but a bat had been in the house.
In addition, 14 nonindigenous cases of rabies in humans
have occurred in the United States since 1980. Recent cases of
rabies in humans have implicated bats as important wildlife
reservoirs for variants of rabies virus transmitted to humans. Even
minor bites by rabid bats are entry portals for the virus.
Subsequently, they become a transmission route for the virus.
These minor bites are often difficult, if not impossible, to identify,
which makes the decision to implement treatment difficult.
Therefore, in situations where the possibility of rabies cannot be
eliminated by testing (ie, the animal is not available), potential
exposure to bats (ie, no demonstrable bite after a bat is found in
the room of a sleeping or mentally challenged person or child)
presents the need for rabies postexposure prophylaxis (PEP).
The single most important standard diagnostic test for
rabies in animals is the direct fluorescent antibody (DFA)
test.8,9 In cases where individuals are aware of an animal
exposure with a known or suspected rabid animal, rapid and
accurate laboratory testing of the animal, if the animal is
available, allows hospital physicians to initiate timely PEP. It is
equally important to know that an animal is not rabid because
then the need for expensive and extended rabies prophylaxis
treatment can be eliminated. Even in instances where a
laboratory diagnosis is delayed, once a negative rabies result is
obtained, the PEP can be halted, preventing any further
unnecessary medical treatment and its associated costs.9The
annual Compendium of Animal Rabies Prevention and
Control10 provides recommendations about the testing of
animals suspected of rabies.
Rabies is fatal in practically all cases once symptoms begin.
Because of this, a differential diagnosis of rabies should be
suspected for individuals with signs or symptoms of
encephalitis or myelitis. Patients with these symptoms who
respond to treatment do not require rabies testing. The absence
of an exposure history does not provide evidence to terminate
any suspicions of a rabies diagnosis because most patients in
the United States have no definitive exposure history.3Indeed,
several recent cases of rabies in humans in the United States
have been diagnosed either retrospectively or after the clinical
course of the disease has progressed, despite compatible clinical
observations. A heightened awareness is needed among the
medical community of possible rabies infections in cases where
clinical signs are compatible with a diagnosis of rabies. In
addition, medical personnel must be aware of appropriate
methods for sample collection for antemortem diagnosis and
must know how to interpret the test results.11
Specimen Submission and Laboratory Procedures
A patient history form detailing the clinical history of the
patient should accompany the specimen, complete with the
name and phone number of the physician who should be
contacted with the test results.12 All samples should be
considered potentially infectious. Test tubes and other sample
containers must be securely sealed (tape around the cap will
ensure that the containers do not open during transit). If
immediate shipment is not possible, all samples, except brain
tissues, should be stored frozen at –20°C (–4.0°F) or below.
Brain tissues should be refrigerated at 0°C to 7.2°C (32°F to
45°F). Samples should be shipped frozen on dry ice (brain
tissues on wet ice or frozen gel packs) by an overnight courier
in watertight primary containers and leakproof secondary
containers that meet the guidelines of the International Air
23
©American Society for Clinical Pathology 2004 MICROBIOLOGY NO. MB-4 TECHSAMPLE
Learning Outcomes
Upon completion of this exercise, the participant should
be able to
• recognize the critical importance of obtaining an animal
exposure history from any patient with an unknown cause
of a progressive encephalopathy.
• list the type of samples to be collected for a suspected
rabies case in a human and the guidelines for collection of
these samples.
• describe the different laboratory methods (human and
animal tests) used to diagnose rabies infections, including
the standard test.
• understand the value of a reference laboratory (regional or
national) for identification of rabies isolates.
RABIES: METHODS AND GUIDELINES FOR ASSESSING A
CLINICAL RARITY
24
TECHSAMPLE MICROBIOLOGY NO. MB-4 2004 ©American Society for Clinical Pathology
Table. Human Deaths in the United States Attributed to Bat Rabies Variants.3-7
Incubation
Exposure Period/PEP†
Year Age, y Sex Location Location Variant* (if any) Exposure History
2002 20 M Iowa Iowa Lasionycteris noctivagans/ Unknown No history of bat contact; lived in house with a peaked attic
Pipistrellus subflavus‡(possibly inhabited by bats)
2002 13 M Tennessee Tennessee Lasionycteris noctivagans/ Approximately Patient picked up bat in woods near home; later released bat.
Pipistrellus subflavus 1.5 mo
2002 28 M California California Tadarida brasiliensis Unknown Patient had bat colony in attic of house; bats occasionally
entered the living quarters; unrecognized exposure to a rabid bat
appears likely.
2000 69 M Wisconsin Wisconsin Lasionycteris noctivagans/ Unknown Patient had removed bats from his house with his bare hands
Pipistrellus subflavus several times a year; a week before admission, patient asked a
friend if rabies could be acquired from an insect bite.
2000 47 M Minnesota Minnesota Lasionycteris noctivagans/ 2 mo Patient had been awakened by a bat on his right hand; he killed
Pipistrellus subflavus the bat and was bitten in the process; did not seek medical care.
2000 26 M Georgia Georgia Tadarida brasiliensis Approximately Patient rented a room in an old house; bats from the attic had
1-3 mo been entering his living quarters and landed on him when he slept.
2000 49 M California California Tadarida brasiliensis 2-3 mo A bat had flown into his house and he removed it.
1998 29 M Virginia Virginia Lasionycteris noctivagans/ Unknown No known exposure to bat (worked outside while in prison);
Pipistrellus subflavus patient too ill to provide information regarding possible exposure
history.
1997 32 M New Jersey New Jersey Lasionycteris noctivagans/ Unknown No known bite; bats found in living room on 2 separate
Pipistrellus subflavus occasions; had captured bats by hand.
1997 71 M Texas Texas Lasionycteris noctivagans/ 2 mo Awoke with bat on shoulder while staying in a motel; removed
Pipistrellus subflavus and disposed of bat; wife did not find bite marks.
1997 65 M Montana Montana Lasionycteris noctivagans 4 mo Wife reports that bat had entered home through bedroom
window; patient forced bat out with a broom; no direct contact
known.
1997 64 M Washington Unknown Eptesicus fuscus 3 mo Bitten by unknown animal/insect while working in garden.
1996 49 M Montana Unknown Lasionycteris noctivagans Unknown Bats seen outside home/work but had no known physical
contact with bats.
1996 42 F Kentucky Unknown Lasionycteris noctivagans/ Unknown Chimney open to outside; bats had opportunity to enter house,
Pipistrellus subflavus but patient denied history of animal bite.
1995 74 M California Unknown Lasionycteris noctivagans Unknown No exposure identified; reclusive rancher; history of catching
bats.
1995 28 M California California Tadarida brasiliensis Unknown Report of bat contact in workplace; family members believe a
bat had landed on patient’s chest and had been brushed off—no
specific details known.
1995 13 F Connecticut Connecticut Lasionycteris noctivagans/ 1 mo Siblings reported flying animal in room where child was sleeping.
Pipistrellus subflavus
1995 4 F Washington Washington Myotis sp§1 mo Found rabid bat in bedroom where child was sleeping.
1994 24 F Alabama Alabama Tadarida brasiliensis Unknown Disposed of dead/dying bats from chimney or attic.
1994 42 F Tennessee Unknown Lasionycteris noctivagans/ Unknown Reported no exposure to rabies but had numerous bats in
Pipistrellus subflavus residence; had 26 unvaccinated pets.
1994 41 M West Virginia West Virginia Lasionycteris noctivagans/ 4 mo? Handled mouth of bat described as red bat (likely was a
Pipistrellus subflavus reddish-colored pipistrelle); woodsman.
1994 44 M California Unknown Lasionycteris noctivagans 9 mo? Cared for sick cat.
25
©American Society for Clinical Pathology 2004 MICROBIOLOGY NO. MB-4 TECHSAMPLE
1993 82 M Texas Texas or Lasionycteris noctivagans/ Unknown No known animal bite (tended sick cow).
Arkansas? Pipistrellus subflavus
1993 11 F New York New York Lasionycteris noctivagans/ Unknown Captive bat in cage in house.
Pipistrellus subflavus
1991 27 F Georgia Georgia or Lasionycteris noctivagans/ Unknown No known animal exposure?; patient not questioned or too ill to
Tennessee? Pipistrellus subflavus provide information.
1991 29 M Arkansas Arkansas Lasionycteris noctivagans/ 3-4 wk? Caught and killed abnormally behaving bat during month preceding
Pipistrellus subflavus onset of symptoms.
1990 22 M Texas Texas Tadarida brasiliensis 47 d Bitten on finger while handling bat.
1984 12 M Pennsylvania Unknown Myotis sp Unknown Bitten by kitten, but only 6 d before onset (couldn’t have been
source); unclear whether patient was coherent during questioning.
1983 5 F Michigan Michigan Lasionycteris noctivagans 5 mo Told parents bat bit her during night; no sign of bat or bite.
1979 45 M Kentucky Unknown Lasionycteris noctivagans/ Unknown No known animal bite (hunter and farmer).
Pipistrellus subflavus
1979 24 M Oklahoma Unknown Lasionycteris noctivagans/ Unknown No known animal bite (spelunker and woodcutter).
Pipistrellus subflavus
1978 37 F Idaho Unknown Lasionycteris noctivagans 30 d Corneal transplant recipient (donor died of rabies).
1978 39 M Oregon Unknown Lasionycteris noctivagans Unknown Cornea donor (transplant recipient had Lasionycteris noctivagans
variant); no known exposure (lumberman and trapper).
1976 55 F Maryland Maryland Lasionycteris noctivagans/ 25 d/HRIG, Superficial bite on finger by Eptesicus fuscus bat.
Pipistrellus subflavus 21 DEV||
1973 26 M Kentucky Kentucky Lasionycteris noctivagans/ 22 d/HRIG? Bitten by bat on ear while asleep.
Pipistrellus subflavus
1971 64 M New Jersey New Jersey Unknown 59 d/DEV Bitten on lip by bat.
1970 6 M Ohio Ohio Unknown 20 d/14 DEV Bitten on thumb by Eptesicus fuscus while asleep (patient survived).
1962 11 M Idaho Idaho Unknown 41 d Unknown
1959 53 M California Frio Cave, Unknown 30 d? Did not recall any bite, but had blood on face after one cave trip.
Texas
1959 44 M Wisconsin Wisconsin Unknown 22 d Bitten on ear by a bat while asleep.
1958 53 F California California Unknown 57 d/PEP Bitten on finger by a Lasionycteris noctivagans bat.
1956 41 M Texas Frio Cave, Unknown Unknown Could have exposed open sores with contaminated gloves
Texas (entomologist at Texas Department of Health—rabies investigator;
had handled thousands of bats).
1951 43 F Texas Texas Unknown 16 d First reported case—bitten on arm by sick bat.
*Nucleotide sequence analysis of the viral nucleic acid implicated variants associated with these particular bat species.
†PEP indicates postexposure rabies prophylaxis.
‡Lasionycteris noctivagans/Pipistrellus subflavus is used for the eastern United States, where both bat species are present, and Lasionycteris noctivagans is used only for western states in which
Pipistrellus subflavus bats are absent.
§Myotis sp lineage with M californicus/ciliolabrum/evotis.
||HRIG indicates human rabies immune globulin; DEV, duck-embryo vaccine.
NNoottee: This information was compiled by Bonny Mayes, MA, and Rodney Rohde, MS, SV (ASCP), from the following sources: Brass, Rabies in Bats4; Centers for Disease Control and Prevention (CDC);
and personal communication with Jean Smith, CDC, and Barbara French, Bat Conservation International.
26
Transport Association. The state health department, regional
reference laboratory, and the rabies laboratory at the Centers
for Disease Control and Prevention (CDC) should be
telephoned at the time of shipment and given information on
the mode of shipment, expected arrival time, and courier
tracking number.11 In most states, it is preferable to ship by bus
or other reliable carrier; the entity that will be receiving the
shipment should be contacted for its recommendations.
Antemortem Testing Procedures
If rabies is considered as a diagnosis, a variety of samples
should be sent for antemortem study. These include nuchal
skin biopsy, saliva, serum, and cerebrospinal fluid (CSF). As
with any disease of unknown origin, personal protective
equipment and barrier protection should be used when samples
are collected. This will not only protect the technologist from
exposure to rabies if the patient is infected, but it will also
protect against any other potential pathogens that have yet to
be identified. The following instructions should be used to
collect samples only after consultation with the state health
department, the regional reference laboratory, or the rabies
laboratory at the CDC.11
Skin samples (5-6 mm in diameter) should be taken via
biopsy from the posterior region of the neck at the hairline. A
minimum of 10 hair follicles, sampled at a depth to include the
cutaneous nerves at the follicle base, should be contained in the
specimen. The specimen should be placed on a piece of sterile
gauze moistened with sterile water and placed in a sealed
container. Preservatives or additional fluids should not be
added. Laboratory tests to be performed include reverse
transcriptase–polymerase chain reaction (RT-PCR) of extracted
nucleic acids and DFA (Image 1) for viral antigen in frozen
sections of the biopsy sample.11
Saliva should be collected with a sterile eyedropper pipette
and placed in a small sterile container that can be sealed securely.
Preservatives or additional material should not be added.
Laboratory tests to be performed include detection of rabies
RNA via RT-PCR and isolation of infectious virus in cell culture.
Tracheal aspirates and sputum are not suitable for rabies tests.11
A minimum of 0.5 mL of serum or CSF should be
collected; no preservatives should be added. Whole blood
should not be submitted because it contains various inhibitors
against nucleic acid amplification techniques. If the patient has
not received vaccine or rabies immune serum, the presence of
antibody to rabies virus in the serum is diagnostic and testing
of CSF is unnecessary. Antibody to rabies virus in the CSF,
regardless of the immunization history, suggests a rabies virus
infection. Laboratory tests for antibody include the DFA and
virus neutralization.11
The rarity of rabies and the lack of an effective treatment
make brain biopsy unwarranted; however, biopsy samples
negative for herpes and other types of encephalitis should be
tested for evidence of rabies infection.11,13 The biopsy sample
should be placed in a sterile sealed container, and preservatives
or additional fluids should not be added. Laboratory tests to be
performed include RT-PCR and the DFA for viral antigen in
touch impressions.11
Integrity, type, and time of collection of antemortem
specimens are critical to the correct diagnosis of a rabies
infection. The neurotropic nature of the virus makes it
important to collect a variety of samples early and intermittently
during the course of a differential diagnosis. Because of the
properties of rabies pathogenesis, limited success of antemortem
diagnostic tests for rabies is assumed. For example, after primary
infection, the virus enters an eclipse phase during which it
cannot be easily detected within the host. This phase may last for
several days or months. Investigations have shown both direct
entry of virus into peripheral nerves at the site of infection and
indirect entry after viral replication in nonnervous tissue (ie,
muscle cells). During the eclipse phase, the host immune
defenses may confer cell-mediated immunity against viral
infection because rabies virus has good antigenic properties.
The uptake of virus into peripheral nerves is important for
progressive infection to occur. After uptake into peripheral
nerves, rabies virus is transported to the central nervous system
(CNS) via retrograde axoplasmic flow. Typically, this occurs via
sensory and motor nerves at the initial site of infection. The
incubation period is the time from exposure to onset of clinical
signs of disease and may vary from a few days to several years,
but is typically 1 to 3 months. Dissemination of virus within the
CNS is rapid and includes early involvement of limbic system
neurons. Active cerebral infection is followed by passive
centrifugal spread of virus to peripheral nerves. The
amplification of infection within the CNS occurs through cycles
of viral replication and cell-to-cell transfer of progeny virus.
Centrifugal spread of virus may lead to the invasion of highly
innervated sites of various tissues, including the salivary glands.
During this period of cerebral infection, the classic behavioral
changes associated with rabies develop, and virus present in the
saliva is intermittent.14
Postmortem Testing Procedures
Postmortem diagnosis of rabies in humans is made by the
standard test: DFA staining of viral antigen in touch
impressions of brain tissue. Portions of the brain stem, the
cerebellum, and the hippocampus should be kept refrigerated
and shipped to a public health laboratory for rabies testing.11
Preservation of tissues by fixation in formalin is not
recommended if rabies diagnosis is desired. However, if tissue
has been placed in formalin, procedures have been described to
analyze the specimen.11,15
Reference laboratories that perform rabies virus variant
characterization can offer several insights into a patient’s case. A
rabies variant characterization can aid in the elucidation of the
mystery that will often be associated with a rabies case. The
identification of the rabies virus variant may result in a clearer
understanding of the type of exposure that the patient may have
had with a rabid animal3,16 or any foreign travel by the patient.
TECHSAMPLE MICROBIOLOGY NO. MB-4 2004 ©American Society for Clinical Pathology
27
In recent years, one of the most important contributions of
rabies virus typing has been the discovery that most of the cases
for which there is no bite exposure history have been attributed
to bat rabies virus variants. A recent publication by Jackson and
Fenton17 illustrates the extremely small puncture wounds
associated with a bat bite (Images 2 and 3).
The combination of these factors led to the enhanced CDC
recommendation for bat exposures discussed previously in that
PEP is considered in all situations in which a bat bite or direct
contact with a bat may have occurred. Clarification of
epizootiologic patterns will augment the creation of appropriate
public health information and policy for prevention and control
of rabies. Indeed, among the recommendations of the National
Working Group on Prevention and Control of Rabies in the
United States are expanded resources for regional and national
virus-typing laboratories.
Public health laboratories are facing critical issues, not the least
of which is the problem of accurate surveillance of rabies virus
variants throughout the United States and other countries.
However, the successful collaboration between the CDC and the
Texas Department of Health rabies laboratory over the last 15 years
has produced the typing data to identify and map rabies variants
common to animal reservoirs in the southwestern United States and
Mexico. Appropriately used, this knowledge will allow those who
survey rabies to recognize when established reservoirs enlarge or
expand into new areas or when different animal species become
involved in cycles of rabies virus transmission. Regional laboratories
can expand and complement the flow of national surveillance data
by increasing their surveillance activities to include antigenic and
molecular typing of virus samples from surrounding states.18-20
Case Conclusion
Rabies was confirmed in the Texas patient by a DFA test
from postmortem brain samples tested by the Houston
Department of Health and Human Services-Bureau of
Laboratory Services. The diagnosis of rabies was duplicated at
the Texas Department of Health (TDH) rabies laboratory
(Rodney E. Rohde, unpublished data) and the CDC by means
of the DFA test and RT-PCR performed on brain tissue
specimens. Monoclonal antibody testing and nucleotide
sequence analysis by TDH and CDC implicated the rabies virus
to be a variant associated with silver-haired (Lasionycteris
noctivagans) and eastern pipistrelle (Pipistrellus sp) bats.
Forty-six people (4 personal contacts and 42 health care
workers) received PEP because of possible percutaneous or
mucous membrane exposure to the patient’s saliva or CSF. The
cost of antirabies prophylactic measures in association with this
case exceeded $40,000.1,2
Summary
Currently in the United States, vaccination of domestic
animals and other public health practices have made cases of
rabies in humans rare. People employed in fields associated with
high risk of exposure to rabies (eg, veterinary and laboratory
personnel, animal care and control personnel) have the added
advantage of rabies preexposure vaccination. However, unknown
exposures to animals (especially bats) will undoubtedly continue
to place people and animals at risk for rabies. Because most early
symptoms of rabies in humans typically result in a visit to a
primary-care physician, it is crucial that medical personnel be
aware of the symptoms associated with rabies infection.
A well-documented history of animal exposure is the first
clue to a possible case of human rabies. Once rabies is
suspected, the proper and timely collection of samples for
testing can determine whether or not further steps are needed,
such as the administration of PEP. Moreover, the use of
regional and national virus reference laboratories can aid in the
diagnosis and epidemiology of the case.
Key to Images
Image 1. Immunofluorescence direct fluorescent
antibody of positive rabies antigen from New York State Health
Department, Rabies Diagnostic and Research Lab (FITC label,
brain tissue, ×400).
Image 2. Puncture wound of a bite from a silver-haired
bat (Lasionycteris noctivagans) (arrow). Reprinted with
permission from Lancet.17 Copyright 2001, Elsevier Science.
Image 3. Skull of a silver-haired bat. Reprinted with
permission from Lancet.17 Copyright 2001, Elsevier Science.
Acknowledgments
We thank Beverlee Nix, DVM, MPH, and Gary Johnson, BS,
of the Texas Department of Health (TDH) Public Health Region
6, Houston, Texas, for the investigation of this case and Jane
Mahlow, DVM, MS, of the TDH Zoonosis Control Division,
Austin, Texas, for critical evaluation of the article in manuscript.
We thank the TDH Bureau of Laboratories-Rabies Section,
Austin, Texas, for diagnostic testing and variant typing of the
rabies samples, and all personnel in the Houston Department of
Health and Human Services-Bureau of Laboratory Services and
the respective hospitals involved in this investigation.
References
1. Texas Department of Health, Associateship for Disease
Control and Prevention, Zoonosis Control Division.
Epidemiology in Texas, 1997 Annual Report. Austin, TX:
1998:58-59.
2. Centers for Disease Control and Prevention. Human
rabies—Texas and New Jersey, 1997. MMWR Morb Mortal
Wkly Rep. 1998;47:1-5.
3. Noah DL, Drenzek CL, Smith JS, et al. Epidemiology of
human rabies in the United States, 1980-1996. Ann Intern
Med. 1998;128:922-930.
©American Society for Clinical Pathology 2004 MICROBIOLOGY NO. MB-4 TECHSAMPLE
28
4. Centers for Disease Control and Prevention. Human
rabies—California, Georgia, Minnesota, New York, and
Wisconsin, 2000. MMWR Morb Mortal Wkly Rep.
2000;49(49):1111-1115.
5. Centers for Disease Control and Prevention. Table of
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http://www.cdc.gov/ncidod/dvrd/rabies/Professional/publi
cations/Surveillance/ Surveillance01/Table2-01.htm.
Accessed February 28, 2003.
6. Brass DA. Rabies in Bats: Natural History and Public Health
Implications. Ridgefield, CT: Livia Press; 1994.
7. Centers for Disease Control and Prevention. Human
rabies—California, 2002. MMWR Morb Mortal Wkly Rep.
2002;51(31):686-688.
8. Dean DJ, Abelseth MK, Atanasui P. The fluorescent
antibody test. In: Meslin FX, Kaplan MM, Koprowski H,
eds. Laboratory Techniques in Rabies. 4th ed. Geneva: World
Health Organization; 1996:88-95.
9. Hanlon CA, Smith JS, Anderson GR, et al. Special series—
recommendations of a national working group on prevention
and control of rabies in the United States. Article II:
laboratory diagnosis of rabies. JAVMA. 1999;215:1444-1446.
10. Centers for Disease Control and Prevention. Compendium
of animal rabies prevention and control. MMWR Morb
Mortal Wkly Rep. 2001;50(RR-8):1-9.
11. Centers for Disease Control and Prevention. Collection of
samples for diagnosis of rabies in humans. Available at:
http://www.cdc.gov/ncidod/dvrd/rabies/professional/Prof.f
orms/antem.htm. Accessed February 28, 2003.
12. Centers for Disease Control and Prevention. Possible
human rabies—human patient form. Available at:
http://www.cdc.gov/ncidod/dvrd/rabies/professional/Prof.f
orms/patienth.htm. Accessed February 28, 2003.
13. Smith JS. Rabies virus. In: Murray PR, Baron EJ, Pfaller MA,
et al, eds. Manual of Clinical Microbiology. 7th ed. Washington,
DC: American Society for Microbiology; 1999:1099-1106.
14. Baer GM, ed. The Natural History of Rabies. Boca Raton,
FL: CRC Press; 1991.
15. Whitfield SG, Fekadu M, Shaddock JH, et al. A
comparative study of the fluorescent antibody test for
rabies diagnosis in fresh and formalin-fixed brain tissue
specimens. J Virol Methods. 2001:95:145-151.
16. Smith JS, Orciari LA, Yager PA. Molecular epidemiology of
rabies in the United States. Semin Virol. 1995;6:387-400.
17. Jackson A, Fenton MB. Human rabies and bat bites.
Lancet. 2001;357(9269):1714.
18. Rohde RE, Neill SU, Fearneyhough MG, et al. Establishing
a regional reference laboratory for rabies virus typing at the
Texas Department of Health: a work in progress. Paper
presented at: 10th Annual Rabies in the Americas Meeting;
October 1999; San Diego, CA.
19. Rohde RE, Neill SU, Clark KA, et al. Molecular
epidemiology of rabies epizootics in Texas. J Clin Virol.
1997;8:209-217.
20. Rohde RE, Mayes B, Smith JS, et al. Bat strain rabies
infections in Arizona skunks. Paper presented at: 52nd
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Transmissible to Man; June 6-7, 2002; Houston, TX.
CMLE Documentation Questions
15. Rabies should be considered in the differential diagnosis
of
A) any patient exhibiting signs and symptoms of encephalitis
or myelitis of unknown cause.
B) a patient who lives in a rural area where rabies is
endemic.
C) a patient with flulike symptoms who has traveled
internationally.
D) a patient bitten by a dog or cat with proof of rabies
vaccination.
16. The standard diagnostic test for the detection of rabies
in postmortem samples (animal or human) is
A) reverse transcriptase–polymerase chain reaction.
B) isolation of virus in culture.
C) the direct fluorescent antibody test.
D) the detection of rabies neutralizing antibody in
cerebrospinal fluid (CSF).
17. What types of specimens should be collected for the
antemortem diagnosis of rabies?
A) None—antemortem specimens are useless in the
diagnosis of rabies
B) Feces and urine
C) Sputum only
D) Nuchal skin biopsy samples, sputum, serum, and CSF
18. A regional or national rabies virus reference laboratory
can provide
A) evidence of the type of rabies virus variant responsible for
a human infection.
B) alternative therapies for a patient with rabies.
C) quarantine measures for suspected animals with rabies.
D) immunization histories of all registered pets in the state.
19. What guideline is universal for all antemortem specimen
collections?
A) The sample should not be frozen.
B) Preservatives should not be added to the sample.
C) Samples should be shipped via regular mail.
D) Preservatives should be added to the sample.
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