1 figure omitted
On September 28, 2002, a man aged 20 years residing in Linn County,
Iowa, died from rabies encephalitis caused by infection with a variant of
rabies virus associated with silver-haired (Lasionycteris
noctivagans) and eastern pipistrelle (Pipistrellus
subflavus) bats. This is the first case of human rabies in Iowa since
1951. This report summarizes the investigation of the case by the Linn County
and Iowa public health departments. Bats found in living quarters should be
submitted to local public health laboratories for rabies testing.
On September 16, the man sought care at the emergency department of
a Cedar Rapids hospital complaining of nausea and vomiting, generalized abdominal
pain, shortness of breath, headache, and back stiffness. He reported drinking
numerous beers and expressed a concern about alcohol poisoning. The patient
was treated with an antiemetic and discharged with prescriptions for antianxiety
and antinausea medications. He returned later the same day for reevaluation
but left without being seen. He returned again the next day complaining of
the same symptoms, at which time he was noted to be hostile, paranoid, and
hallucinating. He was admitted to the hospital with a diagnosis of suspected
drug reaction or withdrawal syndrome. Brain magnetic resonance imaging (MRI)
and electroencephalogram (EEG) performed during the first 24 hours of hospitalization
were normal, and the patient received multiple doses of sedative-hypnotic
drugs for treatment of agitation. His condition deteriorated with development
of fever of 101.5°F (38.6°C) and increasing tremors, followed by intractable
seizure requiring intensive care. On September 19, he was placed on ventilator
support. He received empiric therapy for encephalitis, including acyclovir
and ceftriaxone, and multiple anticonvulsants. On September 23, the patient
had evidence of profound neurologic impairment with fixed and unreactive pupils,
and repeat neuroimaging showed early herniation. A surgical procedure to decrease
intracranial pressure was performed, and a brain biopsy (occipital lobe) was
taken. Contact and droplet precautions were initiated after the procedure.
On September 28, ventilator support was withdrawn, and the patient died.
On September 25, clinical specimens, including occipital lobe biopsy
tissue impression slides, cerebrospinal fluid, and saliva, were submitted
for rabies virus evaluation to the University of Iowa Hygienic Laboratory
(UHL). Direct fluorescent antibody (DFA) staining of the occipital lobe biopsy
slides was inconclusive but suggestive of rabies infection. A subsequent nuchal
biopsy, taken on September 27 and sent to CDC laboratories, was strongly positive
by DFA for rabies virus antigen and was positive by reverse transcription
polymerase chain reaction (RT-PCR) for rabies virus RNA. The virus variant
involved in this infection was determined by DNA sequence analysis to be most
similar to variants found in silver-haired and eastern pipistrelle bats. The
diagnosis was confirmed postmortem at UHL by DFA examination of specimens
from the brain stem and cerebellum.
The source of the patient's infection remains unclear. No specific history
of exposure to bats was reported. The patient had been bitten by a dog approximately
12 days before admission; the animal was determined to be free of rabies.
No evidence of bat infestation in the patient's house was found, and family
and friends did not recount any episodes of potential contact between the
patient and bats.
The patient apparently was healthy before this incident. A substantial
portion of the patient's social activity occurred during evenings, and preliminary
investigation suggested that multiple persons could have been exposed to live
virus from the patient through shared use of glasses, bottles, cigarettes,
and other vehicles for saliva contamination of mucus membranes. The patient
was a musician and had traveled to recording studios in several cities in
Iowa and Illinois during the prodrome of his illness. Because family members
were not able to provide public health authorities with contact information
for many of the patient's associates, a decision was made, with consent of
family members, to release the patient's name to the media to facilitate contact
tracing and screening for rabies post-exposure prophylaxis (PEP). County public
health staff also attended funeral services to counsel associates of the patient
who had not yet come forward. A total of 53 family members or associates of
the patient received PEP. No persons with potential exposure outside of the
Cedar Rapids area were identified.
Several hospital staff also reported potential exposure to the patient's
bodily fluids before isolation precautions were initiated. Public health officials
presented information to potentially exposed employees on September 30. Hospital
staff were requested by hospital administrators to make their own risk assessment
and decision about starting PEP based on the information provided. A total
of 71 hospital staff, including five physicians, received PEP.
F Franks, DO, St. Luke's Hospital, Cedar Rapids; M Gilchrist, PhD, R
Groepper, M Pentella, PhD, Univ of Iowa Hygienic Laboratory, Iowa City; R
Currier, DVM, P Quinlisk, MD, C Lohff, MD, Iowa Dept of Health. C Rupprecht,
VMD, Div of Viral and Rickettsial Diseases, National Center for Infectious
Diseases; MG Reynolds, PhD, T Boo, MD, EIS officers, CDC.
Incidence of human rabies in the United States has declined sharply
during the last several decades, from an average of 11 persons per year in
the 1950s to fewer than three persons per year during the 1990s.1,2 This
decline is associated largely with successful control of rabies in domestic
dogs. Nonbite-associated (i.e., cryptic) cases of rabies—those cases
for which no evidence or history of animal bite is established3—now
constitute the largest category of human rabies cases in the United States
(78% of all cases occurring during the 1990s compared with 23% during the
1950s). A history of animal bite was reported in only seven of the last 35
documented human rabies cases (five dog bites acquired overseas and two bat
bites acquired domestically). The high proportion of cases that are reported
as cryptic probably is attributable to several factors, including the difficulties
associated with obtaining detailed exposure histories from neurologically
impaired patients and the possibility that bites from very small mammals,
such as bats, might go unnoticed.
Molecular typing of viral RNA obtained from clinical specimens permits
rapid identification of the virus variant involved in the infection, but virus
typing in the absence of specific exposure history cannot identify the source
of human rabies infections definitively. Variants specific to one vertebrate
host can be found in animal species other than that of their natural reservoir;
for example, bat-variant rabies viruses have been found in domestic cats.4 However, virus typing provides a valuable epidemiologic clue to the
source of an infection and is important for targeting prevention efforts.
In the case described in this report, the rabies virus type was determined
to be most similar to that found naturally in silver-haired and eastern pipestrelle
bats, which range widely throughout North America, including Linn County.
Both are solitary, forest-dwelling animals not found commonly in human dwellings.
This is the third report of human rabies published during 2002.5,6 All were attributed to viruses identified as bat variants (two silver-haired/eastern
pipistrelle variant and one Mexican free-tail variant); none of the three
cases had a specific history of bat bite recorded. Of 35 human rabies deaths
recorded since 1990 in the United States, 26 (74%) have been associated with
bat-variant rabies viruses, but in only two cases was a bite history documented.2 Human rabies is preventable with properly performed and timely administration
of rabies PEP.7 However, prevention efforts are complicated if
the patient does not recognize that an exposure has occurred.
Although bats have an important role in local ecosystems, they can be
a source of rabies infection in humans. Messages to the public should emphasize
that bats can transmit rabies virus to humans. Bats should be excluded from
human living quarters and should never be handled with bare hands. When a
bat is found in living quarters and the possibility exists that an unrecognized
exposure has occurred, the animal should be submitted to a local public health
laboratory for diagnostic testing. Testing of suspect animals ensures rapid
PEP where indicated and minimizes unnecessary prophylaxis in persons not exposed
to rabies virus.
This report is based on data reported by K Erickson, Linn County Public
Health Dept, Iowa. C Hanlon, VMD, L Orciari, MS, Div of Viral and Rickettsial
Diseases, National Center for Infectious Diseases, CDC.
References: 7 available
Human Rabies—Iowa, 2002. JAMA. 2003;289(10):1235-1236. doi:10.1001/jama.289.10.1235