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Human Rabies --- Tennessee, 2002

On August 31, 2002, a boy aged 13 years residing in Franklin County, Tennessee, died from rabies encephalitis caused by a rabies virus variant associated with silver-haired and eastern pipistrelle bats. This report summarizes the investigation by the Tennessee Department of Health (TDH). Persons should avoid direct contact with bats, other wildlife, and stray or ill domestic animals; however, if direct contact with bats has occurred, exposed persons should see their health-care provider, and the exposure should be reported to local public health officials.

On August 21, the patient complained of headache and neck pain. The next day, he experienced right arm numbness and weakness and a temperature of 100º F (37.8º C). On August 24, the patient was taken to a local hospital emergency department (ED) because of these symptoms and diplopia and was discharged home with a diagnosis of "muscle strain." On August 25, he again sought medical care at the local hospital ED. Symptoms at this time included fever of 102.0º F (39.0º C), right arm weakness, slurred speech, diplopia, nuchal rigidity, and dysphagia. The peripheral white blood cell (WBC) count was 10,000/µL (normal: 4.3--11.0/µL) with 83% lymphocytes. Laboratory results from the cerebrospinal fluid (CSF) revealed a WBC count of 220/mL (normal: 0--7/mL) with 80% lymphocytes, a protein concentration of 96 mg/dL (normal: 5--40 mg/dL), and a glucose concentration of 57 mg/dL (normal: 40--80 mg/dL). A computerized tomography scan of the head revealed no focal lesions. The patient was transferred to a regional children's hospital.

On August 26, the patient had difficulty breathing because of decreased mental status and hypersalivation. He was intubated, mechanically ventilated, and sedated because of agitation. Rabies was suspected on the basis of focal neurologic symptoms and hypersalivation, and TDH was notified. The patient's mental status deteriorated rapidly, and by the next morning, he was unresponsive and no longer required sedation. On August 31, the patient was pronounced brain dead, support was withdrawn, and the patient died.

Patient samples, including serum, CSF, saliva, and a nuchal skin biopsy, were collected and sent to CDC on August 27. No rabies virus--specific antibodies were detected in the serum and CSF samples by the indirect fluorescent antibody test. The nuchal skin biopsy was negative for rabies virus antigen by the direct fluorescent antibody test. Additional samples of serum, CSF, and saliva were sent to CDC on August 29. Rabies virus--specific antibody was detected in both the serum and CSF on August 30. The nuchal skin biopsy and saliva from August 29 were positive for rabies virus RNA by reverse transcription polymerase chain reaction. The virus was identified by genetic sequence analysis as a variant associated with silver-haired and eastern pipistrelle bats.

The patient's family had several pets, including cats, dogs, and horses, none of which had been ill. The parents reported that the patient had found a bat on the ground during the day at a nearby lake on approximately July 1 and brought it home. No other family members handled the bat, which was released the same day. The patient never reported being bitten by the bat, but at the time of the investigation the patient could not be asked directly. The family was unaware of any animal bite, and the patient never sought medical counseling or care related to the bat exposure. The family was unaware that bats might be rabid and can transmit rabies virus to humans.

Four household members and one other family member received postexposure prophylaxis (PEP) for rabies because of possible exposure to the virus through contact with the patient's saliva. In addition, 18 health-care workers who had contact with the patient received PEP.

Reported by: T Dermody, MD, M Spring, MD, K Dixon, MD, W Schaffner, MD, Vanderbilt Univ School of Medicine, Nashville; T Jones, MD, J BeVille, MD, A Craig, MD, G Swinger, DVM, Tennessee Dept of Health. C Rupprecht, VMD, Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases; D Kirschke, MD, M O'Reilly, MD, EIS officers, CDC.

Editorial Note:

This report describes a case of human rabies occurring in Franklin County, Tennessee, caused by a rabies virus variant associated with silver-haired and eastern pipistrelle bats. Overall, rates of human rabies cases in the United States remain low, averaging three cases per year during the previous decade (1). Since 1990, a total of 26 (74%) of the 35 human rabies deaths in the United States have been associated with bat-variant rabies viruses (2). This is a marked contrast with human rabies cases in Asia, Africa, and South America and with human rabies cases in the United States during the first half of the 20th century, in which canine-variant rabies predominate. It is unclear whether bat-variant human rabies virus cases have increased over time or whether more focused surveillance efforts have detected bat-variant rabies more effectively.

Issues of transmission and exposure are more complicated in bat-variant rabies than in terrestrial carnivore--variant rabies. Of the 26 human cases of bat-variant rabies in the United States since 1990, only two had known animal bites. Possible reasons for the cryptogenic nature of transmission of bat-variant rabies include 1) lack of knowledge by the general public that bats might be rabid and can transmit the virus to humans; 2) limited pain and injury inflicted by bites from the relatively small jaws and teeth of bats; and 3) viral mechanisms that might increase virulence, including increased epithelial cell tropism and muted antigenic response associated with silver-haired/eastern pipistrelle bat--variant rabies virus (3). Because the majority of human cases of bat-variant rabies lack a history of a known bite, PEP not only is indicated in the setting of a recognized bite but also might be considered in situations in which there is a reasonable possibility that a bite has occurred. The Advisory Committee on Immunization Practices (ACIP) has outlined specific bat exposure scenarios for which PEP should or should not be recommended (4). Experienced emergency-medicine physicians, infectious disease consultants, and public health officials can provide advice on using PEP for persons with complicated exposure histories.

Bat rabies has been documented throughout the continental United States. Prevention of human cases of bat-variant rabies is complicated by the cryptogenic nature of many exposures. However, certain prevention guidelines should be followed. The public should be informed that bats carry the rabies virus. Unvaccinated or untrained persons should not handle bats unless necessary. If necessary, protective gloves and safety precautions should be used. Bats are not appropriate as pets. Bats should be excluded from buildings and other structures in close proximity to humans. In cases of known or possible exposure to a bat, timely submission of the bat to public health officials facilitates testing for the presence of rabies virus, helps to ensure rapid PEP when indicated, and minimizes the unnecessary use of an expensive therapy.

References

  1. Krebs JW, Mondul AM, Rupprecht CE, Childs JE. Rabies surveillance in the United States during 2000. J Am Vet Med Assoc 2001;219:1687--99.
  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.
  3. Dietzschold B, Morimoto K, Hooper DC, et al. Genotypic and phenotypic diversity of rabies virus variants involved in human rabies: implications for postexposure prophylaxis. J Hum Virol 2000;3:50--7.
  4. CDC. Human rabies prevention---United States, 1999. Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 1999;48(No. RR-1).

Acknowledgments

This report is based on data contributed by K Bloch, MD, M Grzeszczak, MD, M Taylor, MD, J Campbell, MD, T Berutti, MD, H Beverly-Smith, MD, A Haque, MD, Vanderbilt Univ School of Medicine, Nashville, Tennessee. C Hanlon, VMD, L Orciari, MS, M Niezgoda, MS, Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases, CDC.



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