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Human Rabies --- California, 2002

On March 31, 2002, a man aged 28 years residing in Glenn County, California, died from rabies encephalitis caused by a rabies virus variant associated with the Mexican free-tailed bat (Tadarida brasiliensis) (Figure). This report summarizes the investigation by the Glenn County Health Department (GCHD) and the California Department of Health Services (CDHS). Persons who observe abnormal behavior in any wildlife species should contact animal control or animal rescue agencies immediately and should avoid approaching or handling these animals.

On March 18, the patient sought medical care at the emergency department (ED) of a medical center with symptoms including headache, jaw pain, photophobia, agitation, dizziness, numbness, nausea, and vomiting. He was treated for dehydration, administered analgesics, and discharged. On the following day, the patient returned to the ED with increasing headache, pain, agitation, tingling of the head and legs, nausea, and vomiting. The patient was hospitalized later that evening, and treatment was initiated with ceftriaxone. A computerized tomography scan performed on March 19 was unremarkable, except for right-sided ethmoid sinusitis. Lumbar punctures were performed on March 19 and March 22 and yielded normal results. Laboratory results from serum specimens obtained on March 28 indicated hyponatremia of 131 meq/L (normal: 136--145 meq/L), decreased uric acid of 1.5 mg/dL (normal: 2.5--8.0 mg/dL), creatine phosphokinase of 236 units/ml (normal: 25--90 units/ml), and a white blood cell count of 11,500/uL (normal: 3,700--9,400/uL). Blood and cerebrospinal fluid bacterial cultures were negative. The patient's condition continued to deteriorate with symptoms of a rapidly progressive encephalopathy. He had fever, incoherent speech, increased agitation, and copious salivation. The patient became comatose on March 27 and was placed on ventilatory support; support was withdrawn on March 31, and the patient died.

On March 27, rabies was suspected, and samples, including serum, corneal impressions, a nuchal biopsy, and saliva, were collected and sent to the CDHS Viral and Rickettsial Disease Laboratory (VRDL). No rabies virus--specific antibody was detected in the serum, and the direct fluorescent antibody (DFA) test on corneal impressions was inconclusive. On March 29, additional samples of serum and corneal impressions were collected and showed that the corneal impressions were positive for rabies virus--specific antigen by DFA and that the saliva sample was positive for rabies virus RNA by reverse transcription polymerase chain reaction (RT-PCR). The nuchal biopsy was negative by DFA. Rabies was diagnosed presumptively pending confirmation by CDC. Serum samples also were collected on March 30 and 31. The diagnosis was confirmed by CDC on April 1, with a saliva sample positive by RT-PCR. The virus was identified by genetic sequence analysis as a variant associated with the Mexican free-tailed bat. Rabies virus--specific antibody was detected at VRDL by indirect immunofluorescent antibody test in the serum samples from March 30 and 31. Histopathology results of brain tissue obtained from the autopsy showed lymphocytic infiltration of the meninges and perivascular areas within the brain parenchyma. Eosinophilic inclusions consistent with Negri bodies were found primarily in the brainstem. These features were consistent with a diagnosis of rabies viral encephalitis.

The patient's family reported that he had killed a bat in his house on March 10, although he had denied having any direct contact. The family also reported numerous bats in the home environment. An investigation of the patient's home by GCHD revealed a bat colony in the attic of the house. A bat that appeared ill was found inside the living spaces of the house on March 31 and was submitted for rabies testing and species identification. The bat was identified as a Mexican free-tailed bat; it was negative for rabies by DFA.

Four household members, two other family members, and 12 social contacts received postexposure prophylaxis (PEP) because of possible exposure to the patient through saliva. In addition, 28 health-care workers who had contact with the patient also received PEP.

Reported by: C Glaser, MD, Viral and Rickettsial Disease Laboratory; Div of Communicable Disease Control, California Dept of Health Svcs. C Rupprecht, VMD, J Childs, ScD, Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases; M Guerra, DVM, EIS Officer, CDC.

Editorial Note:

This report describes a case of human rabies caused by a Mexican free-tailed bat virus variant occurring in Glenn County, California, in 2002. The last case of human rabies acquired endemically in California occurred in September 2000 in Amador County and was associated with the same variant. A definitive exposure through an animal bite was not established for the patient in this report. The proximity of a bat colony suggests an unrecognized bite as the most probable source of exposure. Because the typical incubation period of rabies extends from weeks to months, it is unlikely that the patient's experience with a bat 1 week before illness was the source of exposure. Because the patient's home housed a bat colony, other unrecognized exposures appear likely.

In the contiguous United States, bats are a reservoir for the rabies virus, and distinct viral variants can be distinguished and associated with particular bat species. During 1990--2000, a total of 24 (75%) of 32 human rabies cases were attributed to variants of rabies virus associated with bats (1). Five cases were associated with the Mexican free-tailed bat rabies virus variant; only one person reported an exposure through a bite. Although they prefer undisturbed habitats, Mexican free-tailed bats roost in buildings, increasing the chance of contact between bats and humans (2). Only two of 24 patients with rabies caused by a bat-associated virus had been bitten by a bat (1,3). Rabies virus can be transmitted into bite wounds, open cuts, abrasions, or mucous membranes through saliva (4).

Because bats have small teeth, a bite might go undetected or be minor. Situations in which an exposure might have occurred in the absence of an obvious bite wound include awakening and observing a bat in the room, finding a bat in the room of an unattended child, or seeing a bat near a mentally impaired or intoxicated person. Persons cannot become infected with rabies from having contact with bat guano (feces), blood, or urine or from touching a bat on its fur. In all cases in which bat-human contact has occurred, the bat should be collected and submitted for rabies testing. If the bat is not available, local or state public health officials should be contacted to evaluate the need for rabies prophylaxis. Human and domestic animal contact with bats may be minimized by physical exclusion of bats from dwellings. Bats and other wildlife should not be handled, fed, or kept as pets. If abnormal behavior is observed in any wildlife species, animal control or animal rescue agencies should be contacted. Additional information about rabies is available from CDC at http://www.cdc.gov/ncidod/dvrd/rabies.

Acknowledgments

This report is based on data contributed by D Schnurr, PhD, R Devlin, MT, S Honarmand, E Tu, A Hewitt, E Yeh, C Kohlmeier, A Wong, D Constantine, DVM, Viral and Rickettsial Disease Laboratory; M Jay, DVM, B Sun, DVM, Div of Communicable Disease Control, California Dept of Health Svcs; D Galvon, MD, G Norton, D Holm, Glenn County Health Dept, Willows; M Lundberg, MD, T Baptista, Butte County Health Dept, Oroville; S Forner, MD, E O'Regan, MD, Enloe Medical Center; L Wong, MD, Path Sciences Medical Group, Chico, California. C Hanlon, VMD, L Orciari, MS, M Niezgoda, MS, J Smith, MS, Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases, CDC.

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. Wilkins KT. Tadarida brasiliensis. Mammalian Species 1989;331:1--10.
  3. Gibbons RV. Cryptogenic rabies, bats, and the question of aerosol transmission. Ann Emerg Med 2002;39:528--36.
  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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