Human Rabies -- Texas and California, 1993

During November 1993, two persons, a resident of Texas and a visitor to California, died from rabies. This report summarizes epidemiologic and clinical information about these cases. Texas

On November 4, an 82-year-old male farmer residing in east Texas was admitted to a nearby hospital in Arkansas because of ataxia and dysphagia for 1 day. Family members reported that he had become forgetful and confused during the preceding 4-5 days. On November 3, a physician had prescribed ampicillin to treat a cough.

On admission, the patient could follow some commands but was hallucinating and uncooperative. Abnormal findings on physical examination included mild elevation of temperature (100.1 F {37.8 C}), increased muscle tone in his extremities, tremors, and decreased reflexes. His total white blood cell count was within normal limits (8400 cells/mm superscript 3), but a differential count showed 90% segmented neutrophils. Examination of cerebrospinal fluid (CSF) revealed 1 lymphocyte/mm3, a glucose level of 60 mg/dL, and a protein level of 42 mg/dL; a computerized tomographic (CT) scan of his brain revealed diffuse atrophy. His admitting diagnosis was cerebrovascular accident.

On November 5, the patient was intubated and pharmacologically paralyzed because of paroxysmal muscle activity. He required inotropic agents to support blood pressure and a heating blanket to maintain temperature. Because of his clinical manifestations, tetanus and rabies were considered as causes of illness; however, no history of travel or animal bite could be elicited from the patient or his family.

An electroencephalogram performed on November 9 demonstrated diffuse slowing with associated burst suppression consistent with a metabolic or toxic encephalopathy. After deep tendon and brain stem reflexes could not be elicited nor response to painful stimuli demonstrated, ventilatory support was withdrawn. The patient died, and a limited autopsy was performed.

Brain specimens were sent to the Arkansas State Health Department Laboratory and were positive for rabies by fluorescent antibody testing. Monoclonal antibody testing at the Texas Department of Health (TDH) and nucleotide sequence analysis of viral ribonucleic acid at CDC implicated a bat strain of rabies virus. Virus isolated from the patient was genetically related to the strain of rabies associated with the silver-haired bat (Lasionycteris noctivagans), a species found in all parts of the United States except the extreme southern coastal areas.

All family members were again questioned about the exposure history of the patient. The only known suspected animal exposure was to a cow that had died of an unknown disease 3 months before onset of the patient's illness. Although bats were not detected during site inspection of the patient's residence, the attic space and the living areas of the home had openings accessible from the outside.

TDH provided information to 27 family members about rabies transmission and individual counseling to determine exposure histories. Persons who had had mucous membrane or nonintact skin contact with the patient's saliva or respiratory secretions (13) and those who specifically requested treatment (two) received postexposure antirabies prophylaxis. One person requested treatment because he had assisted the decedent in providing care for the dying cow. The two morticians involved in the case also were treated. Hospital personnel in Arkansas interviewed 110 employees who had cared for the patient, and 55 received prophylaxis. California

On November 10, a 69-year-old citizen of Mexico who had been visiting relatives in California since September was evaluated at an urgent-care center for a 3-day history of increasing pain in his left jaw, chest, and shoulder; he also complained of sore throat, anxiety, insomnia, nausea, and vomiting and that he was unable to eat or drink. He related the onset to a spider bite he believed he received on his left jaw. He was transferred to a community hospital and treated for chest pain, but evaluation ruled out acute cardiac disease. The patient rejected oral fluids and continued to complain of the spider bite, although no marks were seen. He was referred to the mental health crisis unit of a second hospital, where he was noted to be anxious and dyspneic and to have impaired memory. He was diagnosed with anxiety disorder-unspecified, treated with intramuscular lorazepam, and discharged. On November 11, he returned to the second hospital in acute distress; findings on examination included fever (103 F {39.4 C}), elevated blood pressure, hypersalivation, uncontrollable spitting, and staggering gait. His leukocyte count was 16,100/mm3 (normal: 5000-10,000/mm3). He became increasingly agitated and was admitted to the intensive-care unit.

Two nurses, trained in Republic of the Philippines (where dog rabies is endemic), recognized signs consistent with manifestations of human rabies and elicited from the family a history of a dog bite to the patient in Mexico in late May or early June 1993. He had been bitten on the left side of his neck by a neighbor's puppy and had cleaned the wound with soap and water but had not received rabies prophylaxis. The patient rapidly became unresponsive and required respiratory support. A CSF sample and CT scan of the head were normal.

A nuchal skin biopsy obtained on November 12 and tested at CDC on November 16 was positive for rabies antigen by direct fluorescent antibody staining. Culture of saliva samples obtained November 12 yielded a strain of rabies virus genetically related to the strain associated with dog rabies endemic in Mexico (1 ). Corneal impressions obtained daily from November 12 through November 16 were inconclusive for rabies antigen at the California Department of Health Services Virus and Rickettsial Disease Laboratory. Serum specimens obtained daily from November 12 through November 16 were negative for rabies at both laboratories. The patient became totally unresponsive and died from respiratory failure on November 21. An autopsy was not performed.

Postexposure prophylaxis was provided for 20 health-care workers who had mucous membrane or nonintact skin contact with the patient's saliva or respiratory secretions or who had otherwise requested treatment and for nine family members. Health authorities in Mexico were notified, and they administered postexposure prophylaxis to a child who had been bitten by the same dog, three other children, and the dog's owner. The dog had been taken to another neighborhood and abandoned because it had bitten both humans and other animals. The dog's mother had since had another litter but died later of unknown causes; none of the dog's littermates nor the subsequent litter could be located. Health authorities in Mexico identified a 10-block area in which all owned dogs were to be vaccinated and stray animals were to be destroyed.

Reported by: M White, DVM, A Davis, J Rawlings, MPH, S Neill, PhD, K Hendricks, MD, D Simpson, MD, State Epidemiologist, Texas Dept of Health. W Gann, B Jones, S Rountree, MD, Texarkana, Arkansas. D Vuong, DVM, D Berry, MS, T McChesney, DVM, State Epidemiologist, Arkansas Dept of Health. J Simmons, MD, K Ferris, Merrithew Memorial Hospital, F Wise, MPH, J Reardon, MD, W Brunner, MD, W Walker, MD, Contra Costa County Health Svcs Dept, Martinez; J Rosenberg, MD, R Emmons, MD, RJ Jackson, MD, GW Rutherford, III, MD, State Epidemiologist, California Dept of Health Svcs. PER Resendiz, MD, City of Ecatepec; GB Echeverri, MD, Health Institute of Mexico State, Toluca, United Mexican States. Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: From 1980 through 1993, 18 human rabies cases were diagnosed in the United States. Three human rabies cases were diagnosed in 1993, including the two described in this report (2); the last reported cases from these states occurred in August 1991 (Texas and Arkansas) and in April 1992 (California).

The same strain of rabies virus infecting the patient in Texas had been identified by genetic analysis in previous rabies cases (2,3). This report represents the second recent bat-associated rabies case reported from Texas (4). The case of the patient in Texas is typical: despite laboratory confirmation of a bat rabies virus, histories of exposure to bats are usually not elicited; since 1980, such exposure has not been documented in four of the seven reported bat-associated human rabies cases in the United States. Rabies is diagnosed in approximately 200 cows each year in the United States (184 in 1992) (5); however, no cases of cow-to-human transmission have been documented since national rabies surveillance began in 1946 (6,7). Therefore, it is possible, but unlikely, that the suspected cow could have been infected with a bat strain of rabies and transmitted infection to the patient.

The history for the patient in California is similar to other recent human rabies cases in that state, all of which are believed to have been acquired in other countries where dog rabies is endemic. The last indigenous case in a human in California occurred in 1969 as the result of a bobcat bite; since then, seven imported cases have been reported (6,7).

The rabies strains identified in the two cases in this report are consistent with the established epidemiologic pattern observed in the United States since the decline of endemic dog rabies in the 1950s. Since 1980, bat-associated rabies virus has been isolated from seven of the nine patients known to have acquired rabies in the United States, and dog-associated strains were isolated from all eight patients with imported rabies.

Because of the risk for rabies exposure in countries where dog rabies remains endemic, travelers to these countries should avoid contact with dogs and other animals; preexposure prophylaxis for rabies is recommended for travelers planning stays of at least 30 days in such countries (8). In the United States, dog vaccination programs and control of stray animal populations have eliminated endemic dog rabies from all areas except the Texas-Mexico border. Reservoirs of rabies persist in some wild animals, including raccoons, skunks, foxes, and bats; in addition, reported cases in wildlife are increasing (5). However, prompt treatment of recognized exposures to these animals has reduced human rabies in the United States to a rare occurrence (8). The association of the majority of recent indigenous cases with bats probably reflects the difficulty of recognizing a bat exposure, as underscored by the case in this report. Although many of these exposures may not be preventable, the risk for exposure can be reduced by excluding bats from houses and peridomestic structures and settings (9).

The risk for transmission of rabies from a patient to family members or health-care workers is extremely low (10); human-to-human transmission has been documented only in corneal transplant cases. However, high levels of concern about transmission often make it difficult to limit the number of postexposure treatments administered.

References

1. Smith JS, Orciari LA, Yager PA, Seidel HD, Warner CK. Epidemiologic and historical relationships among 87 rabies virus isolates as determined by limited sequence analysis. J Infect Dis 1992;166:296-307.

2. CDC. Human rabies -- New York, 1993. MMWR 1993;42:799,805-6.

3. CDC. Human rabies -- Texas, Arkansas, and Georgia, 1991. MMWR 1991;40:765-9.

4. CDC. Human rabies -- Texas, 1990. MMWR 1991;40:132-3.

5. Krebs JW, Strine TW, Childs JE. Rabies surveillance in the United States during 1992. J Am Vet Med Assoc 1993;203:1718-31.

6. Held JR, Tierkel ES, Steele JH. Rabies in man and animals in the United States, 1946-65. Public Health Rep 1967;82:1009-18.

7. Anderson LJ, Nicholson KG, Tauxe RV, Winkler WG. Human rabies in the United States, 1960 to 1979: epidemiology, diagnosis, and prevention. Ann Intern Med 1984;100:728-35.

8. ACIP. Rabies prevention -- United States, 1991: recommendations of the Immunization Practices Advisory Committee (ACIP). MMWR 1991;40(no. RR-3).

9. CDC. Compendium of animal rabies control, 1993: National Association of State Public Health Veterinarians, Inc. MMWR 1993;42(no. RR-3).

10. 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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