Human Rabies — Wyoming and Utah, 2015

Case Report

On September 22, 2015, a Wyoming woman aged 77 years with a history of mild dementia was evaluated at a local emergency department with a 5-day history of progressive weakness and ataxia after a fall. On examination, she had slurred speech, could not swallow water, and could not stand without assistance. Initial blood tests did not indicate any specific abnormalities; lumbar puncture was not performed. Urinalysis suggested urinary tract infection, and intravenous ceftriaxone was started; urine culture subsequently grew pansensitive Escherichia coli. Magnetic resonance imaging (MRI) of the brain and spine revealed no acute pathology.

During the first 2 days of hospitalization, the patient’s weakness, dysarthria, and dysphagia progressed. She became increasingly confused and dyspneic and positive pressure ventilation was started. Lumbar puncture was performed on September 24; cerebrospinal fluid (CSF) had elevated protein of 64 mg/dL (normal = 15–45 mg/dL) and a white blood cell count of 7 cells/µL (normal = 0–5 cells/µL) with 72% polymorphonuclear leukocytes and 28% lymphocytes. Electromyography and nerve conduction studies suggested a demyelinating process. A presumptive diagnosis of Guillain-Barré syndrome was made, and intravenous immunoglobulin (Ig) therapy was initiated.

On September 26, the patient required endotracheal intubation for worsening respiratory failure, and on September 27, she was transferred to a referral hospital in Utah. Examination on arrival revealed near complete quadriplegia and spontaneous myoclonus. During the next 5 days the woman became comatose. Repeat brain and spine MRI revealed new enhancement of the dura, trigeminal nerve, and cauda equina, indicative of a central infiltrative process. Tests of blood and CSF for infectious, oncologic, and autoimmune etiologies were unrevealing.

On September 30 (13 days after initial symptom onset and day 8 of hospitalization), family members reported that on August 22, 2015, the patient awoke at night in her home with a bat on her neck, which she swatted away with her hand (Figure). She immediately washed her hand with soap and water; her husband examined her for bite wounds and found none. She did not seek medical attention. Her husband captured the bat with gloved hands and released it outside.

On October 1, the Utah Department of Health coordinated the collection and shipment of specimens to CDC for rabies virus diagnostic evaluation. Rabies virus RNA was detected in nuchal skin biopsy and saliva by reverse transcription–polymerase chain reaction. Rabies virus antigens were found in nuchal skin biopsy by direct fluorescent antibody testing, and rabies IgM and IgG were detected in CSF and serum by indirect fluorescent-antibody assay, and confirmed by the rapid fluorescent focus inhibition test. The rabies virus variant was identified as one enzootic to the silver-haired bat (Lasionycteris noctivagans). The woman died on October 3, 2015. She was the first Wyoming resident with confirmed rabies virus infection since the state began documenting reportable infectious diseases in 1911.

Public Health Investigation

After rabies infection was confirmed on October 2, Salt Lake County Health Department and Wyoming Department of Health (WDH) personnel interviewed 15 family members and community contacts to assess rabies exposure risk from contact with the patient and from bat encounters in the patient’s home. The patient’s husband and one other family member required postexposure prophylaxis (PEP) because of potential contact with the woman’s saliva through kissing or sharing of food and drinks during the woman’s infectious period. Because rabies virus can be shed in saliva and tears 2 weeks before symptom onset, the infectious period began on September 4, 2015, 2 weeks before she fell at home on September 18 (Figure). The patient’s husband also required PEP because of his potential bat exposure on August 22. Two other contacts chose to receive PEP although they did not report exposures that would constitute increased risk for acquiring rabies (Table) (1).

WDH worked with the Wyoming hospital to assess rabies exposure risk among the patient’s health care providers. The employee health department at the Utah hospital instructed personnel with potential exposure of nonintact skin or mucous membranes to the patient’s saliva, tears, respiratory tract secretions, CSF, or nuchal biopsy specimens to discuss PEP with the employee health medical director. Between the Wyoming and Utah hospitals, 100 health care providers had cared for the patient; 22 (22%) received PEP (Table).

During further interviews with the patient’s family, local public health workers and WDH learned that the patient’s husband had consulted a county weed and invasive species authority about the bat incident during the week after it occurred, but he was neither informed about the risk for rabies exposure nor referred to medical or public health officials. The family also reported that during the multiple years they had owned their home, they had often seen bats outside and under the eaves of the home, and that the patient and her husband had occasionally encountered bats inside the home. They reported having contacted multiple authorities from local wildlife, invasive species, and health agencies about bat removal over the years, but said they had never received information concerning rabies.

On October 2, 2015, WDH issued a press release with recommendations for preventing rabies, including when to seek medical attention for possible rabies exposure. WDH staff members also contacted county authorities to provide information regarding rabies risk and ensure that correct referrals to public health agencies would be made in the future.

Discussion

Rabies is a nearly universally fatal zoonotic disease caused by infection with viruses of the genus Lyssavirus and characterized by acute progressive encephalitis (2). Rabies virus is usually transmitted by an animal bite, and is preventable if exposed persons receive appropriate PEP, which includes thorough wound cleansing, human rabies immunoglobulin, and 4 doses of inactivated rabies vaccine on days 0, 3, 7, and 14 (3).

Human rabies presents a diagnostic challenge because of its rare occurrence in the United States and varied clinical presentations; symptoms can be difficult to distinguish from Guillain-Barré syndrome (2). Although the patient had prominent dysphagia, a symptom that is rare in other etiologies of encephalitis (4), diagnosis was complicated by her preexisting dementia and acute urinary tract infection, both of which might have explained some of her symptoms. In this case, the history of bat exposure was critical in leading clinicians to consider a diagnosis of rabies; however, because a history of animal bite cannot be documented in the majority of rabies cases in the United States (5), clinicians should consider a diagnosis of rabies infection in any patient with acute unexplained encephalitis (6).

The prolonged hospitalization of the patient described in this report raised concerns about possible exposures among health care providers. PEP is only indicated for health care providers who have mucous membrane or open skin contact with saliva, tears, or nervous tissue (1). Consistent adherence to standard precautions among providers could have reduced the need for PEP (1,6,7). The Hospital Infection Control Practices Advisory Committee recommends standard precautions for all hospitalized patients, including situations in which a transmissible infectious disease is not initially suspected (7).

The patient described in this report likely acquired rabies through the reported bat exposure in the home. During recent decades, most domestically acquired human rabies cases have been associated with bat exposures, either by history of bat contact or infection with bat-associated rabies virus variants (6,8); however, in the majority of these cases, no bite was reported (5,8). Because bat bites can cause limited injury and therefore can be difficult to detect (9), the Advisory Committee on Immunization Practices recommends that any person with direct bat contact or who might be unaware of bat contact (e.g., awakening with a bat in the room) undergo evaluation for rabies virus exposure (1).

In this case, the patient and her husband, her primary caregiver, were unaware of the risk for rabies in the absence of a visible bite wound, did not seek medical evaluation, and did not receive PEP. The reported multiple past telephone calls by the patient’s family to local authorities regarding bats represent missed opportunities to provide rabies education. Similar missed opportunities were reported in a previous human rabies case in the United States (10). These cases indicate the need to not only increase public awareness of rabies transmission risk from bat exposure, but also the need to educate public agencies outside of the public health domain to ensure that they can provide accurate information and proper referrals.