The death of a woman from Wyoming highlights the need for better public understanding of the risk of rabies infection from bats, according to a report in the Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report.
Alexia Harrist, MD, PhD, of the Epidemic Intelligence Service at the Centers for Disease Control and Prevention (CDC) and the Wyoming Department of Health reported details of a 77-year-old woman with rabies in Wyoming. The woman had a history of mild dementia and reported finding a bat on her neck in September 2015, but did not seek medical care. The patient’s husband contacted local authorities about the encounter, but was not advised to seek treatment.
The report added that the patient’s family had contacted numerous local agencies about bats over several years but were never told to seek medical care. Once rabies symptoms appear, the disease is almost always fatal.
One month after the bat exposure, the woman was admitted to a local hospital with progressive weakness, ataxia, dysarthria and dysphagia. Upon developing respiratory failure, she was transferred to a hospital in Utah where she was diagnosed with progressive encephalitis.
After the woman spent 8 days in the hospital, the patient’s family reported the bat exposure. Specimen samples were sent to the CDC on October 1st, and the next day CDC officials confirmed rabies infection of a type often carried by the silver-haired bat via patient saliva, nuchal skin biopsy and serum samples. The woman died the next day, and became the first confirmed rabies-associated death in Wyoming since the state began reporting in 1911, researchers said.
Dr Harrist and colleagues explained in the report that rabies can be difficult to diagnose because it is rare, symptoms vary, and the disease mimics Guillain-Barré syndrome. “Because a history of animal bite cannot be documented in the majority of rabies cases in the United States, clinicians should consider a diagnosis of rabies infection in any patient with acute unexplained encephalitis,” researchers said.
A quick diagnosis is critical – in this case, many healthcare workers in addition to family members were exposed and needed to receive post-exposure prophylaxis (PEP). This involves wound cleaning, receiving human rabies immunoglobulin and 4 injections of inactivated rabies vaccine on days 0, 3, 7, and 14.
Rabies can be spread among humans through kissing or sharing food and drinks. Healthcare workers may be exposed if they come in contact with mucous membranes, saliva or nervous tissue. Healthcare workers should always employ standard precautions with patients, “including situations in which a transmissible infectious disease is not initially suspected,” Dr Harrist and colleagues said.
The researchers noted that since bat bites can be difficult to detect, the Advisory Committee on Immunization Practices suggests that anyone with direct bat contact or who might be unaware of contact, such as awakening with a bat in the room, be evaluated for rabies exposure. In addition, public health and other local agencies need to be aware of the risk.
“Human infection with rabies virus is rare in the United States, though it is probable that there are some undiagnosed cases. It can present a diagnostic challenge both because of its rarity and because of its varied clinical presentations, but should be considered in any patient with acute unexplained encephalitis. In recent decades, most human rabies cases have been associated with bat exposures, but in the majority of these cases, no bite was reported. In some cases this might be because the patient is unable to report the bite due to their clinical condition. So while a history of bat contact can be helpful in leading clinicians to consider a diagnosis of rabies virus infection, the lack of a reported bite does not mean that a bite did not occur and does not rule out a diagnosis of rabies,” Dr Harrist told Infectious Disease Advisor in an email interview.
1. Harrist A, Styczynski A, Wynn DR et al. Human rabies — Wyoming and Utah, 2015. MMWR. 2016; 65(21):529-533.