Fatal Human Rabies Infection With Suspected Host-Mediated Failure of Post-Exposure Prophylaxis Following a Recognized Zoonotic Exposure-Minnesota, 2021.

BACKGROUND: No human rabies post-exposure prophylaxis (PEP) failure has been documented in the United States using modern cell culture-based vaccines. In January 2021, an 84-year-old male died from rabies 6 months after being bitten by a rabid bat despite receiving timely rabies PEP. We investigated the cause of breakthrough infection. METHODS: We reviewed medical records, laboratory results, and autopsy findings and performed whole-genome sequencing (WGS) to compare patient and bat virus sequences. Storage, administration, and integrity of PEP biologics administered to the patient were assessed; samples from leftover rabies immunoglobulin were evaluated for potency. We conducted risk assessments for persons potentially exposed to the bat and for close patient contacts. RESULTS: Rabies virus antibodies present in serum and cerebrospinal fluid were nonneutralizing. Antemortem blood testing revealed that the patient had unrecognized monoclonal gammopathy of unknown significance. Autopsy findings showed rabies meningoencephalitis and metastatic prostatic adenocarcinoma. Rabies virus sequences from the patient and the offending bat were identical by WGS. No deviations were identified in potency, quality control, administration, or storage of administered PEP. Of 332 persons assessed for potential rabies exposure to the case patient, 3 (0.9%) warranted PEP. CONCLUSIONS: This is the first reported failure of rabies PEP in the Western Hemisphere using a cell culture-based vaccine. Host-mediated primary vaccine failure attributed to previously unrecognized impaired immunity is the most likely explanation for this breakthrough infection. Clinicians should consider measuring rabies neutralizing antibody titers after completion of PEP if there is any suspicion for immunocompromise.

Human Rabies - Texas, 2021.

In late August 2021, a boy aged 7 years was bitten by a bat while he was playing outside his apartment home in Medina County, Texas. He informed his parents; however, no rabies postexposure prophylaxis (PEP) was sought because there were no visible bite marks, and the family was unaware that contact with a bat, including in the absence of visible bite marks, might cause rabies. Approximately 2 months later, the child was hospitalized for altered mental status, seizures, and hypersalivation and ultimately received a diagnosis of rabies. Experimental therapies were attempted; however, the child died 22 days after symptom onset. Fifty-seven persons who met criteria for suspected or known exposure to infectious secretions in this case were advised to consult with a medical provider about the need for rabies PEP in accordance with Advisory Committee on Immunization Practices (ACIP) guidelines (1). Rabies, an acute, progressive neuroencephalitis, is nearly always fatal. Although dogs are the most common source of human rabies deaths worldwide and account for an estimated 59,000 annual cases of human rabies globally (2), bats are the most common source of domestically acquired rabies in the United States and have been implicated in 31 (81.6%) of 38 human infections since 2000 (3). Attempts to prevent death or poor neurologic outcomes once rabies symptoms develop have been largely unsuccessful (4). Administration of rabies PEP, comprising rabies immunoglobulin and a series of doses of rabies vaccine, is critical to preventing rabies after an exposure; enhanced public education about the risk posed by bats, and the availability of PEP to prevent rabies, is needed.

Rabies in a Dog Imported from Azerbaijan - Pennsylvania, 2021.

On June 16, 2021, rabies virus infection was confirmed in a dog included in a shipment of rescue animals imported into the United States from Azerbaijan. A multistate investigation was conducted to prevent secondary rabies cases, avoid reintroduction of a dog-maintained rabies virus variant (DMRVV), identify persons who might have been exposed and would be recommended to receive rabies postexposure prophylaxis, and investigate the cause of importation control failures. Results of a prospective serologic monitoring (PSM) protocol suggested that seven of 32 (22%) animals from the same shipment as the dog with confirmed rabies virus infection and who had available titer results after rabies vaccine booster had not been adequately vaccinated against rabies before importation. A requirement for rabies vaccination certificates alone will not adequately identify improper vaccination practices or fraudulent paperwork and are insufficient as a stand-alone rabies importation prevention measure. Serologic titers before importation would mitigate the risk for importing DMRVV.

Translocation of an Anteater (Tamandua tetradactyla) Infected with Rabies from Virginia to Tennessee Resulting in Multiple Human Exposures, 2021.

On August 16, 2021, the Tennessee Department of Health (TDH) was notified of a positive rabies test result from a South American collared anteater (Tamandua tetradactyla) in Washington County, Tennessee. Tamanduas, or lesser anteaters, are a species of anteater in which rabies has not previously been reported. The animal was living at a Tennessee zoo and had been recently translocated from a zoo in Virginia. TDH conducted an investigation to confirm the rabies result, characterize the rabies variant, and ascertain an exposure risk assessment among persons who came into contact with the tamandua. Risk assessments for 22 persons were completed to determine the need for rabies postexposure prophylaxis (rPEP); rPEP was recommended for 13 persons, all of whom agreed to receive it. Using phylogenetic results of the virus isolated from the tamandua and knowledge of rabies epidemiology, public health officials determined that the animal was likely exposed to wild raccoons present at the Virginia zoo. This report describes expansion of the wide mammalian species diversity susceptible to rabies virus infection and summarizes the investigation, highlighting coordination among veterinary and human public health partners and the importance of preexposure rabies vaccination for animal handlers and exotic zoo animals.

Immunohistochemistry Test for the Lyssavirus Antigen Detection from Formalin-Fixed Tissues.

One of the primary diagnostic modalities for rabies is the detection of viral ribonucleoprotein (RNP) complex (antigen) in the infected tissue samples. While the direct fluorescent antibody (DFA) test or the direct rapid immunohistochemical test (DRIT) are most commonly utilized for the antigen detection, both tests require fresh and/or frozen tissues for impressions on slides prior to the antigen detection using antibodies. If samples are collected and fixed in formalin, neither test is optimal for the antigen detection, however, testing can be performed by conventional immunohistochemistry (IHC) after embedding in paraffin blocks and sectioning. With this IHC method, tissues are stained with anti-rabies antibodies, sections are deparaffinized, antigen retrieved by partial proteolysis or other methods, and incubated with primary and secondary antibodies. Antigens are stained using horseradish peroxidase / amino ethyl carbazole and counterstained with hematoxylin for the visualization using a light microscope. In addition to the specific antigen detection, formalin fixation offers other advantages like the determination of histological changes, relaxed conditions for specimen storage and transport (under ambient temperatures), ability to test retrospective cases and improved biological safety through the inactivation of infectious agents.

Bat and Lyssavirus Exposure among Humans in Area that Celebrates Bat Festival, Nigeria, 2010 and 2013.

Using questionnaires and serologic testing, we evaluated bat and lyssavirus exposure among persons in an area of Nigeria that celebrates a bat festival. Bats from festival caves underwent serologic testing for phylogroup II lyssaviruses (Lagos bat virus, Shimoni bat virus, Mokola virus). The enrolled households consisted of 2,112 persons, among whom 213 (10%) were reported to have ever had bat contact (having touched a bat, having been bitten by a bat, or having been scratched by a bat) and 52 (2%) to have ever been bitten by a bat. Of 203 participants with bat contact, 3 (1%) had received rabies vaccination. No participant had neutralizing antibodies to phylogroup II lyssaviruses, but >50% of bats had neutralizing antibodies to these lyssaviruses. Even though we found no evidence of phylogroup II lyssavirus exposure among humans, persons interacting with bats in the area could benefit from practicing bat-related health precautions.

Human Rabies - Utah, 2018.

On November 3, 2018, the Utah Department of Health (UDOH) was notified of a suspected human rabies case in a man aged 55 years. The patient's symptoms had begun 18 days earlier, and he was hospitalized for 15 days before rabies was suspected. As his symptoms worsened, he received supportive care, but he died on November 4. On November 7, a diagnosis of rabies was confirmed by CDC. This was the first documented rabies death in a Utah resident since 1944. This report summarizes the patient's clinical course and the subsequent public health investigation, which determined that the patient had handled several bats in the weeks preceding symptom onset. Public health agencies, in partnership with affected health care facilities, identified and assessed the risk to potentially exposed persons, facilitated receipt of postexposure prophylaxis (PEP), and provided education to health care providers and the community about the risk for rabies associated with bats. Human rabies is rare and almost always fatal. The findings from this investigation highlight the importance of early recognition of rabies, improved public awareness of rabies in bats, and the use of innovative tools after mass rabies exposure events to ensure rapid and recommended risk assessment and provision of PEP.

Using the LN34 Pan-Lyssavirus Real-Time RT-PCR Assay for Rabies Diagnosis and Rapid Genetic Typing from Formalin-Fixed Human Brain Tissue.

Human rabies post mortem diagnostic samples are often preserved in formalin. While immunohistochemistry (IHC) has been routinely used for rabies antigen detection in formalin-fixed tissue, the formalin fixation process causes nucleic acid fragmentation that may affect PCR amplification. This study reports the diagnosis of rabies in an individual from the Dominican Republic using both IHC and the LN34 pan-lyssavirus real-time RT-PCR assay on formalin-fixed brain tissue. The LN34 assay generates a 165 bp amplicon and demonstrated higher sensitivity than traditional PCR. Multiple efforts to amplify nucleic acid fragments larger than 300 bp using conventional PCR were unsuccessful, probably due to RNA fragmentation. Sequences generated from the LN34 amplicon linked the case to the rabies virus (RABV) strain circulating in the Ouest Department of Haiti to the border region between Haiti and the Dominican Republic. Direct sequencing of the LN34 amplicon allowed rapid and low-cost rabies genetic typing.

An ELISA-based method for detection of rabies virus nucleoprotein-specific antibodies in human antemortem samples.

Rabies is a fatal encephalitic disease in humans and animals caused by lyssaviruses, most commonly rabies virus (RABV). Human antemortem diagnosis of rabies is a complex process involving multiple sample types and tests for the detection of antibodies, antigen (protein), and nucleic acids (genomic RNA). Serological diagnosis of human rabies includes the detection of either neutralizing or binding antibodies in the cerebrospinal fluid (CSF) or serum samples from unimmunized individuals without prior rabies vaccination or passive immunization with purified immunoglobulins. While neutralizing antibodies are targeted against the surface-expressed glycoprotein (G protein), binding antibodies to viral antigens are predominantly against the nucleoprotein (N protein), although there can be antibodies against all RABV-expressed proteins. To determine N protein-specific antibody responses in the CSF and serum during RABV infection, we developed an enzyme-linked immunosorbent assay (ELISA) with purified recombinant N protein expressed in E. coli. N protein-specific immunoglobulin (Ig) subtypes IgG and IgM were detected in the CSF or serum of previously diagnosed human rabies cases. In addition, anti-N protein seroconversion was demonstrated over the course of illness in individual rabies cases. We compared the N protein ELISA results to those of an indirect fluorescent antibody (IFA) test, the current binding antibody assay used in diagnosis, and show that our ELISA is consistent with the IFA test. Sensitivity and specificity of the N protein ELISA ranged from 78.38-100% and 75.76-96.77% with respect to the IFA results. Our data provide evidence for the use of an N protein ELISA as an additional option for the detection of RABV-specific IgG or IgM antibodies in human CSF or serum specimens.

EVALUATION OF ORAL RABIES VACCINATION: PROTECTION AGAINST RABIES IN WILD CAUGHT RACCOONS ( PROCYON LOTOR).

Oral rabies vaccination (ORV) is an effective tactic for wildlife rabies control, particularly for containment of disease spread along epizootic fronts. As part of the continuing evaluation of the ORV program in free-ranging raccoons ( Procyon lotor) in the US, 37 raccoons from ORV-baited areas in Pennsylvania were live-trapped and transferred to captivity to evaluate protection against rabies in animals with varying levels of existing neutralizing antibodies, expressed in international units per milliliter (IU/mL). Among the 37 raccoons at the date of capture, 24% (9/37) of raccoons were seronegative (<0.05 IU/mL), 22% (8/37) were low positive (≥0.05-0.11 IU/mL), 27% (10/37) were medium positive (>0.11-<0.5 IU/mL), and 27% (10/37) were high positive (≥0.5 IU/mL). Raccoons were held for 86-199 d between the date of capture and rabies virus challenge. At challenge, 68% (25/37) raccoons were seronegative. The overall survival rate among challenged animals was 46% (17/37). Based on the antibody titers at the time of challenge, survivorship was 24% (6/25) among seronegative animals, 100% (4/4) among low positive animals, 83% (5/6) among medium positive animals, and 100% (2/2) among high positive animals. Evidence of high-titer seroconversion after vaccination is a good surrogate indicator of rabies survival; however, survival rates of approximately 45% (15/35) were found among raccoons with detectable titers below 0.5 IU/mL. In contrast, any detectable titer at the time of challenge (>3 mo after vaccination) appeared to be a surrogate indicator of survival. Overall, we illustrated significant differences in the value of specific titers as surrogates for survival based on the timing of measurement relative to vaccination. However, survivorship was generally greater than 45% among animals with any detectable titer regardless of the timing of measurement. These findings suggest that lower titer cutoffs may represent a valid approach to measuring immunization coverage within ORV management zones, balancing both sensitivity and specificity for estimating herd immunity.

Potential Confounding of Diagnosis of Rabies in Patients with Recent Receipt of Intravenous Immune Globulin.

Rabies is an acute encephalitis that is nearly always fatal. It is caused by infection with viruses of the genus Lyssavirus, the most common of which is Rabies lyssavirus. The Council of State and Territorial Epidemiologists (CSTE) defines a confirmed human rabies case as an illness compatible with rabies that meets at least one of five different laboratory criteria.* Four of these criteria do not depend on the patient's rabies vaccination status; however, the remaining criterion, "identification of Lyssavirus-specific antibody (i.e. by indirect fluorescent antibody…test or complete [Rabies lyssavirus] neutralization at 1:5 dilution) in the serum," is only considered diagnostic in unvaccinated patients. Lyssavirus-specific antibodies include Rabies lyssavirus-specific binding immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies and Rabies lyssavirus neutralizing antibodies (RLNAs). This report describes six patients who were tested for rabies by CDC and who met CSTE criteria for confirmed human rabies because they had illnesses compatible with rabies, had not been vaccinated for rabies, and were found to have serum RLNAs (with complete Rabies lyssavirus neutralization at a serum dilution of 1:5). An additional four patients are described who were tested for rabies by CDC who were found to have serum RLNAs (with incomplete Rabies lyssavirus neutralization at a serum dilution of 1:5) despite having not been vaccinated for rabies. None of these 10 patients received a rabies diagnosis; rather, they were considered to have been passively immunized against rabies through recent receipt of intravenous immune globulin (IVIG). Serum RLNA test results should be interpreted with caution in patients who have not been vaccinated against rabies but who have recently received IVIG.

Exposure to Lyssaviruses in Bats of the Democratic Republic of the Congo.

Lyssavirus infections in the Democratic Republic of Congo are poorly documented. We examined 218 bats. No lyssavirus antigens were detected but Lagos bat virus (LBV) neutralizing antibodies (VNA) were detected in Eidolon helvum and Myonycteris torquata . Four samples with LBV VNA reacted against Shimoni bat virus.

Serologic response in eight alpacas vaccinated by extralabel use of a large animal rabies vaccine during a public health response to a rabid alpaca in South Carolina.

CASE DESCRIPTION A female alpaca, kept at pasture with 12 other female alpacas, 2 crias, and 5 goats, was evaluated because of clinical signs of aggression. CLINICAL FINDINGS The clinical signs of aggression progressed to include biting at other animals as well as disorientation. Three days later, the alpaca was euthanized because of suspicion of rabies virus infection. TREATMENT AND OUTCOME No physical injuries were found at necropsy. Brain tissue specimens were confirmed positive for rabies on the basis of direct fluorescent antibody test results. Molecular typing identified the rabies virus variant as one that is enzootic in raccoons. The farm was placed under quarantine, restricting movement of animals on and off the property for 6 months. To prevent further rabies cases, 14 alpacas (12 adults and 2 crias) were vaccinated by extralabel use of a large animal rabies vaccine. Of the 14 vaccinated alpacas, 8 had paired serum samples obtained immediately before and 21 days after vaccination; all 8 alpacas had adequate serum antirabies antibody production in response to rabies vaccination. As a result of an adequate serologic response, the quarantine was reduced to 3 months. In the year after the index rabies case, no other animals on the farm developed rabies. CLINICAL RELEVANCE Extralabel use of rabies vaccines in camelids was used in the face of a public health investigation. This report provides an example of handling of a rabies case for future public health investigations, which will undoubtedly need to develop ad-hoc rabies vaccination recommendations on the basis of the unique characteristics of the event.

Human Rabies - Wyoming and Utah, 2015.

In September 2015, a Wyoming woman was admitted to a local hospital with a 5-day history of progressive weakness, ataxia, dysarthria, and dysphagia. Because of respiratory failure, she was transferred to a referral hospital in Utah, where she developed progressive encephalitis. On day 8 of hospitalization, the patient's family told clinicians they recalled that, 1 month before admission, the woman had found a bat on her neck upon waking, but had not sought medical care. The patient's husband subsequently had contacted county invasive species authorities about the incident, but he was not advised to seek health care for evaluation of his wife's risk for rabies. On October 2, CDC confirmed the patient was infected with a rabies virus variant that was enzootic to the silver-haired bat (Lasionycteris noctivagans). The patient died on October 3. Public understanding of rabies risk from bat contact needs to be improved; cooperation among public health and other agencies can aid in referring persons with possible bat exposure for assessment of rabies risk.

Virology, immunology and pathology of human rabies during treatment.

BACKGROUND: Rabies is an acute fatal encephalitis caused by all members of the Lyssavirus genus. The first human rabies survivor without benefit of prior vaccination was reported from Milwaukee in 2005. We report a second unvaccinated patient who showed early recovery from rabies and then died accidentally during convalescence, providing an unparalleled opportunity to examine the histopathology as well as immune and virological correlates of early recovery from human rabies. METHODS: Case report, rapid fluorescent focus inhibition test, enzyme-linked immunosorbent assay, indirect and direct fluorescent antibody assays, reverse-transcriptase polymerase chain reaction, phylogenetic reconstruction, isolation in tissue culture, pathology and immunohistochemistry. RESULTS: The 9 year old died 76 days after presenting with rabies of vampire bat phylogeny transmitted by cat bite. Antibody response in serum and cerebrospinal fluid was robust and associated with severe cerebral edema. No rabies virus was cultured at autopsy. Rabies virus antigen was atypical in size and distribution. Rabies virus genome was present in neocortex but absent in brainstem. CONCLUSIONS: Clinical recovery was associated with detection of neutralizing antibody and clearance of infectious rabies virus in the central nervous system by 76 days but not clearance of detectable viral subcomponents such as nucleoprotein antigen or RNA in brain.

Rabies death attributed to exposure in Central America with symptom onset in a U.S. detention facility - Texas, 2013.

On June 7, 2013, a man was diagnosed in a Texas hospital with rabies. He had been detained in a U.S. detention facility during his infectious period. To identify persons exposed to rabies who might require rabies postexposure prophylaxis (PEP), CDC and the Texas Department of State Health Services (DSHS) conducted investigations at four detention facilities, one medical clinic, and two hospitals. In all, 25 of 742 persons assessed for rabies exposure were advised to receive PEP. Early diagnosis of rabies is essential for implementation of appropriate hospital infection control measures and for rapid assessment of potential contacts for PEP recommendations.

Molecular detection of adenoviruses, rhabdoviruses, and paramyxoviruses in bats from Kenya.

We screened 217 bats of at least 20 species from 17 locations in Kenya during July and August of 2006 for the presence of adenovirus, rhabdovirus, and paramyxovirus nucleic acids using generic reverse transcription polymerase chain reaction (RT-PCR) and PCR assays. Of 217 bat fecal swabs examined, 4 bats were adenovirus DNA-positive, 11 bats were paramyxovirus RNA-positive, and 2 bats were rhabdovirus RNA-positive. Three bats were coinfected by two different viruses. By sequence comparison and phylogenetic analysis, the Kenya bat paramyxoviruses and rhabdoviruses from this study may represent novel viral lineages within their respective families; the Kenya bat adenoviruses could not be confirmed as novel, because the same region sequences from other known bat adenovirus genomes for comparison were lacking. Our study adds to previous evidence that bats carry diverse, potentially zoonotic viruses and may be coinfected with more than one virus.

Isolation and molecular characterization of Fikirini rhabdovirus, a novel virus from a Kenyan bat.

Zoonotic and vector-borne pathogens have comprised a significant component of emerging human infections in recent decades, and bats are increasingly recognized as reservoirs for many of these disease agents. To identify novel pathogens associated with bats, we screened tissues of bats collected in Kenya. Virus isolates were identified by next generation sequencing of viral nucleic acid preparations from the infected cell culture supernatant and characterized. Here we report the identification of Fikirini rhabdovirus, a novel rhabdovirus isolated from a bat, Hipposideros vittatus, captured along the Kenyan coast.

Current and future tools for global canine rabies elimination.

Even though rabies is almost uniformly fatal, it is readily preventable with currently available tools. Vaccination is highly efficacious for the pre-exposure prophylaxis (PrEP) of rabies in humans and animals, and prompt postexposure prophylaxis (PEP) with vaccine and rabies immune globulin (RIG) can reliably prevent disease in humans. However, access to these tools and knowledge of their proper use are often limited, especially in impoverished, rabies-enzootic countries with the highest disease burden. In the absence of reliable diagnostic capacity and risk assessments, vaccines and RIG are often administered inappropriately, leading to chronic supply shortages and otherwise preventable deaths. Rather than focusing solely on human prophylaxis, it is more cost-effective over the long term to eliminate canine rabies in its natural terrestrial reservoirs. Because more than 99% of human rabies deaths result from dog bites, prevention efforts should focus on dogs. A versatile "One Health" strategy for canine rabies elimination should aim to create sustainable herd immunity in dogs, using proven vaccination strategies at the local level, coupled with community education and humane population management. Such strategies have succeeded in both developed and developing countries, and can be adapted to any locality. Numerous examples in Africa, Asia, and Latin America have shown that community-based, locally guided vaccination and education programs, based on a shared vision and long-term commitment, can eliminate canine rabies. Such programs should have specific goals and measurable outcomes, and should be conducted under the guidance of supportive governments, in collaboration with international partners and nongovernmental organizations. In addition to currently available tools, rabies prevention can be augmented by new dose-sparing human vaccine schedules, alternative routes of vaccine administration, monoclonal antibodies as an alternative to RIG, sensitive and specific point-of-care diagnostics and the development of canine immunocontraceptive methods. Accurate risk assessments of potential human exposures and support for decentralized laboratory capacity will be essential to ensure the most effective utilization of vaccines and RIG until canine rabies has been eliminated.