Unexplained rabies in three immigrants in the United States. A virologic investigation

Comparison of Theater Medical Data Store and Reportable Medical Event Records to Theater Animal Bite Reports Submissions, 2018-2019

INTRODUCTION

This analysis evaluates potential reporting discrepancies of the DD2341 Form (Report of Animal Bite-Potential Rabies Exposure) submitted to a forward-deployed Rabies Advisory Board to the Theater Medical Data Store (TMDS) and Reportable Medical Event (RME) systems to identify reporting gaps that can lead to improved best practices that ensure documentation of Post Exposure Prophylaxis (PEP) of potential rabies exposures into service members (SMs) electronic medical records.

MATERIALS AND METHODS

The project compares the number of Service Member animal exposure DD2341 reports submitted to the Camp Arifjan, Kuwait Rabies Advisory Board to in-theater treatment electronic records at the same forward deployed locations from January 1, 2018 to December 31, 2019 recorded in the TMDS and RME databases. Records included active duty and reserve SM deployed to six countries in the United States Central Command (USCENTCOM) area of responsibility. The analysis compared some demographic information, type of potential rabies exposure (e.g., whether a bite or scratch), and PEP to rabies with Human Rabies Immune Globulin (HRIG), Human Rabies Vaccine (HRV), or both between the reporting systems.

RESULTS

There were 44 fewer records of PEP from the TMDS data records than reported from in theater written reports. Electronic record data showed 85 coded rabies exposure diagnoses. Twenty-two received HRV and no HRIG, while four received HRIG and HRV for PEP. Only seven of the 26 SM receiving rabies PEP had a confirmed RME associated with the electronic record. There were 116 SM animal exposure written reports, with 70 reporting PEP. There were 41 records indicating the SM received HRIG and HRV as part of PEP, while 29 reports indicated that the patient received only HRV PEP. Of the 41 SM receiving HRIG, 32 of the exposures were from cat scratches or bites. Seven records specified HRIG was indicated for treatment but not available at the location; therefore, HRV was the only treatment available. The most common reason indicated on the written report for not receiving rabies PEP was that treatment was not indicated based on the risk category of animal exposure.

CONCLUSIONS

This study is the first to compare the electronic medical record data to in theater reports for potential rabies exposure in a theater of operations. The analysis suggests that some written forms generated in the USCENTCOM theater are not entered into SM Military Health System electronic medical records, indicating that electronic medical records may be a less sensitive method than in-theatre reports for rabies program surveillance in a deployed setting. There is under-reporting in electronic medical records of rabies PEP in both TMDS and RME databases. Rabies PEP is an RME according to the Armed Forces Health Surveillance Division guidelines and case definitions. There needs to be better integration of the DD2341 into the electronic medical records system.

Differential pathogenesis of intracerebral and intramuscular inoculation of street rabies virus and CVS-11 strains in a mouse model

Objective(s):

The mechanisms of rabies evasion and immunological interactions with the host defense have not been completely elucidated. Here, we evaluated the dynamic changes in the number of astrocytes, microglial and neuronal cells in the brain following intramuscular (IM) and intracerebral (IC) inoculations of street rabies virus (SRV).

Materials and Methods:

The SRV isolated from a jackal and CVS-11 were used to establish infection in NMRI-female mice. The number of astrocytes (by expression of GFAP), microglial (by Iba1), and neuronal cells (by MAP-2) in the brain following IM and IC inoculations of SRV were evaluated by immunohistochemistry and H & E staining 7 to 30 days post-infection.

Results:

Increased numbers of astrocytes and microglial cells in dead mice infected by SRV via both IC and IM routes were recorded. The number of neuronal cells in surviving mice was decreased only in IC-infected mice, while in the dead group, this number was decreased by both routes.

The risk of death in SRV-infected mice was approximately 3 times higher than in the CVS-11 group. In IC-inoculated mice, viral dilution was the only influential factor in mortality, while the type of strain demonstrated a significant impact on the mortality rate in IM inoculations.

Conclusion:

Our results suggested that microglial cells and their inflammatory cytokines may not contribute to the neuroprotection and recovery in surviving mice following intracerebral inoculation of SRV. An unexpected decrease in MAP2 expression via intramuscular inoculation indicates the imbalance in the integrity and stability of neuronal cytoskeleton which aggravates rabies infection.

Genome-based local dynamics of canine rabies virus epidemiology, transmission, and evolution in Davao City, Philippines, 2018-2019

Rabies is a fatal zoonotic and neglected tropical disease caused by the rabies virus (RABV) and is associated with neuronal dysfunction and death, with dogs as the predominant carrier. The Philippines plans to eradicate rabies by 2022, but this is challenged with sub-optimal coverage of vaccination programs coupled with sustained transmission chains, making it unable to eradicate the disease. We investigated the dynamics of canine rabies in the highly urbanized Davao City of the Philippines and its neighboring localities by assessing genetic relationships, transmission patterns, selection pressure, and recombination events using the whole genome sequence of 49 RABV cases from June 2018 to May 2019, majority of which (46%) were from the district of Talomo, Davao City. Although phylogeographic clustering was observed, local variants also exhibited genetic sub-lineages. Phylogenetic and spatial transmission analysis provided evidence for intra- and inter-city transmission predominantly through the Talomo district of Davao City. Around 84% of the cases were owned dogs, but the genetic similiarity of RABVs from stray and owned dogs further alluded to the role of the former as transmission vectors. The high rate of improper vaccination among the affected dogs (80%) was also a likely contributor to transmission. The RABV population under Investigation is generally under strong purifying selection with no evidence of vaccine evasion due to the genetic homogeneity of viruses from vaccinated and improperly vaccinated dogs. However, some homologous recombination (HR) events were identified along the G and L genes, also predominantly associated with viruses from Talomo. The complementary findings on epidemiology, transmission, and recombination for Talomo suggest that high incidence areas can be seeds for virus dispersal and evolution. We recommend further Investigations on the possibility of HR in future large-scale genome studies. Finally, districts associated with these phenomena can be targeted for evidence-based local strategies that can help break RABV transmission chains and prevent emergence of novel strains in Davao City.

Genetic and Phenotypic Characterization of a Rabies Virus Strain Isolated from a Dog in Tokyo, Japan in the 1940s

The rabies virus strain Komatsugawa (Koma), which was isolated from a dog in Tokyo in the 1940s before eradication of rabies in Japan in 1957, is known as the only existent Japanese field strain (street strain). Although this strain potentially provides a useful model to study rabies pathogenesis, little is known about its genetic and phenotypic properties. Notably, this strain underwent serial passages in rodents after isolation, indicating the possibility that it may have lost biological characteristics as a street strain. In this study, to evaluate the utility of the Koma strain for studying rabies pathogenesis, we examined the genetic properties and in vitro and in vivo phenotypes. Genome-wide genetic analyses showed that, consistent with previous findings from partial sequence analyses, the Koma strain is closely related to a Russian street strain within the Arctic-related phylogenetic clade. Phenotypic examinations in vitro revealed that the Koma strain and the representative street strains are less neurotropic than the laboratory strains. Examination by using a mouse model demonstrated that the Koma strain and the street strains are more neuroinvasive than the laboratory strains. These findings indicate that the Koma strain retains phenotypes similar to those of street strains, and is therefore useful for studying rabies pathogenesis.

Rabies virus-neutralising antibodies in healthy, unvaccinated individuals: What do they mean for rabies epidemiology?

Rabies has been a widely feared disease for thousands of years, with records of rabid dogs as early as ancient Egyptian and Mesopotamian texts. The reputation of rabies as being inevitably fatal, together with its ability to affect all mammalian species, contributes to the fear surrounding this disease. However, the widely held view that exposure to the rabies virus is always fatal has been repeatedly challenged. Although survival following clinical infection in humans has only been recorded on a handful of occasions, a number of studies have reported detection of rabies-specific antibodies in the sera of humans, domestic animals, and wildlife that are apparently healthy and unvaccinated. These 'seropositive' individuals provide possible evidence of exposure to the rabies virus that has not led to fatal disease. However, the variability in methods of detecting these antibodies and the difficulties of interpreting serology tests have contributed to an unclear picture of their importance. In this review, we consider the evidence for rabies-specific antibodies in healthy, unvaccinated individuals as indicators of nonlethal rabies exposure and the potential implications of this for rabies epidemiology. Our findings indicate that whilst there is substantial evidence that nonlethal rabies exposure does occur, serology studies that do not use appropriate controls and cutoffs are unlikely to provide an accurate estimate of the true prevalence of nonlethal rabies exposure.

The spread and evolution of rabies virus: conquering new frontiers

Rabies is a lethal zoonotic disease that is caused by lyssaviruses, most often rabies virus. Despite control efforts, sporadic outbreaks in wildlife populations are largely unpredictable, underscoring our incomplete knowledge of what governs viral transmission and spread in reservoir hosts. Furthermore, the evolutionary history of rabies virus and related lyssaviruses remains largely unclear. Robust surveillance efforts combined with diagnostics and disease modelling are now providing insights into the epidemiology and evolution of rabies virus. The immune status of the host, the nature of exposure and strain differences all clearly influence infection and transmission dynamics. In this Review, we focus on rabies virus infections in the wildlife and synthesize current knowledge in the rapidly advancing fields of rabies virus epidemiology and evolution, and advocate for multidisciplinary approaches to advance our understanding of this disease.

Perspectives in Diagnosis and Treatment of Rabies Viral Encephalitis: Insights from Pathogenesis

Rabies viral encephalitis, though one of the oldest recognized infectious disease of humans, remains an incurable, fatal encephalomyelitis, despite advances in understanding of its pathobiology. Advances in science have led us on the trail of the virus in the host, but the sanctuaries in which the virus remains hidden for its survival are unknown. Insights into host-pathogen interactions have facilitated evolving immunologic therapeutic strategies, though we are far from a cure. Most of the present-day knowledge has evolved from in vitro studies using fixed (attenuated) laboratory strains that may not be applicable in the clinical setting. Much remains to be unraveled about this elusive virus. This review attempts to re-examine the current advances in understanding of the pathobiology of the rabies virus that modulate the diagnosis, treatment, and prevention of this fatal disease.

Rabies: Rare Human Infection - Common Questions

Rabies is an acute, rapidly progressive encephalitis that is almost always fatal. Prophylaxis is highly effective but economics limits disease control. The mechanism of death from rabies is unclear. It is poorly cytopathic and poorly inflammatory. Rabies behaves like an acquired metabolic disorder. There may be a continuum of disease severity. History of animal bite is rare. The diagnosis is often missed. Intermittent encephalopathy, dysphagia, hydrophobia and aerophobia, and focal paresthesias or myoclonic jerks suggest rabies. Laboratory diagnosis is cumbersome but sensitive. Treatment is controversial but survivors are increasingly reported, with good outcomes in 4 of 8 survivors.

Phylogenetic and epidemiologic evidence of multiyear incubation in human rabies

Eight years after emigrating from Brazil, an otherwise healthy man developed rabies. An exposure prior to immigration was reported. Genetic analysis revealed a canine rabies virus variant found only in the patient's home country, and the patient had not traveled internationally since immigrating to the United States. We describe how epidemiological, phylogenetic, and viral sequencing data provided confirmation that rabies encephalomyelitis may present after a long, multiyear incubation period, a consideration that previously has been hypothesized without the ability to exclude a more recent exposure. Accordingly, rabies should be considered in the diagnosis of any acute encephalitis, myelitis, or encephalomyelitis.

Nervous System Complications of Systemic Viral Infections

Invasion of the central nervous system (CNS) by viral agents typically produces a meningoencephalitis in which either meningitis or encephalitis may predominate. Viruses may also infect cranial or spinal blood vessels to produce ischemic injury. Viral and other infections may also elicit a host immune response which is cross-reactive with components of the neural tissue, resulting in encephalomyelitis, transverse myelitis, injury to peripheral nerves, or optic neuritis. This chapter discusses the pathogenesis of CNS viral infections and reviews clinical features of these disorders, major agents responsible in immunocompromised and immunocompetent individuals, and treatment. Prion diseases and postinfectious viral CNS syndromes including postinfectious encephalomyelitis, acute hemorrhagic leukoencephalitis, cerebellar ataxia, and transverse myelitis are also discussed.

Genetic Typing of Feline Rabies Virus Isolated in Greater Bangkok, Thailand

To study the molecular epidemiology of rabies virus that is prevalent among cats in greater Bangkok, Thailand, a total of 17 rabies virus isolates from cats were characterized and compared with 120 rabies virus isolates from dogs. Analyses were performed on the genetic polymorphism in the rabies virus nucleoprotein (N) gene. Rabies virus N gene of isolates was amplified by reverse transcriptionpolymerase chain reaction. The diversity of N gene was revealed by the restriction fragment length polymorphism (RFLP) method. The rabies virus isolates from cats could be classified into 5 types, designated as Dd I-Hf I, Dd II-Hf II, Dd III-Hf I, Dd IV-Hf I, and Dd IV-Hf III. Type Dd I-Hf I was encountered more frequently than the others. It was apparent that no less than five rabies virus types presented in the areas of Bangkok. Moreover, all five RFLP patterns were typical of those which had been observed in dogs. Our findings suggest that there had been viral transmission between the dogs and the cats.

Passive carriage of rabies virus by dendritic cells

The rabies virus (RABV) is highly neurotropic and it uses evasive strategies to successfully evade the host immune system. Because rabies is often fatal, understanding the basic processes of the virus-host interactions, particularly in the initial events of infection, is critical for the design of new therapeutic approaches to target RABV. Here, we examined the possible role of dendritic cells (DCs) in the transmission of RABV to neural cells at peripheral site of exposure. Viral replication only occurred at a low level in the DC cell line, JAWS II, after its infection with either pathogenic RABV (CVS strain) or low-pathogenic RABV (ERA strain), and no progeny viruses were produced in the culture supernatants. However, both viral genomic RNAs were retained in the long term after infection and maintained their infectivity. The biggest difference between CVS and ERA was in their ability to induce type I interferons. Although the ERA-infected JAWS II cells exhibited cytopathic effect and were apparently killed by normal spleen cells in vitro, the CVS-infected JAWS II cells showed milder cytopathic effect and less lysis when cocultured with spleen cells. Strongly increased expression of major histocompatibility complex classes I, costimulatory molecules (CD80 and CD86), type I interferons and Toll- like receptor 3, and was observed only in the ERA-inoculated JAWS II cells and not in those inoculated with CVS. During the silencing of the cellular immune response in the DCs, the pathogenic CVS strain cryptically maintained an infectious viral genome and was capable of transmitting infectious RABV to permissive neural cells. These findings demonstrate that DCs may play a role in the passive carriage of RABV during natural rabies infections.

Enhancement of humoral and cellular immune responses by monophosphoryl lipid A (MPLA) as an adjuvant to the rabies vaccine in BALB/c mice

The development of effective vaccines against the rabies virus could prevent infection with this fatal virus. However, the current rabies vaccine fails to provide a full range of protection because of its limited ability to elicit a cellular immune response and the requirement for repeat vaccination. Monophosphoryl lipid A (MPLA) is well known as a potent adjuvant to enhance immune responses against virus infection. Here we investigated the efficacy of MPLA as an adjuvant to improve the humoral and cellular immune responses to the rabies vaccine in BALB/c mice. Supplementation of the rabies vaccine with MPLA significantly accelerated the production of specific antibodies by 10 days compared to the original vaccines. Furthermore, MPLA promoted the induction of stronger cellular immune responses by the rabies vaccine, including the production of IL-4, IFN-γ and the activation of CD4⁺/CD8⁺ T cells, than those elicited without MPLA. Collectively, our findings indicated that MPLA enhances humoral and cellular immunity and is a promising adjuvant for the development of more effective rabies vaccines.

Encephalitis and postinfectious encephalitis

PURPOSE OF REVIEW

Encephalitis and postinfectious encephalitis represent two important conditions for the neurologist, both in terms of their presentations as neurologic emergencies and their potential to cause death or serious neurologic impairment. This article reviews the major infectious and noninfectious causes of encephalitis and discusses postinfectious encephalitis as an indirect effect of systemic illness.

RECENT FINDINGS

Encephalitis caused by herpes simplex virus type 1 and West Nile virus are of major importance. In addition, within the past few years we have gained improved understanding of the neurologic syndromes caused by varicella-zoster virus, the recognition of enterovirus 71 as a significant human pathogen, and the realization that encephalitis may also occur by autoimmune mechanisms requiring immunosuppressive therapy. We have also learned that postinfectious encephalitis may be recurrent rather than monophasic, and that children and adults initially diagnosed with postinfectious encephalitis may later develop classic multiple sclerosis.

SUMMARY

Encephalitis and postinfectious encephalitis present as neurologic emergencies requiring prompt diagnosis and initiation of treatment. Important concerns are to identify infectious conditions requiring antibiotic or antiviral therapy and postinfectious or other autoimmune encephalitides requiring immunosuppression.

Review of human rabies prophylaxis and treatment

Rabies is a devastating encephalitis caused by RNA viruses that use mammals as reservoirs. In the United States, most naturally acquired human cases have come from bats. The use of appropriate preexposure and postexposure prophylaxis can be nearly 100% effective. If prophylaxis is not used, or is implemented incorrectly, the patient may develop clinical rabies, which is almost universally fatal. All health care practitioners should be familiar with the appropriate evaluation of patients presenting with a possible rabies exposure and ensure that expeditious and appropriate prophylaxis is provided to help prevent the development of this lethal disease.

Rabies viral encephalitis with proable 25 year incubation period!

We report a case of rabies viral encephalitis in a 48-year-old male with an unusually long incubation period, historically suspected to be more than 20 years. The case was referred for histological diagnosis following alleged medical negligence to the forensic department. The histology and immunocytochemical demonstration of rabies viral antigen established the diagnosis unequivocally. The case manifested initially with hydrophobia and aggressive behavior, although he suddenly went to the bathroom and drank a small amount of water. History of dog bite 25 years back was elicited retrospectively following clinical suspicion. There was no subsequent history to suggest nonbite exposure to a rabid dog to consider recent event causing the disease, although this cannot be totally excluded.

Passive immunity in the prevention of rabies

Prevention of clinical disease in those exposed to viral infection is an important goal of human medicine. Using rabies virus infection as an example, we discuss the advances in passive immunoprophylaxis, most notably the shift from the recommended polyclonal human or equine immunoglobulins to monoclonal antibody therapies. The first rabies-specific monoclonal antibodies are undergoing clinical trials, so passive immunisation might finally become an accessible, affordable, and routinely used part of global health practices for rabies. Coupled with an adequate supply of modern tissue-culture vaccines, replacing the less efficient and unsafe nerve-tissue-derived rabies vaccines, the burden of this disease could be substantially reduced.

Preventative childhood vaccination to rabies

INTRODUCTION

Rabies is prevented by post-exposure vaccination with several doses of vaccine given over 4 - 14 weeks. In case of severe exposure, the first dose of vaccine is combined with passive transfer of a rabies virus-specific immunoglobulin preparation. Preventative vaccination for rabies, also referred as pre-exposure vaccination, is reserved for humans at high risk. Although available vaccines are efficacious in preventing disease, rabies still claims the lives of an estimated 55,000 humans residing in Africa and Asia each year. Half of the death occurs in children under the age of 15.

AREAS COVERED

This paper discusses whether preventative vaccination of all children in Africa and Asia, which was deemed non-cost-effective compared to post-exposure vaccination using currently licensed vaccines in Thailand, could be cost-effective using more immunogenic novel vaccines.

EXPERT OPINION

At least in theory, novel one-dose rabies vaccines may be cost-effective for preventative childhood immunization, which in turn should reduce the incidence of this disease. Further clinical testing of such vaccines with the goal to develop a low-cost vaccine that can be incorporated into childhood immunization programs for areas with a high incidence of rabies-related death should be strongly encouraged.

Rabies epidemiology, risk assessment, and pre- and post exposure vaccination

Rabies should always be considered in the differential diagnosis of a neurologic disease in a mammal with an unknown vaccination status. Public health veterinarians are available to assist in risk assessment as well as coordination of animal testing. This article discusses the pathogenesis of rabies and clinical presentation in several domestic species. Prevention, North American prevalence and distribution, exposure considerations, and post-exposure prophylaxis are also discussed. Veterinarians in private practice have an integral role in protection of people and domestic animals against rabies.

Rabies in Asia: the classical zoonosis

Rabies remains a constant threat to humans throughout much of Asia. The dog is the main reservoir and vector with wildlife playing a very minor role. No Asian country or region has been declared rabies free by WHO in over two decades and there is evidence of canine rabies spread to new regions during the past 10 years. We now have the knowledge and technology to control canine rabies. The main barrier in managing this costly endemic is lack of motivation by authorities to address this issue along with regional inability of public health and livestock (agriculture) officials to tackle this issue in cooperation and coordination. Rabies is one of the first recognized zoonoses and a model for a true "One Health" management goal where human; veterinary, and government officials must work together in harmony to defeat this disease.

Clinical and epidemiological features of human rabies cases in the Philippines: a review from 1987 to 2006

BACKGROUND

Rabies viral infection causes a fatal encephalomyelitis. In humans, classic features include hydrophobia, aerophobia, hypersalivation, agitation, and neurological symptoms. In the Philippines, canine rabies contributes to a significant burden of human disease.

METHODS

We retrospectively reviewed the medical records of 1839 patients admitted to San Lazaro Hospital, Manila, Philippines between 1987 and 2006, with a clinical diagnosis of rabies. We used the World Health Organization case definition for clinical rabies, which is defined by the presence of hydrophobia.

RESULTS

Male patients outnumbered females by 2.2 to 1 and twice the number of adults were affected compared with children. Most patients were indigent. Dog bites occurred more than cat bites (97.1% vs. 2.9%) and most cases were caused by a single bite (86.2%), compared to multiple bites (8.7%). Bites to the face, head, and neck led to shorter incubation times, yet the incubation period varied, with most cases (42.7%) occurring in the bracket of 91-365 days post-exposure. Clinical symptoms included hydrophobia in all cases, as per our case definition, and aerophobia in 95.5%; only 9.4% had fever, 9.2% exhibited restlessness, and 6.7% exhibited hypersalivation. Localized neurological symptoms included pain (4.1%), numbness (2.6%), and itching (2.3%). None of the patients received appropriate post-exposure prophylaxis (PEP).

CONCLUSIONS

This study examines the largest cohort of rabies patients reported to-date. Better understanding of clinical disease manifestations may help in salvage efforts to save patients with rabies. Knowledge of epidemiological factors will improve preventative efforts to reduce suffering from rabies.

Isolation and characterization of novel human monoclonal antibodies possessing neutralizing ability against rabies virus

Rabies is a fatal viral encephalitis which is transmitted by exposure to the bite of rabid animals. Human and equine rabies immunoglobulins are indispensable pharmacological agents for severe bite exposure, as is vaccine. However, several disadvantages, including limited supply, adverse reactions, and high cost, hamper their wide application in developing countries. In the present study, two novel huMabs which neutralize rabies virus were established from vaccinated hyperimmune volunteers using the Epstein-Barr virus transformation method. One MAb (No. 254), which was subclass IgG3, effectively neutralized fixed rabies viruses of CVS, ERA, HEP-Flury, and Nishigahara strains and recognized a well-conserved epitope located in antigenic site II of the rabies virus glycoprotein. No. 254 possessed 68 ng/ml of FRNT₅₀ activity against CVS, 3.7 × 10⁻⁷ M of the Kd value, and the enhancing effect of complement-dependent virolysis. In addition, No. 254 showed effective neutralization potency in vivo in the mouse challenge test. The other MAb, 4D4, was subclass IgM and showed neutralizing activity against CVS and Nishigahara strains. 4D4 recognized a novel antigenic site which is associated with the neurovirulence of rabies, a glycoprotein located between antigenic site I and VI. Both human MAbs against rabies are expected to be utilized as a tool for future post-exposure prophylaxis.

Development of real-time reverse transcriptase polymerase chain reaction methods for human rabies diagnosis

To improve timely ante-mortem human rabies diagnosis, methods to detect viral RNA by TaqMan-based quantitative reverse transcriptase polymerase chain reactions (qRT-PCRs) have been developed. Three sets of two primers and one internal dual-labeled probe for each primer set that target distinct conserved regions of the rabies virus N gene were designed and evaluated. Using a collection of 203 isolates representative of the world-wide diversity of rabies virus, all three primers/probe sets were shown to detect a wide range of rabies virus strains with very few detection failures; the RABVD1 set in particular was the most broadly reactive. These qRT-PCR assays were shown to be quantitative over a wide range of viral titer and were 100-1,000 times more sensitive than nested RT-PCR; however, both the standard and real-time PCR methods yielded concordant results when used to test a collection of archived human suspect samples. The qRT-PCR assay was employed to monitor virus load in the saliva of a rabies virus-infected patient undergoing the Milwaukee treatment protocol. However in this case it would appear that reduction of the viral load in the patient's saliva over time did not appear to correlate well with clearance of viral components from the brain.

Intravenous inoculation of a bat-associated rabies virus causes lethal encephalopathy in mice through invasion of the brain via neurosecretory hypothalamic fibers

The majority of rabies virus (RV) infections are caused by bites or scratches from rabid carnivores or bats. Usually, RV utilizes the retrograde transport within the neuronal network to spread from the infection site to the central nervous system (CNS) where it replicates in neuronal somata and infects other neurons via trans-synaptic spread. We speculate that in addition to the neuronal transport of the virus, hematogenous spread from the site of infection directly to the brain after accidental spill over into the vascular system might represent an alternative way for RV to invade the CNS. So far, it is unknown whether hematogenous spread has any relevance in RV pathogenesis. To determine whether certain RV variants might have the capacity to invade the CNS from the periphery via hematogenous spread, we infected mice either intramuscularly (i.m.) or intravenously (i.v.) with the dog-associated RV DOG4 or the silver-haired bat-associated RV SB. In addition to monitoring the progression of clinical signs of rabies we used immunohistochemistry and quantitative reverse transcription polymerase chain reaction (qRT-PCR) to follow the spread of the virus from the infection site to the brain. In contrast to i.m. infection where both variants caused a lethal encephalopathy, only i.v. infection with SB resulted in the development of a lethal infection. While qRT-PCR did not reveal major differences in virus loads in spinal cord or brain at different times after i.m. or i.v. infection of SB, immunohistochemical analysis showed that only i.v. administered SB directly infected the forebrain. The earliest affected regions were those hypothalamic nuclei, which are connected by neurosecretory fibers to the circumventricular organs neurohypophysis and median eminence. Our data suggest that hematogenous spread of SB can lead to a fatal encephalopathy through direct retrograde invasion of the CNS at the neurovascular interface of the hypothalamus-hypophysis system. This alternative mode of virus spread has implications for the post exposure prophylaxis of rabies, particularly with silver-haired bat-associated RV.

Rabies virus (RV) infects mammalian neurons and cycles in regionally distinct animal populations such as the red fox in Europe, domestic canines in Asia, or raccoons, skunks and bats in Northern America. Although human rabies can be prevented by pre- and post-exposure prophylaxis, more than 50,000 people die annually from the severe encephalopathy caused by RV. Recently, two cases of RV transmission by organ transplantation were reported. In our study, using intravenous inoculation of mice, we evaluated the pathogenetic relevance of virions that reach the bloodstream. Mice inoculated intravenously with a canine-derived RV survived the infection in contrast to intramuscularly injected mice, while mice infected with a silver-haired bat-related RV succumbed to the disease regardless of the route of inoculation. We found that the silver-haired bat-related RV was able to transit from the blood to the brain by invading neurosecretory fibers of the hypothalamus, which form neurohemal synapses lacking a blood-brain-barrier. This newly described route of brain invasion might reflect how RV reached the central nervous system from transplanted organs, since it takes longer to establish the neural connections between host and grafted tissue necessary for classical RV migration than the time until the infection became symptomatic in the two reported cases.

Development and evaluation of a rapid neutralizing antibody test for rabies

The level of virus-neutralizing antibody, which plays a crucial role in the prevention of rabies, is determined by rabies virus (RABV) neutralizing test, which are time- and cost-consuming. In order to determine the level of neutralizing antibody in vaccinees, an easy and reliable method is needed. Based on the principle of immunochromatography, we developed a RAPINA (RAPId Neutralizing Antibody) test to determine the presence of neutralizing antibody in serum. In the RAPINA test, if neutralizing antibody equivalent to 0.5IU/ml of serum sample are mixed with an optimal amount of inactivated RABV (iRABV) and are completely absorbed by the virus, none of the iRABV can bind with monoclonal antibody that recognizes the iRABV glycoprotein (G) on the test strip. A total of 115 human sera samples were tested. The sensitivity, specificity and accuracy of the RAPINA test compared with rapid fluorescent focus inhibition test (RFFIT) as a standard test, were 88.7, 91.9 and 90.4%, respectively. The RAPINA test is a simple, safe and rapid method, which can be a substitute for neutralizing tests that use live viruses, cultured cells and fluorescence microscopy. This test might be useful for screening a large number of sera.

Assessing the risks of intervention: immobilization, radio-collaring and vaccination of African wild dogs

Controversy has surrounded the role of intervention in studies of African wild dogs Lycaon pictus. Following the death or disappearance of all wild dogs under study in the Serengeti ecosystem, it was suggested that immobilization, radio-collaring or administration of rabies vaccines might have caused high mortality by compromising wild dogs′ immune response to rabies virus. Planning future management and research on wild dogs and other species demands an assessment of the risks associated with such intervention. This paper critically reviews the available evidence and concludes that it is extremely unlikely that intervention contributed to the extinction of wild dogs in the Serengeti ecosystem. A more likely scenario is that vaccination failed to protect wild dogs exposed to rabies virus. Radio-collaring is an important component of wild dog research; hence, the benefits of immobilization appear to outweigh the risks, as long as (i) research is orientated towards wild dog conservation, (ii) radiocollaring is followed up by efficient monitoring, (iii) the number of animals immobilized is kept to the minimum necessary to maintain scientific rigour, and (iv) full data on disease and genetics are collected from all immobilized animals. By contrast, rabies vaccination currently seems to confer few benefits, at least when a single dose of vaccine is given. Further research, on captive animals, is in progress to establish more effective protocols, and to assess the role that vaccination might play in future management of wild dog populations.

Experimental study of European bat lyssavirus type-2 infection in Daubenton's bats (Myotis daubentonii)

European bat lyssavirus type 2 (EBLV-2) can be transmitted from Daubenton's bats to humans and cause rabies. EBLV-2 has been repeatedly isolated from Daubenton's bats in the UK but appears to be present at a low level within the native bat population. This has prompted us to investigate the disease in its natural host under experimental conditions, to assess its virulence, dissemination and likely means of transmission between insectivorous bats. With the exception of direct intracranial inoculation, only one of seven Daubenton's bats inoculated by subdermal inoculation became infected with EBLV-2. Both intramuscular and intranasal inoculation failed to infect the bats. No animal inoculated with EBLV-2 seroconverted during the study period. During infection, virus excretion in saliva (both viral RNA and live virus) was confirmed up to 3 days before the development of rabies. Disease was manifested as a gradual loss of weight prior to the development of paralysis and then death. The highest levels of virus were measured in the brain, with much lower levels of viral genomic RNA detected in the tongue, salivary glands, kidney, lung and heart. These observations are similar to those made in naturally infected Daubenton's bats and this is the first documented report of isolation of EBLV-2 in bat saliva. We conclude that EBLV-2 is most likely transmitted in saliva by a shallow bite.

Rabies

Rabies remains an important public health problem in developing countries, and the indigenous threat of rabies continues in developed countries because of wildlife reservoirs. A diagnosis of rabies is often not considered by physicians until late in the clinical course or after death in North America and Europe, even with typical clinical presentations. Transmission of rabies virus has occurred in association with transplantation of tissues and also recently with organs. In 2004 a young patient survived rabies in Wisconsin, but the reasons for this favorable outcome remain elusive. This article reviews current information and developments on a variety of neurologic aspects of rabies.

Rabies: a preventable but incurable disease

Rabies is a typical zoonotic disease which has been known for more than 4300 years. To date, no effective medical therapy has been established for overt rabies. The rabies post-exposure prophylaxis (PEP), which is a serial vaccination against rabies starting as soon as possible after the patient was bitten by a suspected rabid animal, is the only way to prevent death. In Japan, no rabies case has been reported for about 50 years. However, rabies is epizootic in many Asian countries, where more than 50% of the rabies deaths in the world occur. The Japanese travelers who visit these countries every year may not be aware of this fact since no rabies occurs in their own country. Therefore, the risk of being bitten by a rabid animal abroad and developing rabies after returning to Japan seems to be high. All medical staff should keep in mind that imported rabies cases can occur at any time. In addition, pre-exposure vaccination against rabies should be recommended to international travelers in order to ensure the preventative effect of PEP.

Antemortem diagnosis and prevention of human rabies

Human rabies still continues to be a significant health problem in India and other developing countries where dogs are the major vectors of transmission. Rabies in humans can present in two clinical forms, i.e., furious and paralytic. While diagnosis of furious rabies can be made based on the typical symptoms and signs, paralytic rabies poses a diagnostic dilemma to the neurologists who may encounter these cases in their practice. Although there are certain clinical features that distinguish this disease from other forms of Guillain-Barre syndromes, confirmation of diagnosis may require laboratory assistance. Conventional techniques such as antigen detection, antibody assays and virus isolation have limited success. The recently introduced molecular techniques show more promise in confirming the cases of paralytic rabies. There has not been much success in the treatment of confirmed rabies cases and recovery from rabies is extremely rare. Therefore, preventive measures of this dreaded disease after an exposure become extremely important. The present article reviews the current status of human rabies with regard to antemortem diagnosis, disease management and post-exposure prophylaxis.

[Progression in studies on pathogenesis of rabies virus]

Rabies virus causes lethal neurological symptoms in humans and animals. Rabies epidemics have continued to occur throughout the world, despite the fact that rabies can be effectively prevented by vaccination. The development of inexpensive and safe attenuated live vaccines and the establishment of cures are the keys to control rabies. To achieve these objectives, it is important to elucidate mechanism by which rabies virus causes disease. Here, previous studies on the pathogenesis of rabies virus are reviewed and ways to apply previous findings to rabies control are also discussed.

Human monoclonal antibody and vaccine approaches to prevent human rabies

Rabies, being a major zoonotic disease, significantly impacts global public health. It is invariably fatal once clinical signs are apparent. The majority of human rabies deaths occur in developing countries. India alone reports more than 50% of the global rabies deaths. Although it is a vaccine-preventable disease, effective rabies prevention in humans with category III bites requires the combined administration of rabies immunoglobulin (RIG) and vaccine. Cell culture rabies vaccines have become widely available in developing countries, virtually replacing the inferior and unsafe nerve tissue vaccines. Limitations inherent to the conventional RIG of either equine or human origin have prompted scientists to look for monoclonal antibody-based human RIG as an alternative. Fully human monoclonal antibodies have been found to be safer and equally efficacious than conventional RIG when tested in mice and hamsters. In this chapter, rabies epidemiology, reservoir control measures, post-exposure prophylaxis of human rabies, and combination therapy for rabies are discussed. Novel human monoclonal antibodies, their production, and the significance of plants as expression platforms are emphasized.

Control of rabies: Epidemiology of rabies in Asia and development of new-generation vaccines for rabies

Rabies is an enzootic viral disease widespread throughout the world. Although it is a vaccine-preventable disease, the annual number of human deaths caused by rabies is estimated to be 32,000 in Asia. Phylogenetic analysis based on sequence data of the partial N gene of rabies viruses in Asia has shown that the viruses are divided into five genogroups, distributed in Middle East, South Asia, South East Asia, Malay, and Arctic regions. The genetic relationships among these rabies viruses agree basically with the results of previous studies. Meanwhile, new types of vaccines are being developed by applying gene manipulation techniques to rabies virus in order to overcome the disadvantages of current vaccines. This article reviews the molecular epidemiology of rabies in Asia and progress made in the development of new-generation rabies vaccines with the goal of elimination or control of rabies in Asia.

Molecular epidemiology of rabies in Guangxi Province, south of China

BACKGROUND

Surveillance data for rabies in Guangxi Province in China showed that human rabies cases have gradually increased since 1996.

OBJECTIVE

To evaluate the epidemiology of rabies at the molecular level and provide suggestions for effective prevention of rabies in Guangxi.

STUDY DESIGN

Since 2000, 1569 brains from suspected rabid animals were collected from different areas of Guangxi. Rabies virus was isolated from 42 samples. RT-PCR was used to amplify a 455 nucleotide segment of the 3'-terminal of the N gene. The sequencing data from that segment was used for phylogenetic analysis.

RESULTS

Nucleotide homology comparisons and phylogenetic tree analysis based on this sequence indicated that all the rabies virus isolates from Guangxi belonged to genotype 1 and could be divided into four groups. Groups I, II and IV included 23, 10 and 8 isolates, respectively. These had nucleotide homologies of 97.1-100%, 98.2-100% and 99.1-99.6%, respectively. Only the GXN119 strain belonged to group III. Group I had two group-specific mutations: T90N and E110D. Group II had one group-specific mutation of T42S.

CONCLUSIONS

This study showed that rabies virus isolates from Guangxi have a close genetic relationship and topographical distribution.

Molecular epidemiology of rabies virus isolates in India

In India, rabies is enzootic and is a serious public health and economic problem. India has a large population of stray dogs which, together with a lack of effective control strategies, might have led to the persistence of rabies virus (RV) in the canine population. Our objective was to study the molecular epidemiology of RV isolates in India based on nucleotide sequence analysis of 29 RV isolates originating from different species of animals in four states. Here we have analyzed two sets of sequence data based upon a 132-nucleotide region of the cytoplasmic domain (CD) of the G gene (G-CD) and a 549-nucleotide region (Psi-L) that combines the noncoding G-L intergenic region (Psi) and a fragment of the polymerase gene (L). Phylogenetic analysis revealed that the RV isolates belong to genotype 1 and that they were related geographically but were not related according to host species. Five different genetic clusters distributed among three geographical regions were identified. Comparison of the deduced amino acid sequences of G-CD between RV isolates revealed three amino acid changes (amino acid 462G [aa462G], aa465H, and aa468K) that distinguished the Indian RVs from RV isolates in other parts of the world. Analysis of the data indicated that the dog rabies virus variants are the major circulating viruses in India that transmit the disease to other domestic animals and humans as well.

Problems in human rabies post-exposure prophylaxis management

This is a prospective study of problems encountered with rabies-exposed patients in an animal bite clinic in a rabies endemic region. Five hundred successive patients were analyzed. The study focused mainly on issues that are not well covered in current WHO and US-CDC rabies manuals. Those dealing with immunoglobulin administration, managing severe and unusual injuries, logistic and financial issues headed the list. Animal bite patients often present challenging problems, which are not or inadequately addressed in official publications. Experience and good clinical judgment are essential in preventing human rabies.

Transmission of rabies virus from an organ donor to four transplant recipients

BACKGROUND

In 2004, four recipients of kidneys, a liver, and an arterial segment from a common organ donor died of encephalitis of an unknown cause.

METHODS

We reviewed the medical records of the organ donor and the recipients. Blood, cerebrospinal fluid, and tissues from the recipients were tested with a variety of assays and pathological stains for numerous causes of encephalitis. Samples from the recipients were also inoculated into mice.

RESULTS

The organ donor had been healthy before having a subarachnoid hemorrhage that led to his death. Encephalitis developed in all four recipients within 30 days after transplantation and was accompanied by rapid neurologic deterioration characterized by agitated delirium, seizures, respiratory failure, and coma. They died an average of 13 days after the onset of neurologic symptoms. Mice inoculated with samples from the affected patients became ill seven to eight days later, and electron microscopy of central nervous system (CNS) tissue demonstrated rhabdovirus particles. Rabies-specific immunohistochemical and direct fluorescence antibody staining demonstrated rabies virus in multiple tissues from all recipients. Cytoplasmic inclusions consistent with Negri bodies were seen in CNS tissue from all recipients. Antibodies against rabies virus were present in three of the four recipients and the donor. The donor had told others of being bitten by a bat.

CONCLUSIONS

This report documenting the transmission of rabies virus from an organ donor to multiple recipients underscores the challenges of preventing and detecting transmission of unusual pathogens through transplantation.