Rabies

Analysis of human rabies deaths reported at two hospitals in Karachi, Pakistan: a call to save lives by reforming rabies prevention facilities

BACKGROUND

Rabies is endemic in low- and middle-income countries. It is caused mainly by the bite of a rabid dog and is fatal if not treated effectively and in a timely manner with quality post-exposure prophylaxis. Despite a profusion of private and public healthcare centres in Sindh province, most are ill-equipped to treat dog bites.

METHODS

We analysed 129 human deaths from rabies who presented at the emergency departments of two tertiary care hospitals in Karachi over 10 y. Demographic data, time, location of the bite and distance travelled to report symptoms of rabies were recorded.

RESULTS

Most victims were male, and children were more often affected; almost none had received post-exposure prophylaxis. A total of 12% of bites were on the face, head or neck. The mean incubation period was 56 d. Most (60%) of the rabies victims travelled long distances, hoping to receive treatment.

CONCLUSIONS

Rabies deaths were either due to a lack of awareness or the non-availability of rabies immunobiologicals within easy reach. Public health services must raise awareness, conduct surveillance and provide appropriately spaced centres for free treatment of dog bites. This lethal disease must be prevented at all costs.

Rabies in Europe: An epidemiological and clinical update

Rabies is a vaccine preventable zoonotic disease with a significant mortality burden worldwide. Several years of vaccination campaigns in wildlife animals have now achieved the control of rabies in Western Europe through a vaccination belt in front of endemic Eastern European countries. Nevertheless, rabies could be imported both by travellers from areas without an active public control of the disease or by animals coming from areas where the virus circulates in wildlife fauna. The knowledge of the current world epidemiology combined with a high index of clinical suspicion are needed to reach a diagnosis of rabies, especially in case of atypical presentation or without a history of animal exposure. The pre-travel counselling to people visiting highly endemic areas is essential to give information on how to reduce exposure to potential sources of infection and to select those subjects who could benefit from pre-travel vaccination. Rabies is almost invariably fatal, but the prompt administration of a vaccine course combined with anti-rabies immunoglobulins significantly reduces the probability to develop life-threatening consequences. In this review, we give a brief epidemiological and clinical update about rabies in Europe.

Rabies: Current Preventive Strategies

Desensitization to rabies is a result of successfully eliminating canine rabies in the United States, which occurred in 2007; however, the need for mandatory rabies vaccination in pets remains. Rabies cases are rare in comparison with other vaccine-preventable diseases in companion animals; however, because it is a zoonotic disease with the highest case fatality rate of any infectious disease demands the establishment of strict laws for disease prevention. Preventive strategies include addressing current concerns in consideration of disease surveillance, appropriate vaccination recommendations, and local regulations protecting public health.

Viral infections of the central nervous system in Africa

Viral infections are a major cause of human central nervous system infection, and may be associated with significant mortality, and long-term sequelae. In Africa, the lack of effective therapies, limited diagnostic and human resource facilities are especially in dire need. Most viruses that affect the central nervous system are opportunistic or accidental pathogens. Some of these viruses were initially considered harmless, however they have now evolved to penetrate the nervous system efficiently and exploit neuronal cell biology thus resulting in severe illness. A number of potentially lethal neurotropic viruses have been discovered in Africa and over the course of time shown their ability to spread wider afield involving other continents leaving a devastating impact in their trail. In this review we discuss key viruses involved in central nervous system disease and of major public health concern with respect to Africa. These arise from the families of Flaviviridae, Filoviridae, Retroviridae, Bunyaviridae, Rhabdoviridae and Herpesviridae. In terms of the number of cases affected by these viruses, HIV (Retroviridae) tops the list for morbidity, mortality and long term disability, while the Rift Valley Fever virus (Bunyaviridae) is at the bottom of the list. The most deadly are the Ebola and Marburg viruses (Filoviridae). This review describes their epidemiology and key neurological manifestations as regards the central nervous system such as meningoencephalitis and Guillain-Barré syndrome. The potential pathogenic mechanisms adopted by these viruses are debated and research perspectives suggested.

Challenges to controlling rabies in skunk populations using oral rabies vaccination: A review

Controlling rabies in skunk populations is an important public health concern in many parts of the United States due to the potential for skunk rabies outbreaks in urban centres and the possible role for skunks in raccoon rabies variant circulation. Oral rabies vaccination (ORV) programmes have supported wildlife rabies control efforts globally but using ORV to control rabies in skunk populations has proven more challenging than with other target species, like foxes, coyotes and raccoons. A review of published studies found that some ORV constructs are immunogenic in skunks and protect against virulent rabies virus challenges, especially when delivered by direct installation into the oral cavity. However, in field ORV programmes using currently available vaccine-bait formats and distribution methods targeting other rabies reservoir species, skunks often fail to seroconvert. Field effectiveness of ORV in skunks appears to be limited by poor bait uptake or inadequate ingestion of vaccine rather than from poor vaccine efficacy. Observations of captive skunks revealed vaccine spillage when handling and biting into baits such that modification of bait formats might improve field effectiveness. In addition, a dose-response relationship between bait distribution density and post-baiting seroconversion among skunks was observed across the limited number of field studies. Additional research is needed to identify opportunities to modify ORV baits and distribution strategies to improve the viability of ORV as a rabies control strategy in skunks.

Microbiological laboratory diagnostics of neglected zoonotic diseases (NZDs)

This review reports on laboratory diagnostic approaches for selected, highly pathogenic neglected zoonotic diseases, i.e. anthrax, bovine tuberculosis, brucellosis, echinococcosis, leishmaniasis, rabies, Taenia solium-associated diseases (neuro-/cysticercosis & taeniasis) and trypanosomiasis. Diagnostic options, including microscopy, culture, matrix-assisted laser-desorption-ionisation time-of-flight mass spectrometry, molecular approaches and serology are introduced. These procedures are critically discussed regarding their diagnostic reliability and state of evaluation. For rare diseases reliable evaluation data are scarce due to the rarity of samples. If bio-safety level 3 is required for cultural growth, but such high standards of laboratory infrastructure are not available, serological and molecular approaches from inactivated sample material might be alternatives. Multiple subsequent testing using various test platforms in a stepwise approach may improve sensitivity and specificity. Cheap and easy to use tests, usually called "rapid diagnostic tests" (RDTs) may impact disease control measures, but should not preclude developing countries from state of the art diagnostics.

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 vaccines: where do we stand, where are we heading?

Rabies being the most lethal zoonotic, vaccine-preventable viral disease with worldwide distribution of reservoir wild animals presents unique challenges for its diagnosis, management and control. Although vaccines available are highly effective, which had played the key role in controlling rabies in North America, western Europe and in a number of Asian and Latin American countries, the requirement of multiple doses along with boosters, associated cost to reduce the incidence in wild animals and prophylactic human vaccination has remained a major impediment towards achieving the same goals in poorer parts of the world such as sub-Saharan Africa and southeast Asia. Current efforts to contain rabies worldwide are directed towards the development of more safe, cheaper and efficacious vaccines along with anti-rabies antibodies for post-exposure prophylaxis. The work presented here provides an overview of the advances made towards controlling the human rabies, particularly in last 10 years, and future perspective.

An overview of the effect and epidemiology of viral central nervous system infections in African children

Viral infections in Africa are common. Polio still persists in the continent despite vaccination campaigns. Many of the common viral infections, such as by the nonpolio enteroviruses, lack effective therapies and leave devastating sequelae to infected neonates and infants. Rarer conditions, such as by West Nile virus, have generated a fascinating conundrum as to how the virus spread to other parts of the world, such as the United States of America. This infection illustrates that these conditions should not be considered isolated to Africa alone but that they represent examples of potentially lethal infections which, although predominantly found in Africa, have the capacity to spread wider afield.

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.

Production, characterization, and antigen specificity of recombinant 62-71-3, a candidate monoclonal antibody for rabies prophylaxis in humans

Rabies kills many people throughout the developing world every year. The murine monoclonal antibody (mAb) 62-71-3 was recently identified for its potential application in rabies postexposure prophylaxis (PEP). The purpose here was to establish a plant-based production system for a chimeric mouse-human version of mAb 62-71-3, to characterize the recombinant antibody and investigate at a molecular level its interaction with rabies virus glycoprotein. Chimeric 62-71-3 was successfully expressed in Nicotiana benthamiana. Glycosylation was analyzed by mass spectroscopy; functionality was confirmed by antigen ELISA, as well as rabies and pseudotype virus neutralization. Epitope characterization was performed using pseudotype virus expressing mutagenized rabies glycoproteins. Purified mAb demonstrated potent viral neutralization at 500 IU/mg. A critical role for antigenic site I of the glycoprotein, as well as for two specific amino acid residues (K226 and G229) within site I, was identified with regard to mAb 62-71-3 neutralization. Pseudotype viruses expressing glycoprotein from lyssaviruses known not to be neutralized by this antibody were the controls. The results provide the molecular rationale for developing 62-71-3 mAb for rabies PEP; they also establish the basis for developing an inexpensive plant-based antibody product to benefit low-income families in developing countries.

Development of Leishmania vaccines: predicting the future from past and present experience

Leishmaniasis is a disease that ranges in severity from skin lesions to serious disfigurement and fatal systemic infection. Resistance to infection is associated with a T-helper-1 immune response that activates macrophages to kill the intracellular parasite in a nitric oxide-dependent manner. Conversely, disease progression is generally associated with a T-helper-2 response that activates humoral immunity. Current control is based on chemotherapeutic treatments which are expensive, toxic and associated with high relapse and resistance rates. Vaccination remains the best hope for control of all forms of the disease, and the development of a safe, effective and affordable antileishmanial vaccine is a critical global public-health priority. Extensive evidence from studies in animal models indicates that solid protection can be achieved by immunization with defined subunit vaccines or live-attenuated strains of Leishmania. However, to date, no vaccine is available despite substantial efforts by many laboratories. Major impediments in Leishmania vaccine development include: lack of adequate funding from national and international agencies, problems related to the translation of data from animal models to human disease, and the transition from the laboratory to the field. Furthermore, a thorough understanding of protective immune responses and generation and maintenance of the immunological memory, an important but least-studied aspect of antiparasitic vaccine development, during Leishmania infection is needed. This review focuses on the progress of the search for an effective vaccine against human and canine leishmaniasis.

Rabies: still a uniformly fatal disease? Historical occurrence, epidemiological trends, and paradigm shifts

Rabies has the highest case fatality of any infectious disease. Pathobiological and clinical insights have questioned the assertion that death is inevitable after onset of acute encephalomyelitis. Relying upon national laboratory-based surveillance, we reviewed records of human rabies acquired in the United States during 1960-2009. Changes in the epidemiology of human rabies were notable, due to improved animal management, safer and more efficacious biologics, and revisions in prevention guidelines. Historically, domestic animals were the most important source of infection. Since the 1990s, more human cases were associated with rabid bats. Prior to 1980, postexposure prophylaxis failures were reported. After development of modern rabies immune globulin and vaccines, none occurred. Of 75 human cases identified, only four patients survived. Rabies remains an extremely high consequence zoonosis, but the disease is not uniformly fatal, per se. Rabies is essentially preventable when primary exposures are averted, or appropriate prophylaxis occurs before illness.

Risk Factors, Prevention and Prophylaxis of Dog Bites for Disaster Response Personnel in the United States

It commonly is rumored that in large scale disasters, packs of dogs present a human health hazard because of dog bites. However, it is likely that factors other than pack behavior comprise greater risk factors for dog bites in disaster-response personnel. Important risk factors include: 1) the density of the human population, which in turn, determines the number of dogs at a disaster site; 2) territorial behavior of dogs at their site of residence, which determines the frequency with which dogs may bite; and 3) whether rabies is present at endemic or epidemic levels within the area in which the disaster is occurring, which determines the likelihood of fatal outcomes. Persons bitten by a dog should seek medical attention as contraction of rabies may result in a fatal outcome from a dog bite. It is recommended that disaster response personnel obtain pre-exposure vaccination against rabies. Vaccinated or not, they immediately should seek post-exposure treatment for rabies following potential exposure.

Development of Vaccines against Visceral Leishmaniasis

Leishmaniasis is a neglected disease resulting in a global morbidity of 2,090 thousand Disability-Adjusted Life Years and a mortality rate of approximately 60,000 per year. Among the three clinical forms of leishmaniasis (cutaneous, mucosal, and visceral), visceral leishmaniasis (VL) accounts for the majority of mortality, as if left untreated VL is almost always fatal. Caused by infection with Leishmania donovani or L. infantum, VL represents a serious public health problem in endemic regions and is rapidly emerging as an opportunistic infection in HIV patients. To date, no vaccine exists for VL or any other form of leishmaniasis. In endemic areas, the majority of those infected do not develop clinical symptoms and past infection leads to robust immunity against reinfection. Thus the development of vaccine for Leishmania is a realistic public health goal, and this paper summarizes advances in vaccination strategies against VL.

The rabies epidemic in Trinidad of 1923 to 1937: an evaluation with a Geographic Information System

BACKGROUND

Rabies, although not preeminent among current infectious diseases, continues to afflict humans with as many as 55,000 deaths annually. The case fatality rate remains the highest among infectious diseases, and medical treatments have proven ineffective.

OBJECTIVE

This study analyzes the rabies epidemic of 1929 to 1937 in Trinidad from a geographical perspective, using Geographic Information System (GIS) software as an analytical tool.

SETTING

A small island developing country at a time when infectious diseases were rampant.

METHODS

A review of the literature was undertaken, and data were collected on the occurrence of disease in both animal and humans populations and mapped using GIS software. Several factors identified in the literature were further explored such as land use/land cover, rainfall and magnetic declination.

RESULTS

The bat rabies epidemic of 1923 to 1937 in Trinidad was migratory and seasonal, shifting to new locations along a definite path. The pattern of spread appears to be spatially linked to land use/land cover. The epidemic continues to present many unexplained peculiarities.

CONCLUSION

Despite the fact that this epidemic occurred almost 7 decades ago, the application of new tools available for public health use can create new knowledge and understanding of events. We showed that the spatial of distribution of the disease followed a distinct pathway possible due to the use of electromagnetic capabilities of bats.

RIG-I mediates nonsegmented negative-sense RNA virus-induced inflammatory immune responses of primary human astrocytes

While astrocytes produce key inflammatory mediators following exposure to neurotropic nonsegmented negative-sense RNA viruses such as rabies virus and measles virus, the mechanisms by which resident central nervous system (CNS) cells perceive such viral challenges have not been defined. Recently, several cytosolic DExD/H box RNA helicases including retinoic acid-inducible gene I (RIG-I) have been described that function as intracellular sensors of replicative RNA viruses. Here, we demonstrate that primary human astrocytes constitutively express RIG-I and show that such expression is elevated following exposure to a model neurotropic RNA virus, vesicular stomatitis virus (VSV). Evidence for the functional nature of RIG-I expression in these cells comes from the observation that this molecule associates with its downstream effector molecule, interferon promoter stimulator-1, following VSV infection and from the finding that a specific ligand for RIG-I elicits astrocyte immune responses. Importantly, RIG-I knockdown significantly reduces inflammatory cytokine production by VSV-infected astrocytes and inhibits the production of soluble neurotoxic mediators by these cells. These findings directly implicate RIG-I in the initiation of inflammatory immune responses by human glial cells and provide a potential mechanism underlying the neuronal cell death associated with acute viral CNS infections.

Estimating the risk of rabies transmission to humans in the U.S.: a Delphi analysis

Background

In the United States, the risk of rabies transmission to humans in most situations of possible exposure is unknown. Controlled studies on rabies are clearly not possible. Thus, the limited data on risk has led to the frequent administration of rabies post-exposure prophylaxis (PEP), often in inappropriate circumstances.

Methods

We used the Delphi method to obtain an expert group consensus estimate of the risk of rabies transmission to humans in seven scenarios of potential rabies exposure. We also surveyed and discussed the merits of recommending rabies PEP for each scenario.

Results

The median risk of rabies transmission without rabies PEP for a bite exposure by a skunk, bat, cat, and dog was estimated to be 0.05, 0.001, 0.001, and 0.00001, respectively. Rabies PEP was unanimously recommended in these scenarios. However, rabies PEP was overwhelmingly not recommended for non-bite exposures (e.g. dog licking hand but unavailable for subsequent testing), estimated to have less than 1 in 1,000,000 (0.000001) risk of transmission.

Conclusions

Our results suggest that there are many common situations in which the risk of rabies transmission is so low that rabies PEP should not be recommended. These risk estimates also provide a key parameter for cost-effective models of human rabies prevention and can be used to educate health professionals about situation-specific administration of rabies PEP.

An evaluation of two commercially available ELISAs and one in-house reference laboratory ELISA for the determination of human anti-rabies virus antibodies

The envelope glycoprotein G of rabies virus in vaccines induces the production of neutralizing antibodies important in the protection against the disease. The measurement of anti-envelope glycoprotein antibodies is a good predictor of the degree of humoral immunity in people during anti-rabies treatment or after vaccination. Several assays exist for the serological determination of antibody protection against rabies virus infection. Antibody neutralization by the rapid fluorescent focus inhibition test (RFFIT) or the fluorescent antibody virus neutralization (FAVN) test is currently the gold standard. Performance of the highly complex RFFIT and FAVN tests, however, requires specialized reference laboratories with expertise with this assay. Although not widely used, ELISA test kits are available and may be an additional option for testing that is more accessible. The aim of the present study was to evaluate available ELISA assays for the determination of anti-rabies antibodies. We compared the Bio-Rad Platelia Rabies II ELISA, DRG Rabies Virus IgG Ab ELISA and Focus Diagnostics Rabies Antibody Detection by ELISA to RFFIT. Bland–Altman plots comparing the Bio-Rad Platelia assay and the Focus Diagnostics assay to RFFIT showed a low degree of variability between the ELISA assays and RFFIT results except in samples with high RFFIT values. The agreement, sensitivity and specificity of Bio-Rad Platelia Rabies II ELISA when compared to RFFIT were 95.1 %, 94.1 % and 95.8 %, respectively. The DRG Rabies assay compared to RFFIT had an agreement of 77.7 %, a sensitivity of 86.7 % and a specificity of 69.4 %. The agreement, sensitivity and specificity of Focus Diagnostics Rabies Detection by ELISA when compared to RFFIT were 82.2 %, 91.7 % and 73.0 %, respectively. Overall, the Bio-Rad Platelia assay showed higher accuracy and specificity than either the DRG or Focus assays. All of these ELISAs, however, measure all antibody types and do not discriminate the neutralizing antibodies as measured by functional assays (RFFIT and FAVN) and cannot be relied upon to predict the neutralizing activity of the sera. The results of this study offer insight into the availability of alternative, less-complex methods to monitor rabies antibody titres in at-risk individuals following vaccination.

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.

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.

The human-canine environment: a risk factor for non-play bites?

Few dog bite risk factor studies have been conducted. This veterinary clinic-based retrospective cohort study was aimed at identifying human-canine environmental risk factors for non-play bites in Kingston, Jamaica (660) and San Francisco (SF), USA (452). Data were analysed using modified Poisson regression with confounders selected using directed acyclic graphs (DAGs) and the change-in-estimate procedure. Dogs acquired for companionship were more likely (RR=1.66; 95% CI 1.02-2.70) to bite than those acquired for protection. Routinely allowing a dog into the presence of visitors was also positively associated with it biting. A dog sleeping in a family member's bedroom was a risk factor for biting in Kingston (RR=2.54; 95% CI 1.43-4.54) but not in SF, while being able to leave the yard unaccompanied was a risk factor for biting in SF (RR=3.40; 95% CI 1.98-5.85) but not in Kingston. Overall, dogs which were less restricted in their interactions with humans were at elevated risk for biting. An observed association with dog bites in one cultural setting might not exist in another.

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.

High level expression of surface glycoprotein of rabies virus in tobacco leaves and its immunoprotective activity in mice

A synthetic gene coding for the surface glycoprotein (G protein) of rabies virus was strategically designed to achieve high-level expression in transgenic plants. The native signal peptide was replaced by that of the pathogenesis related protein, PR-S of Nicotiana tabacum. An endoplasmic reticulum retention signal was included at C-terminus of the G protein. Tobacco plants were genetically engineered by nuclear transformation. Selected transgenic lines expressed the chimeric G protein at 0.38% of the total soluble leaf protein. Mice immunized intraperitoneally with the G protein purified from tobacco leaf microsomal fraction elicited high level of immune response as compared to the inactivated commercial viral vaccine. The plant-derived G protein induced complete protective immunity in mice against intracerebral lethal challenge with live rabies virus. The results establish that plants can provide a safe and effective production system for the expression of immunoprotective rabies virus surface protein.

Rabies: a review of UK management

Rabies is endemic worldwide, and causes approximately 30 000 deaths per year. In the past 20 years, 12 deaths have occurred in the UK, although all but one case were contracted overseas. We have reviewed the current literature regarding the management of possible rabies exposure in the setting of a UK emergency department. The article offers an overview of rabies, including pathology, risk assessment, and current treatment, including both pre-exposure and post-exposure prophylaxis. We have also included a form online, which allows the correct information to be obtained and recorded prior to seeking advice from the local virology services.

Rabies DNA vaccines for protection and therapeutic treatment

Rabies is a successful zoonotic disease that has persisted over time, achieving worldwide distribution in a variety of species. Annually, in developing countries with limited access to high-quality antirabies biologics, approximately 50,000 individuals and millions of animals die of rabies. Many of these countries continue to use vaccines produced in sheep, goat or suckling mouse brain, with ultraviolet light or phenol inactivation of the virus. Although there are several efficacious rabies vaccines derived from cultured cells, such as the human diploid cell vaccine, they are costly to produce and prohibitively expensive for developing countries. DNA vaccines offer a new and powerful approach for the generation of needed vaccines. They are stable, inexpensive to produce, easy to construct and induce a full spectrum of long-lasting humoral and cellular immune responses. This review concerns the present state of rabies DNA vaccines, and addresses the technology that may enhance their therapeutic efficacy.

Rabies deaths in Pakistan: results of ineffective post-exposure treatment

OBJECTIVES

To estimate the incidence of rabies and the effectiveness of post-exposure treatment (PET) in Pakistan.

METHODS

Rabies cases admitted from July 1993 to December 1994 to a public rabies isolation hospital were analyzed. Two samples (one sample each from a separate peripheral site) of a single batch of sheep brain vaccine (SBV) were also tested for potency by the National Institute of Health (NIH) test in May 1997.

RESULTS

Forty patients were admitted with a history of clinical rabies. The median age was 22 years and 55% were under 15. Thirteen (23%) victims did not receive any vaccine; the remaining 27 (67%) received SBV only, and of these, 16 (40%) received a full course of SBV. No rabies immunoglobulins (RIG) or cell culture vaccines were administered. There were frequent power blackouts and no back-up supply at the public hospital. In-house potency testing of the vaccine batch by the manufacturer was adequate, although it was not tested by the World Health Organization (WHO) recommended NIH test. Samples of SBV of the same batch collected at the peripheral sites showed no potency. Rabies incidence was estimated to range between 7.0 to 9.8 cases per million annually.

CONCLUSION

A multi-sectorial approach is needed to decrease rabies incidence in Pakistan. Public and healthcare practitioner education on prompt and appropriate PET, especially the use of cost-effective cell culture intradermal regimens, is needed urgently. The NIH test should be employed for vaccine potency testing. An independent agency is needed for monitoring vaccine quality and strategies are needed for maintaining cold chain. SBV should be replaced by locally manufactured second-generation cell culture rabies vaccine. Purified equine rabies immunoglobulin (ERIG) should be manufactured locally to meet national needs. Furthermore, effective dog control strategies should be implemented to decrease the rabies reservoir.

N-glycosylation at one rabies virus glycoprotein sequon influences N-glycan processing at a distant sequon on the same molecule

Rabies glycoprotein (RGP(WT)) contains N-glycosylation sequons at Asn(37), Asn(247), and Asn(319), although Asn(37) is not efficiently glycosylated. To examine N-glycan processing at Asn(247) and Asn(319), full-length glycosylation mutants, RGP(-2-) and RGP(--3), were expressed, and Endo H sensitivity was compared. When the Asn(247) sequon is present alone in RGP(-2-), 90% of its N-glycans are high-mannose type, whereas only 35% of the N-glycans at Asn(319) in RGP(--3) are high-mannose. When both sequons are present in RGP(-23), 87% of the N-glycans are of complex type. The differing patterns of Endo H sensitivity at sequons present individually or together suggests that glycosylation of one sequon affects glycosylation at another, distant sequon. To explore this further, we constructed soluble forms of RGP: RGP(WT)T441His and RGP(--3)T441His. Tryptic glycopeptides from these purified secreted proteins were isolated by HPLC and characterized by a 3D oligosaccharide mapping technique. RGP(WT)T441His had fucosylated, bi- and triantennary complex type glycans at Asn(247) and Asn(319). However, Asn(247) had half as many neutral glycans, more monosialylated glycans, and fewer disialylated glycans when compared with Asn(319). Moreover, when comparing the N-glycans at Asn(319) on RGP(--3)T441His and RGP(WT)T441His, the former had 30% more neutral, 28% more monosialylated, and 33% fewer disialylated glycans. This suggests that the N-glycan at Asn(247) allows additional N-glycan processing to occur at Asn(319), yielding more heavily sialylated bi- and triantennary forms. The mechanism(s) by which glycosylation at one sequon influences N-glycan processing at a distant sequon on the same glycoprotein remains to be determined.

Live vaccinia-rabies virus recombinants, but not an inactivated rabies virus cell culture vaccine, protect B-lymphocyte-deficient A/WySnJ mice against rabies: considerations of recombinant defective poxviruses for rabies immunization of immunocompromised individuals

Presently, commercially available cell culture rabies vaccines for humans and animals consist of the five inactivated rabies virus proteins. The vaccines elicit a CD4+ helper T-cell response and a humoral B-cell response against the viral glycoprotein (G) resulting in the production of virus neutralizing antibody. Antibody against the viral nucleoprotein (N) is also present, but the mechanism(s) of its protection is unclear. HIV-infected individuals with low CD4+ T-lymphocyte counts and individuals undergoing treatment with immunosuppressive drugs have an impaired neutralizing antibody response after pre- and post-exposure immunization with rabies cell culture vaccines. Here we show the efficacy of live vaccinia-rabies virus recombinants, but not a cell culture vaccine consisting of inactivated rabies virus, to elicit elevated levels of neutralizing antibody in B-lymphocyte deficient A/WySnJ mice. The cell culture vaccine also failed to protect the mice, whereas a single immunization of a vaccinia recombinant expressing the rabies virus G or co-expressing G and N equally protected the mice up to 18 months after vaccination. The data suggest that recombinant poxviruses expressing the rabies virus G, in particular replication defective poxviruses such as canarypox or MVA vaccinia virus that undergo abortive replication in non-avian cells, or the attenuated vaccinia virus NYVAC, should be evaluated as rabies vaccines in immunocompromised individuals.

Rabies cell culture vaccines reconstituted and stored at 4°C for 1 year prior to use protect mice against rabies virus

Human exposure to rabid dogs in developing countries is an ongoing problem that continues to demand effective, safe, and affordable post-exposure rabies vaccinations. Sheep and suckling mouse brain rabies vaccines used in developing countries are being replaced by expensive inactivated-virus cell culture vaccines. Human studies using cell culture vaccines have determined that cost is reduced and protection is maintained by injecting the unused portion of vaccines that have been reconstituted and stored refrigerated for 1 week. Here we determined whether reconstituted purified chick embryo cell and human diploid cell vaccine that had been stored at 4 degrees C for intervals up to 1 year elicit neutralizing antibody, and protect mice against rabies virus. Undiluted, or 1:5 and 1:25 dilutions of both vaccines injected immediately after reconstitution, or after reconstitution and storage at 4 degrees C for 1 week, 1 month, 3 months, 6 months or 1 year elicited high levels of neutralizing antibody and protected 100% of the mice injected with rabies virus.

Overview, prevention, and treatment of rabies

Rabies is a uniformly fatal viral encephalitis that causes 30,000 to 70,000 deaths worldwide each year. Prevention is the primary approach to the disease. In the United States, 25,000 to 40,000 people are treated annually for exposure to rabid or potentially rabid animals at a per-patient cost exceeding 1000 dollars. Rabies is transmitted usually by saliva from infected animal bites. However, recent findings that rabies can be transmitted from bats to humans by relatively casual contact has resulted in dramatic changes in guidelines from the Centers for Disease Control and Prevention for postexposure prophylaxis. We review the 5 clinical stages of rabies, current methods of diagnosis, and prevention in animal reservoirs and in humans. We also discuss the use of rabies immune globulin and active and passive vaccinations for preexposure prophylaxis and postexposure treatment of rabies. Human exposure to rabies will always be a possibility, but methods to prevent the disease both before and after exposure to the virus are safe and readily available.

Public health impact of reemergence of rabies, New York

This report summarizes the spread of a raccoon rabies epizootic into New York in the 1990s, the species of animals affected, and human postexposure treatments (PET). A total of 57,008 specimens were submitted to the state laboratory from 1993 to 1998; 8,858 (16%) animals were confirmed rabid, with raccoons the most common species (75%). After exposure to 11,769 animals, 18,238 (45%) persons received PET, mostly because of contact with saliva or nervous tissue. We analyzed expenditure reports to estimate the cost of rabies prevention activities. An estimated $13.9 million was spent in New York State to prevent rabies from 1993 to 1998. Traditional prevention methods such as vaccinating pets, avoiding wildlife, and verifying an animal's rabies status must be continued to reduce costly PET. To reduce rabid animals, exposures, and costs, oral vaccination of wildlife should also be considered.

Human rabies: a disease of complex neuropathogenetic mechanisms and diagnostic challenges

Rabies is inevitably fatal and presents a horrifying clinical picture. Human rabies can manifest in either encephalitic (furious) or paralytic (dumb) forms. The brainstem is preferentially involved in both clinical forms, though there are no clinical signs of brainstem dysfunction. Differences in tropism at the inoculation site or the CNS, in the route of spread, or in the triggering of immune cascades in the brainstem may account for clinical variation. Rabies still poses diagnostic problems, particularly the paralytic form, which closely resembles Guillain-Barré syndrome, or when a patient is comatose and cardinal signs may be lacking. Molecular methods allow reliable detection of rabies-virus RNA in biological fluids or tissue before death. Deviations from the recommendations on prophylaxis of the World Health Organization lead to unnecessary loss of life. To date, attempts to treat human rabies have been unsuccessful.

Cryptogenic rabies, bats, and the question of aerosol transmission

Human rabies is rare in the United States; however, an estimated 40,000 patients receive rabies postexposure prophylaxis each year. Misconceptions about the transmission of rabies are plentiful, particularly regarding bats. Most cases of human rabies caused by bat variants have no definitive history of animal bite. Three hypotheses are proposed and reviewed for the transmission of rabies from bats to human beings. They include nonbite transmission (including aerosol transmission), the alternate host hypothesis (an intermediate animal host that acquires rabies from a bat and then transmits rabies to human beings), and minimized or unrecognized bat bites. Nonbite transmission of rabies is very rare, and aerosol transmission has never been well documented in the natural environment. The known pathogenesis of rabies and available data suggest that all or nearly all cases of human rabies attributable to bats were transmitted by bat bites that were minimized or unrecognized by the patients.

One-time gene gun or intramuscular rabies DNA vaccination of non-human primates: comparison of neutralizing antibody responses and protection against rabies virus 1 year after vaccination

We have previously shown that Macaca fascicularis (Cynomologus) monkeys receiving a primary and either one or two booster rabies DNA vaccinations are protected against rabies virus. In this study, we determined whether monkeys that had been vaccinated only once via gene gun or intramuscularly (i.m.) with different concentrations of DNA would be protected against rabies virus challenge. Neutralizing antibody responses were assayed for 1 year before the monkeys were challenged. Neutralizing antibody was detected at least 50 days earlier in gene gun vaccinated as compared to i.m. vaccinated animals. Prior to viral challenge, all (6/6, 100%) gene gun vaccinated animals, but only 3/6 (50%) i.m. vaccinated animals seroconverted. In general, antibody titers of the gene gun vaccinated animals were higher than the titers of the i.m. vaccinated animals. There was no correlation between the concentration of DNA used for vaccination, the neutralizing antibody responses elicited and protection against viral challenge. Seven days after viral challenge, a rapid and strong anamnestic antibody response was elicited in 100% of the gene gun vaccinated monkeys and in four i.m. vaccinated monkeys. Neutralizing antibody remained undetectable in two i.m. vaccinated monkeys. Overall, 60% (3/5) of the gene gun vaccinated animals and 87% (5/6) of the i.m. vaccinated monkeys survived viral challenge. This study is the first, to our knowledge, to show long-term protection of non-human primates against a human viral pathogen using a DNA vaccination protocol that did not include a booster immunization.

Preexposure efficacy of a novel combination DNA and inactivated rabies virus vaccine

Several strategies are being examined to enhance the potency of DNA rabies vaccine (DRV) so that it can be used for both prophylaxis and postexposure therapy of rabies. In this study, we report a novel combination rabies vaccine (CRV) containing a low dose of cell culture-derived inactivated rabies virus vaccine and DRV. Mice immunized with CRV develop higher levels of rabies virus-neutralizing antibodies (RVNA) than those immunized with DRV and are completely protected against peripheral as well as intracerebral rabies virus challenge. The quantity of inactivated rabies virus vaccine required for enhancing the potency of DRV can be 625-fold lower than that of a standard dose of inactivated rabies virus vaccine. CRV induces higher levels of RVNA than DRV in cattle as well. Thus, we demonstrate for the first time that co-inoculation of DNA vaccine and a low dose of inactivated virus vaccine can be developed into a novel cost-effective vaccination strategy for combating rabies in particular, and infectious diseases in general.

Risks and prevention of nosocomial transmission of rare zoonotic diseases

Americans are increasingly exposed to exotic zoonotic diseases through travel, contact with exotic pets, occupational exposure, and leisure pursuits. Appropriate isolation precautions are required to prevent nosocomial transmission of rare zoonotic diseases for which person-to-person transmission has been documented. This minireview provides guidelines for the isolation of patients and management of staff exposed to the following infectious diseases with documented person-to-person transmission: Andes hantavirus disease, anthrax, B virus infection, hemorrhagic fevers (due to Ebola, Marburg, Lassa, Crimean-Congo hemorrhagic fever, Argentine hemorrhagic fever, and Bolivian hemorrhagic fever viruses), monkeypox, plague, Q fever, and rabies. Several of these infections may also be encountered as bioterrorism hazards (i.e., anthrax, hemorrhagic fever viruses, plague, and Q fever). Adherence to recommended isolation precautions will allow for proper patient care while protecting the health care workers who provide care to patients with known or suspected zoonotic infections capable of nosocomial transmission.

Diagnosis and prevention of rabies

Over a million Americans are bitten by animals every year. Since the rabies vaccine is uniformly effective and the disease is uniformly fatal when the vaccine is not given, management decisions must be made promptly.

Rabies in Israel: decades of prevention and a human case

Animal rabies is endemic in Israel, with 50-80 laboratory-confirmed cases being diagnosed annually. Despite the high incidence among animals, human rabies has not occurred in Israel for almost four decades. This is likely due to the highly effective prevention policy implemented by the Ministry of Health, based on pre-exposure vaccination of populations at risk, post-exposure treatment, and updated rules. Notwithstanding the previous success, a human case occurred in 1996 when a soldier was bitten, while asleep, by an unidentified small animal, which according to his description was a rat or a mouse. Since injuries by these rodents do not require antirabies treatment, no antirabies post-exposure prophylaxis was administered. Five weeks later the soldier complained of fever and nausea with interchanging periods of rage and calm, confusion, and water aversion. His condition deteriorated gradually, leading to deep coma and death. Immunofluorescence examination of a skin biopsy was positive for rabies, and PCR of saliva revealed Lyssavirus genotype 1. We review the changes in the epizootiology of rabies in Israel, the trends of human exposure to animals, and the pre- and post-exposure prophylaxis guidelines, and discuss possible measures that could have been undertaken to prevent the eventuality of this case. This case of rabies, the first after a long period without human disease, accentuates the importance of strict adherence to prevention guidelines. Considerations of geography, epidemiology, and the circumstances of exposure are crucial in the treatment decision-making process.