Failures of post-exposure rabies prophylaxis

Should travellers to rabies-endemic countries be pre-exposure vaccinated? An assessment of post-exposure prophylaxis and pre-exposure prophylaxis given to Danes travelling to rabies-endemic countries 2000-12

BACKGROUND

Since 2000, a steady increase of vaccines used for both rabies Post-exposure prophylaxis (PEP) and rabies Pre-exposure prophylaxis (PrEP) given to Danish travellers was observed. This study aims to evaluate whether the increase of PEP and PrEP was due to increased travelling, increased awareness of the need for PrEP, or more animal bites per travel, leading to more PEP being administered, in order to assess the need for changing the recommendations. We also described in which countries Danish travelers most frequently reported possible exposure to rabies, and evaluated the timeliness of rabies PEP, including rabies immunoglobulin (RIG).

METHODS

We included all Danes reported to the National Database for Rabies Treatment as having started rabies PEP either abroad or after returning to Denmark, between 2000 and 2012. Data on the yearly number of Danish travelers from 2004 to 2012 to Thailand were collected to calculate the incidence of animal bites at this destination. We also included data on rabies vaccines sold for PrEP or for booster vaccination in Denmark.

RESULTS

PEP after possible exposure to rabies abroad increased yearly by 8.8 %. Likewise vaccines sold for PrEP increased by 8.2% annually. The number of Danish travelers to Thailand increased by 7.3% per year, resulting in a stable incidence of animal bites per 100,000 travelers. Seventy-five % started PEP in the country of exposure, while only 10 % received RIG.

CONCLUSIONS

The yearly increase in PEP and PrEP are parallel to the yearly increase in number of travelers, and can thus be explained by the increased rate of traveling, and not by a rise in awareness of rabies risk or more bites per traveler.Even short term travelers should be given the option of including PrEP in their travel immunisation program, as PEP and especially RIG is not always available in rabies-endemic countries.

Local infiltration of rabies immunoglobulins without systemic intramuscular administration: An alternative cost effective approach for passive immunization against rabies

Presently the dose of rabies immunoglobulin (RIG) which is an integral part of rabies post exposure prophylaxis (PEP) is calculated based on body weight though the recommendation is to infiltrate the wound(s). This practice demands large quantities of RIG which may be unaffordable to many patients. In this background, we conducted this study to know if the quantity and cost of RIG can be reduced by restricting passive immunization to local infiltration alone and avoiding systemic intramuscular administration based on the available scientific evidence. Two hundred and sixty nine category III patients bitten by suspect or confirmed rabid dogs/animals were infiltrated with equine rabies immunoglobulin (ERIGs) in and around the wound. The quantity of ERIG used was proportionate to the size and number of wounds irrespective of their body weight. They were followed with a regular course of rabies vaccination by intra-dermal route. As against 363 vials of RIGs required for all these cases as per current recommendation based on body weight, they required only 42 vials of 5ml RIG. Minimum dose of RIGs given was 0.25 ml and maximum dose given was 8 ml. On an average 1.26 ml of RIGs was required per patient that costs Rs. 150 ($3). All the patients were followed for 9 months and they were healthy and normal at the end of observation period. With local infiltration, that required small quantities of RIG, the RIGs could be made available to all patients in times of short supply in the market. A total of 30 (11%) serum samples of patients were tested for rabies virus neutralizing antibodies by the rapid fluorescent focus inhibition test (RFFIT) and all showed antibody titers >0.5 IU/mL by day 14. In no case the dose was higher than that required based on body weight and no immunosuppression resulted. To conclude, this pilot study shows that local infiltration of RIG need to be considered in times of non-availability in the market or unaffordability by poor patients. This preliminary study needs to be done on larger scale in other centers with long term follow up to substantiate the results of our study.

Worldwide rabies deaths prevention--A focus on the current inadequacies in postexposure prophylaxis of animal bite victims

The World Health Organization reports that over 60,000 humans die of rabies annually, worldwide. Most occur in remote regions of developing countries. Almost all victims received no postexposure rabies prophylaxis (PEP). There are no facilities or health personnel able to provide it in many areas where the disease is prevalent. A first approach to correct this problem would be by extending provision of modern PEP to areas where human rabies is most prevalent.

Novel Approaches to the Prevention and Treatment of Rabies

Rabies is a highly lethal disease caused by the neurotropic rabies virus (RABV), and it remains an important public health problem globally. Effective vaccines have been developed for pre- and post-exposure prophylaxis (PEP). PEP is only effective if it is initiated promptly after recognizing exposure. Once neurological symptoms develop, however, it is widely accepted that there is no effective treatment available. Recent studies indicate that the presence of RABV-specific immunity (i.e. Virus neutralizing antibodies, VNA) and the transient enhancement of the BBB permeability are absolutely required for effective virus clearance from the CNS. In principle, it has been shown in mice using various live-attenuated RABVs or recombinant RABVs expressing three copies of the G or expressing chemokine/cytokines, which can induce high levels of VNA in the serum and also capable of transiently enhancing the BBB permeability that it is possible to clear the virus from CNS. Also, it has been demonstrated that, intravenous administration of VNA together with MCP-1 (shown to transiently open up BBB) can clear RABV from the CNS in both immunocompetent and immunocompromised mice, as late as 5 days after lethal challenge. Novel therapeutic approaches aimed at allowing the peripheral VNA to cross the BBB by administration of the VNA in combination with biological or chemical agents that can transiently open up the BBB would be useful to establish an effective therapy for rabies in humans. In this review, we focus on the some of the approaches that can be used to meet the challenges in the field of rabies treatment.

Rabies encephalitis in a child: a failure of rabies post exposure prophylaxis?

Rabies remains a serious public health problem in many developing countries. The diagnosis is easy when a non-immunised patient presents with hydrophobia and hypersalivation after a bite by a known rabid animal but more difficult when a patient presents atypical symptoms after having received rabies postexposure prophylaxis. Rabies postexposure prophylaxis failure is rare. We report a case of a 6-year-old boy who presented febrile seizure with agitation and cerebellar signs, without hydrophobia or hypersalivation, 17 days after a dog bite. Despite four doses of rabies vaccine and immunoglobulin, he died. Diagnostic confirmation of rabies encephalitis was made in post mortem on brain biopsies by fluorescent antibody technique.

Comparison of safety and immunogenicity of 2 WHO prequalified rabies vaccines administered by one week, 4 site intra dermal regimen (4-4-4-0-0) in animal bite cases

The currently advocated rabies post-exposure prophylaxis regimens are of one month duration with reduced patient compliance. WHO recommended research on shortened vaccination regimens which have a practical and economic advantage over the existing regimens. Hence, the present study was undertaken to assess the safety and immunogenicity of 2 WHO prequalified rabies vaccines administered by one week, 4 site intra dermal regimen (4-4-4-0-0) in animal bite cases. This study was a comparative, open label, phase III, randomized clinical trial conducted at Anti rabies clinic, KIMS Hospital, Bangalore, India. The study was registered in Clinical Trials Registry of India (CTRI) bearing the registration number CTRI/2012/12/003230. Ninety subjects with category II/III animal bites/exposures were enrolled. Equine rabies immunoglobulin was administered to all category III exposures. 0.1 mL of either purified chick embryo cell vaccine (Rabipur) or purified verocell rabies vaccine (Verorab) was administered intradermally into 4 sites on days 0, 3 and 7 to all the study subjects. Serum of subjects collected on day 0, 14, 90 and 365 were analyzed for rabies virus neutralizing antibody (RVNA) concentration. The incidence of ADR in Rabipur and Verorab group was 2.96% and 1.14% respectively. In Rabipur group, geometric mean concentration (95% confidence interval) of RVNA was 14.5 (13.50, 15.57), 11.78 (11.27, 12.31) and 5.95 (5.50, 6.44) IU/mL on days 14, 90 and 365 respectively; In Verorab group geometric mean concentration (95% confidence interval) of RVNA was 14.43 (13.41, 15.53), 11.93 (11.47, 12.40) and 5.67 (5.29, 6.08) IU/mL on days 14, 90 and 365 respectively. In conclusion, Rabipur and Verorab were found to be safe, immunogenic and comparable with each other, when administered using one week, 4 site intradermal regimen (4-4-4-0-0) in animal bite cases.

Enhancement of blood-brain barrier permeability is required for intravenously administered virus neutralizing antibodies to clear an established rabies virus infection from the brain and prevent the development of rabies in mice

Rabies virus (RABV) is a neurotropic virus that causes fatal disease in humans and animals. Currently there is no cure for rabies once clinical signs appear. It is believed that once RABV enters the central nervous system (CNS), virus neutralizing antibodies (VNAs) in the periphery cannot pass through the blood-brain barrier (BBB) and into the CNS. Furthermore, it has been hypothesized that VNAs produced in the CNS by invading B cells, rather than those produced in the periphery and then transported into the CNS, are important in clearing RABV from the CNS. In the present study, mouse serum containing VNA was administered intravenously into mice after infection with wild-type RABV. Our studies demonstrate that exogenous administration of VNAs is crucial in the clearance of RABV from the brain and prevent the development of rabies in both immunocompetent and immunocompromised mice as long as the BBB permeability remains enhanced. This present study therefore provides a foundation for the possibility of developing VNA therapy for clinical rabies in humans.

Limited brain metabolism changes differentiate between the progression and clearance of rabies virus

Central nervous system (CNS) metabolic profiles were examined from rabies virus (RABV)-infected mice that were either mock-treated or received post-exposure treatment (PET) with a single dose of the live recombinant RABV vaccine TriGAS. CNS tissue harvested from mock-treated mice at middle and late stage infection revealed numerous changes in energy metabolites, neurotransmitters and stress hormones that correlated with replication levels of viral RNA. Although the large majority of these metabolic changes were completely absent in the brains of TriGAS-treated mice most likely due to the strong reduction in virus spread, TriGAS treatment resulted in the up-regulation of the expression of carnitine and several acylcarnitines, suggesting that these compounds are neuroprotective. The most striking change seen in mock-treated RABV-infected mice was a dramatic increase in brain and serum corticosterone levels, with the later becoming elevated before clinical signs or loss of body weight occurred. We speculate that the rise in corticosterone is part of a strategy of RABV to block the induction of immune responses that would otherwise interfere with its spread. In support of this concept, we show that pharmacological intervention to inhibit corticosterone biosynthesis, in the absence of vaccine treatment, significantly reduces the pathogenicity of RABV. Our results suggest that widespread metabolic changes, including hypothalamic-pituitary-adrenal axis activation, contribute to the pathogenesis of RABV and that preventing these alterations early in infection with PET or pharmacological blockade helps protect brain homeostasis, thereby reducing disease mortality.

Revised 4-dose vaccine schedule as part of postexposure prophylaxis to prevent human rabies

There is overwhelming evidence that the 4-dose vaccine schedule as part of postexposure prophylaxis to prevent human rabies for previously unvaccinated persons, as recommended by the Advisory Committee on Immunization Practices, United States in 2009, is safe and effective. When used appropriately with timely wound care and administration of human rabies immune globulin, the administration of 4 doses of vaccine on days 0, 3, 7, and 14 is likely to induce an adequate,long-lasting antibody response that is able to neutralize rabies virus and prevent disease in exposed patients. There has been no change in the recommended regimen for pre-exposure prophylaxis and for postexposure prophylaxis of previously vaccinated persons or for immunosuppressed patients.

Challenges facing human rabies control: the Lebanese experience

Rabies is one of the most important zoonotic infections worldwide. The burden of the disease continues to be significant in countries in the Middle East where the most important vector is stray dogs. Control efforts are hindered by lack of awareness and incomplete post-exposure prophylaxis. The aim of this article is to re-assess the situation of rabies in Lebanon and compare it to other Middle Eastern countries. Eight cases of rabies and 5280 incidents of animal bites to humans were reported to the Lebanese Ministry of Public Health between 2001 and 2012. Dogs were the only vector of infection and were responsible for most reported animal bites to humans. An average of 3·2 doses of vaccine per bite was administered as post-exposure prophylaxis. The status of human and canine rabies control, the risks associated with children's behaviour and the hazards of secondary wild reservoirs are discussed. Our data illustrates the importance of prevention through vector control, public awareness and education, and timely administration of active and passive immunization, as well as the significance of regional cooperation and monitoring the circulation of viral variants in wild animals.

Current and future tools for global canine rabies elimination

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

Rabies pre-exposure vaccination of children with purified chick embryo cell vaccine (PCECV)

Human rabies, mainly transmitted by dog bites, remains a major public health problem in developing countries. In Asian countries, such as India or the Philippines, where large free-ranging dog populations exist, the human death toll stays high. Children under the age of 15 y are at particular risk, representing up to half of the dog bite victims. While pre-exposure prophylaxis (PrEP) is commonly used in travelers from developed countries visiting areas of high endemicity, rabies vaccination is rarely used in highly endemic countries in contrast to post-exposure prophylaxis (PEP). Purified Chick Embryo Cell Vaccine (PCECV, Rabipur®/RabAvert®, Novartis Vaccines and Diagnostics) is approved for pre- and post-exposure prophylaxis, either by the intramuscular route, or--where registered--by the intradermal route of administration. In more than 25 y of use, PCECV has been widely used for PrEP in children. This review summarizes the pediatric pre-exposure clinical trials using PCECV. In total, PCECV has been administered to more than 1,200 children in clinical trials, from toddlers to those in elementary school, using intramuscular and intradermal schedules, demonstrating safety and immunogenicity. PrEP as part of routine pediatric vaccination programs may have a major role to play in human rabies prevention. Extensive clinical experience with PCECV supports intramuscular and intradermal PrEP in children as one pillar of human rabies prevention in developing countries.

Eliminating canine rabies, the principal source of human infection: what will it take?

More than 50,000 people die of rabies each year; most are children in developing countries, and almost all have been bitten by dogs. Eliminating canine rabies throughout the world would save thousands of lives and would reduce the economic impact of the disease by dramatically reducing the requirement for postexposure prophylaxis (PEP). Lengthy experience in the industrialized countries and ongoing programs in Latin America, Africa, and Asia have shown that the elimination of rabies in dogs is an achievable goal. The presence of canine rabies in developing countries is associated with poverty, and most deaths occur in the lowest socioeconomic sectors. To be successful, national rabies control programs should share responsibility with local communities for prevention and control activities and maintaining disease-free status. Legislation should be adapted to local conditions and the realities of dog ownership. While the provision of PEP to all bite victims is affordable in many countries, it is usually beyond the capacity of impoverished nations, which deal with many other health priorities. Ministries of health should provide PEP, either free or with a charge preferably at a subsidized price, replacing the current system in many countries, in which biologics are sold by government-owned and private clinics at a cost beyond the means of bite victims. The public health sector should assume responsibility when animal control strategies are not effectively implemented or when PEP is not administered correctly or is not available. A global strategy is needed to identify gaps in surveillance and diagnosis, improve access to PEP and enhance canine immunization and population management. Such approaches based on a "One Health" model should be coordinated across regions, and should extend control efforts to other dog-related zoonoses. This article introduces a symposium in Antiviral Research on the elimination of canine rabies.

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.

Evaluation of a one week intradermal regimen for rabies post-exposure prophylaxis: results of a randomized, open label, active-controlled trial in healthy adult volunteers in India

The currently recommended intradermal regimen for post-exposure prophylaxis spreads over a month period which many times lead to low compliance from the patients. There is a need to introduce and evaluate short course regimens to overcome this problem. This study was conducted to evaluate the immunogenicity and safety of a "new one week intradermal regimen" for rabies post-exposure prophylaxis. A total of 80 healthy adult volunteers were enrolled and allocated randomly either to purified chick embryo cell (PCECV) rabies vaccine or purified verocell rabies vaccine (PVRV), 40 in each group. Each subject received intradermally one of the vaccines , using the one week regimen (4-4-4). Blood samples were collected on Days 0, 7, 14, 28,180 and 365 for estimation of rabies virus neutralizing antibody (RVNA) concentration. The sera samples were analyzed by rapid fluorescent focus inhibition test (RFFIT). All subjects in both the groups had adequate RVNA concentration of  0.5 IU/mL from day 14 to till day 180 and the difference of geometric mean concentrations between the two groups was not significant (P > 0.606). Further to assess the immunological memory produced by this new regimen, a "single visit four site" intradermal booster vaccination was given to those who did not have adequate RVNA concentration on day 365. This resulted in a quick and enhanced RVNA concentration in these subjects thus denoting a successful anamnestic response. The incidence of adverse events was 8.3% in PCECV group and 1.6% in PVRV group (P=0.001) and the regimen was well tolerated without any dropouts. In conclusion, the new "one week intradermal regimen" is immunogenic and safe for rabies post-exposure prophylaxis and needs to be further evaluated in persons exposed to rabies.

Rabies: relevance, prevention, and management in travel medicine

Rabies is a zoonotic viral disease, transmitted only in mammals. Terrestrial rabies, predominantly transmitted by dogs, is the most important rabies cycle threatening humans. The causative neurotropic virus is a negative-stranded RNA virus of the family Rhabdoviridae, genus Lyssavirus. This genus contains several rabies-related viruses. All variants are known or suspected to cause rabieslike diseases. Transmission occurs by the virus entering through the skin or the mucosa after bites, scratches, or preexisting injuries contaminated by the saliva of an infected mammal. Only 51 human rabies cases that have not been transmitted by animal bites are described.

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.

Treatment of rabies in the 21st century: curing the incurable?

Despite the extreme case fatality attributable to rabies, reports of survivors provide a faint glimpse of a possibility of overcoming this deadly disease, even after clinical symptoms manifest. At present, no existing approach fulfills modern medical criteria for the optimal therapy of rabies. Until new efficacious antiviral compounds and optimized treatment protocols are developed, animal population management and vaccination of major reservoirs and vectors, minimization of the risk of viral exposures, and appropriate and early postexposure prophylaxis, remain the hallmarks of modern public health intervention.

Canine Rabies: A Looming Threat to Public Health

Rabies is an acute, fatal viral disease that infects domestic and wild animals and is transmissible to humans. Worldwide, rabies kills over 55,000 people every year. The domestic dog plays a pivotal role in rabies transmission. Domestic dogs are not only part of our daily lives but also of our immediate surroundings, and this is reflected in the rise in pet dog ownership in developed and developing countries. This is important given that more frequent exposures and interactions at the animal-human interface increases the likelihood of contracting zoonotic diseases of companion animals. Despite existing vaccines and post-exposure prophylactic treatment, rabies remains a neglected disease that is poorly controlled throughout much of the developing world, particularly Africa and Asia, where most human rabies deaths occur. It is believed that with sustained international commitments, global elimination of rabies from domestic dog populations, the most dangerous vector to humans, is a realistic goal.

Rabies virus clearance from the central nervous system

Rabies, a neurological disease associated with replication in central nervous system (CNS) tissues of any of a number of rabies viruses endemic in nature, is generally fatal. Prophylactic medical intervention is immune mediated and directed at preventing the spread of the virus from a peripheral site of exposure to the CNS. While individuals rarely develop immune responses capable of clearing the virus from CNS tissues, a variety of laboratory-attenuated rabies viruses are readily cleared from the CNS tissues in animal models. By comparing immune responses to wild-type and attenuated rabies viruses in these models, we have discovered that the latter induce processes required for immune effector infiltration into CNS tissues that are absent from lethal infections. Predominant among these are activities of cells of the neurovascular unit (NVU) that promote an interaction with circulating immune cells. In the absence of this interaction, the specialized barrier function of the NVU remains intact and circulating virus-specific immune effectors are largely excluded from infected CNS tissues. Studies of mixed infections with wild-type and attenuated rabies viruses reveal that wild-type rabies viruses fail to trigger, rather than inhibit, the interactions between immune cells and the NVU required for virus clearance from the CNS. These studies provide insights into how immune effectors with the capacity to clear the virus may be delivered into CNS tissues to contain a wild-type rabies virus infection. However, to apply immunotherapeutic strategies beyond the initial stages of CNS infection, further insights into the fate of the infected cells during virus clearance are needed.

Human rabies post exposure prophylaxis in Bhutan, 2005-2008: trends and risk factors

The aim of this study was to understand the use and distribution of human rabies post exposure prophylaxis (PEP) vaccine in Bhutan and to identify risk factors for receiving an incomplete course of the vaccine. We analyzed post exposure treatment records from 28 medical hospitals from 2005 to 2008. Males (59%) accounted for significantly more PEP events than females (41%) across all age groups (P<0.001). Children - particularly 5-9 years of age - received more rabies PEP than other age groups. Animal bite and non-bite accounted for 27% (n=2239) and 16% (n=1303) of rabies PEP, respectively, whilst 57% (n=4773) of the PEP events had no recorded information about the reasons for post exposure treatment. Post exposure treatment was provided throughout the year with a higher number during the winter and spring months. The number of PEP events significantly (P<0.001) increased between 2005 and 2008, from <1000 to >2800 events, respectively. Significantly (P<0.001) more PEP events were reported from the southern parts of Bhutan that are endemic for rabies or those areas in eastern Bhutan that have reported rabies outbreaks than other parts of Bhutan. Forty percent (n=3360) of the patients received an incomplete course of vaccine (<5-doses of vaccine intramuscular). Results suggest that patients with animal bite injury were less likely to receive an incomplete vaccine course than non-bite recipients, and patients presented to hospitals in rabies endemic or outbreak areas were less likely to receive an incomplete course than in non-rabies areas or rabies free areas. Similarly, patients presenting to hospitals for PEP during spring and summers months were less likely to receive an incomplete vaccine course than those during other seasons. Public education campaigns need to be conducted in Bhutan to reduce dog bite incidents and also to prevent mass exposures to rabies. A thorough assessment of each individual case based on the WHO guidelines would reduce unnecessary PEP (and therefore costs) in Bhutan.

Postexposure prophylaxis for rabies in resource-limited/poor countries

Human rabies is essentially a fatal disease once clinical signs develop. Rabies postexposure prophylaxis (PEP) consists of thorough wound care in combination with administration of rabies immunoglobulin and rabies vaccine. This is highly effective in rabies prevention if carried out diligently. Preexposure rabies prophylaxis simplifies PEP in the event of an exposure by eliminating the need for immunoglobulin. Shortened and more convenient and economical PEP regimens are being developed with promising results. They reduce the cost of PEP as well as travel expenses for the often very poor patients. The intradermal PEP regimen can now reduce the vaccine cost by ~60-70%. Although PEP in humans can prevent death, controlling the canine vector by sustained vaccination remains the mainstay of rabies elimination.

Rupprecht C. Design of future rabies biologics and antiviral drugs

In recent years, no major paradigm shifts have occurred in the utilization of new products for the prevention and control of rabies. Development of new cost-effective rabies biologics and antiviral drugs is critical in continuing to prevent and reduce disease. Current rabies vaccines are highly effective but have developed largely based on technical improvements in the vaccine industry. In the future, alternative approaches for improved vaccines, including novel avirulent rabies virus (RABV) vectors, should be pursued. Any rabies vaccine that is effective without the need for rabies immune globulin (RIG) will contribute fundamentally to disease prevention by reducing the cost and complexity of postexposure prophylaxis (PEP). The lack of high quality, affordable RIG is a continuing problem. Virus-specific monoclonal antibodies (mAbs) will soon fulfill the PEP requirement for passive immunity, currently met with RIG. Several relevant strategies for mAb production, including use of transgenic mice, humanization of mouse mAbs, and generation of human immune libraries, are underway. As a result of successful PEP and pre-exposure prophylaxis in developed countries, until recently, no significant focused efforts have been devoted to RABV-specific antiviral agents. To date, combination therapy including broad spectrum antiviral agents has been successful in only one case, and reports of antiviral activity are often conflicting. Current antiviral strategies target either the nucleoprotein or phosphoprotein, but drugs targeting the viral polymerase should be considered. Considering the lag from creation of new concepts to experimental development and clinical trials, many years will likely elapse between today's ideas and tomorrow's practices.

[The use of passive rabies immunotherapy: from the past to the future]

Rabies is a fatal disease transmitted by infected animals by bite, scratch, licking on broken skin or contamination of mucosis by saliva. The regimen of post-exposure prophylaxis for people not previously vaccinated, that is currently recommended by WHO, consists of a combination of wound cleaning, active immunization and passive immunization when the exposure is of category 3. Most of the products available on the market, in particular human rabies immunoglobulins, highly purified equine rabies immunoglobulins and the derived F(ab')(2) fragments, are now characterized by high potency and safety. Although the interest of passive anti-rabies immunization was first demonstrated in the first half of the 20th century, there is still an inadequate supply of these products to the target populations mostly in developing countries. Therefore, it is urgent to set-up training and information actions for healthcare personnel on the need to use passive immunotherapy and the lack of adverse effects of the related products. For the future, we hope that a scale up of production and a lower price will improve the accessibility to these products. The development of new products based on monoclonal antibodies and molecular biology, and which may be cheaper, is promising.

The production of antibody by invading B cells is required for the clearance of rabies virus from the central nervous system

BACKGROUND

The pathogenesis of rabies is associated with the inability to deliver immune effectors across the blood-brain barrier and to clear virulent rabies virus from CNS tissues. However, the mechanisms that facilitate immune effector entry into CNS tissues are induced by infection with attenuated rabies virus.

METHODOLOGY/PRINCIPAL FINDINGS

Infection of normal mice with attenuated rabies virus but not immunization with killed virus can promote the clearance of pathogenic rabies virus from the CNS. T cell activity in B cell-deficient mice can control the replication of attenuated virus in the CNS, but viral mRNA persists. Low levels of passively administered rabies virus-neutralizing antibody reach infected cells in the cerebellum of B cell-deficient mice but are not sufficient to mediate virus clearance. Production of rabies virus-specific antibody by B cells invading CNS tissues is required for this process, and a substantial proportion of the B cells that accumulate in the CNS of mice infected with attenuated rabies virus produce virus-specific antibodies.

CONCLUSIONS/SIGNIFICANCE

The mechanisms required for immune effectors to enter rabies virus-infected tissues are induced by infection with attenuated rabies virus but not by infection with pathogenic rabies viruses or immunization with killed virus. T cell activities can inhibit rabies virus replication, but the production of rabies virus-specific antibodies by infiltrating B cells, as opposed to the leakage of circulating antibody across the BBB, is critical to elimination of the virus. These findings suggest that a pathogenic rabies virus infection may be treatable after the virus has reached the CNS tissues, providing that the appropriate immune effectors can be targeted to the infected tissues.

Audit of post-exposure treatment to prevent lyssavirus infection in Sydney South West Area Health Service, 2005-2007

OBJECTIVES

To describe the profile of people who received post-exposure treatment to prevent lyssavirus infection in Sydney South West Area Health Service between 2005 and 2007 and to assess treatment compliance with the current NSW Health protocol.

METHODS

Thirty-eight public health files and a subset of 11 medical records were reviewed to collect demographic, exposure and treatment information for the period.

RESULTS

Twenty-nine (76%) potential Lyssavirus exposures occurred overseas. Nine potential exposures occurred within Australia; eight of these resulted from a bat bite or scratch. Thirteen (34%) of all potential exposures resulted from handling an animal.

CONCLUSION

Many potential exposures were the result of a bite or scratch from a domesticated animal; the animal's survival or health status was not routinely recorded. While all people who commenced post-exposure treatment completed the prescribed course, this was often not within the stipulated timeframe.

Post-exposure prophylaxis (PEP) of rabies-infected Indian street dogs

A rabies post-exposure prophylaxis study was carried out to examine the efficacy of two commercially available rabies vaccines and the efficacy of a 5- or 3-dose vaccination regime. Healthy, native breed dogs (N = 40), seronegative for rabies antibody, were challenged intramuscularly with virulent rabies virus brain suspension (10(4.4) MLD50) by direct inoculation into the masseter muscle. The dogs were divided into four equal groups and injected intramuscularly with either Nobivac Rabies (Intervet), Rabisin (Merial) or placebo on multiple occasions (3 or 5-times) over the next 28 days. All dogs were confined in their respective groups for 90 days post-challenge and observed for the development of any clinical signs. Serum samples were assayed for rabies antibody using both the Rapid Fluorescent Focus Inhibition Test (RFFIT) and the Enzyme Linked Immunosorbent Assay (ELISA). None of the vaccinated dogs showed any clinical signs of rabies at any stage of the study. All of their brain tissue samples taken at the end of the study were found negative for rabies viral antigen. Six of the dogs in the control group showed signs of either furious or dumb rabies and died before the end of the study. In all these dogs the diagnosis of rabies was confirmed by means of a specific fluorescent antibody test (FAT) and by the presence of Negri-bodies in brain smears. Four control dogs survived after mild and transient clinical signs showing protective titers at the end of the trial (day 90). Their brain samples were negative for Negri-bodies and in the FAT. Both vaccines were found to be safe and effective in preventing rabies when inoculated intramuscularly applying the 5-dose regime (0, 3, 7, 14 and 28 days). Limited by space only one vaccine could also be tested in a 3-dose schedule. Using this 3-dose regime (0, 5 and 28 days) Nobivac Rabies was also found to be safe and effective in preventing rabies. All vaccinated dogs responded with antibody titers > 0.5 IU by 7 days.

Rabies exposures, post-exposure prophylaxis and deaths in a region of endemic canine rabies

Background

Thousands of human deaths from rabies occur annually despite the availability of effective vaccines following exposure, and for disease control in the animal reservoir. Our aim was to assess risk factors associated with exposure and to determine why human deaths from endemic canine rabies still occur.

Methods and Findings

Contact tracing was used to gather data on rabies exposures, post-exposure prophylaxis (PEP) delivered and deaths in two rural districts in northwestern Tanzania from 2002 to 2006. Data on risk factors and the propensity to seek and complete courses of PEP was collected using questionnaires. Exposures varied from 6–141/100,000 per year. Risk of exposure to rabies was greater in an area with agropastoralist communities (and larger domestic dog populations) than an area with pastoralist communities. Children were at greater risk than adults of being exposed to rabies and of developing clinical signs. PEP dramatically reduced the risk of developing rabies (odds ratio [OR] 17.33, 95% confidence interval [CI] 6.39–60.83) and when PEP was not delivered the risks were higher in the pastoralist than the agro-pastoralist area (OR 6.12, 95% CI 2.60–14.58). Low socioeconomic class and distance to medical facilities lengthened delays before PEP delivery. Over 20% of rabies-exposed individuals did not seek medical treatment and were not documented in official records and <65% received PEP. Animal bite injury records were an accurate indicator of rabies exposure incidence.

Conclusions

Insufficient knowledge about rabies dangers and prevention, particularly prompt PEP, but also wound management, was the main cause of rabies deaths. Education, particularly in poor and marginalized communities, but also for medical and veterinary workers, would prevent future deaths.

Thousands of human deaths from rabies occur annually despite availability of effective vaccines for humans following exposure, and for disease control in domestic dog populations. We established a 5-year contact-tracing study in northwest Tanzania to investigate risk factors associated with rabies exposure and to determine why human deaths from canine rabies still occur. We found that children were at greater risk of being bitten and of developing rabies than adults and that incidence of bites by suspected rabid animals was higher in an area with larger domestic dog populations. A large proportion (>20%) of those bitten by rabid animals are not recorded in official records because they do not seek post-exposure prophylaxis (PEP), which is crucial for preventing the onset of rabies. Of those that seek medical attention, a significant proportion do not receive PEP because of the expense or because of hospital shortages; and victims who are poorer, and who live further from medical facilities, typically experience greater delays before obtaining PEP. Our work highlights the need to raise awareness about rabies dangers and prevention, particularly prompt PEP, but also wound management. We outline practical recommendations to prevent future deaths, stressing the importance of education, particularly in poor and marginalized communities, as well as for medical and veterinary workers.

Immune evasion by rabies viruses through the maintenance of blood-brain barrier integrity

The attenuated rabies virus (RV) strain Challenge Virus Standard (CVS)-F3 and a highly pathogenic strain associated with the silver-haired bats (SHBRV) can both be cleared from the central nervous system (CNS) tissues by appropriate antiviral immune mechanisms if the effectors are provided access across the blood-brain barrier (BBB). In the case of SHBRV infection, antiviral immunity develops normally in the periphery but fails to open the BBB, generally resulting in a lethal outcome. To determine whether or not an absence in the CNS targeted immune response is associated with the infection with other pathogenic RV strains, we have assessed the development of immunity, BBB permeability, and immune cell infiltration into the CNS tissues of mice infected with a variety of RV strains, including the dog variants responsible for the majority of human rabies cases. We demonstrate that the lethal outcomes of infection with a variety of known pathogenic RV strains are indeed associated with the inability to deliver immune effectors across the BBB. Survival from infection with certain of these viruses is improved in mice prone to CNS inflammation. The results suggest that competition between the activity of the immune effectors reaching CNS tissues and the inherent pathological attributes of the virus dictates the outcome and that intervention to deliver RV-specific immune effectors into CNS tissues may have general therapeutic value in rabies.

Rabies awareness in eight Asian countries

Rabies is a deadly zoonotic disease most often transmitted to humans through a dog bite. Human mortality from endemic canine rabies is estimated by WHO to be around 55,000 deaths annually, with over 31,000 deaths in Asia alone, mostly children. Most of these deaths could be prevented through post-exposure prophylaxis (PEP), including immediate wound washing, rabies immunoglobulin administration and vaccination. Unfortunately, at-risk populations are not well-informed of the risk of rabies and what to do in the event of an animal bite. In order to identify the main gaps in rabies information and better define the most urgent information actions to be undertaken, the Asian Rabies Expert Bureau (AREB) conducted a multicentre, multi-country survey of patients seeking rabies post-exposure prophylaxis in rabies prevention centres from 1 July 2007 to 31 January 2008, in Bangladesh, China, India, Indonesia, Pakistan, the Philippines, Sri Lanka, and Thailand. Questionnaires were completed for 4377 subjects in the eight countries. Data was collected regarding the patient, former rabies exposures, the present wound, rabies exposure management, and rabies awareness. Two major issues were identified where active information of the population could make a difference: the necessity to apply appropriate wound care and to consult the nearest rabies prevention centre as soon as possible.

First administration to humans of a monoclonal antibody cocktail against rabies virus: safety, tolerability, and neutralizing activity

Immediate passive immune prophylaxis as part of rabies post-exposure prophylaxis (PEP) often cannot be provided due to limited availability of human or equine rabies immunoglobulin (HRIG and ERIG, respectively). We report first clinical data from two phase I studies evaluating a monoclonal antibody cocktail CL184 against rabies. The studies included healthy adult subjects in the USA and India and involved two parts. First, subjects received a single intramuscular dose of CL184 or placebo in a double blind, randomized, dose-escalation trial. Second, open-label CL184 (20IU/kg) was co-administered with rabies vaccine. Safety was the primary objective and rabies virus neutralizing activity (RVNA) was investigated as efficacy parameter. Pain at the CL184 injection site was reported by less than 40% of subjects; no fever or local induration, redness or swelling was observed. RVNA was detectable from day 1 to day 21 after a single dose of CL184 20 or 40IU/kg. All subjects had adequate (>0.5IU/mL) RVNA levels from day 14 onwards when combined with rabies vaccine. CL184 appears promising as an alternative to RIG in PEP.