Recovery from rabies: a call to arms

Metagenomic next-generation sequencing for the etiological diagnosis of rabies virus in cerebrospinal fluid

Background

Rabies is a highly fatal disease. Once symptoms develop, death usually occurs within days. Survivors were occasionally reported in the literatures. Ante-mortem diagnosis remains a challenge in most rabies endemic countries. A novel, accurate diagnostic assay is highly desirable.

Methods

We used metagenomic next-generation sequencing (mNGS) to examine the cerebrospinal fluid (CSF) samples of a 49-year-old patient with rabies and validated the results by TaqMan PCR and RT-PCR/Sanger sequencing.

Results

Metagenomic next-generation sequencing identified sequence reads uniquely aligned to the rabies virus (RABV). PCR confirmed the presence of the partial RABV N gene in the CSF. Phylogenetic analysis showed that the RABV grouped as an Asian clade, which is the most broadly distributed clade in China.

Conclusion

Metagenomic next-generation sequencing may be a useful screening tool for the etiological diagnosis of rabies, especially in the absence of timely rabies laboratory testing or in patients with no exposure history.

Rabies virus isolated from insectivorous bats induces different inflammatory responses in experimental model

Rabies virus (RABV) is a neurotropic virus that causes fatal neuroinflammation in mammals. The insectivorous bat RABV strains are less pathogenic for mice than strains associated with other reservoirs. We characterized the tissue inflammatory response in the CNS of RABV isolated from insectivorous bats. Eptesicus furinalis (EPBRV)-infected mice had a robust inflammatory response and a greater amount of IL-1β, IL-6 and TNF-α, while Myotis nigricans (MNBRV)-infected mice showed a higher expression of IL-17 and greater activation of IFN-β. New approaches to understand the inflammatory response to different mechanisms of action may provide insights for the development of novel therapies for rabies.

A new choice for human rabies diagnosis: A case report of metagenomics next-generation sequencing in diagnosis of human rabies

PURPOSE

We report a case of human rabies diagnosed by the metagenomics next-generation sequencing (mNGS). A 59-year-old man developed clinical rabies 20 days after he was bitten by dogs. Treatment included induction of coma initially; rabies vaccine was not administered. The patient was treated with propofol, midazolam, recombinant human interferon α2b, ribavirin, and amantadine. Penehyclidine was administrated to relieved the rabies induced pulmonary edema and the salivation.

RESULTS

The patient's situation got worse on the 26th day after admition, and died on the 29th day finally.

CONCLUSION

The mNGS might be a new choice for human rabies diagnosis，penehyclidine was effective in decreasing the rabies induced pulmonary edema and the salivation.

Rabies: Presentation, case management and therapy

Several Lyssaviruses are known to be a causative agent of rabies and rabies like syndrome. There are no proven effective treatment strategies for symptomatic rabies patient. Risk of infection from dog variant of rabies virus is highest with deep bite reaching muscular layer and much higher when compared to scratch. Failure of viral eradication at the central nervous system (CNS) is partly due to inadequate immune response. Favipiravir selectively inhibit viral RNA polymerase and has been shown to reduce rabies replication in neuronal cell and mouse model system. Endocannabinoid system has emerged as an important regulator for CNS integrity, cell fate and may serve as an important novel neuroprotective agent. Cannabinoid may be able to regulate the impaired homeostasis induced by rabies virus by promoting infected cell survival and promote complete autophagy in infected cell.

Kinase inhibitors tyrphostin 9 and rottlerin block early steps of rabies virus cycle

Rabies virus (RABV) is a neurotropic virus that causes fatal encephalitis in humans and animals and still kills up to 59,000 people worldwide every year. To date, only preventive or post-exposure vaccination protects against the disease but therapeutics are missing. After screening a library of 80 kinases inhibitors, we identified two compounds as potent inhibitors of RABV infection: tyrphostin 9 and rottlerin. Mechanism of action studies show that both inhibitors interfere with an early step of viral cycle and can prevent viral replication. In presence of tyrphostin 9, the viral entry through endocytosis is disturbed leading to improper delivery of viral particles in cytoplasm, whereas rottlerin is inhibiting the transcription, most likely by decreasing intracellular ATP concentration, and therefore the replication of the viral genome.

[Сases of human convalescence from rabies and lifetime diagnostics of lyssavirus encephalitis.]

Notwithstanding the availability of effective vaccines, 40 - 60 thousand rabies cases in humans are reported every year. Almost always the disease is fatal because therapeutic treatment of lyssavirus encephalitis has not been developed. Since 1970 the number of reports on rare cases of convalescence including those using experimental treatment protocols has been gradually increasing 20 cases of convalescence, "partial" convalescence or long-term survival of humans (1970-2015) were selected as they were complaint with laboratory criteria of active lyssavirus infection. Children and teenagers were predominant in the analyzed group (85%). The cases were irregularly spread between the continents: Asia - 6 cases, North America - 6 cases, Africa - 2 cases and Europe - 1 case. India and the USA were on the top of the list of countries by the number of described cases. More than 60% humans were infected from dogs, three cases got infection from bats and 2 cases were allegedly associated with an unknown lyssavirus and an unidentified infection source. 70% cases were vaccinated and 10% cases were treated with gamma globulin before the disease onset. Serological tests for detection of antibodies to lyssaviruses in cerebrospinal fluid of infected humans were typically used for diagnostic laboratory verification. Less than 30% IFA and PCR positives were obtained. Lyssaviruses were never detected. Only 4 convalescent patients were treated using experimental protocols. 80% cases demonstrated severe neurological consequences, four (may be more) patients died afterwards within the period from two months to four years. Different perspectives on prospects of Milwaukee protocol use and other therapeutic techniques are given.

Combination therapy of rabies-infected mice with inhibitors of pro-inflammatory host response, antiviral compounds and human rabies immunoglobulin

Recent studies demonstrated that inhibitors of pro-inflammatory molecular cascades triggered by rabies infection in the central nervous system (CNS) can enhance survival in mouse model and that certain antiviral compounds interfere with rabies virus replication in vitro. In this study different combinations of therapeutics were tested to evaluate their effect on survival in rabies-infected mice, as well as on viral load in the CNS. C57Bl/6 mice were infected with Silver-haired bat rabies virus (SHBRV)-18 at virus dose approaching LD₅₀ and LD₁₀₀. In one experimental group daily treatments were initiated 4 h before-, in other groups 48 or 96 h after challenge. In the first experiment therapeutic combination contained inhibitors of tumour necrosis factor-α (infliximab), caspase-1 (Ac-YVAD-cmk), and a multikinase inhibitor (sorafenib). In the treated groups there was a notable but not significant increase of survival compared to the virus infected, non-treated mice. The addition of human rabies immunoglobulins (HRIG) to the combination in the second experiment almost completely prevented mortality in the pre-exposure treatment group along with a significant reduction of viral titres in the CNS. Post-exposure treatments also greatly improved survival rates. As part of the combination with immunomodulatory compounds, HRIG had a higher impact on survival than alone. In the third experiment the combination was further supplemented with type-I interferons, ribavirin and favipiravir (T-705). As a blood-brain barrier opener, mannitol was also administered. This treatment was unable to prevent lethal consequences of SHBRV-18 infection; furthermore, it caused toxicity in treated mice, presumably due to interaction among the components. In all experiments, viral loads in the CNS were similar in mice that succumbed to rabies regardless of treatment. According to the findings, inhibitors of detrimental host response to rabies combined with antibodies can be considered among the possible therapeutic and post-exposure options in human rabies cases.

The Imperative of Palliation in the Management of Rabies Encephalomyelitis

The aim of this review is to guide clinicians in the practical management of patients suffering from rabies encephalomyelitis. This condition is eminently preventable by modern post-exposure vaccination, but is virtually always fatal in unvaccinated people. In the absence of any proven effective antiviral or other treatment, palliative care is an imperative to minimise suffering. Suspicion of rabies encephalomyelitis depends on recognising the classic symptomatology and eliciting a history of exposure to a possibly rabid mammal. Potentially treatable differential diagnoses must be eliminated, notably other infective encephalopathies. Laboratory confirmation of suspected rabies is not usually possible in many endemic areas, but is essential for public health surveillance. In a disease as agonising and terrifying as rabies encephalomyelitis, alleviation of distressing symptoms is the primary concern and overriding responsibility of medical staff. Calm, quiet conditions should be created, allowing relatives to communicate with the dying patient in safety and privacy. Palliative management must address thirst and dehydration, fever, anxiety, fear, restlessness, agitation, seizures, hypersecretion, and pain. As the infection progresses, coma and respiratory, cardiovascular, neurological, endocrine, or gastrointestinal complications will eventually ensue. When the facilities exist, the possibility of intensive care may arise, but although some patients may survive, they will be left with severe neurological sequelae. Recovery from rabies is extremely rare, and heroic measures with intensive care should be considered only in patients who have been previously vaccinated, develop rabies antibody within the first week of illness, or were infected by an American bat rabies virus. However, in most cases, clinicians must have the courage to offer compassionate palliation whenever the diagnosis of rabies encephalomyelitis is inescapable.

Delayed progression of rabies transmitted by a vampire bat

Here, we compared the growth kinetics, cell-to-cell spread, and virus internalization kinetics in N2a cells of RABV variants isolated from vampire bats (V-3), domestic dogs (V-2) and marmosets (V-M) as well as the clinical symptoms and mortality caused by these variants. The replication rate of V-3 was significantly higher than those of V-2 and V-M. However, the uptake and spread of these RABV variants into N2a cells were inversely proportional. Nevertheless, V-3 had longer incubation and evolution periods. Our results provide evidence that the clinical manifestations of infection with bat RABV variant occur at a later time when compared to what was observed with canine and marmoset rabies virus variants.

Global epidemiology of canine rabies: past, present, and future prospects

The rabies virus, a public health scourge from ancient times, is currently responsible for an estimated 59,000 human deaths a year, almost all transmitted via dog bites. It causes considerable economic impacts on developing countries, primarily in Africa and Asia, which can least afford these losses. However, despite its almost 100% case fatality rate, canine rabies is a completely preventable disease, and historic examples of canine rabies elimination in the developed world attest to this. Over the last decade, programs based on eliminating the source of the disease from dogs have shown success in reducing the public health burden of canine rabies in developing countries, notably across Latin America, and this has contributed to the growing evidence base necessary to change attitudes toward the feasibility of global canine rabies elimination. More recently, assessments of the current economic burden of canine rabies and the potential cost savings achievable through mass dog vaccinations have been added to this evidence base. Tools and support are available from the international community to help countries move progressively toward canine rabies elimination, and there is optimism that global freedom from canine rabies can be achieved within the next few decades.

Rabies: the clinical features, management and prevention of the classic zoonosis

The diagnosis of rabies encephalitis relies on awareness of the varied clinical features and eliciting a history of unusual contact with a mammal throughout the endemic area. The diagnosis is easily missed. Laboratory tests are not routine and only confirm clinical suspicion. Rabies infection carries a case fatality exceeding 99.9%. Palliation is appropriate, except for previously-vaccinated patients or those infected by American bats, for whom intensive care is probably indicated. However, as rabies vaccines are outstandingly effective, no one should die of dog-transmitted infection. Vaccines and rabies immunoglobulin are expensive and usually scarce in Asia and Africa. All travellers to dog rabies enzootic areas should be strongly encouraged to have pre-exposure immunisation before departure. There is no contraindication to vaccination but the cost can be prohibitive. Intradermal immunisation, using 0.1 ml and sharing vials of vaccine, is cheaper and is now permitted by UK regulations. Returning travellers may need post-exposure prophylaxis. Economical intradermal post-exposure vaccination is practicable and should be introduced into rural areas of Africa and Asia immediately. Eliminating rabies in dogs is now feasible and would dramatically reduce human mortality, if funds were made available. The high current economic burden of human prophylaxis would then be largely relieved.

Current status of rabies and prospects for elimination

Rabies is one of the most deadly infectious diseases, with a case-fatality rate approaching 100%. The disease is established on all continents apart from Antarctica; most cases are reported in Africa and Asia, with thousands of deaths recorded annually. However, the estimated annual figure of almost 60,000 human rabies fatalities is probably an underestimate. Almost all cases of human rabies result from bites from infected dogs. Therefore, the most cost-effective approach to elimination of the global burden of human rabies is to control canine rabies rather than expansion of the availability of human prophylaxis. Mass vaccination campaigns with parenteral vaccines, and advances in oral vaccines for wildlife, have allowed the elimination of rabies in terrestrial carnivores in several countries worldwide. The subsequent reduction in cases of human rabies in such regions advocates the multidisciplinary One Health approach to rabies control through the mass vaccination of dogs and control of canine populations.

Antiviral therapy for human rabies

Human rabies is virtually always fatal despite numerous attempts at aggressive therapy. Most survivors received one or more doses of rabies vaccine prior to the onset of the disease. The Milwaukee Protocol has proved to be ineffective for rabies and should no longer be used. New approaches are needed and an improved understanding of basic mechanisms responsible for the clinical disease in rabies may prove to be useful for the development of novel therapeutic approaches. Antiviral therapy is thought to be an important component of combination therapy for the management of human rabies, and immunotherapy and neuroprotective therapy should also be strongly considered. There are many important issues for consideration regarding drug delivery to the central nervous system in rabies, which are in part related to the presence of the blood-brain barrier and also the blood-spinal cord barrier. Ribavirin and interferon-α have proved to be disappointing agents for the therapy of rabies. There is insufficient evidence to support the continued use of ketamine or amantadine for the therapy of rabies. Minocycline or corticosteroids should not be used because of concerns about aggravating the disease. A variety of new antiviral agents are under development and evaluation, including favipiravir, RNA interference (for example, small interfering [si]RNAs) and novel targeted approaches, including interference with viral capsid assembly and viral egress.