Borna disease virus infection of a horse in Great Britain

Bornavirus (BoDV-1) Encephalitis in Children: Update on Diagnosis and Treatment

Infectious encephalitis in children can be caused by several pathogens, very rarely this can be caused by bornaviruses (BoDV-1). Due to the recent discovery of the disease in humans and the small number of cases, especially pediatric infections, knowledge about the disease pathology as well as therapeutic options is limited. Therefore, this review shall help raise awareness of this rare and mostly fatal disease, promote an early diagnosis, and present current knowledge about possible treatment options.

Clinical analysis of Bornavirus Encephalitis cases demonstrates a small time window for Etiological Diagnostics and treatment attempts, a large case series from Germany 1996-2022

PURPOSE

The emerging zoonotic Borna disease virus 1 (BoDV-1) and the variegated squirrel bornavirus 1 (VSBV-1) cause severe and fatal human encephalitis in Germany. We conducted the first systematic clinical analysis of acute, molecularly confirmed fatal bornavirus encephalitis cases comprising 21 BoDV-1 and four VSBV-1 patients to identify options for better diagnosis and timely treatment.

METHODS

Analyses were based on medical records and, for BoDV-1, on additional medical interviews with patients' relatives.

RESULTS

Disease onset was unspecific, often with fever and headache, inconsistently mixed with early fluctuating neurological symptoms, all rapidly leading to severe encephalopathy and progressive vigilance decline. Very shortly after seeking the first medical advice (median time interval 2 and 0 days for BoDV-1 and VSBV-1, respectively), all except one patient were hospitalised upon manifest neurological symptoms (median 10 and 16 days respectively after general symptom onset). Neurological symptoms varied, always progressing to coma and death. BoDV-1 and VSBV-1 patients required ventilation a median of three and five days, and died a median of 32 and 72 days, after hospitalisation. Death occurred mostly after supportive treatment cessation at different points in time based on poor prognosis. Disease duration therefore showed a wide, incomparable range.

CONCLUSION

The extremely rapid progression is the most obvious clinical characteristic of bornavirus encephalitis and the timeframe for diagnosis and targeted therapy is very short. Therefore, our results demand an early clinical suspicion based on symptomatology, epidemiology, imaging, and laboratory findings, followed by prompt virological testing as a prerequisite for any potentially effective treatment.

Lethal Borna disease virus 1 infections of humans and animals - in-depth molecular epidemiology and phylogeography

Borna disease virus 1 (BoDV-1) is the causative agent of Borna disease, a fatal neurologic disorder of domestic mammals and humans, resulting from spill-over infection from its natural reservoir host, the bicolored white-toothed shrew (Crocidura leucodon). The known BoDV-1-endemic area is remarkably restricted to parts of Germany, Austria, Switzerland and Liechtenstein. To gain comprehensive data on its occurrence, we analysed diagnostic material from suspected BoDV-1-induced encephalitis cases based on clinical and/or histopathological diagnosis. BoDV-1 infection was confirmed by RT-qPCR in 207 domestic mammals, 28 humans and seven wild shrews. Thereby, this study markedly raises the number of published laboratory-confirmed human BoDV-1 infections and provides a first comprehensive summary. Generation of 136 new BoDV-1 genome sequences from animals and humans facilitated an in-depth phylogeographic analysis, allowing for the definition of risk areas for zoonotic BoDV-1 transmission and facilitating the assessment of geographical infection sources. Consistent with the low mobility of its reservoir host, BoDV-1 sequences showed a remarkable geographic association, with individual phylogenetic clades occupying distinct areas. The closest genetic relatives of most human-derived BoDV-1 sequences were located at distances of less than 40 km, indicating that spill-over transmission from the natural reservoir usually occurs in the patient´s home region.

Interactions of Equine Viruses with the Host Kinase Machinery and Implications for One Health and Human Disease

Zoonotic pathogens that are vector-transmitted have and continue to contribute to several emerging infections globally. In recent years, spillover events of such zoonotic pathogens have increased in frequency as a result of direct contact with livestock, wildlife, and urbanization, forcing animals from their natural habitats. Equines serve as reservoir hosts for vector-transmitted zoonotic viruses that are also capable of infecting humans and causing disease. From a One Health perspective, equine viruses, therefore, pose major concerns for periodic outbreaks globally. Several equine viruses have spread out of their indigenous regions, such as West Nile virus (WNV) and equine encephalitis viruses (EEVs), making them of paramount concern to public health. Viruses have evolved many mechanisms to support the establishment of productive infection and to avoid host defense mechanisms, including promoting or decreasing inflammatory responses and regulating host machinery for protein synthesis. Viral interactions with the host enzymatic machinery, specifically kinases, can support the viral infectious process and downplay innate immune mechanisms, cumulatively leading to a more severe course of the disease. In this review, we will focus on how select equine viruses interact with host kinases to support viral multiplication.

Avian Bornavirus Research—A Comprehensive Review

Avian bornaviruses constitute a genetically diverse group of at least 15 viruses belonging to the genus Orthobornavirus within the family Bornaviridae. After the discovery of the first avian bornaviruses in diseased psittacines in 2008, further viruses have been detected in passerines and aquatic birds. Parrot bornaviruses (PaBVs) possess the highest veterinary relevance amongst the avian bornaviruses as the causative agents of proventricular dilatation disease (PDD). PDD is a chronic and often fatal disease that may engulf a broad range of clinical presentations, typically including neurologic signs as well as impaired gastrointestinal motility, leading to proventricular dilatation. It occurs worldwide in captive psittacine populations and threatens private bird collections, zoological gardens and rehabilitation projects of endangered species. In contrast, only little is known about the pathogenic roles of passerine and waterbird bornaviruses. This comprehensive review summarizes the current knowledge on avian bornavirus infections, including their taxonomy, pathogenesis of associated diseases, epidemiology, diagnostic strategies and recent developments on prophylactic and therapeutic countermeasures.

Healthcare-associated exposure to Borna disease virus 1 (BoDV-1)

The Borna disease virus 1 (BoDV-1) causes severe and often fatal encephalitis in humans. The virus is endemic in parts of Germany, Liechtenstein, Switzerland and Austria. As an increasing number of human BoDV-1 encephalitis cases is being diagnosed, the chance for healthcare professionals to come into contact with infected tissues and bodily fluids from patients with known acute bornavirus encephalitis is also increasing. Therefore, risk assessments are needed. Based on three different incidences of possible exposure to BoDV-1 including an autopsy knife injury, a needlestick injury, and a spill accident with cerebrospinal fluid from patients with acute BoDV-1 encephalitis, we perform risk assessments and review published data. BoDV-1 infection status of the index patient's tissues and bodily fluids to which contact had occurred should be determined. There is only scarce evidence for possible postexposure prophylaxis, serology, and imaging in healthcare professionals who possibly came into contact with the virus. Despite decade-long laboratory work with BoDV-1, not a single clinically apparent laboratory infection has been published. Given the increasing number of severe or fatal BoDV-1 encephalitis cases, there is a growing need for efficacy-tested, potent antiviral therapeutics against BoDV-1 in humans, both in clinically ill patients and possibly as postexposure prophylaxis in healthcare professionals.

Emerging Microbes & Infections - Original Article: Human Borna disease virus 1 (BoDV-1) encephalitis cases in the north and east of Germany

In 2021, three encephalitis cases due to the Borna disease virus 1 (BoDV-1) were diagnosed in the north and east of Germany. The patients were from the states of Thuringia, Saxony-Anhalt, and Lower Saxony. All were residents of known endemic areas for animal Borna disease but without prior diagnosed human cases. Except for one recently detected case in the state of Brandenburg, all >30 notified cases had occurred in, or were linked to, the southern state of Bavaria. Of the three detected cases described here, two infections were acute, while one infection was diagnosed retrospectively from archived brain autopsy tissue samples. One of the acute cases survived, but is permanently disabled. The cases were diagnosed by various techniques (serology, molecular assays, and immunohistology) following a validated testing scheme and adhering to a proposed case definition. Two cases were classified as confirmed BoDV-1 encephalitis, while one case was a probable infection with positive serology and typical brain magnetic resonance imaging, but without molecular confirmation. Of the three cases, one full virus genome sequence could be recovered. Our report highlights the need for awareness of a BoDV-1 etiology in cryptic encephalitis cases in all areas with known animal Borna disease endemicity in Europe, including virus-endemic regions in Austria, Liechtenstein, and Switzerland. BoDV-1 should be actively tested for in acute encephalitis cases with residence or rural exposure history in known Borna disease-endemic areas.

Investigation of fatal human Borna disease virus 1 encephalitis outside the previously known area for human cases, Brandenburg, Germany - a case report

Background

The true burden and geographical distribution of human Borna disease virus 1 (BoDV-1) encephalitis is unknown. All detected cases so far have been recorded in Bavaria, southern Germany.

Case presentation

A retrospective laboratory and epidemiological investigation of a 2017 case of fatal encephalitis in a farmer in Brandenburg, northeast Germany, demonstrated BoDV-1 as causative agent by polymerase chain reaction, immunohistochemistry and in situ hybridization. Next-generation sequencing showed that the virus belonged to a cluster not known to be endemic in Brandenburg. The investigation was triggered by a recent outbreak of animal Borna disease in the region. Multiple possible exposures were identified. The next-of-kin were seronegative.

Conclusions

The investigation highlights clinical awareness for human BoDV-1 encephalitis which should be extended to all areas endemic for animal Borna disease. All previously diagnosed human cases had occurred > 350 km further south. Further testing of shrews and livestock with Borna disease may show whether this BoDV-1 cluster is additionally endemic in the northwest of Brandenburg.

Borna disease outbreak with high mortality in an alpaca herd in a previously unreported endemic area in Germany

Borna disease virus 1 (BoDV-1) is the causative agent of Borna disease, an often fatal neurologic condition of domestic mammals, including New World camelids, in endemic areas in Central Europe. Recently, BoDV-1 gained further attention by the confirmation of fatal zoonotic infections in humans. Although Borna disease and BoDV-1 have been described already over the past decades, comprehensive reports of Borna disease outbreaks in domestic animals employing state-of-the-art diagnostic methods are missing. Here, we report a series of BoDV-1 infections in a herd of 27 alpacas (Vicugna pacos) in the federal state of Brandenburg, Germany, which resulted in eleven fatalities (41%) within ten months. Clinical courses ranged from sudden death without previous clinical signs to acute or chronic neurologic disease with death occurring after up to six months. All animals that underwent necropsy exhibited a non-suppurative encephalitis. In addition, six apparently healthy seropositive individuals were identified within the herd, suggesting subclinical BoDV-1 infections. In infected animals, BoDV-1 RNA and antigen were mainly restricted to the central nervous system and the eye, and sporadically detectable in large peripheral nerves and neuronal structures in other tissues. Pest control measures on the farm resulted in the collection of a BoDV-1-positive bicoloured white-toothed shrew (Crocidura leucodon), while all other trapped small mammals were negative. A phylogeographic analysis of BoDV-1 sequences from the alpacas, the shrew and BoDV-1-positive equine cases from the same region in Brandenburg revealed a previously unreported endemic area of BoDV-1 cluster 4 in North-Western Brandenburg. In conclusion, alpacas appear to be highly susceptible to BoDV-1 infection and display a highly variable clinical picture ranging from peracute death to subclinical forms. In addition to horses and sheep, they can serve as sensitive sentinels used for the identification of endemic areas.

Equine viral encephalitis: prevalence, impact, and management strategies

Members of several different virus families cause equine viral encephalitis, the majority of which are arthropod-borne viruses (arboviruses) with zoonotic potential. The clinical signs caused are rarely pathognomonic; therefore, a clinical diagnosis is usually presumptive according to the geographical region. However, recent decades have seen expansion of the geographical range and emergence in new regions of numerous viral diseases. In this context, this review presents an overview of the prevalence and distribution of the main viral causes of equine encephalitis and discusses their impact and potential approaches to limit their spread.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): Borna disease

Borna disease has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on the eligibility of Borna disease to be listed, Article 9 for the categorisation of Borna disease according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species related to Borna disease. The assessment has been performed following a methodology composed of information collection and compilation, expert judgement on each criterion at individual and, if no consensus was reached before, also at collective level. The output is composed of the categorical answer, and for the questions where no consensus was reached, the different supporting views are reported. Details on the methodology used for this assessment are explained in a separate opinion. According to the assessment performed, Borna disease cannot be considered eligible to be listed for Union intervention as laid down in Article 5(3) of the AHL because there was no compliance on criterion 5 A(v). Consequently, the assessment on compliance of Borna disease with the criteria as in Annex IV of the AHL, for the application of the disease prevention and control rules referred to in Article 9(1) is not applicable, as well as which animal species can be considered to be listed for Borna disease according to Article 8(3) of the AHL.

Landscape features and reservoir occurrence affecting the risk for equine infection with Borna disease virus

Borna disease (BD) is a severe endemic and fatal disorder caused by the neurotropic Borna disease virus (BDV) which mainly occurs in horses and sheep. Borna disease virus belongs to the order Mononegavirales, which includes many reservoir-bound viruses with high zoonotic and pathogenic properties including the filoviruses and lyssaviruses. Clinically manifest BD occurs in endemic areas of Germany, Switzerland, Liechtenstein, and Austria. A seasonal accumulation of cases in spring and summer, incidences that vary from year to year, and the recent detection of BDV in bicolored shrews (Crocidura leucodon) in Swiss endemic areas argue for a natural reservoir. We established a geographic information system analysis of the distribution of 485 equine BD cases in Bavarian (Germany) endemic areas and of the occurrence of 285 records of C. leucodon captured in Bavaria. Boosted regression trees were used to identify driving factors of habitat choice and virus prevalence. The distribution model of C. leucodon and the prevalence model for BDV had very good accuracy. Mean annual precipitation <900 mm, mean annual temperatures of 8 C, elevation <350 m, low forest cover, and a high percentage of urban fabric and arable land describe the optimal habitat for C. leucodon. Occurrence probability of C. leucodon was significantly higher in Bavarian BDV-endemic areas than in random areas in Bavaria. The prevalence of BD was higher in urban areas with annual mean precipitation of 800-900 mm, annual mean temperature of 8 C, and elevation >500 m. Our results indicate that the distribution model can accurately predict BD occurrence. Based on these results, practical safety precautions could be derived. The BDV model represents a suitable system for reservoir-bound, neurotropic Mononegavirales because it allows analyzing ecologic and biologic aspects that determine virus abundance, maintenance in reservoir species, and transmission to end host species.

Impact of antigenic diversity on laboratory diagnosis of Avian bornavirus infections in birds

Avian bornaviruses (ABVs) are a group of genetically diverse viruses within the Bornaviridae family that can infect numerous avian species and represent the causative agents of proventricular dilatation disease, an often fatal disease that is widely distributed in captive populations of parrots and related species. The current study was designed to assess the antigenic variability of the family Bornaviridae and to determine its impact on ABV diagnosis by employing fluorescent antibody assays. It was shown that polyclonal rabbit sera directed against recombinant bornavirus nucleoprotein, X protein, phosphoprotein, and matrix protein provided sufficient cross-reactivity for the detection of viral antigen from a broad range of bornavirus genotypes grown in cell culture. In contrast, a rabbit anti-glycoprotein serum and 2 monoclonal antibodies directed against nucleoprotein and phosphoprotein proteins reacted more specifically. Antibodies were readily detected in sera from avian patients infected with known ABV genotypes if cells persistently infected with a variety of different bornavirus genotypes were used for analysis. For all sera, calculated antibody titers were highest when the homologous or a closely related target virus was used for the assay. Cross-reactivity with more distantly related genotypes of other phylogenetic groups was usually reduced, resulting in titer reduction of up to 3 log units. The presented results contribute to a better understanding of the antigenic diversity of family Bornaviridae and further emphasize the importance of choosing appropriate diagnostic tools for sensitive detection of ABV infections.

Glutamate and lipid metabolic perturbation in the hippocampi of asymptomatic borna disease virus-infected horses

Borna disease virus (BDV) is a neurotropic, enveloped, non-segmented, negative-stranded RNA virus that infects a wide variety of vertebrate species from birds to humans across a broad global geographic distribution. Animal symptomatology range from asymptomatic infection to behavioral abnormalities to acute meningoencephalitis. Asymptomatic BDV infection has been shown to be more frequent than conventionally estimated. However, the molecular mechanism(s) underyling asymptomatic BDV infection remain largely unknown. Here, based on real-time quantitative PCR and Western blotting, a total of 18 horse hippocampi were divided into BDV-infected (n = 8) and non-infected control (n = 10) groups. A gas chromatography coupled with mass spectrometry (GC-MS) metabolomic approach, in conjunction with multivariate statistical analysis, was used to characterize the hippocampal metabolic changes associated with asymptomatic BDV infection. Multivariate statistical analysis showed a significant discrimination between the BDV-infected and control groups. BDV-infected hippocampi were characterized by lower levels of D-myo-inositol-1-phosphate, glutamate, phosphoethanolamine, heptadecanoic acid, and linoleic acid in combination with a higher level of ammonia. These differential metabolites are primarily involved in glutamate and lipid metabolism. These finding provide an improved understanding of hippocampal changes associated with asymptomatic BDV infection.

The bicolored white-toothed shrew Crocidura leucodon (HERMANN 1780) is an indigenous host of mammalian Borna disease virus

Borna disease (BD) is a sporadic neurologic disease of horses and sheep caused by mammalian Borna disease virus (BDV). Its unique epidemiological features include: limited occurrence in certain endemic regions of central Europe, yearly varying disease peaks, and a seasonal pattern with higher disease frequencies in spring and a disease nadir in autumn. It is most probably not directly transmitted between horses and sheep. All these features led to the assumption that an indigenous virus reservoir of BDV other than horses and sheep may exist. The search for such a reservoir had been unsuccessful until a few years ago five BDV-infected shrews were found in a BD-endemic area in Switzerland. So far, these data lacked further confirmation. We therefore initiated a study in shrews in endemic areas of Germany. Within five years 107 shrews of five different species were collected. BDV infections were identified in 14 individuals of the species bicolored white-toothed shrew (Crocidura leucodon, HERMANN 1780), all originating from BD-endemic territories. Immunohistological analysis showed widespread distribution of BDV antigen both in the nervous system and in epithelial and mesenchymal tissues without pathological alterations. Large amounts of virus, demonstrated by presence of viral antigen in epithelial cells of the oral cavity and in keratinocytes of the skin, may be a source of infection for natural and spill-over hosts. Genetic analyses reflected a close relationship of the BDV sequences obtained from the shrews with the regional BDV cluster. At one location a high percentage of BDV-positive shrews was identified in four consecutive years, which points towards a self-sustaining infection cycle in bicolored white-toothed shrews. Analyses of behavioral and population features of this shrew species revealed that the bicolored white-toothed shrew may indeed play an important role as an indigenous host of BDV.

Epidemiology and host spectrum of Borna disease virus infections

Borna disease virus (BDV) has gained lot of interest because of its zoonotic potential, ability to introduce cDNA of its RNA transcripts into host genomes, and ability to cause severe neurobehavioural diseases. Classical Borna disease is a progressive meningoencephalomyelitis in horses and sheep, known in central Europe for centuries. According to current knowledge, BDV or a close relative also infects several other species, including humans at least occasionally, in central Europe and elsewhere, but the existence of potential 'human Borna disease' with its suspected neuropsychiatric symptoms is highly controversial. The recent detection of endogenized BDV-like genes in primate and various other vertebrate genomes confirms that at least ancient bornaviruses did infect our ancestors. The epidemiology of BDV is largely unknown, but accumulating evidence indicates vectors and reservoirs among small wild mammals. The aim of this review is to bring together the current knowledge on epidemiology of BDV infections. Specifically, geographical and host distribution are addressed and assessed in the critical light of the detection methods used. We also review some salient clinical aspects.