Clinical & epidemiological significance of Kyasanur forest disease

Computational Exploration of Potential Pharmacological Inhibitors Targeting the Envelope Protein of the Kyasanur Forest Disease Virus

The limitations of the current vaccination strategy for the Kyasanur Forest Disease virus (KFDV) underscore the critical need for effective antiviral treatments, highlighting the crucial importance of exploring novel therapeutic approaches through in silico drug design. Kyasanur Forest Disease, caused by KFDV, is a tick-borne disease with a mortality of 3-5% and an annual incidence of 400 to 500 cases. In the early stage of infection, the envelope protein plays a crucial role by facilitating host-virus interactions. The objective of this research is to develop effective antivirals targeting the envelope protein to disrupt the virus-host interaction. In line with this, the 3D structure of the envelope protein was modeled and refined through molecular modeling techniques, and subsequently, ligands were designed via de novo design and pharmacophore screening, yielding 12 potential hits followed by ADMET analysis. The top five candidates underwent geometry optimization and molecular docking. Notably, compounds L4 (SA28) and L3 (CNP0247967) are predicted to have significant binding affinities of -8.91 and -7.58 kcal/mol, respectively, toward the envelope protein, based on computational models. Both compounds demonstrated stability during 200 ns molecular dynamics simulations, and the MM-GBSA binding free-energy values were -85.26 ± 4.63 kcal/mol and -66.60 ± 2.92 kcal/mol for the envelope protein L3 and L4 complexes, respectively. Based on the computational prediction, it is suggested that both compounds have potential as drug candidates for controlling host-virus interactions by targeting the envelope protein. Further validation through in-vitro assays would complement the findings of the present in silico investigations.

Hard Ticks as Vectors: The Emerging Threat of Tick-Borne Diseases in India

Hard ticks (Ixodidae) play a critical role in transmitting various tick-borne diseases (TBDs), posing significant global threats to human and animal health. Climatic factors influence the abundance, diversity, and vectorial capacity of tick vectors. It is imperative to have a comprehensive understanding of hard ticks, pathogens, eco-epidemiology, and the impact of climatic changes on the transmission dynamics of TBDs. The distribution and life cycle patterns of hard ticks are influenced by diverse ecological factors that, in turn, can be impacted by changes in climate, leading to the expansion of the tick vector's range and geographical distribution. Vector competence, a pivotal aspect of vectorial capacity, involves the tick's ability to acquire, maintain, and transmit pathogens. Hard ticks, by efficiently feeding on diverse hosts and manipulating their immunity through their saliva, emerge as competent vectors for various pathogens, such as viruses, parasites and bacteria. This ability significantly influences the success of pathogen transmission. Further exploration of genetic diversity, population structure, and hybrid tick vectors is crucial, as they play a substantial role in influencing vector competence and complicating the dynamics of TBDs. This comprehensive review deals with important TBDs in India and delves into a profound understanding of hard ticks as vectors, their biology, and the factors influencing their vector competence. Given that TBDs continue to pose a substantial threat to global health, the review emphasizes the urgency of investigating tick control strategies and advancing vaccine development. Special attention is given to the pivotal role of population genetics in comprehending the genetic diversity of tick populations and providing essential insights into their adaptability to environmental changes.

Kyasanur Forest Disease: A Comprehensive Review

Vector-borne microbial diseases are ubiquitous, and their management remains elusive. Such diseases with zoonotic potential result in public health challenges requiring additional control and preventive measures. Despite their cosmopolitan presence, vector-borne infections are neglected due to their endemicity in specified geographical regions. The Kyasanur forest disease (KFD) caused by the Kyasanur forest disease virus (KFDV) is among such diseases transmitted through ticks and localized to India. Despite its prevalence, high transmissibility, and potential to cause fatalities, KFDV has not been given the deserved attention by the governments. Further, KFDV circulates in the rural and wild geographical areas threatening infections to people living in these areas with limited access to medical and healthcare. Therefore, physicians, healthcare workers, and the general population need to understand the KFDV and its ecology, epidemiology, transmission, pathogenesis, laboratory diagnosis, and control and prevention as described comprehensively in this review.

Square the Circle: Diversity of Viral Pathogens Causing Neuro-Infectious Diseases

Neuroinfections rank among the top ten leading causes of child mortality globally, even in high-income countries. The crucial determinants for successful treatment lie in the timing and swiftness of diagnosis. Although viruses constitute the majority of infectious neuropathologies, diagnosing and treating viral neuroinfections remains challenging. Despite technological advancements, the etiology of the disease remains undetermined in over half of cases. The identification of the pathogen becomes more difficult when the infection is caused by atypical pathogens or multiple pathogens simultaneously. Furthermore, the modern surge in global passenger traffic has led to an increase in cases of infections caused by pathogens not endemic to local areas. This review aims to systematize and summarize information on neuroinvasive viral pathogens, encompassing their geographic distribution and transmission routes. Emphasis is placed on rare pathogens and cases involving atypical pathogens, aiming to offer a comprehensive and structured catalog of viral agents with neurovirulence potential.

Characterization of host receptor interaction with envelop protein of Kyasanur forest disease virus and predicting suitable epitopes for vaccine candidate

Kyasanur forest disease (KFD) is a zoonotic disease that is endemic to southern India and caused by KFD virus (KFDV) belonging to the family Flaviviridae. Humans are the dead-end host of the KFDV life cycle. The absence of effective treatment strategies against KFD can be attributed to a lack of studies on the mechanistic part of the spread of the disease. Hypothesizing molecular etiological similarity of KFDV to other well characterized flaviviruses, such as dengue virus (DENV), we focused on predicting the target receptor protein(s) in host and provided molecular basis of receptor-mediated recognition of the human host by KFDV envelop protein (EKFDV), drawing from the extant knowledge on the dengue counterpart, EDENV. Indeed, in silico approach helped to identify that the EKFDV structure closely resembles the EDENV structure and indicated DC-SIGN and/or Mannose receptors to be the plausible target host receptors. Immune-informatics approach aided in predicting 10 epitopes from E, NS1, NS2A, and NS2B proteins of the KFDV-P9605 genotype for vaccine design against KFDV. Further, molecular dynamics simulation (MDS) analyses of their complexes with human leukocyte antigens (HLAs) identified the epitopes DISLTCRVT and YAMEIRPVH as two high ranking candidates for vaccine design.Communicated by Ramaswamy H. Sarma.

Lakshmikanth B, K. Siddaramegowda C, Rizwan A, Byregowda SM, Venkatesha MD, Munivenkatarayappa A, Hegde R. Studies on the sequential pathology of Kyasanur Forest Disease (KFD) in Mouse brain: KFD virus induces apoptosis of neurons in cerebrum and hippocampus

The sequential pathology of Kyasanur forest disease (KFD) in mouse brain was assessed in this study. Kyasanur forest disease virus (KFDV) strain P9605 used in this study was confirmed by real-time reverse transcriptase-polymerase chain reaction targeting the NS5 gene. Mouse Lethal Dose 50 (MLD50) of the virus was determined by in-vivo mice inoculation test. One MLD50 of the KFDV was inoculated intra-cerebrally into 36 mice aged 2-3 weeks. Another group of 36 age-matched mice that served as control group were inoculated with plain media. Six mice each from infected and control groups were euthanized every 24 hrs intervals for six days. Brain tissues were collected in 10% NBF. The collected brain tissues were processed and subjected to histopathological studies by Hematoxylin and Eosin staining. Grossly, the infected mice showed symptoms of dullness, hunched back appearance, weakness, sluggish movements with indication of hind quarter paralysis on day four post-infection. These symptoms got aggravated with complete paralysis of the hind quarters, inability to move and death on 5th and 6th day post-infection. Microscopically, the brain showed apoptosis of neurons, perivascular cuffing, gliosis, congestion, neuropil vacuolation, meningitis, degeneration, and necrotic neurons. The real-time RT-PCR on hippocampus of the KFDV-infected mouse brain showed three-fold higher expression levels of Caspase 3, a crucial mediator of apoptosis. The cerebral cortex, cerebellum and hippocampus that control the motor neuron activities and muscle tone were primarily affected, possibly correlating with the gross symptoms of hind quarter paralysis, ataxia, and other motor neuron dysfunctions noticed. Taken together, these findings reveal that KFDV induces apoptosis of neurons in the cerebrum and hippocampus of KFDV infected mice. Further studies are needed to confirm if the lesions noticed in mice brain simulate the brain lesions in humans since gross motor-neuron symptoms are similar in mice as well as humans.

Sociodemographic factors associated with Kyasanur forest disease in India - a retrospective study

Objectives

Kyasanur forest disease (KFD) is a tick-borne disease in India affecting humans and two local non-human primate species. A critical knowledge gap in the scientific literature is the lack of information on how people's sociodemographic factors influence KFD occurrence.

Methods

We analyzed available data on KFD from three data sources: (a) 104 peer-reviewed articles using keyword searches on PubMed Central and Google Scholar, (b) 116 Program for Monitoring Emerging Diseases reports, and (c) an acute febrile illness surveillance data set on KFD from a report by the government of India. We performed statistical analyses to calculate the prevalence of KFD by state and differences in KFD cases by sex and age group.

Results

All three data sets used indicate that KFD cases and deaths have occurred predominantly in the 15-64 years age group (literature: 87% cases and 95% deaths, Program for Monitoring Emerging Diseases: 78% cases and 78% deaths, acute febrile illness: 96% cases [no breakdown for acute febrile illness death data]). Data reporting varies across states and is non-standardized.

Conclusions

The inconsistent reporting of sociodemographic data on KFD in India has created a gap in our understanding of its impact on different social groups. Collecting and reporting data on sociodemographic factors is critical to understanding the epidemiology of KFD and designing effective public health interventions.

Clinical, epidemiological, and molecular investigation of Kyasanur forest disease from Karnataka state, India during 2018-2019

BACKGROUND

In this study, we carried out an investigation of Kyasanur Forest Disease (KFD) suspected human cases reported in Karnataka state, India from December 2018 to June 2019.

METHODS

The clinical samples of KFD suspected cases (n = 1955) from 14 districts of Karnataka were tested for KFD using real-time RT-PCR and IgM ELISA. Further, the KFD-negative samples were tested for IgM antibodies against dengue and chikungunya viruses. Monkey samples (n = 276) and tick pools (n = 11582) were also screened using real-time RT-PCR. KFD-positive samples were further analysed using next-generation sequencing along with clinico-epidemiological analysis.

RESULTS

Of all, 173 (8.8%) cases tested positive for KFD either by real-time RT-PCR (n = 124), IgM ELISA (n = 53) or both tests (n = 4) from seven districts. Among KFD-negative cases, IgM antibody positivity was observed for dengue (2.6%), chikungunya (5.8%), dengue and chikungunya coinfection (3.7%). KFD cases peaked in January 2019 with fever, conjunctivitis, and myalgia as the predominant symptoms and a mortality of 4.6%. Among confirmed cases, 41% received a single dose and 20% received two doses of the KFD vaccine. Of the seven districts with KFDV positivity, Shivamogga and Hassan districts reported KFD viral RNA positivity in humans, monkeys, and ticks. Sequencing analysis of 2019 cases demonstrated a difference of less than 1.5% amino acid compared to prototype KFDV.

CONCLUSION

Although the KFD has been endemic in many districts of Karnataka state, our study confirms the presence of KFDV for the first time in two new districts, i.e. Hassan and Mysore. A comparative analysis of KFDV infection among the KFD-vaccinated and non-vaccinated populations demonstrated an insignificant difference.

Knowledge, Attitudes, and Practices Regarding Ticks, Tick-Borne Diseases, and Ethnomedicine Among an at-Risk Population in Kerala

Tick and tick-borne diseases (TBDs) are increasing annually, and the study of ticks has gained importance after the outbreak of Kyasanur Forest disease (KFD) in the South Western Ghats of India. Wayanad district of Kerala, with the highest tribal population in South India, is a KFD endemic state, owing to the lack of knowledge, attitude, and practice studies on TBDs and ethnomedicines against ticks. This study was carried out to assess their baseline knowledge, attitude, and ethnomedicinal practice against ticks. A structured questionnaire was used to conduct a survey of 499 tribal members living in forest fringe areas. Logistic regression analysis was performed to identify the factors that influence the knowledge, attitude, and practice of tribes on TBDs. More than 70% of the population visit the forests on a regular basis, with 65.7% of the population regularly exposed to tick bites; however, only 47.7% were aware of TBDs. About 47.4% of the respondents took precautions like therapeutics and natural remedies to avoid tick bites. Ten species of medicinal plant belonging to eight different families have been identified from the survey. The tribal population use these plants to repel ticks as well as treat tick bites. From the study, we concluded that the limited in-depth knowledge displayed by the tribes can be strengthened by conducting community programs such as awareness classes on TBD and its control measures. The ethnobotanicals identified can be used to formulate novel tick repellents in the future.

Simplified visual detection of Kyasanur Forest Disease virus employing Reverse Transcriptase-Polymerase Spiral Reaction (RT-PSR)

Among recently prevalent tick-borne infections in India, Kyasanur Forest Virus Disease (KFD) is an important public health concern. During last decade the emergence of cases apart from endemic zone raised concern about case positivity. Early diagnosis is therefore very important in disease management and primary containment. This study, aimed to develop a simplified viral RNA extraction in combination to dry down format of novel isothermal assay for (Reverse Transcription- Polymerase Spiral reaction) specific and rapid identification of Kyasanur Forest Disease Virus targeting viral envelope gene. The one step method was optimized by magnetic bead based viral RNA extraction followed by isothermal RT-PSR assay in heat bath at 63⁰C for 60 minutes. Further, visual results interpretation was done by color change of Hydroxy Naphthol Blue dye. The detection limit of the assay was found 10 RNA copies/rxn with comparable to silica column based viral RNA combined real time qPCR. No cross reactivity was observed with other closely related flaviviruses. The assay was evaluated with clinical samples has shown >99% concordance between two methods. This is the first report of sample extraction coupled isothermal detection of KFD in a simplified manner without a need of any hi-end equipment. The assay developed here has potential to use as an alternate for field-based detection in resource limited settings for KFD.

Single-dose VSV-based vaccine protects against Kyasanur Forest disease in nonhuman primates

Kyasanur Forest disease virus (KFDV) is an endemic arbovirus in western India mainly transmitted by hard ticks of the genus Haemaphysalis. KFDV causes Kyasanur Forest disease (KFD), a syndrome including fever, gastrointestinal symptoms, and hemorrhages. There are no approved treatments, and the efficacy of the only vaccine licensed in India has recently been questioned. Here, we studied the protective efficacy of a vesicular stomatitis virus (VSV)-based vaccine expressing the KFDV precursor membrane and envelope proteins (VSV-KFDV) in pigtailed macaques. VSV-KFDV vaccination was found to be safe and elicited strong humoral and cellular immune responses. A single-dose vaccination reduced KFDV loads and pathology and protected macaques from KFD-like disease. Furthermore, VSV-KFDV elicited cross-reactive neutralizing immune responses to Alkhurma hemorrhagic fever virus, a KFDV variant found in Saudi Arabia.

Latest Advances in Arbovirus Diagnostics

Arboviruses are a diverse family of vector-borne pathogens that include members of the Flaviviridae, Togaviridae, Phenuviridae, Peribunyaviridae, Reoviridae, Asfarviridae, Rhabdoviridae, Orthomyxoviridae and Poxviridae families. It is thought that new world arboviruses such as yellow fever virus emerged in the 16th century due to the slave trade from Africa to America. Severe disease-causing viruses in humans include Japanese encephalitis virus (JEV), yellow fever virus (YFV), dengue virus (DENV), West Nile virus (WNV), Zika virus (ZIKV), Crimean-Congo hemorrhagic fever virus (CCHFV), severe fever with thrombocytopenia syndrome virus (SFTSV) and Rift Valley fever virus (RVFV). Numerous methods have been developed to detect the presence of these pathogens in clinical samples, including enzyme-linked immunosorbent assays (ELISAs), lateral flow assays (LFAs) and reverse transcriptase-polymerase chain reaction (RT-PCR). Most of these assays are performed in centralized laboratories due to the need for specialized equipment, such as PCR thermal cyclers and dedicated infrastructure. More recently, molecular methods have been developed which can be performed at a constant temperature, termed isothermal amplification, negating the need for expensive thermal cycling equipment. In most cases, isothermal amplification can now be carried out in as little as 5-20 min. These methods can potentially be used as inexpensive point of care (POC) tests and in-field deployable applications, thus decentralizing the molecular diagnosis of arboviral disease. This review focuses on the latest developments in isothermal amplification technology and detection techniques that have been applied to arboviral diagnostics and highlights future applications of these new technologies.

Ophthalmic consequences of viral hemorrhagic fevers: Insights from the clinic and laboratory

Viral hemorrhagic fevers (VHFs) are a diverse group of RNA virus-mediated systemic diseases with significant morbidity and mortality and represent a significant public health concern. Given the high systemic morbidity and mortality in a number of these entities, delays in diagnosis can lead to downstream public health consequences. Many viral hemorrhagic fevers have ophthalmic manifestations and ophthalmologists thus play a key role in disease recognition and the management of ocular complications associated with specific hemorrhagic fevers. This review summarizes the key ophthalmic consequences of viral hemorrhagic fevers, viral disease pathogenesis, disease findings, and areas of unmet research need.

The role of social vulnerability in improving interventions for neglected zoonotic diseases: The example of Kyasanur Forest Disease in India

Forest-based communities manage many risks to health and socio-economic welfare including the increasing threat of emerging zoonoses that are expected to disproportionately affect poor and marginalised groups, and further impair their precarious livelihoods, particularly in Low-and-Middle Income (LMIC) settings. Yet, there is a relative dearth of empirical research on the vulnerability and adaptation pathways of poor and marginalised groups facing emerging zoonoses. Drawing on a survey of 229 households and a series of key-informant interviews in the Western Ghats, we examine the factors affecting vulnerability of smallholder and tribal households to Kyasanur Forest Disease (KFD), an often-fatal tick-borne viral haemorrhagic fever endemic in south India. Specifically, we investigate how different socio-demographic and institutional factors interact to shape KFD vulnerability and the strategies employed by households to adapt to disease consequences. Although surveyed households generally perceived KFD as an important health issue in the study region, there was variability in concern about contracting the disease. Overall results showed that poor access to land (AOR = 0.373, 95% CI: 0.152-0.916), being at or below the poverty line (AOR = 0.253, 95% CI: 0.094-0.685) and being headed by an older person (AOR = 1.038, 95% CI: 1.006-1.071) were all significant determinants of perceived KFD vulnerability. Furthermore, KFD vulnerability is also modulated by important extra-household factors including proximity to private hospitals (AOR = 3.281, 95% CI: 1.220-8.820), main roads (AOR = 2.144, 95% CI: 1.215-3.783) and study location (AOR = 0.226, 95% CI: 0.690-0.743). Our findings highlight how homogenous characterisation of smallholder and tribal communities and the 'techno-oriented' approach of existing interventions may further marginalise the most vulnerable and exacerbate existing inequalities. These findings are important for designing context-specific and appropriate health interventions (including the prioritisation of awareness raising, knowledge networks, livelihood diversification) that enhances the resilience of at-risk social groups within the KFD context. More broadly, our findings highlight how a focus on social vulnerability can help national and international health planners improve health interventions and prioritise among diseases with respect to neglected endemic zoonoses.

Sofosbuvir and its tri-phosphate metabolite inhibit the RNA-dependent RNA polymerase activity of non-structural protein 5 from the Kyasanur forest disease virus

Kyasanur forest disease is a neglected zoonotic disease caused by a single-stranded RNA-based flavivirus, the incidence of which was first recorded in 1957 in the Southern part of India. Kyasanur forest disease virus is transmitted to monkeys and humans through the infected tick bite of Haemophysalis spinigera. Kyasanur forest disease is a febrile illness, which in severe cases, results in neurological complications leading to mortality. The current treatment regimens are symptomatic and supportive, and no targeted therapies are available for this disease. In this study, we evaluated the ability of FDA-approved drugs sofosbuvir (and its active metabolite) and Dasabuvir to inhibit the RNA-dependent RNA polymerase activity of NS5 protein from the Kyasanur forest disease virus. NS5 protein containing the N-terminal methyl transferase domain and C-terminal RNA-dependent RNA polymerase domain was expressed in Escherichia coli, and RNA-dependent RNA polymerase activity was demonstrated with the purified protein. The RNA-dependent RNA polymerase assay conditions were optimized, followed by the determination of apparent K_m,ATP to validate the enzyme preparation. Half maximal-inhibitory concentrations against RNA-dependent RNA polymerase activity were determined for Sofosbuvir and its active metabolite. Dasabuvir did not show detectable inhibition with the tested conditions. This is the first demonstration of the inhibition of RNA-dependent RNA polymerase activity of NS5 protein from the Kyasanur forest disease virus with small molecule inhibitors. These initial findings can potentially facilitate the discovery and development of targeted therapies for treating Kyasanur forest disease.

Exploring potential inhibitors against Kyasanur forest disease by utilizing molecular dynamics simulations and ensemble docking

Kyasanur forest disease (KFD) is a tick-borne, neglected tropical disease, caused by KFD virus (KFDV) which belongs to Flavivirus (Flaviviridae family). This emerging viral disease is a major threat to humans. Currently, vaccination is the only controlling method against the KFDV, and its effectiveness is very low. An effective control strategy is required to combat this emerging tropical disease using the existing resources. In this regard, in silico drug repurposing method offers an effective strategy to find suitable antiviral drugs against KFDV proteins. Drug repurposing is an effective strategy to identify new use for approved or investigational drugs that are outside the scope of their initial usage and the repurposed drugs have lower risk and higher safety compared to de novo developed drugs, because their toxicity and safety issues are profoundly investigated during the preclinical trials in human/other models. In the present work, we evaluated the effectiveness of the FDA approved and natural compounds against KFDV proteins using in silico molecular docking and molecular simulations. At present, no experimentally solved 3D structures for the KFD viral proteins are available in Protein Data Bank and hence their homology model was developed and used for the analysis. The present analysis successfully developed the reliable homology model of NS3 of KFDV, in terms of geometry and energy contour. Further, in silico molecular docking and molecular dynamics simulations successfully presented four FDA approved drugs and one natural compound against the NS3 homology model of KFDV. Communicated by Ramaswamy H. Sarma.

Species distribution and ecological suitability analysis for potential tick vectors of Kyasanur forest disease in the Western Ghats of Kerala

Kyasanur forest disease (KFD) is a tick-borne zoonotic viral disease with an estimated case fatality rate of 3% to 5% in humans. The KFD virus is transmitted to both humans and animals by infected ticks, primarily the Haemaphysalis species. Our study was undertaken following reports of five confirmed cases and three deaths due to KFD in Malappuram district of Kerala in 2014 to determine the diversity of Ixodidae ticks on vegetation and their possible infection with the KFD virus. Overall, 3502 hard ticks belonging to three genera and eight species were collected from two forest divisions. Haemaphysalis was the predominant tick species (92.72%). Tick positivity for the KFD virus was 4 (5.33%) of 75 pools of ticks tested. Kyasanur forest disease viral RNA was detected from the genera Haemaphysalis and Amblyomma. The KFD virus was detected in 2 of 35 pools (5.71%) of Haemaphysalis spinigera, 1 of 30 pools (3.33%) of Haemaphysalis turturis, and 1 of 3 pools (3.33%) of Amblyomma integrum from the south forest division. The ticks reached their peak density between December and February and then decreased from the end of May. The temperature in the area ranges from 28°C to 30°C, which is suitable for tick survival.

A live-attenuated viral vector vaccine protects mice against lethal challenge with Kyasanur Forest disease virus

Kyasanur Forest disease virus (KFDV) is a tick-borne flavivirus endemic in India known to cause severe hemorrhagic and encephalitic disease in humans. In recent years, KFDV has spread beyond its original endemic zone raising public health concerns. Currently, there is no treatment available for KFDV but a vaccine with limited efficacy is used in India. Here, we generated two new KFDV vaccine candidates based on the vesicular stomatitis virus (VSV) platform. We chose the VSV-Ebola virus (VSV-EBOV) vector either with the full-length or a truncated EBOV glycoprotein as the vehicle to express the precursor membrane (prM) and envelope (E) proteins of KFDV (VSV-KFDV). For efficacy testing, we established a mouse disease model by comparing KFDV infections in three immunocompetent mouse strains (BALB/c, C57Bl/6, and CD1). Both vaccine vectors provided promising protection against lethal KFDV challenge in the BALB/c model following prime-only prime-boost and immunizations. Only prime-boost immunization with VSV-KFDV expressing full-length EBOV GP resulted in uniform protection. Hyperimmune serum derived from prime-boost immunized mice protected naïve BALB/c mice from lethal KFDV challenge indicating the importance of antibodies for protection. The new VSV-KFDV vectors are promising vaccine candidates to combat an emerging, neglected public health problem in a densely populated part of the world.

A pigtailed macaque model of Kyasanur Forest disease virus and Alkhurma hemorrhagic disease virus pathogenesis

Kyasanur Forest disease virus (KFDV) and the closely related Alkhurma hemorrhagic disease virus (AHFV) are emerging flaviviruses that cause severe viral hemorrhagic fevers in humans. Increasing geographical expansion and case numbers, particularly of KFDV in southwest India, class these viruses as a public health threat. Viral pathogenesis is not well understood and additional vaccines and antivirals are needed to effectively counter the impact of these viruses. However, current animal models of KFDV pathogenesis do not accurately reproduce viral tissue tropism or clinical outcomes observed in humans. Here, we show that pigtailed macaques (Macaca nemestrina) infected with KFDV or AHFV develop viremia that peaks 2 to 4 days following inoculation. Over the course of infection, animals developed lymphocytopenia, thrombocytopenia, and elevated liver enzymes. Infected animals exhibited hallmark signs of human disease characterized by a flushed appearance, piloerection, dehydration, loss of appetite, weakness, and hemorrhagic signs including epistaxis. Virus was commonly present in the gastrointestinal tract, consistent with human disease caused by KFDV and AHFV where gastrointestinal symptoms (hemorrhage, vomiting, diarrhea) are common. Importantly, RNAseq of whole blood revealed that KFDV downregulated gene expression of key clotting factors that was not observed during AHFV infection, consistent with increased severity of KFDV disease observed in this model. This work characterizes a nonhuman primate model for KFDV and AHFV that closely resembles human disease for further utilization in understanding host immunity and development of antiviral countermeasures.

Experiences of Indian Council of Medical Research with tick-borne zoonotic infections: Kyasanur Forest disease & Crimean-Congo haemorrhagic fever in India with One Health focus

Emergence and re-emergence of several pathogens have been witnessed by this century in the form of outbreaks, epidemics and pandemics. In India, the influencing factor that promotes dissemination of emerging and re-emerging viral infections is the biogeographical zones: a megadiverse country, characterized by varied geographical, climatic conditions and ever-changing socio-economical and geopolitical issues. These influence the movement of humans and animals and add layers of complexity for the identification and timely management of infectious diseases. This review focuses on two tick-borne infections: Crimean-Congo haemorrhagic fever (CCHF) and Kyasanur forest disease (KFD). In the last two decades, these viruses have emerged and caused outbreaks in different parts of India. KFD virus was initially identified in 1957 and was known to be endemic in Karnataka State while CCHF virus was first identified during 2010 in Gujarat State, India. These viruses have managed to emerge in new areas within the last decade. With changing epidemiology of these arboviruses, there is a probability of the emergence of these viruses from new areas in future. The investigations on these two diseases under the One Health focus involved early detection, quickly developing diagnostic tools, identifying stakeholders, capacity building by developing collaboration with major stakeholders to understand the epidemiology and geographical spread in domestic animal reservoirs and tick vectors in the affected areas, developing laboratory network, providing diagnostic reagents and biosafety and laboratory diagnosis training to the network laboratories to control these diseases.

Tick-virus interactions: Current understanding and future perspectives

Ticks are the primary vector of arboviruses in temperate climates worldwide. They are both the vector of these pathogens to humans and an integral component of the viral sylvatic cycle. Understanding the tick-pathogen interaction provides information about the natural maintenance of these pathogens and informs the development of countermeasures against human infection. In this review, we discuss currently available information on tick-viral interactions within the broader scope of general tick immunology. While the tick immune response to several pathogens has been studied extensively, minimal work centres on responses to viral infection. This is largely due to the high pathogenicity of tick-borne viruses; this necessitates high-containment laboratories or low-pathogenicity substitute viruses. This has biased most research towards tick-borne flaviviruses. More work is required to fully understand the role of tick-virus interaction in sylvatic cycling and transmission of diverse tick-borne viruses.

Dynamics of human B and T cell adaptive immune responses to Kyasanur Forest disease virus infection

Kyasanur Forest disease (KFD) is a tick-borne, acute, febrile viral illness endemic in southern India. No major studies have been done to understand the adaptive immune response during KFDV infection in humans. In this study, KFDV-positive patients were prospectively enrolled, and repeated peripheral blood collections were performed. Clinical and virologic characterization of these samples is reported along with phenotypic analysis of cellular immunity and quantitation of humoral immunity. We noted robust T and B cell responses, particularly of CD8 T cells, during KFDV infection in most of the patients. Virus clearance from the blood coincided with peak CD8 T cell activation and the appearance of KFDV-specific IgG. Increased frequency of plasmablasts and very few activated B cells were observed in the acute phase of KFD infection. Notably, only humoral immunity and activated B cell frequency in the acute phase correlated with prior KFDV vaccination, and only with 2 or more doses. This novel work has implications in KFD vaccine research as well as in understanding the pathogenesis.

Kyasanur Forest Disease and Alkhurma Hemorrhagic Fever Virus-Two Neglected Zoonotic Pathogens

Kyasanur Forest disease virus (KFDV) and Alkhurma hemorrhagic fever virus (AHFV) are tick-borne flaviviruses that cause life-threatening hemorrhagic fever in humans with case fatality rates of 3-5% for KFDV and 1-20% for AHFV, respectively. Both viruses are biosafety level 4 pathogens due to the severity of disease they cause and the lack of effective countermeasures. KFDV was discovered in India and is restricted to parts of the Indian subcontinent, whereas AHFV has been found in Saudi Arabia and Egypt. In recent years, both viruses have spread beyond their original endemic zones and the potential of AHFV to spread through ticks on migratory birds is a public health concern. While there is a vaccine with limited efficacy for KFDV used in India, there is no vaccine for AHFV nor are there any therapeutic concepts to combat infections with these viruses. In this review, we summarize the current knowledge about pathogenesis, vector distribution, virus spread, and infection control. We aim to bring attention to the potential public health threats posed by KFDV and AHFV and highlight the urgent need for the development of effective countermeasures.

Kyasanur Forest disease virus non-mouse animal models: a pilot study

Objectives

Mouse models have delivered variable recapitulation of Kyasanur Forest disease (KFD) pathology and consistently demonstrated neurological involvement which may be a limited feature of human disease. With the purpose of more accurately modelling human disease progression we infected several small-mammalian models: guinea pigs, hamsters and ferrets with a titered infectious dose of Kyasanur Forest disease virus (KFDV). Clinical indicators of disease severity were observed for seventeen days, on day eighteen a visual post-mortem analysis of visceral organs was conducted. Viral load in selected tissues was measured to infer disease signs and the establishment of viral replication.

Data description

Daily monitoring did not reveal any observable signs of illness; weight loss was minimal across species and gross pathology did not indicate severe viral infection. Tissue specific tropism and establishment of viral infection was monitored by quantitative real-time polymerase chain reaction (qRT-PCR). No viral replication was detected in ferrets (n = 0/3), but was present in the spleen of guinea pigs (n = 3/3) and the brain of hamsters (n = 3/3). Low levels of viral RNA were detected in multiple hamster tissues (kidney, liver, lung and spleen) suggesting the possibility of viral tropism and possible adaptation to the host. No serological tests were performed.

Viral Hemorrhagic Fevers Other than Ebola and Lassa

Viral hemorrhagic fevers represent a group of diseases caused by enveloped RNA viruses. The epidemiology is broadly variable, ranging from geographically localized to more diffuse infections. Viral hemorrhagic fevers are classified as category A bioweapon agents by the Centers for Disease Control and Prevention. Viral hemorrhagic fevers are severe febrile illnesses with hemorrhagic phenomena. Laboratory diagnosis takes place in highly specialized reference laboratories. Treatment is essentially supportive. In this article, we focus the attention on yellow fever and viral hemorrhagic fevers other than Ebola and Lassa virus diseases that have been described elsewhere in this issue.

Development of a quantitative real-time RT-PCR assay that differentiates between Kyasanur Forest disease virus and Alkhurma hemorrhagic fever virus

Kyasanur Forest disease virus (KFDV) and Alkhurma hemorrhagic fever virus (AHFV) are enveloped, positive-stranded RNA viruses of clinical importance with complex enzootic life cycles involving hematophagous ticks which feed on small and large mammals. Humans and monkeys are dead-end hosts for these viruses. Recent trends in epidemiological data suggest both virus incidences are steadily increasing and their geographical distribution expanding out of previously known circulation regions. For the detection and discrimination of these two closely related flaviviruses, we have developed quantitative real-time RT-PCR assays with 100 % sensitivity and 100 % specificity for KFDV, 100 % sensitivity and 99.4 % specificity for AHFV as determined using 550 clinical samples collected between 2015-2018 from Western Ghats region of India. This rapid and sensitive assay will enable researchers to accurately diagnose the presence of the virus during viremia in human and animal blood samples, and also from tick specimens. Incorporation of these new tests into a routine diagnosis will help in the diagnosis of KFDV as well as AHFV in the endemic areas and also would provide an early warning of the spread of this virus to newer regions with similar epidemiology.

[Arthropod-borne viruses (arboviruses)]

"Arbovirus" is a term for a virus transmitted to mammals by hematophagous arthropods; arboviruses; replicate in both mammals and arthropods. Since the life cycle of arboviruses is highly dependent on arthropods, control of the arthropods (vectors) is generally considered important for the control of arbovirus infection. Various pathogens that cause diseases in the medical and veterinary fields are grouped into arboviruses with a history of their discoveries since the early 20th century. Furthermore, because of recent advances in sequencing technology, new arboviruses have been discovered one after another. Here we would like to overview the known arboviruses and their infections.

Kyasanur Forest Disease in India: innovative options for intervention

Kyasanur Forest Disease (KFD) is a tick-borne hemorrhagic fever of human, caused by Kyasanur forest disease virus (KFDV) in India. The tick, Haemaphysalis spinigera, has been incriminated as the vector of KFDV. In human, KFD clinically presents with high fever, frontal headache, and severe myalgia, followed by bleeding from the nasal cavity, throat, gingivae, and in some cases, gastrointestinal tract. The mortality rate in KFDV infected cases is estimated to be 3-10%. Monkeys infected with the virus also develop the disease and die. Though the incidence of KFD was found to be confined only to the sylvatic area of Shimoga district in Karnataka state in India during 1967, recent reports indicate its expanding potential to the neighboring states such as Kerala, Tamil Nadu, and Goa. The administration of an indigenous, inactivated tissue culture vaccine was found to drastically decrease the percentage of incidence; however, the recurrence of KFD in vaccinated subjects warrants innovative strategies for effective control of the infection. The present communication proposes and discusses innovative intervention strategies for the effective prevention and control of KFD in India.

Emerging/re-emerging viral diseases & new viruses on the Indian horizon

Infectious diseases remain as the major causes of human and animal morbidity and mortality leading to significant healthcare expenditure in India. The country has experienced the outbreaks and epidemics of many infectious diseases. However, enormous successes have been obtained against the control of major epidemic diseases, such as malaria, plague, leprosy and cholera, in the past. The country's vast terrains of extreme geo-climatic differences and uneven population distribution present unique patterns of distribution of viral diseases. Dynamic interplays of biological, socio-cultural and ecological factors, together with novel aspects of human-animal interphase, pose additional challenges with respect to the emergence of infectious diseases. The important challenges faced in the control and prevention of emerging and re-emerging infectious diseases range from understanding the impact of factors that are necessary for the emergence, to development of strengthened surveillance systems that can mitigate human suffering and death. In this article, the major emerging and re-emerging viral infections of public health importance have been reviewed that have already been included in the Integrated Disease Surveillance Programme.