Alkhurma viral hemorrhagic fever virus: proposed guidelines for detection, prevention, and control in Saudi Arabia

Human Alkhumra hemorrhagic Fever: Emergence, history and epidemiological and clinical profiles

Alkhumra hemorrhagic fever (AHF) is a severe, often fatal hemorrhagic disease in humans. It is caused by Alkhumra hemorrhagic fever virus (AHFV), a newly described flavivirus first isolated in 1995 in Alkhumra district, south of Jeddah City, Saudi Arabia. It is transmitted from infected livestock animals to humans by direct contact with infected animals or by tick bites. In the recent past, the incidence of AHF has increased, with a total of 604 confirmed cases have been reported in Saudi Arabia between 1995 and 2020. Yet, no specific treatment or control strategies have been developed and implemented against this infection. Hence, the likelihood of increased prevalence or the occurrence of outbreaks is high, particularly in the absence of appropriate prevention and control strategies. This narrative review presents an overview of the current knowledge and future concerns about AHF globally.

Alkhurma haemorrhagic fever virus causes lethal disease in IFNAR-/- mice

Alkhurma haemorrhagic fever virus (AHFV), a tick-borne flavivirus closely related to Kyasanur Forest disease virus, is the causative agent of a severe, sometimes fatal haemorrhagic/encephalitic disease in humans. To date, there are no specific treatments or vaccines available to combat AHFV infections. A challenge for the development of countermeasures is the absence of a reliable AHFV animal disease model for efficacy testing. Here, we used mice lacking the type I interferon (IFN) receptor (IFNAR^-/-). AHFV strains Zaki-2 and 2003 both caused uniform lethality in these mice after intraperitoneal injection, but strain 2003 seemed more virulent with a median lethal dose of 0.4 median tissue culture infectious doses (TCID₅₀). Disease manifestation in this animal model was similar to case reports of severe human AHFV infections with early generalized signs leading to haemorrhagic and neurologic complications. AHFV infection resulted in early high viremia followed by high viral loads (<10⁸ TCID₅₀/g tissue) in all analyzed organs. Despite systemic viral replication, virus-induced pathology was mainly found in the spleen, lymph nodes, liver and heart. This uniformly lethal AHFV disease model will be instrumental for pathogenesis studies and countermeasure development against this neglected zoonotic pathogen.

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.

Hemorrhagic fever in Saudi Arabia: challenge to public health, effective management and future considerations

Background

Viral hemorrhagic fevers (VHF) refers to a group of febrile illnesses caused by different viruses that result in high mortality in animals and humans. Many risk factors like increased human-animal interactions, climate change, increased mobility of people and limited diagnostic facility have contributed to the rapid spread of VHF.

Materials

The history of VHFs in the Saudi Arabian Peninsula has been documented since the 19^th century, in which many outbreaks have been reported from the southwestern region of Saudi Arabia. Despite presence of regional network of experts and technical organizations, which expedite support and respond during outbreaks, there are some more challenges that need to be addressed immediately. Gaps in funding, exhaustive and inclusive response plans and improved surveillance systems are some areas of concern in the region which can be dealt productively. This review primarily focusses on the hemorrhagic fevers that are caused by three most common viruses namely, the Alkhurma hemorrhagic fever virus, Rift valley fever virus, and Dengue fever virus.

Conclusion

In summary, effective vector control, health education, possible use of vaccine and concerted synchronized efforts between different government organizations and private research institutions will help in planning effective outbreak-prevention and response strategies in future.

Alkhurma hemorrhagic fever virus

Alkhurma hemorrhagic fever virus (AHFV) was first isolated in Jeddah, Saudi Arabia, in the 1990s from the blood of a butcher. Subsequently, the virus was recognized in many patients in Saudi Arabia and rarely from Egypt and Djibouti. In this review, we summarize the current literature on AHFV globally with special focus on Saudi Arabia.

A case of Alkhumra virus infection

Alkhumra virus (ALKV) is an emerging tick-borne flavivirus known to cause a neglected tropical disease in the Middle East. The magnitude of the disease among European returning travelers is still unknown probably because the inadequate knowledge about the real geographic distribution of ALKV infection have limited its diagnosis. Up to now in Italy were reported only three cases; here we report the fourth case of ALKV in a returning traveler from south Egypt.

Homology Modeling and Conformational Epitope Prediction of Envelope Protein of Alkhumra Haemorrhagic Fever Virus

BACKGROUND

The aim of this study was to generate in silico 3D-structure of the envelope protein of AHFV using homology modeling method to further predict its conformational epitopes and help other studies to investigate its structural features using the model.

METHODS

A 3D-structure prediction was developed for the envelope protein of Alkhumra haemorrhagic fever virus (AHFV), an emerging tick-borne flavivirus, based on a homology modeling method using M4T and Modweb servers, as the 3D-structure of the protein is not available yet. Modeled proteins were validated using Modfold 4 server and their accuracies were calculated based on their RSMDs. Having the 3D predicted model with high quality, conformational epitopes were predicted using DiscoTope 2.0.

RESULTS

Model generated by M4T was more acceptable than the Modweb-generated model. The global score and P-value calculated by Modfold 4 ensured that a certifiable model was generated by M4T, since its global score was almost near 1 which is the score for a high resolution X-ray crystallography structure. Furthermore, itsthe P-value was much lower than 0.001 which means that the model is completely acceptable. Having 0.46 Å rmsd, this model was shown to be highly accurate. Results from DiscoTope 2.0 showed 26 residues as epitopes, forming conformational epitopes of the modeled protein.

CONCLUSION

The predicted model and epitopes for envelope protein of AHFV can be used in several therapeutic and diagnostic approaches including peptide vaccine development, structure based drug design or diagnostic kit development in order to facilitate the time consuming experimental epitope mapping process.

Kyasanur Forest disease virus infection in mice is associated with higher morbidity and mortality than infection with the closely related Alkhurma hemorrhagic fever virus

BACKGROUND

Kyasanur Forest disease virus (KFDV) and Alkhurma hemorrhagic fever virus (AHFV) are closely related members of the Flavivirus genus and are important causes of human disease in India and the Arabian Peninsula, respectively. Despite high genetic similarity, the viruses have distinctly different host ranges and ecologies. Human cases of KFDV or AHFV develop a spectrum of disease syndromes ranging from liver pathology to neurologic disease. Case reports suggest KFDV is more commonly associated with hepatic and gastrointestinal manifestations whereas AHFV is more commonly associated with neurologic disease.

METHODOLOGY/PRINCIPAL FINDINGS

Inoculation of three immunocompetent laboratory mouse strains revealed that KFDV was consistently more lethal than AHFV. In subsequent studies utilizing C57BL/6J mice, we demonstrated that KFDV infection was associated with higher viral loads and significantly higher mortality. KFDV-infected mice rapidly developed more severe disease than AHFV-infected mice, as evidenced by significant abnormalities on clinical chemistry panels and more severe pathology in the brain and gastrointestinal tract.

CONCLUSIONS/SIGNIFICANCE

Infections of C57BL/6J mice with KFDV or AHFV resulted in clinical disease syndromes that closely approximate the diseases seen in human cases. Despite high genetic similarity, there were clear differences in survival, viral kinetics, clinical chemistry data and histology. These results suggest that distinct mouse models for AHFV and KFDV are necessary in order to gain a better understanding of the unique pathogenesis of each virus, as well as to provide platforms for testing promising vaccines and therapeutics.

Comparative pathogenesis of Alkhumra hemorrhagic fever and Kyasanur forest disease viruses in a mouse model

Kyasanur Forest disease virus (KFDV) and Alkhumra hemorrhagic fever virus (AHFV) are genetically closely-related, tick-borne flaviviruses that cause severe, often fatal disease in humans. Flaviviruses in the tick-borne encephalitis (TBE) complex typically cause neurological disease in humans whereas patients infected with KFDV and AHFV predominately present with hemorrhagic fever. A small animal model for KFDV and AHFV to study the pathogenesis and evaluate countermeasures has been lacking mostly due to the need of a high biocontainment laboratory to work with the viruses. To evaluate the utility of an existing mouse model for tick-borne flavivirus pathogenesis, we performed serial sacrifice studies in BALB/c mice infected with either KFDV strain P9605 or AHFV strain Zaki-1. Strikingly, infection with KFDV was completely lethal in mice, while AHFV caused no clinical signs of disease and no animals succumbed to infection. KFDV and high levels of pro-inflammatory cytokines were detected in the brain at later time points, but no virus was found in visceral organs; conversely, AHFV Zaki-1 and elevated levels of cytokines were found in the visceral organs at earlier time points, but were not detected in the brain. While infection with either virus caused a generalized leukopenia, only AHFV Zaki-1 induced hematologic abnormalities in infected animals. Our data suggest that KFDV P9605 may have lost its ability to cause hemorrhagic disease as the result of multiple passages in suckling mouse brains. However, likely by virtue of fewer mouse passages, AHFV Zaki-1 has retained the ability to replicate in visceral organs, cause hematologic abnormalities, and induce pro-inflammatory cytokines without causing overt disease. Given these striking differences, the use of inbred mice and the virus passage history need to be carefully considered in the interpretation of animal studies using these viruses.

Kyasanur Forest disease virus (KFDV) and Alkhumra hemorrhagic fever virus (AHFV) are tick-borne flaviviruses that cause severe hemorrhagic disease in humans. The pathogenesis of the disease is still not very well understood mostly due to the lack of suitable animal models. Despite sharing a high degree of genetic sequence similarity, KFDV replicates primarily in the brain and is uniformly lethal for BALB/c mice. In contrast, AHFV does not cause clinically overt signs in mice, replicates in the visceral organs, and induces pro-inflammatory cytokines and hematological changes. Given the striking differences in pathogenesis and tissue tropism, the use of inbred mice as well as the passage history of the virus needs to be carefully considered in the interpretation of animal studies using these viruses.

Is the epidemiology of alkhurma hemorrhagic fever changing?: A three-year overview in Saudi Arabia

BACKGROUND

The epidemiology of Alkhurma hemorrhagic fever disease is yet to be fully understood since the virus was isolated in 1994 in the Kingdom of Saudi Arabia.

SETTING

Preventive Medicine department, Ministry of Health, Kingdom of Saudi Arabia.

DESIGN

Retrospective analysis of all laboratory confirmed cases of Alkhurma hemorrhagic fever disease collected through active and passive surveillance from 1(st)-January 2009 to December, 31, 2011.

RESULTS

Alkhurma hemorrhagic fever (AHFV) disease increased from 59 cases in 2009 to 93 cases in 2011. Cases are being discovered outside of the region where it was initially diagnosed in Saudi Arabia. About a third of cases had no direct contact with animals or its products. Almost all cases had gastro-intestinal symptoms. Case fatality rate was less than 1%.

CONCLUSIONS

Findings in this study showed the mode of transmission of AHFV virus may not be limited to direct contact with animals or its products. Gastro-intestinal symptoms were not previously documented. Observed low case fatality rate contradicted earlier reports. Close monitoring of the epidemiology of AHFV is recommended to aid appropriate diagnosis. Housewives are advised to wear gloves when handling animals and animal products as a preventive measure.

Animal models of tick-borne hemorrhagic Fever viruses

Tick-borne hemorrhagic fever viruses (TBHFV) are detected throughout the African and Eurasian continents and are an emerging or re-emerging threat to many nations. Due to the largely sporadic incidences of these severe diseases, information on human cases and research activities in general have been limited. In the past decade, however, novel TBHFVs have emerged and areas of endemicity have expanded. Therefore, the development of countermeasures is of utmost importance in combating TBHFV as elimination of vectors and interrupting enzootic cycles is all but impossible and ecologically questionable. As in vivo models are the only way to test efficacy and safety of countermeasures, understanding of the available animal models and the development and refinement of animal models is critical in negating the detrimental impact of TBHFVs on public and animal health.