Diagnostic assays for Crimean-Congo hemorrhagic fever

Seromolecular survey and risk factor analysis of Crimean-Congo haemorrhagic fever orthonairovirus in occupationally exposed herdsmen and unexposed febrile patients in Kwara State, Nigeria

Crimean-Congo haemorrhagic fever virus (CCHFV) is a globally significant tick-borne zoonotic pathogen that causes fatal haemorrhagic disease in humans. Despite constituting an ongoing public health threat, limited research exists on the presence of CCHFV among herdsmen, an occupationally exposed population that has prolonged contact with ruminants and ticks. This cross-sectional study, conducted between October 2018 and February 2020 in Kwara State, Nigeria, was aimed at assessing CCHFV seroprevalence among herdsmen and non-herdsmen febrile patients, and identifying the associated risk factors. Blood samples from herdsmen (n = 91) and febrile patients in hospitals (n = 646) were analyzed for anti-CCHFV IgG antibodies and CCHFV S-segment RNA using ELISA and RT-PCR, respectively. Results revealed a remarkably high CCHFV seroprevalence of 92.3% (84/91) among herdsmen compared to 7.1% (46/646) in febrile patients. Occupational risk factors like animal and tick contact, tick bites, and hand crushing of ticks significantly contributed to higher seroprevalence in the herdsmen (p<0.0001). Herdsmen were 156.5 times more likely (p<0.0001) to be exposed to CCHFV than febrile patients. Notably, the odds of exposure were significantly higher (OR = 191.3; p<0.0001) in herdsmen with a history of tick bites. Although CCHFV genome was not detectable in the tested sera, our findings reveal that the virus is endemic among herdsmen in Kwara State, Nigeria. CCHFV should be considered as a probable cause of febrile illness among humans in the study area. Given the nomadic lifestyle of herdsmen, further investigations into CCHF epidemiology in this neglected population are crucial. This study enhances our understanding of CCHFV dynamics and emphasizes the need for targeted interventions in at-risk communities.

Molecular and serological evidence of Crimean-Congo hemorrhagic fever orthonairovirus prevalence in livestock and ticks in Cameroon

Introduction

Despite a high fatality rate in humans, little is known about the occurrence of Crimean-Congo hemorrhagic fever virus (CCHFV) in Cameroon. Hence, this pioneer study was started with the aim of determining the prevalence of CCHFV in domestic ruminants and its potential vector ticks in Cameroon.

Methods

A cross-sectional study was carried out in two livestock markets of Yaoundé to collect blood and ticks from cattle, sheep, and goats. CCHFV-specific antibodies were detected in the plasma using a commercial ELISA assay and confirmed using a modified seroneutralization test. Ticks were screened for the presence of orthonairoviruses by amplification of a fragment of the L segment using RT-PCR. Phylogeny was used to infer the genetic evolution of the virus.

Results

Overall, 756 plasma samples were collected from 441 cattle, 168 goats, and 147 sheep. The seroprevalence of CCHFV was 61.77% for all animals, with the highest rate found in cattle (433/441, 98.18%) followed by sheep (23/147, 15.65%), and goats (11/168, 6.55%), (p-value < 0.0001). The highest seroprevalence rate was found in cattle from the Far North region (100%). Overall, 1500 ticks of the Rhipicephalus (773/1500, 51.53%), Amblyomma (341/1500, 22.73%), and Hyalomma (386/1500, 25.73%) genera were screened. CCHFV was identified in one Hyalomma truncatum pool collected from cattle. Phylogenetic analysis of the L segment classified this CCHFV strain within the African genotype III.

Conclusion

These seroprevalence results call for additional epidemiological studies on CCHFV, especially among at-risk human and animal populations in high-risk areas of the country.

Leukotriene metabolism and proiflammatory cytokines in Crimean Congo hemorrhagic fever

Crimean-Congo hemorrhagic fever (CCHF) is an emerging acute viral infection disease, yet its pathophysiology remains largely uncharacterized. Lipid mediators are molecules that play numerous roles in the physiologic and pathophysiologic conditions in certain viral diseases. No previous study evaluated the status of cysteinyl leukotrienes (CYSLT) and 5-lipoxygenase (5-LO) and their relationship with proinflammatory cytokines in CCHF. A total of 90 subjects including 60 CCHF patients and 30 healthy controls were enrolled the study. Serum CYSLT, 5-LO, interleukin-6 (IL-6), and ferritin levels were determined in the study population. Lower median 5-LO level was determined in patients compared to healthy controls (p = 0.0004). Higher ferritin (p < 0.001) and IL-6 (p < 0.001) levels in patients than healthy controls. No statistically significant difference was observed between patients and controls in terms of CYSLT levels. No statistically significant differences were observed between mild, moderate, and severe groups in terms of both 5-LO and CYSLT levels. IL-6 and ferritin levels were higher in severe group compared mild and moderate groups. In conclusion, changes in 5-LO enzyme and increased inflammation are related with the disease molecular mechanism. Higher inflammatory status contributes to the impaired hemostatic balance in CCHF. Thus, treatment strategies to reduce inflammation may help to prevent bleeding and DIC in patients. IL-6 and ferritin can be used to as an additional biomarker in the estmation of the prognosis and diagnosis of the patients.

Evaluation of Nucleoprotein-Based Enzyme-Linked Immunosorbent Assay for Serodiagnosis of Acute Crimean-Congo Hemorrhagic Fever Virus Infections in a Turkish Population

Background: Crimean-Congo hemorrhagic fever virus (CCHFV) causes a highly contagious tick-borne disease with high case-fatality rates in humans. It is circulating not only in many Asian and African countries, but also spreading to and within Europe. To cope better with future outbreaks of Crimean-Congo hemorrhagic fever (CCHF), the WHO has prioritized the need for the development and validation of CCHF diagnostics, including serological assays. In this study, we evaluated the performance of the new EUROIMMUN anti-CCHFV IgM and IgG enzyme-linked immunosorbent assays (ELISAs). Materials and Methods: Both ELISAs were compared to the Vector-Best VectoCrimean-CHF-IgM and -IgG ELISAs using the EUROIMMUN CCHFV Mosaic 2 IgM and IgG indirect immunofluorescence assays (IFA) as reference. Forty-nine acute-phase serum samples from patients with CCHFV infection confirmed by reverse transcription-polymerase chain reaction (RT-PCR) and/or anti-CCHFV IgM IFA positivity were used to determine assay sensitivity. The assessment of specificity was based on sera from 30 control patients, 30 healthy blood donors, and 29 patients with hantavirus or sandfly fever virus infections. All samples originated from Turkey. Results: Sensitivity of the EUROIMMUN ELISAs (IgM 98.0%, IgG 47.1%) exceeded that of the Vector-Best ELISAs (IgM 95.9%, IgG 35.3%). Specificity of the EUROIMMUN ELISA IgM (86.4%) was slightly higher compared with the Vector-Best ELISA IgM (84.7%), while specificity for IgG was 100% for both assays. Qualitative agreement between the EUROIMMUN and Vector-Best ELISAs was substantial for detecting anti-CCHFV IgM (84.1%, ĸ = 0.673) and IgG (94.9%, ĸ = 0.791), whereas the quantitative results indicated a very strong positive correlation (IgM: r = 0.868, IgG: r = 0.913). Conclusion: The new EUROIMMUN anti-CCHFV ELISAs are standardized and easy-to-use tools that reliably support the identification of acute CCHF cases, and thus suitable for laboratories involved in on-site outbreak support.

Presence of antibodies to Crimean Congo haemorrhagic fever virus in sheep in Tunisia, North Africa

Crimean–Congo haemorrhagic fever (CCHF) is an emerging tick‐borne disease causing severe and fatal haemorrhagic syndrome in humans. Hyalomma spp. ticks are the primary vectors and sheep are important CCHF virus (CCHFV)‐amplifying hosts. In this study, blood samples and ticks collected in October 2019 from 270 sheep from 15 farms across Tunisia constituted the main research material. Moreover, the sera of the same animals taken at different periods between 2018 and 2019 were also used to obtain comparative results. To investigate the presence of anti‐CCHFV antibodies in sheep, all sera were tested using ELISA. Reactive sera were further characterised by a virus neutralisation test (VNT). Overall, one out of the 270 tested sheep was both ELISA‐ and strongly VNT‐positive to CCHFV. Another two sheep were borderline ELISA‐positive but did not exhibit neutralising antibodies. Ninety‐one ticks were collected from all sampled sheep, of which 34 (37.4%) belonged to Hyalomma spp. This is the first report of anti‐CCHFV antibodies in sheep from Tunisia. Both the results of this study and the recent CCHFV detection in ticks collected from camels in southern Tunisia indicate that further studies are needed to determine the competent tick vector in the country and to characterise the epidemiological cycle of CCHFV.

Laboratory Diagnosis of Tropical Infections

Highlights

(1) Blood culture is the gold standard for the diagnosis of bacterial infections. (2) Bone marrow culture is more sensitive than blood culture even in patients with enteric fever receiving antibiotics. (3) Microscopic agglutination test is considered the gold standard for diagnosing leptospirosis; however, now IgM ELISA and polymerase chain reaction (PCR) are more frequently used for diagnosis. (4) Tuberculosis is diagnosed with the help of nucleic acid amplification tests like Xpert MTB/RIF Ultra which also detects rifampicin resistance. Other tests include microscopy, Lowenstein-Jensen and mycobacteria growth indicator tube culture, line probe assay. (5) Tropical rickettsial infections are diagnosed by serological reactions (Weil-Felix, ELISA for antibodies) and PCR. (6) For Brucellosis culture from blood, bone marrow or tissue specimens remain the mainstay in diagnosis. (7) Dengue, Zika, Crimean-Congo hemorrhagic fever, Ebola, hantavirus, rabies are diagnosed with reverse transcriptase-polymerase chain reaction. Serological tests like IgM ELISA or paired sera samples for IgG are also used for diagnosis.

How to cite this article

Basu S, Shetty A. Laboratory Diagnosis of Tropical Infections. Indian J Crit Care Med 2021;25(Suppl 2):S122-S126.

Prevalence and phylogenetic analysis of Crimean-Congo hemorrhagic fever virus in ticks collected from Punjab province of Pakistan

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne zoonotic disease of human that caused by CCHF virus. To study the epidemiological distribution of CCHFV, 2183 tick samples were collected from sheep, goats, cattle and buffalo of different livestock farms of ten districts of Punjab province of Pakistan. Detection of CCHFV was done using enzyme link immunosorbent assay (ELISA) after proper identification of tick samples. The partial S-segment of CCHFV from ELISA positive tick samples was amplified by PCR and sequenced to determine the genotype of CCHFV. Out of2183 collected tick samples, 1913 ticks belonged to 5 species of genus Hyalomma as H. antolicum (48%), H. marginatum (30.2%), H. rufipes (10.82%), H. impressum (5.43%) and H. dromedarii (5.27%). While 270 ticks belonged to 3 species of genus Rhipicephalus as R. microplus (44.8%), R. sanguineus (32.22%) and R. turanicus (24.8%). The overall antigenic prevalence of CCHFV was found to be 12.13% in collected tick samples and 21 tick pools were sequenced for partial S-segment of CCHFV. All of the 21 tick pools were clustered in genotype IV (Asia-1). The highest prevalence of CCHFV was found in district Chakwal (24.13%) followed by Mianwali (23.68%), Rawalpindi (23.07%), Attock (20.0%), Rajanpur (10.52%) and Lahore (8.33%). In positive tick pools, the highest prevalence of CCHFV antigen was found in H. antolicum (39.6%) followed by H. marginatum (30.18%), H. rufipes (13.2%), H. impressum (3.77%), H. dromedarii (1.88%), R. microplus (5.66%) and R. sanguineus (5.66%). The current study confirms the presence of CCHFV in the ticks population of Punjab. The CCHF virus present in Punjab belongs to Asia-1 genotype. It is important to control the tick infestation of the animals present in these areas. So that the transmission cycle of CCHF can be inhibited.

Crimean-Congo hemorrhagic fever virus antibody prevalence in Mauritanian livestock (cattle, goats, sheep and camels) is stratified by the animal's age

Crimean-Congo hemorrhagic fever virus (CCHFV) is one of the most widespread zoonotic arthropod-borne viruses in many parts of Africa, Europe and Asia. It belongs to the family of Nairoviridae in the genus of Orthonairovirus. The main reservoir and vector are ticks of the genus Hyalomma. Livestock animals (such as cattle, small ruminants and camels) develop a viremias lasting up to two weeks with absence of clinical symptoms, followed by seroconversion. This study was carried out to assess risk factors that affect seroprevalence rates in different species. In total, 928 livestock animal samples (cattle = 201; sheep = 247; goats = 233; camels = 247) from 11 out of 13 regions in Mauritania were assayed for CCHFV-specific immunoglobulin G (IgG) antibodies using enzyme-linked immunosorbent assays (ELISA) (including a novel indirect camel-IgG-specific CCHFV ELISA). Inconclusive results were resolved by an immunofluorescence assay (IFA). A generalized linear mixed-effects model (GLMM) was used to draw conclusions about the impact of certain factors (age, species, sex and region) which might have influenced the CCHFV antibody status of surveyed animals. In goats and sheep, about 15% of the animals were seropositive, whereas in cattle (69%) and camels (81%), the prevalence rate was significantly higher. On average, cattle and camels were up to twice to four times older than small ruminants. Interestingly, the seroprevalence in all species was directly linked to the age of the animals, i.e. older animals had significantly higher seroprevalence rates than younger animals. The highest CCHFV seroprevalence in Mauritania was found in camels and cattle, followed by small ruminants. The large proportion of positive animals in cattle and camels might be explained by the high ages of the animals. Future CCHFV prevalence studies should at least consider the age of surveyed animals in order to avoid misinterpretations.

Crimean-Congo hemorrhagic fever virus (CCHFV) is a silent threat that repeatedly causes severe hemorrhagic disease in humans who have been in close contact with livestock of endemic countries. The detection of CCHFV IgG antibodies in livestock can be a first indication whether the virus circulates in a given region and is thus a valuable diagnostic tool for determining the endemic status. Interestingly, earlier data from Mauritania showed a noticeable difference in IgG prevalence between sheep (18%) and cattle (67%). In contrast to sheep and cattle, current monitoring data on CCHFV IgG antibody presence in camels and goats in Mauritania is very limited. This study was conducted to provide a comprehensive up-to-date overview of CCHFV seroprevalences in the four most important Mauritanian livestock species (cattle, sheep, goats and camels). It attempts to highlight the role of potential risk factors responsible for deviating prevalences. In addition, we developed a camel-specific IgG ELISA, which can be used in future CCHFV seroprevalence studies. Furthermore, findings of this study contribute to a better understanding of the current epidemiological CCHFV situation in sub-Saharan Africa and which role different livestock species play regarding the viral circulation in endemic regions.

Comparison of diagnostic performances of ten different immunoassays detecting anti-CCHFV IgM and IgG antibodies from acute to subsided phases of Crimean-Congo hemorrhagic fever

Crimean-Congo Hemorrhagic Fever Virus (CCHFV) is a geographically widespread tick-borne arbovirus that has been recognized by the WHO as an emerging pathogen needing urgent attention to ensure preparedness for potential outbreaks. Therefore, availability of accurate diagnostic tools for identification of acute cases is necessary. A panel comprising 121 sequential serum samples collected during acute, convalescent and subsided phase of PCR-proven CCHFV infection from 16 Kosovar patients was used to assess sensitivity. Serum samples from 60 healthy Kosovar blood donors were used to assess specificity. All samples were tested with two IgM/IgG immunofluorescence assays (IFA) from BNITM, the CCHFV Mosaic 2 IgG and IgM indirect immunofluorescence tests (IIFT) from EUROIMMUN, two BlackBox ELISAs for the detection of CCHFV-specific IgM and IgG antibodies (BNITM), two Anti-CCHFV ELISAs IgM and IgG from EUROIMMUN using recombinant structural proteins of CCHFV antigens, and two ELISAs from Vector-Best (IgM: μ-capture ELISA, IgG: indirect ELISA using immobilized CCHFV antigen). Diagnostic performances were compared between methods using sensitivity, specificity, concordance and degree of agreement with particular focus on the phase of the infection. In early and convalescent phases of infection, the sensitivities for detecting specific IgG antibodies differed for the ELISA test. The BlackBox IgG ELISA yielded the highest, followed by the EUROIMMUN IgG ELISA and finally the VectorBest IgG ELISA with the lowest sensitivities. In the subsided phase, the VectorBest IgM ELISA detected a high rate of samples that were positive for anti-CCHFV IgM antibodies. Both test systems based on immunofluorescence showed an identical sensitivity for detection of anti-CCHFV IgM antibodies in acute and convalescent phases of infection. Available serological test systems detect anti-CCHFV IgM and IgG antibodies accurately, but their diagnostic performances vary with respect to the phase of the infection.

Risk Factors for and Seroprevalence of Tickborne Zoonotic Diseases among Livestock Owners, Kazakhstan

Crimean-Congo hemorrhagic fever (CCHF), Q fever, and Lyme disease are endemic to southern Kazakhstan, but population-based serosurveys are lacking. We assessed risk factors and seroprevalence of these zoonoses and conducted surveys for CCHF-related knowledge, attitudes, and practices in the Zhambyl region of Kazakhstan. Weighted seroprevalence for CCHF among all participants was 1.2%, increasing to 3.4% in villages with a known history of CCHF circulation. Weighted seroprevalence was 2.4% for Lyme disease and 1.3% for Q fever. We found evidence of CCHF virus circulation in areas not known to harbor the virus. We noted that activities that put persons at high risk for zoonotic or tickborne disease also were risk factors for seropositivity. However, recognition of the role of livestock in disease transmission and use of personal protective equipment when performing high-risk activities were low among participants.

Purification of Crimean-Congo hemorrhagic fever virus nucleoprotein and its utility for serological diagnosis

Crimean-Congo hemorrhagic fever virus (CCHFV) causes a zoonotic disease, Crimean-Congo hemorrhagic fever (CCHF) endemic in Africa, Asia, the Middle East, and Southeastern Europe. However, the prevalence of CCHF is not monitored in most of the endemic countries due to limited availability of diagnostic assays and biosafety regulations required for handling infectious CCHFV. In this study, we established a protocol to purify the recombinant CCHFV nucleoprotein (NP), which is antigenically highly conserved among multiple lineages/clades of CCHFVs and investigated its utility in an enzyme-linked immunosorbent assay (ELISA) to detect CCHFV-specific antibodies. The NP gene was cloned into the pCAGGS mammalian expression plasmid and human embryonic kidney 293 T cells were transfected with the plasmid. The expressed NP molecule was purified from the cell lysate using cesium-chloride gradient centrifugation. Purified NP was used as the antigen for the ELISA to detect anti-CCHFV IgG. Using the CCHFV NP-based ELISA, we efficiently detected CCHFV-specific IgG in anti-NP rabbit antiserum and CCHFV-infected monkey serum. When compared to the commercially available Blackbox CCHFV IgG ELISA kit, our assay showed equivalent performance in detecting CCHFV-specific IgG in human sera. These results demonstrate the usefulness of our CCHFV NP-based ELISA for seroepidemiological studies.

Serological and molecular study of Crimean-Congo Hemorrhagic Fever Virus in cattle from selected districts in Uganda

BACKGROUND

Crimean-Congo Hemorrhagic Fever (CCHF) is a severe tick-borne viral hemorrhagic disease caused by Crimean-Congo Hemorrhagic Fever Virus (CCHFV) that poses serious public health challenges in many parts of Africa, Europe and Asia.

METHODS

We examined 500 cattle sera samples from five districts for CCHFV antibodies using in-house and commercially available (IDVet) ELISA, Immunofluorescent assay (IFA) and Real-time polymerase chain reaction (RT-PCR).

RESULTS

500 cattle (73.8 % females) were analyzed; CCHFV seropositivity was 12.6 % (n = 63) and 75.0 % (n = 375) with the in-house and IDVet ELISAs, respectively. Seropositivity was associated with geographical location, increasing age, being female, and having a higher tick burden. Twenty four out of the 37 (64.8 %) were seropositive for CCHFV using IFA and all were negative for virus on RT-PCR. The IFA results were more comparable to IDVet (κ_coefficient = 0.88, p = <0.01) than to in-house (κ_coefficient = 0.32, p = 0.02).

CONCLUSIONS

Our study confirmed the presence and high prevalence of anti-CCHF antibodies in cattle based on three methods from all the five study districts, confirming presence and exposure of CCHFV. Given the zoonotic potential for CCHFV, we recommend a multidisciplinary public health surveillance and epidemiology of CCHFV in both animals and humans throughout the country.

Crimean-Congo haemorrhagic fever (CCHF) virus-specific antibody detection in blood donors, Castile-León, Spain, summer 2017 and 2018

BackgroundCrimean-Congo haemorrhagic fever virus (CCHFV) is considered an emerging or even a probable re-emerging pathogen in southern Europe. Presence of this virus had been reported previously in Spain in 2010.AimWe aimed to evaluate the potential circulation of CCHFV in western Spain with a serosurvey in asymptomatic adults (blood donors).MethodsDuring 2017 and 2018, we conducted a CCHFV serosurvey in randomly selected asymptomatic blood donors from western Spain. Three assays using specific IgG antibodies against CCHFV were performed: the VectoCrimea ELISA test, an in-house ELISA and indirect immunofluorescence (EuroImmun) test with glycoprotein and nucleoprotein.ResultsA total of 516 blood donors participated in this cross-sectional study. The majority of the study participants were male (68.4%), and the mean age was 46.3 years. Most of the participants came from rural areas (86.8%) and 68.6% had contact with animals and 20.9% had animal husbandry practices. One in five participants (109/516, 21.1%) were engaged in at-risk professional activities such as agriculture and shepherding, slaughtering, hunting, veterinary and healthcare work (mainly nursing staff and laboratory technicians). A total of 15.3% of the participants were bitten by ticks in the days or months before the date of sampling. We detected anti-CCHFV IgG antibodies with two diagnostic assays in three of the 516 individuals and with one diagnostic assay in six of the 516 individuals.ConclusionSeroprevalence of CCHFV was between 0.58% and 1.16% in Castile-León, Spain. This is the first study in western Spain that showed circulation of CCHFV in healthy people.

Epidemiological investigation of Crimean-Congo haemorrhagic fever virus infection among the one-humped camels (Camelus dromedarius) in southern Tunisia

Crimean-Congo haemorrhagic fever is a viral tick-borne zoonotic disease caused by a Nairovirus, Crimean-Congo haemorrhagic fever virus (CCHFV). The present survey aimed to determine the exposure of one-humped camels (Camelus dromedarius) from southern Tunisia to CCHFV. A total of 273 sera from extensively reared camels were collected from Tataouine district, Tunisia, and tested by CCHFV-specific enzyme linked immunosorbent assays. By combining the results of three serological tests, the overall seroprevalence of CCHFV was estimated as 89.7% (245/273). No viral RNA was detected from camel sera using quantitative real-time PCR (RT-qPCR). A total of 165 ticks were collected from camels and tested with RT-qPCR, and only one Hyalomma impeltatum tick was positive for virus RNA.

New geographical area on the map of Crimean-Congo hemorrhagic fever virus: First serological evidence in the Hungarian population

Crimean-Congo hemorrhagic fever (CCHF) is an emerging tick-borne disease that is endemic in Africa, Asia, the Middle East, and the Balkan region of Europe; the disease is spreading northwards following widespread distribution of the main vector, Hyalomma marginatum, which was first found in Hungary in 2011. The aim of this pilot sero-surveillance study was to assess CCHF seroprevalence in Hungary. A total of 2700 serum samples obtained from healthy volunteer blood donors were screened using an in-house immunofluorescence assay and a commercially available ELISA kit. We found ten (0.37 %) seropositive donors. The western and central regions proved to be the most affected areas, with a prevalence of 2.97 %. Higher positivity was found among male donors (0.55 %) and younger donors (18-34 years; 0.78 %). Based on these results, a more extended surveillance focusing on specific at-risk populations and animals is advised. The results should also raise the awareness of clinicians and other high-risk populations, such as foresters and hunters, about the emerging threat of CCHF in Hungary.

Towards a Sustainable One Health Approach to Crimean-Congo Hemorrhagic Fever Prevention: Focus Areas and Gaps in Knowledge

Crimean–Congo hemorrhagic fever virus (CCHFV) infection is identified in the 2018 World Health Organization Research and Development Blueprint and the National Institute of Allergy and Infectious Diseases (NIH/NIAID) priority A list due to its high risk to public health and national security. Tick-borne CCHFV is widespread, found in Europe, Asia, Africa, the Middle East, and the Indian subcontinent. It circulates between ticks and several vertebrate hosts without causing overt disease, and thus can be present in areas without being noticed by the public. As a result, the potential for zoonotic spillover from ticks and animals to humans is high. In contrast to other emerging viruses, human-to-human transmission of CCHFV is typically limited; therefore, prevention of spillover events should be prioritized when considering countermeasures. Several factors in the transmission dynamics of CCHFV, including a complex transmission cycle that involves both ticks and vertebrate hosts, lend themselves to a One Health approach for the prevention and control of the disease that are often overlooked by current strategies. Here, we examine critical focus areas to help mitigate CCHFV spillover, including surveillance, risk assessment, and risk reduction strategies concentrated on humans, animals, and ticks; highlight gaps in knowledge; and discuss considerations for a more sustainable One Health approach to disease control.

Laboratory management of Crimean-Congo haemorrhagic fever virus infections: perspectives from two European networks

Background

Crimean-Congo haemorrhagic fever virus (CCHFV) is considered an emerging infectious disease threat in the European Union. Since 2000, the incidence and geographic range of confirmed CCHF cases have markedly increased, following changes in the distribution of its main vector, Hyalomma ticks.

Aims

To review scientific literature and collect experts’ opinion to analyse relevant aspects of the laboratory management of human CCHF cases and any exposed contacts, as well as identify areas for advancement of international collaborative preparedness and laboratory response plans.

Methods

We conducted a literature review on CCHF molecular diagnostics through an online search. Further, we obtained expert opinions on the key laboratory aspects of CCHF diagnosis. Consulted experts were members of two European projects, EMERGE (Efficient response to highly dangerous and emerging pathogens at EU level) and EVD-LabNet (Emerging Viral Diseases-Expert Laboratory Network).

Results

Consensus was reached on relevant and controversial aspects of CCHF disease with implications for laboratory management of human CCHF cases, including biosafety, diagnostic algorithm and advice to improve lab capabilities. Knowledge on the diffusion of CCHF can be obtained by promoting syndromic approach to infectious diseases diagnosis and by including CCHFV infection in the diagnostic algorithm of severe fevers of unknown origin.

Conclusion

No effective vaccine and/or therapeutics are available at present so outbreak response relies on rapid identification and appropriate infection control measures. Frontline hospitals and reference laboratories have a crucial role in the response to a CCHF outbreak, which should integrate laboratory, clinical and public health responses.

Diagnostic Testing for Crimean-Congo Hemorrhagic Fever

Crimean-Congo hemorrhagic fever is the most geographically widespread tick-borne virus, with infection resulting in mortality in up to 30% of cases. Clinical diagnosis alone is difficult due to the nonspecific nature of symptoms; therefore, laboratory diagnostics should be utilized for patients with residence in or travel to regions of endemicity in whom the disease is suspected. This minireview provides an overview of laboratory tests available for Crimean-Congo hemorrhagic fever (CCHF) and their utility in diagnosis with a focus on diagnosing CCHF in humans.

Seroprevalence of Crimean-Congo hemorrhagic fever in humans in the World Health Organization European region: A systematic review

BACKGROUND

Crimean-Congo hemorrhagic fever (CCHF) is an emerging infectious disease caused by a Nairovirus. CCHF is a tick-borne disease that is predominantly associated with Hyalomma ticks and have a widespread distribution in Africa, Asia and Europe. CCHF usually presents as a subclinical disease, but in some cases, it may present as a hemorrhagic fever with a high mortality rate. This systematic review of the literature was performed to identify the available evidence on the prevalence of CCHF in the European Region of the World Health Organization, based on seroprevalence (IgG antibodies).

METHODOLOGY

A systematic review was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement protocol. PubMed, Embase, and the Web of Science were used for the search (up to January 31, 2019), combining the following MeSH terms: ["Crimean-Congo haemorrhagic fever" OR "Crimean-Congo hemorrhagic fever virus" OR "Congo-Crimea" OR "Crimea-Congo"] AND ["Europe"] AND ["epidemiology" OR "seroprevalence"]. The abstracts were screened. Subsequently, full-text articles were selected and reviewed based on the PICOS (Population-Intervention-Comparison-Outcomes-Study type) criteria by two independent reviewers for inclusion in the final analysis. The data were qualitatively synthesized without quantitative pooling due to the heterogeneity in the study populations and methodologies.

PRINCIPAL FINDINGS

Thirty articles (9 from western Europe, 18 from central Europe and 3 from eastern Europe) were included in the analysis. All articles were cross-sectional studies (descriptive studies).

CONCLUSIONS

The highest seroprevalence of CCHF is found in central and eastern European countries. Southern and western Europe countries, such as Greece and Spain, have low levels of endemicity, but the spread of the infection, which is associated with climate change, is a possibility that we should keep in mind. Further studies, especially larger seroprevalence studies in humans and animals, are needed to establish the current status of the CCHF epidemiology and to generate standardized guidelines for action in the region.

Crimean-Congo haemorrhagic fever presenting with acute compartment syndrome of the extremities (think beyond normal infections)

Crimean-Congo haemorrhagic fever (CCHF) is a viral zoonosis transmitted to humans and animals (which act as a reservoir) through the bite of a 'Hyalomma' tick. CCHF virus belongs to the genus Nairovirus Humans are infected when they come in direct contact with the blood or secretions of infected livestock or other infected humans. This disease initially presents with non-specific febrile symptoms common to many viral illnesses and later progresses to disseminated intravascular coagulation (DIC) with haemorrhagic manifestations.We present the case of a middle-aged man with CCHF. He presented to the hospital with DIC and acute compartment syndrome in the right forearm, requiring urgent orthopaedic intervention. The diagnosis was delayed because there was no clear history of contact. The patient was started taking ribavirin on the fifth day of hospital admission. He recovered fully.

Survey of Crimean-Congo Hemorrhagic Fever Enzootic Focus, Spain, 2011-2015

During 2011–2015, we conducted a Crimean-Congo hemorrhagic fever virus (CCHFV) survey in captured ticks that were feeding mainly on wild and domestic ungulates in Spain, where presence of this virus had been reported previously. We detected CCHFV RNA in Hyalomma lusitanicum and H. marginatum ticks for 3 of the 5 years. The rate of infected ticks was 2.78% (44/1,579), which was similar to those for other countries in Europe with endemic foci for CCHFV (Kosovo, Bulgaria, and Albania). These data confirm the established spread of CCHFV into western Europe. Phylogenetic study of the small RNA segment showed Africa-3 clade as the only genotype identified, although we observed cocirculation of genetic variants during 2011 and 2015. We could not rule out genetic reassortments because of lack of sequence data for the medium and large RNA segments of the virus genome.

Evaluation of Crimean-Congo Hemorrhagic Fever Orthonairovirus AviTagged Nucleoprotein for Potential Application in Diagnosis

Background

Crimean-Congo hemorrhagic fever (CCHF) is an acute viral zoonotic disease, with a mortality rate of 30-50%. There is no approved vaccine or any specific antiviral treatment for CCHF; therefore, the rapid diagnosis seems to be crucial for both efficient supportive therapy and control of infection spread. In this study, the potency of recombinant nucleoprotein of virus expressed in prokaryotic system was investigated for diagnosis of the infection.

Methods

The DNA sequence of complete nucleoprotein ORF was codon optimized based on E. coli codon usage and synthesized commercially. The gene was subcloned in pCA4 vector and expressed in E. coli BL21 (DE3). Refolding and simultaneous purification of nucleoprotein were performed using protein folding liquid chromatography method. The recombinant nucleoprotein was analyzed by Western blotting, ELISA, immunofluorescence assay, and circular dichroism. Forty eight human samples, in three IgM positive and three negative control groups, were evaluated using recombinant nucleoprotein in a capture ELISA setting. Serum from healthy individuals, those suspected to viral hemorrhagic fevers, and positive samples of Chikungunya and Dengue were considered as negative controls.

Results

The existence and structure of recombinant nucleoprotein were verified and confirmed. Capture IgM ELISA detected all positive samples (sensitivity of 100%), but none of the 25 negative samples was detected as positive (specificity of 100%). The test also detected all the included genotypes of virus.

Discussion

Our recombinant nucleoprotein can be used in IgM capture ELISA for easy and efficient detection of CCHF in any lab in endemic regions.

Crimean-Congo hemorrhagic fever: An update

Crimean-Congo hemorrhagic fever (CCHF) is a severe form of hemorrhagic fever caused by a virus of the genus Nairovirus. The amplifying hosts are various mammal species that remain asymptomatic. Humans are infected by tick bites or contact with animal blood. CCHF has a broad geographic distribution and is endemic in Africa, Asia (in particular the Middle East) and South East Europe. This area has expanded in recent years with two indigenous cases reported in Spain in 2016 and 2018. The incubation period is short with the onset of symptoms in generally less than a week. The initial symptoms are common to other infectious syndromes with fever, headache, myalgia and gastrointestinal symptoms. The hemorrhagic syndrome occurs during a second phase with sometimes major bleeding in and from the mucous membranes and the skin. Strict barrier precautionary measures are required to prevent secondary and nosocomial spread. CCHF may be documented by PCR detection of the virus genome during the first days after the onset of illness, and then by serological testing for IgM antibodies as from the 2nd week after infection. Patient management is mainly based on supportive care. Despite a few encouraging retrospective reports, there is no confirmed evidence that supports the use of ribavirin for curative treatment. Nevertheless, the World Health Organization continues to recommend the use of ribavirin to treat CCHF, considering the limited medical risk related to short-term treatment. The prescription of ribavirin should however be encouraged post-exposure for medical professionals, to prevent secondary infection.

Development of Multispecies Recombinant Nucleoprotein-Based Indirect ELISA for High-Throughput Screening of Crimean-Congo Hemorrhagic Fever Virus-Specific Antibodies

Crimean-Congo hemorrhagic fever (CCHF) is a re-emerging zoonotic viral disease prevalent in many parts of Asia, Europe, and Africa. The causative agent, Crimean-Congo hemorrhagic fever orthonairovirus (CCHFV), is transmitted through hard ticks. Tick vectors especially belonging to the Hyalomma species serve as the reservoir and amplifying host. The vertebrate animals including sheep, goat, and bovine act as a short-lasting bridge linking the virus and ticks. CCHFV causes fatal hemorrhagic fever in humans. Humans are usually infected with CCHFV either through the bite of infected ticks or by close contact with infected animals. Immunological assays, primarily enzyme-linked immunosorbent assay (ELISA) using whole viral antigen, are widely used for serosurveillance in animals. However, the whole virus antigen poses a high biohazard risk and can only be produced in biosafety level 4 laboratories. The present study focuses on the development and evaluation of safe, sensitive, and specific IgG indirect enzyme-linked immunosorbent assay (iELISA) using recombinant nucleoprotein (NP) of CCHF virus as an antigen. The codon-optimized NP gene sequence was synthesized, cloned, and expressed in pET28a+ vector. The recombinant NP was purified to homogeneity by affinity chromatography and characterized through Western blot and MALDI-TOF/MS analysis. The characterized protein was used to develop an indirect IgG microplate ELISA using a panel of animal sera. The in-house ELISA was comparatively evaluated vis-à-vis a commercially available ELISA kit (Vector-Best, Russia) with 76 suspected samples that revealed a concordance of 90% with a sensitivity and specificity of 79.4 and 100%, respectively. The precision analysis revealed that the assay is robust and reproducible in different sets of conditions. Further, the assay was used for serosurveillance in ruminants from different regions of India that revealed 18% seropositivity in ruminants, indicating continued circulation of virus in the region. The findings suggest that the developed IgG iELISA employing recombinant NP is a safe and valuable tool for scalable high-throughput screening of CCHFV-specific antibodies in multiple species.

Hitit Index to distinguish patients with and without Crimean-Congo hemorrhagic fever

Crimean-Congo hemorrhagic fever (CCHF) is fatal. Therefore, it is very important to use an inexpensive, easily accessible, quick and accurate screening index based on clinical signs and laboratory parameters to identify patients suspected of having CCHF. Laboratory test results on the day of hospitalization for 268 inpatients suspected of having CCHF were used to calculate the laboratory section of the Hitit Index, while 65 of these were also monitored daily during their hospital stay to develop the clinical section of the Hitit Index. Two-hundred CCHF-negative outpatients were also evaluated. One-hundred and forty-nine inpatients were CCHF-positive and 119 inpatients were CCHF-negative. The Hitit Index is 5.6 - (5.3*lymphocyte) - (0.02*fibrinogen) - (12*direct bilirubin) + (0.04*AST) + (0.32*hematocrit) - (0.5*neutrophil) - (0.07*CKD-EPI) - (0.001*CK) ± conjunctival hyperemia (+1.5 in conjunctival hyperemia presence and -1.5 in conjunctival hyperemia absence). In 65 inpatients monitored daily, Hitit Index results for CCHF-positive and negative inpatients were 6.10(1.90-12.30) and -5.35(-8.83- -1.95), while CCHF-negative outpatients were -10.99(-15.64- -6.95) (P < 0.001), respectively. On hospitalization day, just one inpatient was false-negative in 27 CCHF-positive inpatients, while four were false-positive among 38 CCHF-negative inpatients using the Hitit Index. After 24 h, just one inpatient was diagnosed falsely among 27 CCHF-positive and 38 CCHF-negative inpatients, and there was no change after 48 h. Management of patients living in endemic regions suspected of having CCHF could be achieved within minutes using the Hitit Index. Patients with Hitit Index less than zero can be monitored as outpatients, while patients with Hitit Index results above zero must be hospitalized in infectious diseases wards. This study was not registered since it was retrospective.

Crimean-Congo Haemorrhagic Fever: Case study analysis of a sporadic outbreak from Chakwal, Pakistan

Crimean-Congo Haemorrhagic Fever (CCHF) is a deadly viral zoonotic disease, which is endemic in Pakistan. We report a case study analysis of three cases of CCHF which occurred in Chakwal, Pakistan in 2016. The disease was suspected in three patients exhibiting clinical symptoms suggestive of CCHF; two of the three patients died. The presence of CCHF was detected by seroconversion (IgG) from the surviving patient, while the antigen was detected in Hyalomma ticks originating from animals in the vicinity. This report indicates increase threat emergence of CCHF in Pakistan and highlights its zoonotic implications requiring immediate interventions under the "One-Health" concept.

Diagnostic approaches for Crimean-Congo hemorrhagic fever virus

Introduction: Crimean-Congo hemorrhagic fever (CCHF) is a potentially severe tick-borne viral disease endemic in several regions of Europe, Africa, and Asia. Rapid and reliable diagnosis is essential for early initiation of patient's treatment and for prompt implementation of appropriate precaution and infection control measures to prevent further spread of the disease. Areas covered: A literature search was undertaken on available approaches for laboratory diagnosis of CCHF infections, and the advantages and limitations of the assays are discussed. Expert opinion: Given that the genetic variability among CCHFV strains is high, attention has to be paid on the molecular protocols to detect all currently known genetic lineages of the virus as the emergence of CCHFV strains belonging to various lineages in new environments is not unexpected. In severe cases, the antibody production may be delayed or absent. It is important that the laboratories involved in CCHFV diagnostics to run quality control assays. Standardized assays and point-of-care tests with high sensitivity and specificity are needed. It is expected that the application of next-generation sequencing will be a powerful tool for CCHF diagnostics. Awareness, preparedness, and surveillance are required for prompt detection of CCHF cases.

Diagnostic tests for Crimean-Congo haemorrhagic fever: a widespread tickborne disease

Crimean-Congo haemorrhagic fever (CCHF) is a widespread tickborne disease that circulates in wild and domestic animal hosts, and causes severe and often fatal haemorrhagic fever in infected humans. Due to the lack of treatment options or vaccines, and a high fatality rate, CCHF virus (CCHFV) is considered a high-priority pathogen according to the WHO R&D Blueprint. Several commercial reverse transcriptase PCR (RT-PCR) and serological diagnostic assays for CCHFV are already available, including febrile agent panels to distinguish CCHFV from other viral haemorrhagic fever agents; however, the majority of international laboratories use inhouse assays. As CCHFV has numerous amplifying animal hosts, a cross-sectoral 'One Health' approach to outbreak prevention is recommended to enhance notifications and enable early warning for genetic and epidemiological shifts in the human, animal and tick populations. However, a lack of guidance for surveillance in animals, harmonisation of case identification and validated serodiagnostic kits for animal testing hinders efforts to strengthen surveillance systems. Additionally, as RT-PCR tests tend to be lineage-specific for regional circulating strains, there is a need for pan-lineage sensitive diagnostics. Adaptation of existing tests to point-of-care molecular diagnostic platforms that can be implemented in clinic or field-based settings would be of value given the potential for CCHFV outbreaks in remote or low-resource areas. Finally, improved access to clinical specimens for validation of diagnostics would help to accelerate development of new tests. These gaps should be addressed by updated target product profiles for CCHFV diagnostics.

Crimean-Congo hemorrhagic fever and expansion from endemic regions

Crimean-Congo hemorrhagic fever (CCHF) is a virus-mediated hemorrhagic disease that occurs over a wide geographic region. In recent years, a variety of active and passive surveillance networks have improved our knowledge of areas with existing circulation of Crimean-Congo hemorrhagic fever virus (CCHFV), the etiologic agent of CCHF. These investigations aid in better defining the distribution of the virus. Expansion of a virus into new areas can occur through a variety of means, including introduction of infected humans, vectors, or animals. Here, these potential contributors to expansion of CCHFV into neighboring countries and geographically distant locations are reviewed, and the likelihood and possible implications of these events, based on known characteristics of the virus and its natural maintenance and transmission cycles are explored. Furthermore, this report discusses limitations in the currently described distribution of CCHFV, and the challenges in assessing viral circulation identified in a new region as geographic expansion of the virus.

Evaluation of first rapid diagnostic kit for Anti-Crimean-Congo Hemorrhagic Fever virus IgM antibody using clinical samples from Iran

Crimean-Congo Hemorrhagic Fever (CCHF) is a potentially fatal tick-borne viral disease, which is in the WHO list for emerging infections likely to cause major epidemics in the near future. Early diagnosis of CCHF is very important for both patient treatment and infection control. An efficient CCHF rapid test therefore is of great significance. This study was conducted to evaluate the sensitivity and specificity of the first CCHF rapid diagnostic kit (CCHF Sero K-SeT, CORIS BioConcept, Belgium) for detection of IgM specific antibody in patients' sera or plasma, using 87 clinical serum samples from Iranian patients. Although the assay showed an acceptable specificity of 92.9% (13/14), a low sensitivity rate of 39.7% (29/73) was observed. There was no association between the results of CCHF rapid diagnostic kit and the genotype of CCHF virus. This evaluation revealed that the CCHF Sero K-SeT is not suitable for screening of CCHF suspected cases due to its poor sensitivity.

Sequence Optimized Real-Time Reverse Transcription Polymerase Chain Reaction Assay for Detection of Crimean-Congo Hemorrhagic Fever Virus

Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne virus of the genus Nairovirus within the family Bunyaviridae. Infection can result in general myalgia, fever, and headache with some patients developing hemorrhagic fever with mortality rates ranging from 5% to 30%. CCHFV has a wide geographic range that includes Africa, Asia, the Middle East, and Europe with nucleotide sequence variation approaching 20% across the three negative-sense RNA genome segments. While phylogenetic clustering generally aligns with geographic origin of individual strains, distribution can be wide due to tick/CCHFV dispersion via migrating birds. This sequence diversity negatively impacts existing molecular diagnostic assays, leading to false negative diagnostic results. Here, we updated a previously developed CCHFV real-time reverse transcription polymerase chain reaction (RT-PCR) assay to include strains not detected using that original assay. Deep sequencing of eight different CCHFV strains, including three that were not detectable using the original assay, identified sequence variants within this assay target region. New primers and probe based on the sequencing results and newly deposited sequences in GenBank greatly improved assay sensitivity and inclusivity with the exception of the genetically diverse strain AP92. For example, we observed a four log improvement in IbAr10200 detection with a new limit of detection of 256 PFU/mL. Subsequent comparison of this assay to another commonly used CCHFV real-time RT-PCR assay targeting a different region of the viral genome showed improved detection, and both assays could be used to mitigate CCHFV diversity for diagnostics. Overall, this work demonstrated the importance of continued viral sequencing efforts for robust diagnostic assay development.

Epitope-mapping of the glycoprotein from Crimean-Congo hemorrhagic fever virus using a microarray approach

Crimean-Congo hemorrhagic fever virus (CCHFV) causes severe acute human disease with lethal outcome. The knowledge about the immune response for this human health threat is highly limited. In this study, we have screened the glycoprotein of CCHFV for novel linear B-cell epitopic regions using a microarray approach. The peptide library consisted of 168 synthesized 20mer peptides with 10 amino acid overlap covering the entire glycoprotein. Using both pooled and individual human sera from survivors of CCHF disease in Turkey five peptide epitopes situated in the mucin-like region and GP 38 (G15-515) and G_N G516-1037 region of the glycoprotein were identified as epitopes for a CCHF immune response. An epitope walk of the five peptides revealed a peptide sequence located in the G_N region with high specificity and sensitivity. This peptide sequence, and a sequence downstream, reacted also against sera from survivors of CCHF disease in South Africa. The cross reactivity of these peptides with samples from a geographically distinct region where genetically diverse strains of the virus circulate, enabled the identification of unique peptide epitopes from the CCHF glycoprotein that could have application in development of diagnostic tools. In this study clinical samples from geographically distinct regions were used to identify conserved linear epitopic regions of the glycoprotein of CCHF.

Crimean-Congo hemorrhagic fever (CCHF) is a widespread disease caused by a tick-borne virus belonging to the genus Orthonairovirus of the Nairoviridae family. The virus is responsible for outbreaks of severe viral hemorrhagic fever with a case fatality rate of approximately 30%. The CCHF virus is transmitted to people either by tick bites or through contact with infected animal blood or tissues. A mouse brain-derived vaccine against CCHF has been developed (included in this study) and used on a small scale in eastern Europe. There is no safe and effective vaccine widely available for human use. Currently, there are a limited number of serological assays commercially available for testing for CCHFV specific IgG and IgM. There are enzyme linked immunosorbent assays (ELISA) and imunnofluorescent assays (IFA) designed for screening human samples for diagnostic purposes however they are not cost effective for surveillance studies. The limiting factor for the replication of these protocols in other laboratories is the availability of antigens and (where relevant) specified monoclonal antibodies. To contribute to the improvement of the diagnostic methods for CCHFV, we aimed to identify and characterize new synthetic antigens that were more sensitive and specific and could be applied in epidemiologic surveys.

The Development of a Novel Diagnostic Assay That Utilizes a Pseudotyped Vesicular Stomatitis Virus for the Detection of Neutralizing Activity against Crimean-Congo Hemorrhagic Fever Virus

Crimean-Congo hemorrhagic fever virus is a risk group 4 pathogen, which mandates the use of maximum containment facilities, often termed biosafety level 4 or containment level 4 when working with infectious materials. Diagnostic and research work involving live viruses in such laboratories is time-consuming and inconvenient, resulting in delays. Herein, we show that serum neutralizing activity against the virus can be measured in low-containment laboratories using a pseudotyped virus.

Sensitive and specific detection of Crimean-Congo Hemorrhagic Fever Virus (CCHFV)-Specific IgM and IgG antibodies in human sera using recombinant CCHFV nucleoprotein as antigen in μ-capture and IgG immune complex (IC) ELISA tests

As the most widespread tick-borne arbovirus causing infections in numerous countries in Asia, Africa and Europe, Crimean-Congo Hemorrhagic Fever Virus (CCHFV, family Nairoviridae) was included in the WHO priority list of emerging pathogens needing urgent Research & Development attention. To ensure preparedness for potential future outbreak scenarios, reliable diagnostic tools for identification of acute cases as well as for performance of seroprevalence studies are necessary. Here, the CCHFV ortholog of the major bunyavirus antigen, the nucleoprotein (NP), was recombinantly expressed in E.coli, purified and directly labeled with horseradish peroxidase (HRP). Employing this antigen, two serological tests, a μ-capture ELISA for the detection of CCHFV-specific IgM antibodies (BLACKBOX CCHFV IgM) and an IgG immune complex (IC) ELISA for the detection of CCHFV-specific IgG antibodies (BLACKBOX CCHFV IgG), were developed. Test performance was evaluated and compared with both in-house gold standard testing by IgM/IgG indirect immunofluorescence (IIF) and commercially available ELISA tests (VectoCrimean-CHF-IgM/IgG, Vector-Best, Russia) using a serum panel comprising paired samples collected in Kosovo during the years 2013–2016 from 15 patients with an acute, RT-PCR-confirmed CCHFV infection, and 12 follow-up sera of the same patients collected approximately one year after having overcome the infection. Reliably detecting IgM antibodies in all acute phase sera collected later than day 4 after onset of symptoms, both IgM ELISAs displayed excellent diagnostic and analytical sensitivity (100%, 95% confidence interval (CI): 85.2%–100.0%). While both IgG ELISAs readily detected the high IgG titers present in convalescent patients approximately one year after having overcome the infection (sensitivity 100%, 95% CI: 73.5%–100.0%), the newly developed BLACKBOX CCHFV IgG ELISA was superior to the commercial IgG ELISA in detecting the rising IgG titers during the acute phase of the disease. While all samples collected between day 11 and 19 after onset of symptoms tested positive in both the in-house gold standard IIFT and the BLACKBOX CCHFV IgG ELISA (sensitivity 100%, 95% CI: 71.5%–100.0%), only 27% (95% CI: 6.0%–61.0%) of those samples were tested positive in the commercial IgG ELISA. No false positive signals were observed in either IgM/IgG ELISA when analyzing a priori CCHFV IgM/IgG negative serum samples from healthy blood donors, malaria patients and flavivirus infected patients as well as CCHFV IgM/IgG IIFT negative serum samples from healthy Kosovar blood donors (for BLACKBOX CCHFV IgM/IgG: n = 218, 100% specificity, 95% CI: 98.3%–100.0%, for VectoCrimean-CHF-IgM/IgG: n = 113, 100% specificity, 95% CI: 96.8%–100.0%).

Being endemic in several countries in Asia, Africa, the Middle East and Southeastern Europe, the Crimean-Congo Hemorrhagic Fever Virus (CCHFV) is the geographically most widespread tick-borne arbovirus. As evidenced by the recent occurrence of an autochthonous CCHFV infection in Spain, it possesses also a significant potential to spread to as yet non-endemic regions. Due to the severity of the disease caused by this bunyavirus, the lack of specific prophylactic and therapeutic measures and the infection’s epidemic potential, CCHFV was included in the WHO priority list of diseases needing urgent R&D attention, in particular the development and improvement of diagnostic tools. Here we present the development and validation of two novel ELISAs (BLACKBOX CCHFV IgM, BLACKBOX CCHFV IgG) for the detection of CCHFV-specific IgM and IgG antibodies employing recombinant CCHFV nucleoprotein (NP) as antigen. Test performance in comparison to both in-house gold standard testing (CCHFV IgM/IgG immunofluorescence test (IIFT)) and commercial ELISA kits (VectoCrimean-CHF-IgM/IgG; Vector-Best) was evaluated using a thoroughly characterized serum panel that was obtained from 15 Kosovar patients with an RT-PCR-confirmed CCHFV-infection collected during the years 2013–2016 and that comprised samples from both the acute and convalescent phase of the disease. While both IgM ELISAs, like the CCHFV IgM IIFT, detected CCHFV-specific IgM antibodies in all sera collected during the acute phase of the disease on day 5 after onset of symptoms or later, the BLACKBOX CCHFV IgG ELISA and the CCHFV IgG IIFT were found to be significantly more sensitive than the VectoCrimean-CHF-IgG ELISA in detecting the rising IgG antibody titers in samples collected between days 11 and 19 after onset of symptoms.

The protective effect and diagnostic performance of NOX-5 in Crimean-Congo haemorrhagic fever patients

INTRODUCTION

Crimean-Congo haemorrhagic fever (CCHF) is an acute viral haemorrhagic disease. Reactive oxygen species that are mainly generated by the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) enzyme family have a pivotal role in the pathophysiology of many diseases. The serum levels of NOX isoforms in patients with CCHF have yet to be assessed.

METHODS

This prospective study was conducted at Cumhuriyet University, Turkey. Only patients with CCHF confirmed by the National Reference Virology Laboratory were enrolled in the study. The study subjects comprised 67 CCHF patients and 70 healthy control subjects. The quantitative sandwich ELISA technique was used for the determination of serum NOX 1, 2, 4 and 5.

RESULTS

Higher median median NOX-1 (P=0.001) and NOX-5 (P<0.001) levels were found in patients compared to the control group. Higher median serum NOX-5 levels were found in the low-grade disease group compared to the intermediate-high disease group according to two different severity scores (P=0.003). Negative correlations were also found between the serum NOX-5 levels and the severity scores [(P<0.05, r=-0.259), (P<0.01, r=-0.417)]. The area under the curve (AUC) values for the NOX-1 and NOX-5 were 0.67 (confidence interval: 0.58-0.75) and 0.99 (confidence interval: 0.95-1.00), respectively. Lower NOX-5 levels were found in patients receiving thrombocyte suspension (P=0.004)Conclusions. NOX-5 may have a protective effect on CCHF patients and the measurement of serum NOX-5 levels may be used as a novel biochemical test in the diagnosis of CCHF.

Long-lived CD8+ T cell responses following Crimean-Congo haemorrhagic fever virus infection

Crimean-Congo haemorrhagic fever virus (CCHFV) is a member of the Orthonairovirus genus of the Nairoviridae family and is associated with haemorrhagic fever in humans. Although T lymphocyte responses are known to play a role in protection from and clearance of viral infections, specific T cell epitopes have yet to be identified for CCHFV following infection. A panel of overlapping peptides covering the CCHFV nucleoprotein and the structural glycoproteins, GN and GC, were screened by ELISpot assay to detect interferon gamma (IFN-γ) production in vitro by peripheral blood mononuclear cells from eleven survivors with previous laboratory confirmed CCHFV infection. Reactive peptides were located predominantly on the nucleoprotein, with only one survivor reacting to two peptides from the glycoprotein GC. No single epitope was immunodominant, however all but one survivor showed reactivity to at least one T cell epitope. The responses were present at high frequency and detectable several years after the acute infection despite the absence of continued antigenic stimulation. T cell depletion studies confirmed that IFN-γ production as detected using the ELISpot assay was mediated chiefly by CD8+ T cells. This is the first description of CD8+ T cell epitopic regions for CCHFV and provides confirmation of long-lived T cell responses in survivors of CCHFV infection.

Serosurvey of Crimean-Congo Hemorrhagic Fever Virus in Cattle, Mali, West Africa

AbstractCrimean-Congo hemorrhagic fever is a tick-borne disease caused by the arbovirus Crimean-Congo hemorrhagic fever virus (CCHFV, family Bunyaviridae, genus Nairovirus). CCHFV can cause a severe hemorrhagic fever with high-case fatality rates in humans. CCHFV has a wide geographic range and has been described in around 30 countries in the Middle East, Asia, Europe, and Africa including Mali and neighboring countries. To date, little is known about the prevalence rates of CCHFV in Mali. Here, using banked bovine serum samples from across the country, we describe the results of a seroepidemiological study for CCHFV aimed at identifying regions of circulation in Mali. In total, 1,074 serum samples were tested by a modified in-house CCHFV-IgG-enzyme-linked immunosorbent assay (ELISA) with confirmatory testing by commercial ELISA and immunofluorescence assay. Overall, 66% of samples tested were positive for CCHFV-specific IgG antibodies. Regional seroprevalence rates ranged from 15% to 95% and seemed to correlate with cattle density. Our results demonstrate that CCHFV prevalence is high in many regions in Mali and suggest that CCHFV surveillance should be established.

Plant-produced Crimean-Congo haemorrhagic fever virus nucleoprotein for use in indirect ELISA

Crimean-Congo haemorrhagic fever (CCHF) is a disease of serious public concern caused by the CCHF virus (CCHFV). Anti-CCHFV IgG in humans can be detected using ELISA with native antigen prepared from cell cultures which have been infected with virus or from brain tissue of suckling mice which have been inoculated with virus. However, the preparation of these reagents requires high biosafety levels and is expensive. A safer, more cost-effective recombinantly-produced NP reagent is desirable. Recently, plants have been shown to be a cost-effective and safe system for expression of recombinant proteins. This work describes cloning of the CCHFV NP gene into three different plant expression systems and comparison of expression in Nicotiana benthamiana. The highest expressing construct was selected. Expressed NP was purified by ammonium sulphate fractionation prior to histidine affinity chromatography. Purified NP was tested in an indirect ELISA to determine if the recombinant antigen was able to detect anti-CCHFV IgG in sera from convalescent patients. Plant-produced NP detected IgG antibodies against CCHFV in 13/13 serum samples from convalescent patients and 0/13 samples collected from volunteers with no history of CCHFV infection. Results were compared with commercially available immunofluorescent assays and 100% concordance was obtained between the two assays. This suggests that a full evaluation of the plant produced NP for application as a safe recombinant is warranted.

Crimean-Congo Hemorrhagic Fever Knowledge, Attitudes, Practices, Risk Factors, and Seroprevalence in Rural Georgian Villages with Known Transmission in 2014

In 2014 the highest annual case count of Crimean-Congo hemorrhagic fever (CCHF) was detected in Georgia since surveillance began in 2009. CCHF is a high-fatality hemorrhagic syndrome transmitted by infected ticks and animal blood. In response to this immediate public health threat, we assessed CCHF risk factors, seroprevalence, and CCHF-related knowledge, attitudes, and practices in the 12 rural villages reporting a 2014 CCHF case, to inform CCHF prevention and control measures. Households were randomly selected for interviewing and serum sample collection. Data were weighted by non-response and gender; percentages reflect weighting. Among 618 respondents, median age was 54.8 years (IQR: 26.5, range: 18.6–101.4); 215 (48.8%) were male. Most (91.5%) participants reported ≥1 CCHF high-risk activity. Of 389 participants with tick exposure, 286 (46.7%) participants handled ticks bare-handed; 65/216 (29.7%) knew the risk. Of 605 respondents, 355 (57.9%) reported animal blood exposure; 32/281 (12.7%) knew the risk. Of 612 responding, 184 (28.8%) knew protective measures against CCHF and tick exposures, but only 54.3% employed the measures. Of 435 serum samples collected, 12 were anti-CCHF IgG positive, indicating a weighted 3.0% seroprevalence. Most (66.7%) seropositive subjects reported tick exposure. In these villages, CCHF risk factors are prevalent, while CCHF-related knowledge and preventive practices are limited; these findings are critical to informing public health interventions to effectively control and prevent ongoing CCHF transmission. Additionally, CCHF seroprevalence is higher than previously detected (0.03%), highlighting the importance of this disease in the South Caucuses and in supporting ongoing regional investigations.

Current situation of Crimean-Congo hemorrhagic fever in Southeastern Europe and neighboring countries: a public health risk for the European Union?

Crimean-Congo hemorrhagic fever (CCHF) is the most widespread tick-borne viral infection of humans, occurring across western China through southern Asia, Middle East, and Southeastern Europe (SEE) and in the most of African countries. CCHF virus is maintained through vertical and horizontal transmission in several genera of ticks, mainly in Hyalomma, which spreads the virus to a variety of wild and domestic mammals, which develop a transient viremia without signs of illness. Human infections occur through tick bite or exposure to the blood or other body fluids of an infected animal or of a CCHF patient. In SEE the number of clinical cases of CCHF as well as the areal of the infected ticks continuously rapidly increased after 2000. The aim of this study was to present actual situation of CCHF in SEE. Sources of information include published literature and personal unpublished data.

CONCLUSIONS

Based on: 1. Hyaloma's presence in Western EU countries, 2. Changes in climatic conditions and 3. Absence of an active vaccination against CCHF, it can be expected that this disease will continue to present real threat for human health in SEE and Southwestern Europe (SWE).

Crimean-Congo hemorrhagic fever in Turkey: Current status and future challenges

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne viral disease of humans that affects a wide geographic area of Africa and Eurasia, including Turkey, Iran, Pakistan, Afghanistan and Russia. Since the first detection of CCHF cases in Turkey in 2002, more than 9700 patients have been reported, with an overall mortality rate just under 5%. This article assesses the present epidemiological situation of CCHF in Turkey, with an updated literature review, describes national practices and summarizes lessons learned in preparation for future outbreaks.

Crimean-Congo hemorrhagic fever: Risk factors and control measures for the infection abatement

Crimean-Congo hemorrhagic fever (CCHF) is a vector-borne viral disease, widely distributed in different regions of the world. The fever is caused by the CCHF virus (CCHFV), which belongs to the Nairovirus genus and Bunyaviridae family. The virus is clustered in seven genotypes, which are Africa-1, Africa-2, Africa-3, Europe-1, Europe-2, Asia-1 and Asia-2. The virus is highly pathogenic in nature, easily transmissible and has a high case fatality rate of 10-40%. The reservoir and vector of CCHFV are the ticks of the Hyalomma genus. Therefore, the circulation of this virus depends upon the distribution of the ticks. The virus can be transmitted from tick to animal, animal to human and human to human. The major symptoms include headache, high fever, abdominal pain, myalgia, hypotension and flushed face. As the disease progresses, severe symptoms start appearing, which include petechiae, ecchymosis, epistaxis, bleeding gums and emesis. Enzyme-linked immunosorbent assay, quantitative polymerase chain reaction, antigen detection, serum neutralization and isolation of the virus by cell culture are the diagnostic techniques used for this viral infection. There is no specific antiviral therapy available thus far. However, ribavirin has been approved by the World Health Organization for the treatment of CCHFV infection. Awareness campaigns regarding the risk factors and control measures can aid in reducing the spread of this disease to a greater extent, particularly in developing countries.

Diagnosis of Crimean-Congo hemorrhagic fever

Crimean-Congo hemorrhagic fever (CCHF) virus is the most extensive tick-borne virus, it causes a severe infection, which occurs widely in Africa, Eastern Europe and Asia. In recent years, the dramatic increase in the global distribution of CCHF, with the high mortality rates, highlights the importance of improving diagnostic capacity. Clinical and epidemiological data play a crucial role for early recognition of CCHF. However, CCHF is clinically difficult to diagnose and to distinguish, a rapid and reliable laboratory confirmation is necessary. Confirmation of infection in the acute phase of the disease can be made by detection of viral nucleic acid using reverse transcription-PCR, by demonstration of viral antigen or by virus isolation. In the convalescent phase of the disease, the diagnosis is confirmed by demonstration of an antibody response. The consideration of viral replication kinetics and antiviral humoral immune responses facilitates the selection of appropriate laboratory tests and accurate interpretation of laboratory findings.

Molecular and serological findings in suspected patients with Crimean-Congo hemorrhagic fever virus in Iran

Crimean-Congo hemorrhagic fever (CCHF) is an arthropod-borne disease of humans associated with a severe clinical picture, including hemorrhagic syndrome and a high mortality rate. CCHF virus is widely distributed throughout large areas of the world. To characterize the serological status in CCHF patients, paired clinical samples were collected from suspected CCHF patients and analyzed by microbiological and other laboratory analyses with the aim of: determining the presence of neutralizing antibodies against CCHF virus; investigating the cross-reactivity of these neutralizing antibodies against virus isolated from the same outbreak and against other available laboratory strain; and studying the relationship between the isolated virus with other virus by whole genome sequencing. Patients at Boo-Ali Hospital, Zahedan, Iran, with clinical symptoms ranging from mild to severe hemorrhagic fever were included in the study. Two serum samples were taken from each patient, the first as soon as the patient matched the criteria for CCHF notification and the second when the patient was discharged from hospital (2 weeks later). Commercial and in-house assays revealed a positive IgM signal in acute serum samples from six patients. A novel finding was that CCHF patients develop neutralizing antibodies soon after infection. Interestingly these antibodies were able to neutralize other CCHF virus strains too. The complete sequence of the Zahedan 2007 isolate, including the hitherto unknown first L-segment sequence, was identified using an original clinical sample from one patient with confirmed CCHF infection.

Single-Stranded RNA Viruses

In this chapter, we describe 73 zoonotic viruses that were isolated in Northern Eurasia and that belong to the different families of viruses with a single-stranded RNA (ssRNA) genome. The family includes viruses with a segmented negative-sense ssRNA genome (families Bunyaviridae and Orthomyxoviridae) and viruses with a positive-sense ssRNA genome (families Togaviridae and Flaviviridae). Among them are viruses associated with sporadic cases or outbreaks of human disease, such as hemorrhagic fever with renal syndrome (viruses of the genus Hantavirus), Crimean–Congo hemorrhagic fever (CCHFV, Nairovirus), California encephalitis (INKV, TAHV, and KHATV; Orthobunyavirus), sandfly fever (SFCV and SFNV, Phlebovirus), Tick-borne encephalitis (TBEV, Flavivirus), Omsk hemorrhagic fever (OHFV, Flavivirus), West Nile fever (WNV, Flavivirus), Sindbis fever (SINV, Alphavirus) Chikungunya fever (CHIKV, Alphavirus) and others. Other viruses described in the chapter can cause epizootics in wild or domestic animals: Geta virus (GETV, Alphavirus), Influenza A virus (Influenzavirus A), Bhanja virus (BHAV, Phlebovirus) and more. The chapter also discusses both ecological peculiarities that promote the circulation of these viruses in natural foci and factors influencing the occurrence of epidemic and epizootic outbreaks

Prevalence of Crimean-Congo hemorrhagic fever virus in healthy population, livestock and ticks in Kosovo

Crimean-Congo hemorrhagic fever (CCHF) is an acute, tick borne disease often associated with hemorrhagic presentations and high case fatality rate. Kosovo is a highly endemic area for CCHF, with a significant case fatality rate. The aim of our study was to determine the prevalence of CCHF in Kosovo. We tested 1105 serum samples from healthy population in both endemic and non-endemic areas in the country. Our results revealed a seroprevalence of 4.0% (range 0-9.3%) which is comparable to the seroprevalence in other countries. We show that seroprevalence is correlated to the disease incidence in each studied municipality. We also tested 401 animal sera (353 cow, 30 sheep, 10 goat and 8 chicken) in four endemic municipalities in Kosovo. We detected specific antibodies in all animals except in chicken. Seroprevalence in cows is comparable to other endemic areas and correlates to the seroprevalence in humans. No CCHF RNA could be detected in 105 tick samples obtained in 2012 and 2013. Sequencing of CCHFV positive ticks from 2001 revealed that the virus is most closely related to viral strains that were detected in CCHF patients from Kosovo. Results suggest that mild CCHF cases are most probably underdiagnosed and consequently that the burden of disease is higher than reported. Our study provides key information for CCHF surveillance and raises awareness for possible imported cases in CCHF non-endemic countries.