Seroprevalence and risk factors of Crimean-Congo hemorrhagic fever in selected seven provinces in Turkey

Seroprevalence of Crimean Congo Hemorrhagic Fever Virus in Occupational Settings: Systematic Review and Meta-Analysis

Crimean Congo Hemorrhagic Fever (CCHF) Virus can cause a serious human disease, with the case fatality ratio previously estimated to be 30-40%. Our study summarized seroprevalence data from occupational settings, focusing on the following occupational groups: animal handlers, abattoir workers, farmers, healthcare workers, veterinarians, rangers, and hunters. Systematic research was performed on three databases (PubMed, EMBASE, MedRxiv), and all studies reporting seroprevalence rates (IgG-positive status) for CCHF virus were retrieved and their results were reported, summarized, and compared. We identified a total of 33 articles, including a total of 20,195 samples, i.e., 13,197 workers from index occupational groups and 6998 individuals from the general population. Pooled seroprevalence rates ranged from 4.751% (95% confidence intervals (95% CI) 1.834 to 11.702) among animal handlers, to 3.403% (95% CI 2.44 to 3.932) for farmers, 2.737% (95% CI 0.896 to 8.054) among rangers and hunters, 1.900% (95% CI 0.738 to 4.808) for abattoir workers, and 0.644% (95% CI 0.223-1.849) for healthcare workers, with the lowest estimate found in veterinarians (0.283%, 95% CI 0.040-1.977). Seroprevalence rates for abattoir workers (odds ratio (OR) 4.198, 95% CI 1.060-16.464), animal handlers (OR 2.399, 95% CI 1.318-4.369), and farmers (OR 2.280, 95% CI 1.419 to 3.662) largely exceeded the official notification rates for CCHF in the general population. CCHF is reasonably underreported, and pooled estimates stress the importance of improving the adherence to personal protective equipment use and appropriate preventive habits.

Crimean-Congo Hemorrhagic Fever Virus: Progress in Vaccine Development

Crimean-Congo hemorrhagic fever virus (CCHFV), a member of the Nairoviridae family and Bunyavirales order, is transmitted to humans via tick bites or contact with the blood of infected animals. It can cause severe symptoms, including hemorrhagic fever, with a mortality rate between 5 to 30%. CCHFV is classified as a high-priority pathogen by the World Health Organization (WHO) due to its high fatality rate and the absence of effective medical countermeasures. CCHFV is endemic in several regions across the world, including Africa, Europe, the Middle East, and Asia, and has the potential for global spread. The emergence of the disease in new areas, as well as the presence of the tick vector in countries without reported cases, emphasizes the need for preventive measures to be taken. In the past, the lack of a suitable animal model susceptible to CCHFV infection has been a major obstacle in the development of vaccines and treatments. However, recent advances in biotechnology and the availability of suitable animal models have significantly expedited the development of vaccines against CCHF. These advancements have not only contributed to an enhanced understanding of the pathogenesis of CCHF but have also facilitated the evaluation of potential vaccine candidates. This review outlines the immune response to CCHFV and animal models utilized for the study of CCHFV and highlights the progress made in CCHFV vaccine studies. Despite remarkable advancements in vaccine development for CCHFV, it remains crucial to prioritize continued research, collaboration, and investment in this field.

Crimean-Congo haemorrhagic fever virus

Crimean-Congo haemorrhagic fever (CCHF) is a severe tick-borne illness with a wide geographical distribution and case fatality rates of 30% or higher. Caused by infection with the CCHF virus (CCHFV), cases are reported throughout Africa, the Middle East, Asia and southern and eastern Europe. The expanding range of the Hyalomma tick vector is placing new populations at risk for CCHF, and no licensed vaccines or specific antivirals exist to treat CCHF. Furthermore, despite cases of CCHF being reported annually, the host and viral determinants of CCHFV pathogenesis are poorly understood. CCHFV can productively infect a multitude of animal species, yet only humans develop a severe illness. Within human populations, subclinical infections are underappreciated and may represent a substantial proportion of clinical outcomes. Compared with other members of the Bunyavirales order, CCHFV has a more complex genomic organization, with many viral proteins having unclear functions in viral pathogenesis. In recent years, improved animal models have led to increased insights into CCHFV pathogenesis, and several antivirals and vaccines for CCHFV have shown robust efficacy in preclinical models. Translation of these insights and candidate therapeutics to the clinic will hopefully reduce the morbidity and mortality caused by CCHFV.

The spatial pattern of human exposure to Crimean-Congo haemorrhagic fever virus is not consistent with red deer-based risk predictions

The objective of this study was to evaluate the spatial risk of exposure to Crimean-Congo haemorrhagic fever virus (CCHFV) infection of healthy blood donors in an enzootic region with a predicted risk gradient based on a virus-animal interaction risk model. We designed a cross-sectional study to test if the exposure pattern of the human population to CCHFV spatially matches the predicted risk. We randomly selected 1384 donors from different risk gradients and analyzed their sera searching for CCHFV antibodies. None of the selected blood donors showed exposure to CCHFV. This study shows that exposure risk spatial patterns, as predicted from animal-tick-virus models, does not necessarily match the pattern of human-infected tick interactions leading to CCHFV infection and CCHF cases, at least in a region of predicted moderate infection risk. The findings suggest that future studies should bear the potential drivers of tick-human encounter rates into account to more accurately predict risks.

Crimean-Congo Hemorrhagic Fever in Differential Diagnosis During the Coronavirus Disease-2019 Pandemic

OBJECTIVE

Crimean-Congo Hemorrhagic Fever (CCHF) is a disease of the viral hemorrhagic fever group and is endemic in certain regions in Turkey. Here, the demographic, clinical, and laboratory findings of patients diagnosed with CCHF during the Coronavirus disease-2019 (COVID-19) pandemic were examined, and differential diagnosis was stressed.

METHODS

This study comprised 12 patients over the age of 18 who were admitted to our clinic after the onset of the COVID-19 pandemic on March 11, 2020 and whose CCHF diagnosis was confirmed by reverse transcription-polymerase chain reaction with viral-RNA or enzyme-linked immunosorbent assay with immunoglobulin M antibodies. Epidemiological, clinical, and laboratory findings as well as treatment and prognosis of the patients were investigated.

RESULTS

Of the 12 cases, 10 (83.3%) were men and 2 (16.7%) were women. The median (interquartile range) age was 51 (27-64) years. Eleven (91.7%) patients lived in rural regions, and seven (58.3%) had a history of tick contact. Five patients were hospitalized in an external center with a preliminary diagnosis of COVID-19 and transferred to our center due to clinical and laboratory deterioration. Loss of appetite, headache, fever, weakness, and muscle-joint pain were the most common complaints of the patients. Following the suspicion of COVID-19, thoracic computed tomography (CT) was performed in six patients, five of whom were transferred to an external center. None of the patients had any pathological findings following thoracic CT.

CONCLUSION

Although it is thought that the COVID-19 pandemic will end in the following months owing to vaccine applications, it can be predicted that sporadic cases will still occur for a long time. Therefore, clinicians should take CCHF into consideration in their differential diagnosis. Also, it should be remembered that co-infections can be observed in endemic areas.

Determination of Seroprevalence and Risk Factors of Crimean-Congo Haemorrhagic Fever (CCHF) in the Endemic Region in Turkey: A Population-Based Cross-Sectional Study

Objectives

Turkey is one of the countries that has the most cases of CCHF in recent years among the endemic countries. The disease also poses an important health threat with high mortality rate. The aim of the study was to determine the seroprevalence and risk factors of CCHF in adults aged ≥20 years in Tokat in the endemic region, Turkey.

Methods

In this population-based cross-sectional study, a total of 85 Family Medicine Units (FMUs), from over 170 in Tokat, were randomly selected using 50% sampling. The sample size was determined among the subjects aged ≥20 who registered with the FMUs, due to gender, age group, and the urban/rural population size of Tokat using the stratified cluster sampling method. Subjects were invited to the FMUs. A questionnaire was performed face to face. The blood samples were taken, and anti-CCHFV IgG antibodies were measured with ELISA method.

Results

1272 (54.9%) out of 2319 participants were female, and the mean age was 47.3 ± 15.3. Anti-CCHFV IgG seropositivity was 5.6% (n = 130). Seropositivity rates in terms of adjusted odds ratios (AOR) were higher 2.53 times (95% CI: 1.57–4.08; p=0.001) in males; 4.05 (95% CI: 2.14–7.65; p < 0.001) in age group ≥65; 0.33 (95% CI: 0.14–0.76; p < 0.001) in graduates of high school and above; 0.71 (95%CI: 0.33–1.52; p < 0.001) in ones with good income; 1.84 (95%CI: 1.18–2.86; p < 0.001) in farmers; 1.64 (95% CI: 1.04–2.27; p < 0.001) in people dealing with animal husbandry; and 1.02 (95% CI: 1.03–2.29; p < 0.001) in those with history of tick contact.

Conclusions

CCHF seroprevalence is still a common public health problem in Tokat, Turkey. Male gender, advanced age group, low-educated, low-income, farmers, animal husbandry, and history of tick contact were found to be risk factors for CCHF. The importance of this kind of community-based studies to identify the seroprevalence in regional and national level increases even more.

Sporadic outbreaks of crimean-congo haemorrhagic fever in Uganda, July 2018-January 2019

Introduction

Crimean-Congo haemorrhagic fever (CCHF) is a tick-borne, zoonotic viral disease that causes haemorrhagic symptoms. Despite having eight confirmed outbreaks between 2013 and 2017, all within Uganda’s ‘cattle corridor’, no targeted tick control programs exist in Uganda to prevent disease. During a seven-month-period from July 2018-January 2019, the Ministry of Health confirmed multiple independent CCHF outbreaks. We investigated to identify risk factors and recommend interventions to prevent future outbreaks.

Methods

We defined a confirmed case as sudden onset of fever (≥37.5°C) with ≥4 of the following signs and symptoms: anorexia, vomiting, diarrhoea, headache, abdominal pain, joint pain, or sudden unexplained bleeding in a resident of the affected districts who tested positive for Crimean-Congo haemorrhagic fever virus (CCHFv) by RT-PCR from 1 July 2018–30 January 2019. We reviewed medical records and performed active case-finding. We conducted a case-control study and compared exposures of case-patients with age-, sex-, and sub-county-matched control-persons (1:4).

Results

We identified 14 confirmed cases (64% males) with five deaths (case-fatality rate: 36%) from 11 districts in western and central region. Of these, eight (73%) case-patients resided in Uganda’s ‘cattle corridor’. One outbreak involved two case-patients and the remainder involved one. All case-patients had fever and 93% had unexplained bleeding. Case-patients were aged 6–36 years, with persons aged 20–44 years more affected (AR: 7.2/1,000,000) than persons ≤19 years (2.0/1,000,000), p = 0.015. Most (93%) case-patients had contact with livestock ≤2 weeks before symptom onset. Twelve (86%) lived <1 km from grazing fields compared with 27 (48%) controls (OR_M-H = 18, 95% CI = 3.2-∞) and 10 (71%) of 14 case-patients found ticks attached to their bodies ≤2 weeks before symptom onset, compared to 15 (27%) of 56 control-persons (OR_M-H = 9.3, 95%CI = 1.9–46).

Conclusions

CCHF outbreaks occurred sporadically during 2018–2019, both within and outside ‘cattle corridor’ districts of Uganda. Most cases were associated with tick exposure. The Ministry of Health should partner with the Ministry of Agriculture, Animal Industry and Fisheries to develop joint nationwide tick control programs and strategies with shared responsibilities through a One Health approach.

Uganda has had multiple Crimean-Congo haemorrhagic fever outbreaks since 2013 when the first outbreak was confirmed. Tick exposure has been identified as the major risk factor by our study and this finding was similar with other studies done during outbreaks in Uganda. However, Uganda still lacks national tick control guidelines and indiscriminate use of acaricides (pesticides specially for ticks) has been observed widely. This has been cited to influence increased tick resistance to acaricides. Our study might not indicate whether tick resistance to acaricides has increased tick populations in Uganda however it is imperative that tick control is considered in efforts of prevention and control of CCHF outbreaks. We therefore recommend improved tick control in Uganda through national regulations on acaricide distribution and use, development of strategies to reduce tick resistance to acaricides in the country, and more community-based engagement of tick control in livestock management.

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.

Immunocompetent mouse model for Crimean-Congo hemorrhagic fever virus

Crimean-Congo hemorrhagic fever (CCHF) is a severe tick-borne febrile illness with wide geographic distribution. CCHF is caused by infection with the Crimean-Congo hemorrhagic fever virus (CCHFV) and case fatality rates can be as high as 30%. Despite causing severe disease in humans, our understanding of the host and viral determinants of CCHFV pathogenesis are limited. A major limitation in the investigation of CCHF has been the lack of suitable small animal models. Wild-type mice are resistant to clinical isolates of CCHFV and consequently, mice must be deficient in type I interferon responses to study the more severe aspects of CCHFV. We report here a mouse-adapted variant of CCHFV that recapitulates in adult, immunocompetent mice the severe CCHF observed in humans. This mouse-adapted variant of CCHFV significantly improves our ability to study host and viral determinants of CCHFV-induced disease in a highly tractable mouse model.

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 hemorrhagic fever (CCHF) seroprevalence: A systematic review and meta-analysis

Crimean-Congo haemorrhagic fever (CCHF) is the most widespread, tick-borne viral disease affecting humans and therefore this paper performed a meta-analysis to highlight seroprevalence features of CCHF in a global context. After a preliminary review of the 396 papers representing areas throughout the world, 206 were selected for detailed meta-analysis. In general the total means of CCHF seroprevalence were, respectively 4.7 and 24.6% for humans and animals; and 17.1, 18.9, 24.3, 29.3 and 27.1% for camels, cattle, goats, sheep and livestock. Statistical analysis revealed a significant difference in seroprevalence between humans and camels (P = 0.043), cattle (P = 0.010), goats (P = 0.015), sheep (P = 0.005) and livestock (P = 0.017). Regionally, there also was a difference between humans, and goats (P = 0.0001), sheep (P = 0.007) and livestock (P = 0.002). Globally, CCHF seroprevalence in at-risk professionals was 7.5 fold greater than in normal humans, while CCHF seroprevalence was 5 fold greater in animals, camels, cattle, goats, sheep and livestock than normal humans. Animal contact, animal husbandry, farming, tick bite history and secretion exposure were the most frequently reported CCHF seropositivity risk factors. This study serves as an important resource for epidemiological discussions related to CCHF and CCHF seroprevalence features, providing specific information in understanding human and animal mean and trend CCHF seroprevalence for different regions of the world and on an aggregate global scale; seroprevalence in at-risk professionals; and total mean and trend CCHF seropositivity involving risk factors.

Serological Investigation of Occupational Exposure to Zoonotic Crimean-Congo Hemorrhagic Fever Infection

Objective

Crimean-Congo hemorrhagic fever (CCHF) is an acute and highly fatal disease. In this study, our aim was to compare and evaluate the prevalence of CCHF virus (CCHFV) antibody among occupational high-risk groups by using the enzyme-linked immunosorbent assay and draw attention to the occupational groups that are at high risk for CCHF infection in an endemic region for this zoonotic infection in Erzurum, Turkey.

Materials and Methods

The antibody levels against CCHFV were surveyed among slaughterhouse workers, animal breeders, and veterinarians. The study population was composed of 72 participants having direct contact with animals and 19 blood donors who were not in direct contact with animals.

Results

The overall rate of CCHF immunoglobulin G positivity in risk groups was found to be 6.94% (5/72). CCHFV antibodies were found in 4 (12.5%) individuals of the animal breeder group. This ratio was considered significantly higher compared with the healthy control group. CCHFV antibodies were found in only one person (4.0%) who was an abattoir worker. In the veterinarian group, all people were found negative.

Conclusion

In our study, the variables showing important associations with the prevalence of anti-CCHFV antibodies were livestock breeding, rural areas, and age. It was concluded that our region is endemic with regard to CCHF infection and persons who had direct contact with animals are at high risk. Thus, these participants must take necessary measures to protect themselves from CCHF and should be trained by health authorities.

Importance of biochemical parameters in order to predict clinical severity in patients diagnosed with Crimean-Congo haemorrhagic fever

Objective

We aimed to investigate new biochemical indicators to predict the clinical course of patients following the diagnosis of Crimean-Congo haemorrhagic fever (CCHF).

Material and methods

We retrospectively evaluated patients diagnosed with CCHF. They were divided into three groups based on a scoring system known as severity grading score in order to predict severity. Red cell distribution width (RDW), mean platelet volume (MPV), creatinine phosphokinase (CPK), alkaline phosphatase (ALP), glutamyl transferase (GGT) and C-reactive protein (CRP) levels were evaluated on the first day of admission. These biochemical parameters may predict the clinical course of our three patient groups.

Results

In our study, there were 38 (70.4%) male and 16 (29.6%) female patients, and the mean age was 44.33±16.94 years. Based on our scoring system, 17 (31.4%), 30 (55.5%) and 7 (12.9%) patients were in group 1, 2 and 3, respectively. Statistically significant difference was observed between groups 1–3 and groups 2–3 for ALP values; however, a statistically significant difference was observed among all three groups for GGT values. Significant differences were not observed among the groups for RDW, MPW, CPK and CRP levels (p>0.05).

Conclusion

ALP and GGT values can be used as auxiliary indicators to predict the clinical course for patients with CCHF. However, CPK, CRP, MPV and RDW values were not observed to be important for prognosis.

Evaluation of Crimean-Congo hemorrhagic fever suspected cases admitted to a secondary care hospital in Kastamonu, Turkey between 2014-2017

Background

Crimean-Congo hemorrhagic fever (CCHF) is an endemic zoonosis in Kastamonu, Turkey. Clinical and laboratory findings may not be specific in the early phase of the disease, hence bringing a challenge to the clinician.

Objective

We aimed to distinguish CCHF cases among all suspected cases by comparing them with non-CCHF cases with respect to characteristics during admission.

Methods

Cases with a presumptive diagnosis of CCHF at a secondary care hospital in Kastamonu in between 2014–2017 were evaluated, retrospectively. CCHF and non-CCHF cases were compared with respect to their clinical, laboratory and epidemiological characteristics during admission.

Results

Among 76 suspected patients, CCHF was found in 46.1% of them. Four-year fatality rate was 9.6% in CCHF cases. The frequency of headache, nausea/vomiting, leukopenia, thrombocytopenia less than 50x109/L, AST-ALT and LDH elevation, tick bites and contact with blood or body fluids of animals in CCHF cases were significantly higher than in non-CCHF cases (p<0.05).

Conclusion

Headache and nausea/vomiting accompanied with leukopenia, thrombocytopenia less than 50x109/L, AST-ALT and LDH elevations raise the possibility of CCHF in endemic regions especially when there is a history of tick bite and contact with blood or body fluids of animals.

Seroepidemiological and molecular investigations of infections with Crimean-Congo haemorrhagic fever virus in Kazakhstan

OBJECTIVES

The aim of this study was to detect the seroprevalence of Crimean-Congo haemorrhagic fever virus (CCHFV) in patients with fever of unknown origin (FUO) in endemic (Kyzylorda) and non-endemic (Almaty) oblasts of Kazakhstan.

METHODS

Paired serum samples from 802 patients with FUO were collected. Serum samples were investigated by ELISA to detect IgG and IgM antibodies against CCHFV. Sera with suspected acute infection were further investigated by RT-PCR to detect the viral RNA.

RESULTS

IgG antibodies were detected in 12.7% of the sera from both oblasts. Acute infection was shown by IgM ELISA in four patients from Kyzylorda, with only one developing severe CCHF. Viral RNA was found by RT-PCR in the other three patients' sera. Phylogenetic analysis of partial L and S segments revealed CCHFV genotype Asia 2 and a possible reassortment between the genotypes Asia 1/Asia 2. Animal husbandry, such as working with cattle and horses, was significantly associated with CCHFV seropositivity.

CONCLUSIONS

The antibodies and viral RNA detected in sera indicate that mild or even asymptomatic CCHFV infections are presented in Kazakhstan. This study describes the circulation of CCHFV in the so far non-endemic Almaty oblast for the first time. In conclusion, physicians treating patients with FUO in Kazakhstan should be aware of mild CCHF.

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.

Crimean-Congo Hemorrhagic Fever Virus in Bulgaria and Turkey

Infections of humans with the tick-borne Crimean-Congo hemorrhagic fever virus (CCHFV) can cause a severe hemorrhagic fever with case fatality rates of up to 80%. Most humans are infected by tick bite, crushing infected ticks by hand or by unprotected contact with blood of viremic mammals. Next to the notified human CCHF cases, the real distribution and the situation in animals in Southeastern Europe are nearly unknown. Since domestic ruminants play a crucial role in the life cycle of the vector ticks and the transmission and amplification of the virus, the antibody prevalence in those animals is a good indicator for the presence of CCHFV in a region. Therefore, the prevalence of CCHFV-specific antibodies was investigated in domestic ruminants of different regions of Bulgaria and Turkey. Sera of 1165 ruminants were tested and a prevalence of up to 90% was identified. The overall prevalence for Bulgaria was 26% and for Turkey 57%. The results highlight the risk of human infections in those regions and the importance of the investigation of the prevalence in animals for identification of risk areas. This article provides a unique overview about published CCHFV antibody prevalence in animals in comparison to human incidences in different areas of Bulgaria and Turkey. Although it will help to complete the understanding of the CCHFV situation in these countries, it also demonstrates the lack of unpublished and published data even in these highly endemic areas.

Seroprevalence of Crimean-Congo Hemorrhagic Fever Virus in Erzincan Province, Turkey, Relationship with Geographic Features and Risk Factors

To determine the seroprevalence and risk factors associated with Crimean-Congo hemorrhagic fever virus (CCHFV) in residents of Erzincan, Turkey. Although CCHFV is endemic in Erzincan, this is the first study to evaluate its seroprevalence in this region. This study included a total of 372 subjects, 174 of whom had been exposed to or bitten by ticks, 145 of whom worked with livestock, and 53 of whom resided in the city and did not have exposure to livestock. Data on CCHFV IgG and IgM antibodies were extracted from serum samples collected from all subjects using an ELISA. All samples were tested for CCHFV IgG and CCHFV IgM. Only IgM-positive samples were processed for detection of viral RNA through RT-PCR. Using seropositive cases only, we performed spatial analyses to evaluate correlations between seroprevalence and geographic location (i.e., proximity to rivers, altitude, and slope angle of land). In this study, 14.0% (52/322) of the total subjects were positive for CCHFV IgG. Seven of the individuals were positive both for CCHFV IgG and CCHFV IgM. Of these seven, only one sample tested positive for CCHFV RNA. Individuals who worked with livestock in the rural areas and had a history of tick exposure were statistically more likely to test positive for CCHFV IgG than individuals from the city and not exposed to ticks (p < 0.05). Seroprevalence was affected by geographic characteristics, including distance to rivers, altitude, and slope angle of land. We observed a high seroprevalence of CCHFV in Erzincan, which is similar to that observed in other endemic regions of Turkey. CCHFV seroprevalence rates are found to be quite high in the people who live in the sloping fields at certain heights and where there are a lot of rivers and streams.

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.

Consensus report: Preventive measures for Crimean-Congo Hemorrhagic Fever during Eid-al-Adha festival

Crimean-Congo hemorrhagic fever (CCHF) is endemic in Eurasian countries such as, Turkey, Pakistan, Afghanistan and Iran. CCHF virus is spread by the Hyalomma tick, which is found mainly on cattle and sheep. Muslim countries, in which these animals are sacrificed during Eid-Al-Adha, are among the countries where CCHF is endemic, and it has been observed that CCHF is associated with practices surrounding the Eid-ad-Adha festival. The dates for Eid-Al-Adha drift 10 days earlier in each year according to Georgian calendar. In previous years Eid-al-Adha occurred in autumn-winter months however in the next 10-15 years it will be take place in the summer months when CCHF is more prevalent. This may lead to a rise in the number of cases due to increased dissemination of CCHF virus with uncontrolled animal movements in and between countries. This consensus report focuses on the variable practices regarding animal handling in different regions and possible preventative measures to reduce the incidence of CCHF. Environmental hygiene and personal protection are essential parts of prevention. There is a need for international collaborative preparedness and response plans for prevention and management of CCHF during Eid-Al-Adha in countries where the disease is prevalent.

Spatial cluster analysis of human cases of Crimean Congo hemorrhagic fever reported in Pakistan

Background

Crimean Congo hemorrhagic fever (CCHF) is a tick-borne viral zoonotic disease that has been reported in almost all geographic regions in Pakistan. The aim of this study was to identify spatial clusters of human cases of CCHF reported in country.

Methods

Kulldorff’s spatial scan statisitc, Anselin’s Local Moran’s I and Getis Ord Gi* tests were applied on data (i.e. number of laboratory confirmed cases reported from each district during year 2013).

Findings

The analyses revealed a large multi-district cluster of high CCHF incidence in the uplands of Balochistan province near it border with Afghanistan. The cluster comprised the following districts: Qilla Abdullah; Qilla Saifullah; Loralai, Quetta, Sibi, Chagai, and Mastung. Another cluster was detected in Punjab and included Rawalpindi district and a part of Islamabad.

Conclusion

We provide empirical evidence of spatial clustering of human CCHF cases in the country. The districts in the clusters should be given priority in surveillance, control programs, and further research.

Electronic supplementary material

The online version of this article (doi:10.1186/2049-9957-4-9) contains supplementary material, which is available to authorized users.

Evaluation of cases with a preliminary diagnosis of Crimean- Congo hemorrhagic fever and comparison of characteristics in patients admitted to a secondary care hospital in Kastamonu, Turkey

BACKGROUND

Crimean-Congo hemorrhagic fever (CCHF) is an endemic disease in Turkey. The clinical presentation and laboratory findings are not specific especially in cases without hemorrhagic findings.

OBJECTIVE

We aimed to evaluate CCHF cases and compare them with non-CCHF cases in terms of their characteristics during admission.

METHODS

Cases with a preliminary diagnosis of CCHF at a secondary care hospital in Kastamonu in 2013 were evaluated, retrospectively. Cases testing RNA/IgM positive were considered as CCHF. Cases testing both RNA and IgM negative were considered as non-CCHF. The two groups were then compared in terms of their clinical, laboratory and epidemiological characteristics during admission.

RESULTS

A total of 41 cases were tested and CCHF was found in 46.3% of cases. Fatality was 5.3% in CCHF cases. The frequency of tick bites and CK elevation in CCHF cases was significantly higher than non-CCHF cases (p<0.05). There were no significant differences between the two groups regarding other characteristics (p>0.05).

CONCLUSIONS

In cases with a preliminary diagnosis of CCHF, especially in cases without a history of tick bite and with normal CK levels during admission, performing tests for the differential diagnosis may be advisable without waiting for the results of tests for CCHF.

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.