Genetic analysis of the M RNA segment of Crimean-Congo hemorrhagic fever virus strains in Turkey

Perception of Ticks and Tick-Borne Diseases Worldwide

In this comprehensive review study, we addressed the challenge posed by ticks and tick-borne diseases (TBDs) with growing incidence affecting human and animal health worldwide. Data and perspectives were collected from different countries and regions worldwide, including America, Europe, Africa, Asia, and Oceania. The results updated the current situation with ticks and TBD and how it is perceived by society with information bias and gaps. The study reinforces the importance of multidisciplinary and international collaborations to advance in the surveillance, communication and proposed future directions to address these challenges.

Changing Disease Course of Crimean-Congo Hemorrhagic Fever in Children, Turkey

Crimean-Congo hemorrhagic fever (CCHF), endemic in certain regions of the world, is listed as a priority disease with pandemic potential. Since CCHF was first identified in Turkey, children have been known to experience milder disease than adults. However, during the COVID-19 pandemic, we observed an unusually severe disease course, including hemophagocytic lymphohistiocytosis (HLH). We examined cytokine/chemokine profiles of 9/12 case-patients compared with healthy controls at 3 time intervals. Interferon pathway-related cytokines/chemokines, including interleukin (IL) 18, macrophage inflammatory protein 3α, and IL-33, were elevated, but tumor necrosis factor-α, IL-6, CXCL8 (formerly IL-8), and cytokines acting through C-C chemokine receptor 2 and CCR5 were lower among case-patients than controls. Interferon pathway activation and cytokines/chemokines acting through CCR2 and CCR5 improved health results among children with severe CCHF. Children can experience severe CCHF, including HLH, and HLH secondary to CCHF can be successfully treated with intravenous immunoglobulin and steroid therapy.

Seroprevalence and Risk Factors of Crimean-Congo Hemorrhagic Fever in Cattle of Smallholder Farmers in Central Malawi

Crimean-Congo hemorrhagic fever virus (CCHFV) is endemic in Africa, Asia, and Eastern Europe where it circulates among animals and ticks causing sporadic outbreaks in humans. Although CCHF is endemic in sub-Saharan Africa, epidemiological information is lacking in many countries, including Malawi. To assess the risk of CCHF in Malawi, we conducted an epidemiological study in cattle reared by smallholder livestock farmers in central Malawi. A cross-sectional study was conducted in April 2020 involving seven districts, four from Kasungu and three from Lilongwe Agriculture Development Divisions. A structured questionnaire was administered to farmers to obtain demographic, animal management, and ecological risk factors data. Sera were collected from randomly selected cattle and screened for CCHF virus (CCHFV) specific antibodies using a commercial ELISA kit. Ticks were collected from cattle and classified morphologically to species level. An overall CCHFV seropositivity rate of 46.9% (n = 416; 95% CI: 42.0–51.8%) was observed. The seropositivity was significantly associated with the age of cattle (p < 0.001), sex (p < 0.001), presence of ticks in herds (p = 0.01), district (p = 0.025), and type of grazing lands (p = 0.013). Five species of ticks were identified, including Hyalomma truncatum, a known vector of CCHFV. Ticks of the species Hyalomma truncatum were not detected in two districts with the highest seroprevalence for CCHF and vector competency must be further explored in the study area. To our knowledge, this is the first report of serologic evidence of the presence of CCHV among smallholder cattle in central Malawi. This study emphasizes the need for continued monitoring of CCHFV infection among livestock, ticks, and humans for the development of data-based risk mitigation strategies.

THE RELATIONSHIP BETWEEN CRIMEAN-CONGO HEMORRHAGIC FEVER AND CLIMATE: DOES CLIMATE AFFECT THE NUMBER OF PATIENTS?

- Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne viral zoonosis. The incidence of zoonotic diseases has been shown to be affected by climatic factors. In this study, we evaluated patients endemic to the CCHF region and examined the relationship between the number of patients and climatic properties of the region where they lived. The study included 548 CCHF patients. Along with the patient demographic and clinical characteristics, we recorded temperature, humidity and precipitation in the places where they lived at the time of their admission to the hospital. In addition to temperature, humidity and precipitation at the time of patient admission, these values were assessed at one month and three months prior to admission. The relationship between the number of patients and the above-mentioned values was examined. Humidity at the time of and one month prior to hospital admission, and precipitation three months prior to hospital admission were found to affect the number of patients admitted to the hospital for CCHF. In conclusion, climate appeared to affect the number of CCHF patients. We believe that the number of patients presenting to the hospital with CCHF could be predicted by taking into account climatic properties of the places where CCHF has been recorded, along with undertaking necessary measures.

Immunization of knock-out α/β interferon receptor mice against high lethal dose of Crimean-Congo hemorrhagic fever virus with a cell culture based vaccine

Crimean-Congo hemorrhagic fever (CCHF) is an acute tick-borne zoonotic disease. The disease has been reported in many countries of Africa, Asia, the Middle East, and in Eurasia. During the past decade, new foci of CCHF have emerged in the Balkan Peninsula, southwest Russia, the Middle East, western China, India, Africa, and Turkey. CCHF virus produces severe hemorrhagic manifestations in humans with fatality rates up to 30%. Vaccine development efforts have been significantly hampered by a lack of animal models and therefore, no protective vaccine has been achieved. Lately, IFN α/β receptor deficient (IFNAR^−/−) mice have been established as a novel small animal model of CCHF virus infection. In the present study, we found that IFNAR^−/− mice highly susceptible to CCHF virus Turkey-Kelkit06 strain. Immunization with the cell culture based vaccine elicited a significant level of protection against high dose challenge (1,000 PPFU) with a homologous CCHF virus in IFNAR^−/− mice.

The CCHF virus is one of the most geographically widespread tick-borne viruses, and has been reported in many countries of Africa, Asia, the Middle East, and in Eurasia. Since 2002, there have been more than 8000 cases in Turkey, with mortality rate around 5%, making CCHF a public health concern. There are currently no specific antiviral therapies or licensed vaccines for CCHF. Due to limitations in treatment options and difficulties posed by vector control vaccination remains the most logical method of disease control. In the present study, we showed that immunization with the cell culture based vaccine against CCHF elicited a significant level of protection against a high dose challenge (1,000 PPFU) with a homologous CCHF virus Turkey-Kelkit06 strain in IFNAR^−/− mice. The animals vaccinated with 5, 20, 40 μg dose of the cell culture based vaccine were partially protected (60%, 80% and 80% protection, respectively) with a significant delay in time to death. Neutralizing antibody responses are essential for the increased of protection in the mice vaccinated with the cell culture based vaccine but this cannot be the only mechanism of protection.

Molecular identification of Theileria and Babesia in ticks collected from sheep and goats in the Black Sea region of Turkey

A molecular survey was undertaken in the Black Sea region of Turkey to determine the presence of Theileria and Babesia species of medical and veterinary importance. The ticks were removed from sheep and goats, pooled according to species and locations, and analyzed by PCR-based reverse line blot (RLB) and sequencing. A total of 2241 ixodid ticks belonging to 5 genus and 12 species were collected and divided into 310 pools. Infection rates were calculated as the maximum likelihood estimation (MLE) with 95% confidence intervals (CI). Of the 310 pools tested, 46 (14.83%) were found to be infected with Theileria or Babesia species, and the overall MLE of the infection rate was calculated as 2.27% (CI 1.67-2.99). The MLE of the infection rates were calculated as 0.691% (CI 0.171-1.78) in Haemaphysalis parva, 1.47% (CI 0.081-6.37) in Rhipicephalus sanguineus, 1.84% (CI 0.101-7.87) in Ixodes ricinus, 2.86% (CI 1.68-4.48) in Rhipicephalus turanicus, 5.57% (CI 0.941-16.3) in Hyalomma marginatum, and 6.2% (CI 4.02-9.02) in Rhipicephalus bursa. Pathogens identified in ticks included Theileria ovis, Babesia ovis, Babesia bigemina, and Babesia microti. Most tick pools were infected with a single pathogen. However, five pools displayed mixed infections with T. ovis and B. ovis. This study provides the first molecular evidence for the presence of B. microti in ticks in Turkey.

Pseudo-plaque reduction neutralization test (PPRNT) for the measurement of neutralizing antibodies to Crimean-Congo hemorrhagic fever virus

Background

Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne virus of the genus Nairovirus family Bunyaviridae, which are enveloped viruses containing tripartite, negative polarity, single-stranded RNA. CCHF is characterized by high case mortality, occurring in Asia, Africa, the Middle East and Europe. Currently, there are no specific treatments or licensed vaccines available for CCHFV. Recently, two research groups have found adult mice with defective interferon responses allowed to lethal CCHFV infection. These mouse models could provide invaluable information for further studies. Efforts to develop a vaccine against CCHFV are being made. To determine the efficacy of vaccine candidates it is important to conduct serological studies that can accurately measure levels of protective antibodies. In the present study, a pseudo-plaque reduction neutralization test (PPRNT) based on enzyme-catalyzed color development of infected cells probed with anti-CCHFV antibodies was used to measure neutralization antibody of CCHFV.

Methods

Sixty-nine human serum samples (20 acute and 49 convalescent) were tested. The presence of CCHFV antibodies was determined and confirmed by a commercial ELISA kit. CCHFV RNA was determined by RT-PCR. All the samples were analyzed by PPRNT and fluorescent focus reduction neutralization test (FFRNT) to measure of CCHFV-neutralizing antibodies.

Results

Pseudo-plaque reduction neutralization test showed a high sensitivity (98%), specificity (100%) and agreement (96,6%) in qualitative comparison with those of the FFRNT. There was a high correlation between the titers obtained in PPRNT and FFRNT (R2 = 0.92). The inter- and intra-assay variation of PPRNT revealed good reproducibility and positive cut-off of PPRNT was defined as 1:4 by the geometric mean titers for the individual samples distributed.

Conclusion

The pseudo-plaque reduction neutralization test described in this study is a fast, reproducible and sensitive method for the measurement of CCHF neutralizing antibodies. This novel assay could serve as useful tools for CCHF research in epidemiology, vaccine development and other studies of immunity. It also provides an alternative to PRNT when viruses with no or poor CPE in cell culture.

Application of the pseudo-plaque assay for detection and titration of Crimean-Congo hemorrhagic fever virus

A pseudo-plaque assay was developed for detection and quantitation of Crimean-Congo hemorrhagic fever virus Turkey-Kelkit06. Enzyme-catalyzed color development of infected cells probed with anti-Crimean-Congo hemorrhagic fever virus antibodies was used for determining the titer of Crimean-Congo hemorrhagic fever Turkey-Kelkit06 and for its detection in samples from persons infected with the Crimean-Congo hemorrhagic fever virus. The pseudo-plaque assay accuracy was confirmed by comparing pseudo-plaque assay titers with fluorescent immunofocus assay and focus formation assay titers using three stocks of virus. No significant difference in virus titers of Crimean-Congo hemorrhagic fever Turkey-Kelkit06 among the three methods was observed. The pseudo-plaque assay is more sensitive than the fluorescent immunofocus assay for detecting the virus in primary isolates of Crimean-Congo hemorrhagic fever virus collected from humans, but no difference in sensitivity between the two methods was observed in the cell-adapted strain of Crimean-Congo hemorrhagic fever Turkey-Kelkit06. The pseudo-plaque assay is suitable for titration of Crimean-Congo hemorrhagic fever Turkey-Kelkit06, which does not develop plaques, suggesting it may also be suitable for the detection of other viruses.

Crimean-Congo haemorrhagic fever in Eurasia

Crimean-Congo haemorrhagic fever (CCHF) is a tick-borne infectious disease characterized by fever, malaise, headache, nausea, vomiting, diarrhoea, sore throat, muscle aches, haemorrhage and thrombocytopenia. It is a challenge for the population of endemic rural areas, and for healthcare workers, and carries a considerable mortality. The disease is widely distributed in Africa, Europe and Asia, and has become a serious threat to public health in Eurasia. The intention of this review is to summarize the current status of CCHF in Eurasia.

Molecular epidemiology of Crimean-Congo hemorrhagic fever virus in Turkey: occurrence of local topotype

The goal of this study was to investigate the molecular epidemiology of Crimean-Congo hemorrhagic fever virus (CCHFV) in Turkey. The study was performed on a total of 48 confirmed human CCHF cases from 2006 to 2008. The majority of the CCHF viral strains in Turkey were found to belong to the European lineage. Local CCHF viral strains are grouped into two main clusters, which can be further divided into two sub-groups. We also identified an AP92-like virus causing clinical disease in Corum (a mid-Anatolian province). Phylogenetic analysis revealed that the most recent CCHFV infections were caused by intrinsic (or native) CCHF viral strains, which we identified as the local topotype. Comparison of deduced amino acid sequences of S-segment RNAs indicated that the local topotype was derived from viruses of previous years, most likely by a low rate recombination. No genetic differences, based on S- and M-segment RNA sequences, were found between human and tick viral isolates. This data suggest that replication of CCHFV in the tick vector, whether Rhiphicephalus spp. or Hyalomma spp., has no effect on the viral genomic structure.

The complete genome analysis of Crimean-Congo hemorrhagic fever virus isolated in Turkey

Crimean-Congo hemorrhagic fever virus (CCHFV) is the causative agent of a tick-borne disease with high mortality rates in humans. The distribution of CCHFV includes over 30 countries in Asia, the Middle East, southeastern Europe, and Africa. It was first recognized in Turkey in 2002, with an increasing number of cases reported between 2002 and 2009. Recent analysis of complete genome sequences of CCHFV isolates has revealed that the genomic plasticity of the virus is surprisingly high for an arthropod-borne virus. We have determined the complete nucleotide and deduced amino acid sequences of strain CCHFV Turkey-Kelkit06 isolated from the blood of a patient in an endemic region of Turkey in 2006. The complete sequence length of the CCHFV Turkey-Kelkit06 strain is 19,186 nt, consisting of a 1673 nt S segment, a 5364 nt M segment, and a 12,149 nt L segment. Based on the analysis of S, M, and L segments, CCHFV Turkey-Kelkit06 clustered in Group V, which represents the Europe/Turkey geographic lineage. Although glycoproteins encoded by the M gene are the most variable part of the CCHFV Turkey-Kelkit06 strain, some functional domains of the glycoproteins are well conserved. Here, we report the complete sequence and genome organization of the CCHFV Turkey-Kelkit06 strain and its phylogenetic relationship to other strains of CCHFV. Collecting data on viral sequences among isolates from CCHF epidemics may provide valuable information regarding the molecular basis of the epidemic potential of the virus.

Towards an understanding of the migration of Crimean-Congo hemorrhagic fever virus

Crimean-Congo haemorrhagic fever (CCHF) is a lethal disease caused by Crimean-Congo hemorrhagic fever virus (CCHFV). It is one of the most widespread medically significant tick-borne pathogens, with a distribution that coincides well with the geographical occurrence of its tick vector, Hyalomma marginatum marginatum. Sporadic outbreaks of CCHF have previously been recognized in Asia, Africa, the Middle East and Europe but, in the 21st century, outbreaks have become more frequent in former Yugoslavia, Turkey and Iran. It has been suggested that CCHFV is a migrating pathogen, but it is not clear to what extent. We have, for the first time, analysed the worldwide migration pattern of CCHFV. Our results showed that Turkey may be a donor in Europe, towards both the east and the west, while the United Arab Emirates acted as a donor in the Middle East, and China was found to be the origin for genotype 2. Finally, we showed that migration of CCHFV was unrestricted between Iran and Pakistan. Considering the distribution and coincidence of the tick vector with CCHFV and CCHF, and the fact that the tick vector is present in western Europe, future outbreaks may extend to include hitherto-naïve areas, suggesting that increased surveillance and geographical mapping of this lethal pathogen are needed.

Crimean-Congo haemorrhagic fever among children in north-eastern Turkey

AIM

To analyse the epidemiological and clinical features of children with Crimean-Congo haemorrhagic fever (CCHF) in north-eastern Turkey.

METHODS

A retrospective study of demographic features and physical and laboratory findings in 21 children with CCHF is described. Clinical course, treatment modalities and outcome were analysed.

RESULTS

Most patients were admitted in June and July 2008; most were from the Gumushane and Kelkit valleys and half of them lived in rural areas. Mean (SD) age was 10.3 (3.9) years and the disease was more common in males (71.4%). Approximately 70% had a history of tick bite. The main symptoms were fever (17, 80.9%), nausea (11, 52.3%), malaise (10, 47.6%) and headache (7, 33.3%). At initial examination, approximately 70% of patients had leukopenia and 65% had thrombocytopenia. Anaemia developed during follow-up in six patients. Liver involvement was seen in 12 patients and one patient had acute tubular necrosis. Six patients had haemophagocytosis. Patients were hospitalised for a median 8 days (range 3-22) and nine patients had bleeding from various sites approximately 3-5 days after hospitalisation. Subcutaneous haematoma (6), especially epistaxis and at venepuncture sites (6) were the most common sites of bleeding. Pulmonary haemorrhage developed in two patients and they required ventilatory support. Overall mortality related to CCHF was 4.7% (one patient).

CONCLUSION

Early diagnosis of CCHF and early referral to specialised centres are important for outcome. Exceptional epidemics may be seen in future owing to ecological and environmental changes.