Serosurvey and molecular detection of Crimean–Congo hemorrhagic fever virus (CCHFV) in northern Turkey

Detection of the Crimean-Congo Hemorrhagic Fever Virus Genome in Questing Ixodes spp. and Haemaphysalis spp. in the Periurban Forestry Areas of Istanbul: Has a New Biorisk Emerged?

Background: Istanbul is one of the world's most densely populated metropolitan cities, with various geographical areas that possess distinct characteristics. These areas have different climates, vegetation, and host populations that can support the survival of diverse tick species. Turkey is a region with a high risk of Crimean-Congo hemorrhagic fever (CCHF) disease, making it crucial to screen for this risk, especially in densely populated regions such as Istanbul and its surrounding areas. However, the presence of potential vectors for CCHF virus (CCHFV) in these areas has not been studied in the past 12 years. Materials and Methods: In this study, a total of 676 ticks were collected from 6 centers using the flagging and dragging method. Ticks were identified as Ixodes ricinus (7.85%), Ixodes spp. immature form (73.22%), Haemaphysalis parva (0.89%), Haemaphysalis inermis (0.15%), and Haemaphysalis spp. immature form (17.89%). Pooled samples were screened for the CCHFV genome (S segment) by RT-nested PCR. Results: A total of 14.28% of the samples were found as positive. Phylogenetic analysis revealed that all the CCHFV sequences obtained from the positive samples were clustered in clade V: Europe/Turkey genogroup. Conclusion: This study suggests that ixodes spp. and Haemaphysalis spp. may have the potential to pose a biorisk for Crimean-Congo hemorrhagic fever.

Crimean–Congo hemorrhagic fever in the Arab world: A systematic review

Crimean-Congo hemorrhagic fever (CCHF) is an important tick-borne viral infection with a fatality rate of up to 50% during outbreaks. Crimean-Congo hemorrhagic fever virus (CCHFV) is sustained in the ecosystem in benign form through vertical and horizontal transmission cycles involving tick vectors, wildlife, and livestock. Hyalomma ticks are considered the major source of human infection. CCHF occurs most often among butchers, slaughterhouse workers, and farmworkers through infected tick bites or/and contact with blood and tissues of infected livestock. The nosocomial transmission can occur in auxiliary nurses and physicians through contact with the infected patients. The widespread distribution of CCHFV most probably occurred by ticks on migratory birds, or through international travel and trade of livestock and wildlife. During co-infections of ticks and vertebrates, reassortment among genome segments could play a significant role in generating diversity, and hence, a potential risk for the emergence of novel variants. In this systematic review, we aimed to determine the epidemiology, transmission, distribution, mortality, and clinical features of CCHF in 22 Arab countries, comprising the Arab world. Based on the analysis of 57 studies published from 1978 to 2021, we found 20 tick species that could be associated with CCHFV transmission. During the 43-year period, 321 cases of CCHF were reported from 9/22 Arab countries, Iraq, Kuwait, UAE, Saudi Arabia, Oman, Sudan, Egypt, Tunisia, and Mauritania. The mean case fatality rate was 29% during various outbreaks. Individuals working in abattoirs/slaughter houses, livestock farms, and healthcare were most at risk. Contact with blood or body secretions from infected animals and patients was the most common mode of transmission. A number of different animals, including cattle, goats, sheep, and camels were reported to be seropositive for CCHFV. The highest seroprevalence was observed in camels (29%), followed by cattle (21%), goats (15%), and sheep (14%). We discuss these results in the context of policy-making and potential preventative measures that can be implemented to reduce the burden of CCHF in the Arab world.

The Seroprevalence of Crimean-Congo Hemorrhagic Fever in Wild and Domestic Animals: An Epidemiological Update for Domestic Animals and First Seroevidence in Wild Animals from Turkiye

Simple Summary

Crimean-Congo hemorrhagic fever is a tick-borne and zoonotic emerging viral disease that is characterized by the sudden development of high fever and vascular bleeding in humans. The seroevidence among livestock has been reported, but it is less known in wild animals. Due to the importance and emerging state of the disease, we conducted a serosurvey on both domestic and wild animals in different areas of Turkiye. Serological investigations conducted on cattle, goats, and sheep revealed 10.81%, 15.15%, and 19.23% seropositivity, respectively, in the collected serum samples. We also found seropositivity rates in hare (23.81%) and wild boars (2.5%) indicating the substantial role of wild animals in virus epidemiology in Turkiye. This study provides first seroevidence of Crimean Congo hemorrhagic fever in wild animals in Turkiye.

Abstract

Crimean-Congo hemorrhagic fever virus (CCHFV) is a zoonotic, tick-borne pathogen that is endemic to some parts of Europe, Africa, and Asia. The disease causes fever and hemorrhagic manifestations in humans but not in animals. Domestic and wild animals are asymptomatic hosts of CCHFV and are critical in the transmission cycle. Hyalomma marginatum spp. has been identified as the natural reservoir and vector of the virus in Turkiye. A few studies have been conducted on domesticated animals showing the seroprevalence of CCHFV in them, but seroevidence in wild animals is absent. For contributing this antrum to the understanding of virus transmission in Turkiye, we performed a seroprevalence investigation of CCHFV in both wild and domesticated animals in various geographical areas of Turkiye. In-house IgG iELISA was performed for the screening of sera IgG in a total of 582 animal samples collected from boar (n = 40), cattle (n = 259), goat (n = 132), hare (n = 21), and sheep (n = 130). Results from ELISA performed on domestic animals revealed 10.81%, 15.15%, and 19.23% anti-CCHF virus seropositivity in cattle, goats, and sheep, respectively, in collected serum samples. ELISA tests performed in wild animals showed 23.81% and 2.5% positivity in hare and wild boars, respectively, suggesting the importance of wild animals in CCHF virus epidemiology in Turkiye. This study performed the first serological investigation of CCHFV in wild animals and provided the first seroevidence of CCHFV in wild boars and hare in Turkiye.

Serologic and molecular evidence for circulation of Crimean-Congo hemorrhagic fever virus in ticks and cattle in Bosnia and Herzegovina

Crimean-Congo haemorrhagic fever virus is a tick-borne zoonotic agent of the genus Orthonairovirus, and the causal agent of Crimean-Congo haemorrhagic fever in humans. The study is aimed at investigating the presence of CCHFV RNA in ticks and cattle in Bosnia and Herzegovina (B&H), as well as the exposure of cattle to CCHFV in this country. Only one pool of three male Hyalomma marginatum ticks tested positive for viral RNA (3/760, 0.39%). No viral RNA was detected in 206 bovine blood samples using real-time reverse-transcriptase PCR (RT-qPCR). The overall seroprevalence of CCHFV in the cattle population was estimated as 14.97% (72/481). The results indicate the presence and the established circulation of CCHFV in B&H. Considering the endemic character of CCHFV in the Balkans as well as our results, the possibility that CCHFV is endemic in the territory of Bosnia and Herzegovina is considered to be very high.

First Serological Evidence of Crimean-Congo Hemorrhagic Fever Virus and Rift Valley Fever Virus in Ruminants in Tunisia

Crimean-Congo hemorrhagic fever virus (CCHFV, Nairoviridae family) and Rift Valley fever virus (RVFV, Phenuiviridae family) are zoonotic vector-borne pathogens with clinical relevance worldwide. Our study aimed to determine seroprevalences of these viruses and potential risk factors among livestock (cattle, sheep, and goats) in Tunisia. Sera were tested for antibodies against CCHFV (n = 879) and RVFV (n = 699) using various enzyme-linked immunosorbent assays (ELISAs) and indirect immunofluorescence assays (IIFA). The overall seroprevalence of IgG antibodies was 8.6% (76/879) and 2.3% (16/699) against CCHFV and RVFV, respectively. For CCHF seropositivity bioclimatic zones and breed were potential risk factors for the three tested animal species; while the season was associated with cattle and sheep seropositivity, tick infestation was associated with cattle and goats seropositivity and age as a risk factor was only associated with cattle seropositivity. Age and season were significantly associated with RVFV seropositivity in sheep. Our results confirm the circulation of CCHFV and RVFV in Tunisia and identified the principal risk factors in ruminants. This knowledge could help to mitigate the risk of ruminant infections and subsequently also human infections.

High prevalence and different genotypes of Crimean-Congo hemorrhagic fever virus genome in questing unfed adult Hyalomma marginatum in Thrace, Turkey

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne viral disease in the old continents, in many countries south of the 50 °North Parallel. The agent is known to be the most prevalent and major cause of severe and fatal human hemorrhagic diseases among the tick-borne viruses, and is the second most widespread of all medically critical arboviruses following dengue. Members of the Hyalomma genus are mainly involved in the natural transmission of the CCHF virus (CCHFV); of those, H. marginatum is known to be the primary vector of the disease in the Western Palaearctic. In general, epidemiological studies have been based on serological detections in the hosts and/or virus screening of ticks collected from the hosts. To the best of our knowledge, only a few studies have been carried out to screen the virus in unfed, questing field ticks. Nevertheless, detection of the virus in questing ticks is known to be a crucial parameter to determine the possible vector roles of the ticks and to understand the ecological dynamics of related diseases. In this study, 200 (75 males,125 females) questing H. marginatum adults collected from the field in nine villages in Thrace, located in the European part of Turkey, were screened individually for CCHFV using nested PCR. As a result, 103 (51.5 %) ticks were determined as positive with various strains of CCHFV. High positivity in questing vectors in a region where a significantly lower number of human cases have been encountered suggests that there should be some region-specific drivers that are effective in the natural dynamics of the disease. Detailed etiological and epidemiological studies are needed to reveal the possible reason for this unexpected discrepancy.

Investigation of Crimean-Congo hemorrhagic fever virus in ruminant species slaughtered in several endemic provinces in Turkey

A total of 1,337 serum and plasma specimens (939, 393 and 15 from cattle, sheep and goats, respectively) were collected monthly for one a year from ruminant species slaughtered in three Turkish cities endemic for Crimean-Congo hemorrhagic fever virus (CCHFV), Samsun, Sivas and Tokat. The serum samples were tested by commercial indirect ELISA to detect CCHFV antibodies, and positive or equivocal samples were later confirmed by a virus neutralization test (VNT). The seroprevalence in cattle, sheep, and goats was 36.21% (340/939), 6.27% (24/383), and 6.67% (1/15), respectively. Quantitative real-time RT-PCR was employed to detect viraemic animals at slaughter time. The percentage of CCHFV-viraemic animals was 0.67% (9/1337). The virus load varied between 4.1 x 10¹ and 2.4 x 10³ RNA equivalent copies/mL in viraemic animals. The plasma samples that were positive for CCHFV genomic RNA were collected between April and May, when Hyalomma ticks are active. This study presents quantitative CCHFV load data in ruminant species at slaughter and interprets the likelihood of transmission for employees working in slaughterhouses in CCHFV-endemic regions.

Investigation of Vector-Borne Viruses in Ticks, Mosquitos, and Ruminants in the Thrace District of Turkey

There is a considerable increase in vector-borne zoonotic diseases around the world, including Turkey, such as Crimean-Congo hemorrhagic fever (CCHF), tick borne encephalitis (TBE), Rift Valley fever (RVF), and West Nile fever (WNF), causing disease and death in humans and animals and significant economical losses. Hence, the aim of this study was to investigate the presence of CCHF virus (CCHFV) and TBE virus (TBEV) in ticks and RVF virus (RVFV) and WNF virus (WNV) in mosquitos, as well as in sheep and cattle, in the Thrace district of the Marmara region, which borders Bulgaria and Greece. Buffy-coat samples from 86 cattle and 81 sheep, as well as 563 ticks and 7390 mosquitos, were collected and examined by quantitative real-time RT-PCR for the presence of CCHFV, TBEV, RVFV, and WNV. All buffy-coat samples from cattle and sheep were negative for these viruses. Similarly, all tick samples were negative for CCHFV-RNA and TBEV-RNA. Among 245 pools representing 7390 mosquitos, only 1 pool sample was found to be positive for WNV-RNA and was confirmed by sequencing. Phylogenetic analysis revealed that it was WNV lineage-2. No RVFV-RNA was detected in the 245 mosquito pools. In conclusion, results of this study indicate that CCHFV, TBEV, and RVFV are not present in livestock and respective vectors in the Thrace district of Marmara region of Turkey, whereas WNV-RNA was found in mosquitos from this region.

Seroepidemiological Investigation of Crimean-Congo Hemorrhagic Fever Virus in Sheep and Camels of Inner Mongolia of China

Crimean-Congo hemorrhagic fever (CCHF) is a highly lethal infectious disease in humans caused by tick-borne Crimean-Congo hemorrhagic fever virus (CCHFV). To determine the potential risk of CCHF in the pastoral area of Northwestern China, the presence of antibody to CCHFV in the sera of two most common tick hosts, sheep and camels, in Inner Mongolia of China was evaluated. The purified recombinant nucleocapsid protein (NP) of CCHFV was prepared from a prokaryotic vector expressing the NP encoding gene, which was employed as the antigen to probe antibody against CCHFV in tick vectors using an immunoblotting assay. In total, 58.3% (35/60) and 54% (12/22) of camels were positive of antibody to CCHFV in sera at Alxa Youqi County and Ulan Hudu Gacha Village of Inner Mongolia Province, respectively. However, only 6.7% (2/30) of sera of sheep were determined positive in antibody to CCHFV in the Wulan Hudug check area in this study. Consequently, these results indicate that 54-58.3% camels were infected by CCHFV after exposure to tick bites in Inner Mongolia, which was significantly higher than 6.7% of infection in the sheep in this area, suggesting there is a certain relationship between the serological reactivity and exposure time to ticks, range of activity, living behaviors, and breeding time. Further intensive surveillance of livestock and exposed population is required to better understand the spread of CCHFV in this area.

Epidemiological investigations of Crimean-Congo haemorrhagic fever virus infection in sheep and goats in Balochistan, Pakistan

Crimean-Congo haemorrhagic fever (CCHF) is a tick-borne zoonotic disease caused by the arbovirus Crimean-Congo haemorrhagic fever virus (CCHFV). Livestock serve as a transient reservoir for CCHFV, but do not show clinical signs. In this cross-sectional study, sheep and goats in Balochistan, Pakistan, were examined to determine the CCHFV seroprevalence, spatial distribution of seropositive sheep and goats, and to identify potential risk factors for seropositivity to CCHFV in these animals. To this end, farms and animals were selected by systematic sampling, blood samples from 800 sheep and 800 goats were collected and information regarding farm management and the kept animals were retrieved using a standard questionnaire. Sera were tested for antibodies against CCHFV in two independent ELISA formats and an immunofluorescence assay (IFA) following a hierarchical diagnostic decision tree. By these assays 149 (19 %, 95 %-CI: 16-21 %) out of 800 sheep serum samples and 37 (5 %, 95 %-CI: 3-6 %) out of 800 goat serum samples were positive for CCHFV-specific IgG antibodies. Interestingly, at least 8 (5 %, 95 %-CI: 2-10 %) out of 160 sera pools were from CCHFV viraemic sheep, as sera (in pools of 5) tested positive for CCHFV genome by real-time PCR (RT-qPCR). Risk factor analysis revealed that the open type of housing (OR = 3.76, 95 %-CI:1.57-9.56, p-value = 0.003), grazing (OR = 4.18, 95 %-CI:1.79-10.37, p-value = 0.001), presence of vegetation in or around the farm (OR = 3.13, 95 %-CI: 1.07-10.15, p-value = 0.043), lack of treatment against ticks (OR = 3.31, 95 %-CI: 1.16-10.21, p-value = 0.029), absence of rural poultry (OR = 2.93, 95 %-CI: 1.41-6.29, p-value = 0.004), animals with age ≥ 2 years (OR = 4.15, 95 %-CI: 2.84-6.19, p-value<0.001), animals infested with ticks (OR = 2.35, 95 %-CI: 1.59-3.52, p-value<0.001), and sheep species (OR = 4.72, 95 %-CI:3.24-6.86, p-value<0.001) represented statistically significant risk factors associated with seropositivity to CCHFV. Taken together this study confirms the circulation of CCHFV in livestock in Balochistan, Pakistan. The identification of risk factors might help to reduce the risk of infection in sheep and goats, which may also mitigate the risk for human infection. An interesting option for reducing the risk of CCHFV infection in small ruminants is keeping also chickens, since they pick ticks that transmit CCHFV.

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.

The role of ticks in the maintenance and transmission of Crimean-Congo hemorrhagic fever virus: A review of published field and laboratory studies

This manuscript is part of a series of reviews that aim to cover published research on Crimean-Congo hemorrhagic fever (CCHF) and its etiological agent, CCHF virus (CCHFV). The virus is maintained and transmitted in a vertical and horizontal transmission cycle involving a variety of wild and domestic vertebrate species that act as amplification hosts, without showing signs of illness. These vertebrates have traditionally been considered reservoirs of CCHFV, but in fact they develop only a transient viremia, while the virus can persist in ticks for their entire lifespan, and can also be transmitted vertically to the next generation. As a result, ticks are now considered to be both the vector and the reservoir for the virus. CCHFV has been detected in a wide range of tick species, but only a few have been proven to be vectors and reservoirs, mainly because most published studies have been performed under a broad variety of conditions, precluding definitive characterization. This article reviews the published literature, summarizes current knowledge of the role of ticks in CCHFV maintenance and transmission and provides guidance for how to fill the knowledge gaps. Special focus is given to existing data on tick species in which vertical passage has been demonstrated under natural or experimental conditions. At the same time, we identify earlier reports that used unreliable methods and perceptions to ascribe a vector role to some species of ticks, and have contributed to confusion regarding viral transmission. We also examine epidemiological pathways of CCHFV circulation and discuss priority areas for future research.

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.

Molecular detection of Crimean-Congo haemorrhagic fever virus in ticks collected from infested livestock populations in a New Endemic Area, South of Iran

OBJECTIVE

Crimean-Congo haemorrhagic fever (CCHF) is a viral zoonotic disease with potentially fatal systemic effects on man. We aimed to determine the presence of CCHF virus among collected ticks from domestic livestock from October 2012 to September 2013.

METHODS

A total of 1245 hard and soft ticks were collected from naturally infested ruminants in Marvdasht County, Fars Province, south of Iran. Nine tick species and one unidentified species in four disparate genera were detected. A total of 200 ticks were randomly selected and analysed by reverse transcription-polymerase chain reaction (RT-PCR) for the presence of CCHF virus genome.

RESULTS

The viral genome was detected in 4.5% (9 samples) of the studied tick population. The infected ticks belonged to the species of Hyalomma marginatum' Hyalomma anatolicum and Rhipicephalus sanguineus. The viruses detected in these three tick species were clustered in the same lineage as Matin and SR3 strains in Pakistan and some other Iranian strains. These results indicate that the ticks were wildly infected with a genetically closely related CCHF virus in the region.

CONCLUSION

Regular controls and monitoring of livestock to reduce the dispersion of ticks and providing information to those involved in high-risk occupations are urgently required.

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.

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

Turkey has been one of the most endemic regions since 2002, when Crimean-Congo hemorrhagic fever emerged worldwide. The aim of the present study was to estimate the seroprevelance of CCHF virus in humans who reside in rural and urban areas of known endemic and nonendemic selected provinces of Turkey by using commercial ELISA kit. CCHFV IgG antibodies were detected in 2.3% of the population. The most important risk factors for CCHF seropositivity, were older age, male gender, illiterate, farmer, animal husbandry, living in rural residence in adobe houses, and a previous tick bite history.