Seroepidemiological Studies of Crimean-Congo Hemorrhagic Fever Virus in Domestic and Wild Animals

Experimental Challenge of Sheep and Cattle with Dugbe Orthonairovirus, a Neglected African Arbovirus Distantly Related to CCHFV

Dugbe orthonairovirus (DUGV) is a tick-borne arbovirus within the order Bunyavirales. DUGV was first isolated in Nigeria, but virus isolations in ten further African countries indicate that DUGV is widespread throughout Africa. Humans can suffer from a mild febrile illness, hence, DUGV is classified as a biosafety level (BSL) 3 agent. In contrast, no disease has been described in animals, albeit serological evidence exists that ruminants are common hosts and may play an important role in the transmission cycle of this neglected arbovirus. In this study, young sheep and calves were experimentally inoculated with DUGV in order to determine their susceptibility and to study the course of infection. Moreover, potential antibody cross-reactivities in currently available diagnostic assays for Crimean-Congo hemorrhagic fever orthonairovirus (CCHFV) were assessed as DUGV is distantly related to CCHFV. Following subcutaneous inoculation, none of the animals developed clinical signs or viremia. However, all ruminants seroconverted, as demonstrated by two DUGV neutralization test formats (micro-virus neutralization test (mVNT), plaque reduction (PRNT)), by indirect immunofluorescence assays and in bovines by a newly developed DUGV recombinant N protein ELISA. Sera did not react in commercial CCHFV ELISAs, whereas cross-reactivities were observed by immunofluorescence and immunoblot assays.

Identification of a novel lineage of Crimean-Congo haemorrhagic fever virus in dromedary camels, United Arab Emirates

Crimean-Congo haemorrhagic fever virus (CCHFV) is a tick-borne virus causing Crimean-Congo haemorrhagic fever (CCHF), a disease reported to have a high fatality rate in numerous countries. The virus is geographically widespread due to its vector, and numerous wild and domestic animals can develop asymptomatic infection. Serological and limited molecular evidence of CCHFV has previously been reported in Camelus dromedarius (the dromedary, or one-humped camel) in the United Arab Emirates (UAE). In this study, 238 camel samples were screened for CCHFV RNA where 16 camel samples were positive for CCHFV by RT-PCR. Analysis of full-length CCHFV genome sequences revealed a novel lineage in camels from the UAE, and potential reassortment of the M segment of the genome.

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.

Tick-borne pathogens, including Crimean-Congo haemorrhagic fever virus, at livestock markets and slaughterhouses in western Kenya

Vectors of emerging infectious diseases have expanded their distributional ranges in recent decades due to increased global travel, trade connectivity and climate change. Transboundary range shifts, arising from the continuous movement of humans and livestock across borders, are of particular disease control concern. Several tick-borne diseases are known to circulate between eastern Uganda and the western counties of Kenya, with one fatal case of Crimean-Congo haemorrhagic fever (CCHF) reported in 2000 in western Kenya. Recent reports of CCHF in Uganda have highlighted the risk of cross-border disease translocation and the importance of establishing inter-epidemic, early warning systems to detect possible outbreaks. We therefore carried out surveillance of tick-borne zoonotic pathogens at livestock markets and slaughterhouses in three counties of western Kenya that neighbour Uganda. Ticks and other ectoparasites were collected from livestock and identified using morphological keys. The two most frequently sampled tick species were Rhipicephalus decoloratus (35%) and Amblyomma variegatum (30%); Ctenocephalides felis fleas and Haematopinus suis lice were also present. In total, 486 ticks, lice and fleas were screened for pathogen presence using established molecular workflows incorporating high-resolution melting analysis and identified through sequencing of PCR products. We detected CCHF virus in Rh. decoloratus and Rhipicephalus sp. cattle ticks, and 82 of 96 pools of Am. variegatum were positive for Rickettsia africae. Apicomplexan protozoa and bacteria of veterinary importance, such as Theileria parva, Babesia bigemina and Anaplasma marginale, were primarily detected in rhipicephaline ticks. Our findings show the presence of several pathogens of public health and veterinary importance in ticks from livestock at livestock markets and slaughterhouses in western Kenya. Confirmation of CCHF virus, a Nairovirus that causes haemorrhagic fever with a high case fatality rate in humans, highlights the risk of under-diagnosed zoonotic diseases and calls for continuous surveillance and the development of preventative measures.

Sheep and Cattle Are Not Susceptible to Experimental Inoculation with Hazara Orthonairovirus, a Tick-Borne Arbovirus Closely Related to CCHFV

Hazara orthonairovirus (HAZV) is a tick-borne arbovirus closely related to Crimean–Congo hemorrhagic fever orthonairovirus (CCHFV). Whereas CCHFV is a biosafety level (BSL) 4 agent, HAZV is classified as BSL 2, as it is not known to cause any disease in humans. Belonging to the same serogroup as CCHFV, HAZV might act as a model which can provide a better understanding of this important zoonosis. Furthermore, the serological relatedness may cause diagnostic problems if antibodies against HAZV interfere with current CCHFV serological assays. Therefore, sheep and cattle—important natural hosts for CCHFV—were experimentally infected with HAZV to prove their susceptibility and evaluate potential antibody cross-reactivities. According to this study, neither sheep nor cattle are susceptible to experimental HAZV infections. Consequently, the HAZV infection in ruminants is clearly distinct from CCHFV infections. Sera of immunized animals weakly cross-reacted between HAZV and CCHFV in immunofluorescence and immunoblot assays, but not in commercial CCHFV ELISAs commonly used for field studies.

A DNA-based vaccine protects against Crimean-Congo haemorrhagic fever virus disease in a Cynomolgus macaque model

There is currently no specific prophylaxis or vaccine against Crimean-Congo hemorrhagic fever virus (CCHFV). Crimean-Congo hemorrhagic fever (CCHF) is a severe febrile-illness transmitted by Hyalomma ticks in endemic areas, handling of infected livestock or care of infected patients. We report here the successful protection against CCHFV-mediated disease in a non-human primate disease model. Cynomolgus macaques were vaccinated with a DNA-based vaccine using in vivo electroporation-assisted delivery. The vaccine contained two plasmids encoding the glycoprotein precursor (GPC) and the nucleoprotein (NP) of CCHFV. Animals received three vaccinations and we recorded potent antibody and T-cell responses after vaccination. While all sham-vaccinated animals developed viremia, high tissue viral loads and CCHF-induced disease, the NP + GPC vaccinated animals were significantly protected. In conclusion, this is the first evidence of a vaccine that can protect against CCHFV-induced disease in a non-human primate model. This supports clinical development of the vaccine to protect groups at risk for contracting the infection.

A DNA-based vaccine confers significant protection from CCHFV infection in Cynomolgus macaques

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.

Detection of Hyalomma rufipes in a recently arrived asylum seeker to the EU

The importation of novel tick species to Europe and the emergence of tick-borne diseases have been of rising concern over the last decades. In May 2019, a total of 349 asylum seekers arrived in Malta by boat. Public health syndromic surveillance was conducted on all migrant boat arrivals. The incidental finding of a tick with anomalous morphology in a newly arrived migrant in Malta prompted an epidemiological investigation. Morphological identification of the tick followed by species identification using keys specific to North Africa was conducted and molecular testing for Crimean Congo haemorrhagic fever virus (CCHFV) was performed. Detailed interview and clinical examination of the case were conducted on arrival and follow-up interviews were undertaken 1- and 4-weeks post-arrival. A Hyalomma rufipes tick was identified on the chest of a 28-year-old male from Sudan. The patient reported malaise and headache on arrival. No further symptoms were reported during follow-up. There was no evidence of previous CCHFV infection or the presence of other ticks or pathogens on the patient. The investigation revealed that the H. rufipes tick had likely been acquired in Libya. This is the first report of the presence of a H. rufipes tick, the main vector for CCHFV, on a recently arrived migrant in Europe. This event highlights the importance of increasing awareness on the risk of tick-borne infections among recently arrived migrants in the Mediterranean countries and the need to consider tick screening as part of the health screening offered in the EU.

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.

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.

Seroprevalence of Crimean-Congo Hemorrhagic Fever in Domesticated Animals in Northwestern Senegal

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne disease that can be contracted by direct contact with viremic animals or humans. In West Africa, recurrent CCHF outbreaks have been constantly observed in Mauritania and Senegal. Moreover, acquisition and epidemiology of the infection in humans are correlated with the occurrence and the seroprevalence of the virus in livestock. The main objective of this study is to provide updated information on the local spread of CCHF in animals in the northern region of Senegal. Out of a total of 283 animal sera collected, CCHF-specific antibodies were identified in 92 (32.5%; confidence interval [CI]_95% 27.1-38.3) sera by double antigen sandwich enzyme-linked immunosorbent assay (ELISA) test. The prevalence of CCHF virus (CCHFV) infection among horses, cattle, sheep, dogs, donkeys, and goats was 70.3% (45/64), 57.1% (8/14), 22.1% (30/136), 18.2% (2/11), 17.2% (5/29), and 6.9% (2/29), respectively. The antibody titers were found significantly affected by age (p < 0.0001) and gender (p < 0.05). High tick infestation by Rhipicephalus spp. and Hyalomma spp. was recorded on horses. The high seroprevalence to CCHFV among animals in the northern region of Senegal observed in this study indicates the permanent presence of the infection in the northern region of the country suggesting the need to strengthen surveillance plans for CCHF in Senegal.

Endemic and Emerging Arboviruses in Domestic Ruminants in East Asia

Epizootic congenital abnormalities caused by Akabane, Aino, and Chuzan viruses have damaged the reproduction of domestic ruminants in East Asia for many years. In the past, large outbreaks of febrile illness related to bovine ephemeral fever and Ibaraki viruses severely affected the cattle industry in that region. In recent years, vaccines against these viruses have reduced the occurrence of diseases, although the viruses are still circulating and have occasionally caused sporadic and small-scaled epidemics. Over a long-term monitoring period, many arboviruses other than the above-mentioned viruses have been isolated from cattle and Culicoides biting midges in Japan. Several novel arboviruses that may infect ruminants (e.g., mosquito- and tick-borne arboviruses) were recently reported in mainland China based on extensive surveillance. It is noteworthy that some are suspected of being associated with cattle diseases. Malformed calves exposed to an intrauterine infection with orthobunyaviruses (e.g., Peaton and Shamonda viruses) have been observed. Epizootic hemorrhagic disease virus serotype 6 caused a sudden outbreak of hemorrhagic disease in cattle in Japan. Unfortunately, the pathogenicity of many other viruses in ruminants has been uncertain, although these viruses potentially affect livestock production. As global transportation grows, the risk of an accidental incursion of arboviruses is likely to increase in previously non-endemic areas. Global warming will also certainly affect the distribution and active period of vectors, and thus the range of virus spreads will expand to higher-latitude regions. To prevent anticipated damages to the livestock industry, the monitoring system for arboviral circulation and incursion should be strengthened; moreover, the sharing of information and preventive strategies will be essential in East Asia.

Mapping the environmental suitability of etiological agent and tick vectors of Crimean-Congo hemorrhagic fever

Crimean-Congo hemorrhagic fever (CCHF) is one of the most important public health threats in many regions across Africa, Europe, and Asia. This study used ecological niche modeling analyses to map the environmental suitability of both CCHF virus (CCHFV), and its tick vectors (Amblyomma variegatum, Dermacentor marginatus, Hyalomma marginatum, Hyalomma rufipes, Hyalomma truncatum, Rhipicephalus appendiculatus, and Rhipicephalus evertsi evertsi) in the Old World countries. The CCHFV was anticipated to occur with high environmental suitability across southern and central Europe, northwestern Africa, central Asia, and western Mediterranean region. Ecological niche models of tick vectors anticipated diverse patterns based on the tick species in question; D. marginatus and H. marginatum showed high environmental suitability in southern and central Europe, and North Africa. The remaining vector species were anticipated to occur in Africa. All models were statistically robust and performed better than random (P < 0.001). Finally, we tested the niche similarities between CCHFV and diverse tick vectors and could not reject the null hypotheses of niche similarity in all vector-virus combinations (P > 0.05) except the combinations of CCHFV with A. variegatum, R. evertsi evertsi and R. appendiculatus (P < 0.05).

European Brown hare (Lepus europaeus) as a source of emerging and re-emerging pathogens of Public Health importance: A review

European brown hare (Lepus europaeus, EBH) is probably the most important game animal in Europe throughout its historical distribution. The decline in its populations across its geographic range in Europe have been attributed to factors such as reproductive rate and the ability for adaptation, climate, feed availability, predators, anthropogenic factors and diseases. Apart from common diseases of hares with a high impact on their mortality such as European Brown hare Syndrome, EBH has been involved in the epidemiology of pathogens with zoonotic potential. In this work, the role of EBH as a source of Crimean–Congo haemorrhagic fever virus (CCHFV), Hepatitis E virus (HEV), Yersinia spp., Brucella spp., Francisella tularensis, Toxoplasma gondii and Leishmania infantum is discussed. Hares may significantly contribute to the epidemiology of important emerging zoonotic pathogens through maintenance of high endemicity levels as in the case of CCHFV, as a reservoir of important pathogens such as Yersinia spp., B. suis, F. tularensis and L. infantum and as a potential source of T. gondii for other animals, especially for carnivores but also for humans. However, EBH may also be a host of minor importance as in the case of HEV. The continuous surveillance of hare populations will enable the collection of information on the population health status and the pathogens currently circulating in the area posing risk for wildlife, domestic animals and humans. The possible live animal translocations of infected hares, the fact that this species acts as a host of vectors (fleas, ticks, mosquitoes and sandflies) and the prey of carnivores and omnivores that travel in great distances getting into contact with domestic animals and humans, further highlights the need to be included in surveillance studies. Besides, the hunter‐harvested EBH population is an excellent indicator for recent pathogen transmission due to its short lifespan.

The present review provides an overview of the role of European Brown Hare as a source of Crimean–Congo haemorrhagic fever virus (CCHFV), Hepatitis E virus (HEV), Yersinia spp., Brucella spp., Francisella tularensis, Toxoplasma gondii and Leishmania infantum aiming to highlight the contribution of this species to the epidemiology of important emerging zoonotic pathogens.

New aspects about Crimean-Congo hemorrhagic fever (CCHF) cases and associated fatality trends: A global systematic review and meta-analysis

Crimean-Congo hemorrhagic fever (CCHF) is the most popular tick-borne disease causing by Crimean-Congo hemorrhagic fever virus (CCHFV). There are several valuable reviews considering some fields of the CCHF aspects. While there is no a systematic review about means and trends of CCHF cases and fatality rate, means and trends of CCHF cases and fatality rates of human occupations involved in CCHF. Therefore, this meta-analysis review performed to highlight and provide a global detailed of the above CCHF aspects. Among 398 collected papers, 173 papers were become this meta-analysis review. The study results confirm that an apparent increasing CCHF cases occurred through the past decades. The trends of annually and periodically CCHF cases and fatality rates were also increased. The means of annually and periodically CCHF cases and fatality rates were 57 and 432 cases, and 10 cases and 32.2 % and 49 cases and 28.8 %, respectively. The means of annually and periodically CCHF fatality rates are about one-tenth of CCHF human cases. The mean of CCHF fatality rates in Africa (22.0 %) is lower than Asia (33.5 %) and Europe (33.8 %). Among occupations involved in CCHF, agricultural (28.9 %), health-care (19.2 %) and slaughterhouse (16.7 %) workers, and farmers (13.9 %) had the maximum CCHF fatality rates in order. Based on literature review of CCHFV S-segment aspects, several clades and genotypes are reported to distribute in Africa, Asia and Europe regions. There are very wide fields to investigate the epidemiology characteristics of CCHFV clades, genotypes and their distribution in the future.

Emerging Tick-Borne Diseases

Increases in tick-borne disease prevalence and transmission are important public health issues. Efforts to control these emerging diseases are frustrated by the struggle to control tick populations and to detect and treat infections caused by the pathogens that they transmit. This review covers tick-borne infectious diseases of nonrickettsial bacterial, parasitic, and viral origins. While tick surveillance and tracking inform our understanding of the importance of the spread and ecology of ticks and help identify areas of risk for disease transmission, the vectors are not the focus of this document. Here, we emphasize the most significant pathogens that infect humans as well as the epidemiology, clinical features, diagnosis, and treatment of diseases that they cause. Although detection via molecular or immunological methods has improved, tick-borne diseases continue to remain underdiagnosed, making the scope of the problem difficult to assess. Our current understanding of the incidence of tick-borne diseases is discussed in this review. An awareness of the diseases that can be transmitted by ticks in specific locations is key to detection and selection of appropriate treatment. As tick-transmitted pathogens are discovered and emerge in new geographic regions, our ability to detect, describe, and understand the growing public health threat must also grow to meet the challenge.

Determining the molecular drivers of species-specific interferon-stimulated gene product 15 interactions with nairovirus ovarian tumor domain proteases

Tick-borne nairoviruses (order Bunyavirales) encode an ovarian tumor domain protease (OTU) that suppresses the innate immune response by reversing the post-translational modification of proteins by ubiquitin (Ub) and interferon-stimulated gene product 15 (ISG15). Ub is highly conserved across eukaryotes, whereas ISG15 is only present in vertebrates and shows substantial sequence diversity. Prior attempts to address the effect of ISG15 diversity on viral protein-ISG15 interactions have focused on only a single species' ISG15 or a limited selection of nairovirus OTUs. To gain a more complete perspective of OTU-ISG15 interactions, we biochemically assessed the relative activities of 14 diverse nairovirus OTUs for 12 species' ISG15 and found that ISG15 activity is predominantly restricted to particular nairovirus lineages reflecting, in general, known virus-host associations. To uncover the underlying molecular factors driving OTUs affinity for ISG15, X-ray crystal structures of Kupe virus and Ganjam virus OTUs bound to sheep ISG15 were solved and compared to complexes of Crimean-Congo hemorrhagic fever virus and Erve virus OTUs bound to human and mouse ISG15, respectively. Through mutational and structural analysis seven residues in ISG15 were identified that predominantly influence ISG15 species specificity among nairovirus OTUs. Additionally, OTU residues were identified that influence ISG15 preference, suggesting the potential for viral OTUs to adapt to different host ISG15s. These findings provide a foundation to further develop research methods to trace nairovirus-host relationships and delineate the full impact of ISG15 diversity on nairovirus infection.

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: 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.

Molecular and seroepidemiological survey on Crimean-Congo Hemorrhagic Fever Virus in Northeast of Iran

Background: Crimean-Congo hemorrhagic fever (CCHF) is a prevalent tick-borne disease in different regions of Iran. This molecular and serologic study was performed to investigate the Crimean-Congo hemorrhagic fever virus (CCHFV) in collected ticks and in blood samples of some domestic animals in North Khorasan, Northeast of Iran. Methods: In this cross sectional study, 136 blood samples from domestic animals (sheep, goats, and cows) collected in the Northeast region in Iran were examined using IgG ELISA assay. Ticks (n = 1478) were collected from sheep, goats, and cows. Out of all collected ticks, 62 specimens were investigated for CCHF virus genome using RT-PCR technique. The data were descriptively presented by median and 95% confidence interval (CI). Results: CCHFV infection rate was 8.1% in studied ticks. Two species of ticks, Hy. anatolicum (n=3; 15%, 95% CI 9.41-20.59) and Rh. sanguineus (n=2; 6.9%, 95%CI 4.33-8.58), were infected with CCHFV genome and were probable vectors of CCHF virus in the area. Infection rate was 15.4% for CCHFV in tested domestic animals. Serologic tests detected CCHFV specific IgG antibodies in 16.2% (95% CI 13.49-18.83) (99/16) and 19.2% (95% CI 13.26-25.20) (26/5) of sheep and goats, respectively. Conclusion: The present study showed that domestic animals and ticks were infected with Crimean-Congo hemorrhagic fever virus and that the disease was endemic in North Khorasan province, Iran. However, further surveillance and prevention programs are recommended.

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.

Stable Occupancy of the Crimean-Congo Hemorrhagic Fever Virus-Encoded Deubiquitinase Blocks Viral Infection

Crimean-Congo hemorrhagic fever virus is an important human pathogen with a wide global distribution for which no therapeutic interventions are available. CCHFV encodes a cysteine protease belonging to the ovarian tumor (OTU) family which is involved in host immune suppression. Here we demonstrate that artificially prolonged binding of the OTU to a substrate inhibits virus infection. This provides novel insights into CCHFV OTU function during the viral replicative cycle and highlights the OTU as a potential antiviral target.

Crimean-Congo hemorrhagic fever virus (CCHFV) infection can result in a severe hemorrhagic syndrome for which there are no antiviral interventions available to date. Certain RNA viruses, such as CCHFV, encode cysteine proteases of the ovarian tumor (OTU) family that antagonize interferon (IFN) production by deconjugating ubiquitin (Ub). The OTU of CCHFV, a negative-strand RNA virus, is dispensable for replication of the viral genome, despite being part of the large viral RNA polymerase. Here, we show that mutations that prevent binding of the OTU to cellular ubiquitin are required for the generation of recombinant CCHFV containing a mutated catalytic cysteine. Similarly, the high-affinity binding of a synthetic ubiquitin variant (UbV-CC4) to CCHFV OTU strongly inhibits viral growth. UbV-CC4 inhibits CCHFV infection even in the absence of intact IFN signaling, suggesting that its antiviral activity is not due to blocking the OTU’s immunosuppressive function. Instead, the prolonged occupancy of the OTU with UbV-CC4 directly targets viral replication by interfering with CCHFV RNA synthesis. Together, our data provide mechanistic details supporting the development of antivirals targeting viral OTUs.

Serologic survey of the Crimean-Congo haemorrhagic fever virus infection among wild rodents in Hungary

Crimean-Congo haemorrhagic fever virus (CCHFV) is a tick-borne pathogen, which causes an increasing number of severe infections in many parts of Africa, Asia and in Europe. The virus is primarily transmitted by ticks, however, the spectrum of natural hosts regarding CCHFV includes a wide variety of domestic and wild animals. Although the presence of CCHFV was hypothesized in Hungary, data in support of CCHFV prevalence has thus far, proven insufficient. In the present study, rodents belonging to four species, the yellow-necked mouse (Apodemus flavicollis), the striped field mouse (A. agrarius), the wood mouse (A. sylvaticus) and the bank vole (Myodes glareolus), were all systematically trapped in the Mecsek Mountain region (Southwest Hungary), from 2011 through 2013. Rodent sera were collected and screened for CCHFV antibodies with dot-blot pre-screening and immunofluorescence assay. Among the 2085 tested rodents, 20 (0.96%) were positive for IgG antibody against CCHFV. Seroprevalence was the highest (1.25%) in A. flavicollis serum samples. Distinctly, we now provide the first data regarding CCHFV occurrence and seroprevalence among wild rodents in Hungary. This observation represents a need for large-scale surveillance to effectively assess the enzootic background and the potential public health risk of CCHFV in Hungary.

Crimean-Congo Hemorrhagic Fever Virus, Mongolia, 2013-2014

During 2013–2014, we collected 1,926 serum samples from humans and 4,583 ticks (Hyalomma asiaticum or Dermacentor nuttalli) in select regions of Mongolia to determine the risk for Crimean-Congo hemorrhagic fever virus (CCHFV) infection among humans in this country. Testing of human serum samples by ELISA demonstrated an overall CCHFV antibody prevalence of 1.4%; Bayankhongor Province had the highest prevalence, 2.63%. We pooled and analyzed tick specimens by real-time reverse transcription PCR; 1 CCHFV-positive H. asiaticum tick pool from Ömnögovi was identified. In phylogenetic analyses, the virus’s partial small segment clustered with CCHFV isolates from Central Asia, and the complete medium segment grouped with CCHFV isolates from Africa, Asia, and the Middle East. This study confirms CCHFV endemicity in Mongolia and provides information on risk for CCHFV infection. Further research is needed to better define the risk for CCHFV disease to improve risk mitigation, diagnostics, and surveillance.

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.

Identification and characterization of vaccine candidates against Hyalomma anatolicum-Vector of Crimean-Congo haemorrhagic fever virus

Crimean-Congo haemorrhagic fever (CCHF) is a tick borne viral disease reported from different parts of the world. The distribution of the CCHF cases are linked with the distribution of the principal vector, Hyalomma anatolicum in the ecosystem. Presently, vector control is mainly dependent on repeated application of acaricides, results in partial efficacy and generated acaricide resistant tick strains. Amongst the different components of integrated management programme, immunization of hosts is considered as one of the sustainable component. To restrict CCHF virus spreading, use of anti-Hyalomma vaccines appears as a viable solution. Accordingly, present study was under taken to characterize and evaluate vaccine potential of two conserved molecules, ferritin2 (FER2) and tropomyosin (TPM). Silencing of the genes conferred a cumulative reduction (rejection + unable to engorge) of 61.3% in FER2 and 70.2% in TPM respectively. Furthermore, 44.2% and 72.7% reduction in engorgement weight, 63.6% and 94.9% reduction in egg masses in FER2 and TPM silenced ticks in comparison to LUC-control group was recorded. The recombinant protein, rHaFER2 was characterized as 35 kDa protein with pI of 5.84 and possesses iron binding domains. While rHaTPM is a 51kDa protein with pI of 4.94 having calcium binding domains. Immunization of cross-bred calves by rHaFER2 conferred 51.7% and 51.2% protection against larvae and adults of H. anatolicum challenge infestations. While rHaTPM conferred 63.7% and 66.4% protection against larvae and adults infestations, respectively. The results were comparable with the data generated by RNAi and it clearly showed the possibility for the development of anti-hyalomma vaccine to manage CCHF virus and Theileria annulata infection in human and animals.

Recent advances in understanding Crimean-Congo hemorrhagic fever virus

Crimean-Congo hemorrhagic fever virus (CCHFV) is a widely distributed hemorrhagic fever virus and the cause of hemorrhagic disease in Africa, Southern and Eastern Europe, the Middle East, India and Asia. Recent emergence of CCHFV into Spain indicates that the geographic range of this virus is expanding and the presence of its tick vector in several countries without reported disease suggest that CCHFV will continue to spread. Research into CCHFV was historically limited by a lack of suitable animal models and tools to study viral pathogenesis. However, in the past few years the toolset for studying CCHFV has expanded with small animal and non-human primate models for CCHFV being developed along with a reverse genetics system that allows for investigation of viral determinants of disease. These tools have been utilized to understand how CCHFV antagonizes host restriction factors and to develop novel vaccine candidates that may help limit the substantial morbidity and mortality in humans caused by CCHFV.

RECENT CHANGES IN INFECTIOUS DISEASES IN EUROPEAN WILDLIFE

Many infectious diseases originating from, or carried by, wildlife affect wildlife conservation and biodiversity, livestock health, or human health. We provide an update on changes in the epidemiology of 25 selected infectious, wildlife-related diseases in Europe (from 2010-16) that had an impact, or may have a future impact, on the health of wildlife, livestock, and humans. These pathogens were selected based on their: 1) identification in recent Europe-wide projects as important surveillance targets, 2) inclusion in European Union legislation as pathogens requiring obligatory surveillance, 3) presence in recent literature on wildlife-related diseases in Europe since 2010, 4) inclusion in key pathogen lists released by the Office International des Epizooties, 5) identification in conference presentations and informal discussions on a group email list by a European network of wildlife disease scientists from the European Wildlife Disease Association, or 6) identification as pathogens with changes in their epidemiology during 2010-16. The wildlife pathogens or diseases included in this review are: avian influenza virus, seal influenza virus, lagoviruses, rabies virus, bat lyssaviruses, filoviruses, canine distemper virus, morbilliviruses in aquatic mammals, bluetongue virus, West Nile virus, hantaviruses, Schmallenberg virus, Crimean-Congo hemorrhagic fever virus, African swine fever virus, amphibian ranavirus, hepatitis E virus, bovine tuberculosis ( Mycobacterium bovis), tularemia ( Francisella tularensis), brucellosis ( Brucella spp.), salmonellosis ( Salmonella spp.), Coxiella burnetii, chytridiomycosis, Echinococcus multilocularis, Leishmania infantum, and chronic wasting disease. Further work is needed to identify all of the key drivers of disease change and emergence, as they appear to be influencing the incidence and spread of these pathogens in Europe. We present a summary of these recent changes during 2010-16 to discuss possible commonalities and drivers of disease change and to identify directions for future work on wildlife-related diseases in Europe. Many of the pathogens are entering Europe from other continents while others are expanding their ranges inside and beyond Europe. Surveillance for these wildlife-related diseases at a continental scale is therefore important for planet-wide assessment, awareness of, and preparedness for the risks they may pose to wildlife, domestic animal, and human health.

Favipiravir (T-705) but not ribavirin is effective against two distinct strains of Crimean-Congo hemorrhagic fever virus in mice

Crimean-Congo hemorrhagic fever virus (CCHFV) is a cause of serious hemorrhagic disease in humans. Humans infected with CCHFV develop a non-specific febrile illness and then progress to the hemorrhagic phase where case fatality rates can be as high as 30%. Currently there is lack of vaccines and the recommended antiviral treatment, ribavirin, has inconsistent efficacy in both human and animal studies. In this study we developed a model of CCHFV infection in type I interferon deficient mice using the clinical CCHFV isolate strain Hoti. Mice infected with strain Hoti develop a progressively worsening and ultimately fatal disease. We utilized this model along with our established model using the prototypical CCHFV strain 10200 to evaluate treatment with ribavirin or the antiviral favipiravir. While ribavirin treatment was able to suppress viral loads at early time points it was ultimately unable to prevent development of terminal disease in mice infected with either strain of CCHFV. In contrast, favipiravir showed clinical benefit even when administered late in the clinical progression of CCHF. Interestingly, in a small subset of mice, late-onset of CCHF was observed after favipiravir treatment was stopped and persistence of viral RNA in favipiravir treated survivors was also seen. Nevertheless, favipiravir showed significant clinical benefit against two distinct strains of CCHFV suggesting it may be a potent antiviral for treatment of human CCHFV infections.

Global Spread of Hemorrhagic Fever Viruses: Predicting Pandemics

As successive epidemics have swept the world, the scientific community has quickly learned from them about the emergence and transmission of communicable diseases. Epidemics usually occur when health systems are unprepared. During an unexpected epidemic, health authorities engage in damage control, fear drives action, and the desire to understand the threat is greatest. As humanity recovers, policy-makers seek scientific expertise to improve their "preparedness" to face future events.Global spread of disease is exemplified by the spread of yellow fever from Africa to the Americas, by the spread of dengue fever through transcontinental migration of mosquitos, by the relentless influenza virus pandemics, and, most recently, by the unexpected emergence of Ebola virus, spread by motorbike and long haul carriers. Other pathogens that are remarkable for their epidemic expansions include the arenavirus hemorrhagic fevers and hantavirus diseases carried by rodents over great geographic distances and the arthropod-borne viruses (West Nile, chikungunya and Zika) enabled by ecology and vector adaptations. Did we learn from the past epidemics? Are we prepared for the worst?The ultimate goal is to develop a resilient global health infrastructure. Besides acquiring treatments, vaccines, and other preventive medicine, bio-surveillance is critical to preventing disease emergence and to counteracting its spread. So far, only the western hemisphere has a large and established monitoring system; however, diseases continue to emerge sporadically, in particular in Southeast Asia and South America, illuminating the imperfections of our surveillance. Epidemics destabilize fragile governments, ravage the most vulnerable populations, and threaten the global community.Pandemic risk calculations employ new technologies like computerized maintenance of geographical and historical datasets, Geographic Information Systems (GIS), Next Generation sequencing, and Metagenomics to trace the molecular changes in pathogens during their emergence, and mathematical models to assess risk. Predictions help to pinpoint the hot spots of emergence, the populations at risk, and the pathogens under genetic evolution. Preparedness anticipates the risks, the needs of the population, the capacities of infrastructure, the sources of emergency funding, and finally, the international partnerships needed to manage a disaster before it occurs. At present, the world is in an intermediate phase of trying to reduce health disparities despite exponential population growth, political conflicts, migration, global trade, urbanization, and major environmental changes due to global warming. For the sake of humanity, we must focus on developing the necessary capacities for health surveillance, epidemic preparedness, and pandemic response.

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.

Host preferences support the prominent role of Hyalomma ticks in the ecology of Crimean-Congo hemorrhagic fever

Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne zoonotic agent that is maintained in nature in an enzootic vertebrate-tick-vertebrate cycle. Hyalomma genus ticks have been implicated as the main CCHFV vector and are key in maintaining silent endemic foci. However, what contributes to their central role in CCHFV ecology is unclear. To assess the significance of host preferences of ticks in CCHFV ecology, we performed comparative analyses of hosts exploited by 133 species of ticks; these species represent 5 genera with reported geographical distribution over the range of CCHFV. We found that the composition of vertebrate hosts on which Hyalomma spp. feed is different than for other tick genera. Immatures of the genus Hyalomma feed preferentially on species of the orders Rodentia, Lagomorpha, and the class Aves, while adults concentrate mainly on the family Bovidae. With the exception of Aves, these hosts include the majority of the vertebrates consistently reported to be viremic upon CCHFV infection. While other tick genera also feed on these hosts, Hyalomma spp. almost completely concentrate their populations on them. Hyalomma spp. feed on less phylogenetically diverse hosts than any other tick genus, implying that this network of hosts has a low resilience. Indeed, removing the most prominent hosts quickly collapsed the network of parasitic interactions. These results support the intermittent activity of CCHFV foci: likely, populations of infected Hyalomma spp. ticks exceed the threshold of contact with humans only when these critical hosts reach adequate population density, accounting for the sporadic occurence of clinical tick-transmitted cases. Our data describe the association of vertebrate host preferences with the role of Hyalomma spp. ticks in maintaining endemic CCHFV foci, and highlight the importance of host-tick dynamics in pathogen ecology.

Second International Conference on Crimean-Congo Hemorrhagic Fever

The Second International Conference on Crimean-Congo Hemorrhagic Fever (CCHF) was held in Thessaloniki, Greece, from September 10-13, 2017, and brought together international public health professionals, clinicians, ecologists, and basic laboratory researchers. Nearly 100 participants, representing 24 countries and the World Health Organization (WHO), were in attendance. Meeting sessions covered the epidemiology of CCHF in humans; ticks and virus-tick interactions; wild and domestic animal hosts; molecular virology; taxonomic classification; pathogenesis and animal models; clinical aspects and diagnosis; clinical management and clinical trials; and disease prevention in humans. The concluding session focused on recent WHO recommendations for public health measures and future research. This report summarizes lectures by the invited speakers and highlights advances in the field.

A novel double-antigen sandwich ELISA for the species-independent detection of Crimean-Congo hemorrhagic fever virus-specific antibodies

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne disease in humans caused by the CCHF virus (CCHFV). The detection of anti-CCHFV antibodies in animals is used to reveal infection risk areas. Therefore a simple, quick and reliable multispecies assay for the detection of CCHFV-specific antibodies is needed. This work presents the development and validation of a novel CCHF double-antigen ELISA for the detection of anti-CCHFV nucleoprotein antibodies. The test requires 30 μl of serum, and results are obtained within 90 min. As the ELISA is based on recombinant N-protein of the IbAr10200 virus, it can be run under standard biosafety conditions. For assay validation, sera from 95 cattle and 176 small ruminants from CCHF-endemic regions (origin: Albania, Cameroon, Kosovo, Former Yugoslav Republic of Macedonia, Mauritania, Pakistan, Turkey) served as a positive reference serum panel. The CCHF antibody status of the positive reference samples had been previously confirmed by two serological assays (species-adapted VectorBest ELISA and Euroimmun IFA). CCHFV strains belonging to three different clades are known to circulate in the countries where the positive samples originated. Sera from 402 cattle and 804 small ruminants from Germany and France served as the negative serum panel, as both countries are considered outside of the CCHFV endemic zone. Sera from monkeys, camels, rats, ferrets, raccoon dogs, raccoons, foxes, hares, pigs and humans were also tested, to determine the suitability of this novel ELISA for these species. All negative reference sera were confirmed by the CCHF double-antigen ELISA, indicating a specificity of 100%. 268 of 271 positive reference sera tested positive for CCHFV-specific antibodies, 8sensitivity of 99%9. Further analysis are needed to ensure a recognition of the IbAr10200 nucleoprotein by antibodies directed against all known CCHFV clades. This is planned to be realized with sera from other regions covering the three missing clades.

Crimean-Congo Hemorrhagic Fever in Humanized Mice Reveals Glial Cells as Primary Targets of Neurological Infection

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne viral hemorrhagic disease seen exclusively in humans. Central nervous system (CNS) infection and neurological involvement have also been reported in CCHF. In the current study, we inoculated NSG-SGM3 mice engrafted with human hematopoietic CD34+ stem cells with low-passage CCHF virus strains isolated from human patients. In humanized mice, lethal disease develops, characterized by histopathological change in the liver and brain. To date, targets of neurological infection and disease have not been investigated in CCHF. CNS disease in humanized mice was characterized by gliosis, meningitis, and meningoencephalitis, and glial cells were identified as principal targets of infection. Humanized mice represent a novel lethal model for studies of CCHF countermeasures, and CCHF-associated CNS disease. Our data suggest a role for astrocyte dysfunction in neurological disease and identify key regions of infection in the CNS for future investigations of CCHF.

Genome Sequences of Crimean-Congo Hemorrhagic Fever Virus Strains Isolated in South Africa, Namibia, and Turkey

We report here the full-length sequences of 16 historical isolates of Crimean-Congo hemorrhagic fever orthonairovirus (CCHFV) obtained in Turkey, Namibia, and South Africa. The strains may be useful for future work to develop molecular diagnostics or viral evolution studies.

A recombinase polymerase amplification assay for rapid detection of Crimean-Congo Haemorrhagic fever Virus infection

BACKGROUND

Crimean-Congo Haemorrhagic fever Virus (CCHFV) is a rapidly emerging vector-borne pathogen and the cause of a virulent haemorrhagic fever affecting large parts of Europe, Africa, the Middle East and Asia.

METHODOLOGY/PRINCIPLE FINDINGS

An isothermal recombinase polymerase amplification (RPA) assay was successfully developed for molecular detection of CCHFV. The assay showed rapid (under 10 minutes) detection of viral extracts/synthetic virus RNA of all 7 S-segment clades of CCHFV, with high target specificity. The assay was shown to tolerate the presence of inhibitors in crude preparations of mock field samples, indicating that this assay may be suitable for use in the field with minimal sample preparation. The CCHFV RPA was successfully used to screen and detect CCHFV positives from a panel of clinical samples from Tajikistan.

CONCLUSIONS/SIGNIFICANCE

The assay is a rapid, isothermal, simple-to-perform molecular diagnostic, which can be performed on a light, portable real-time detection device. It is ideally placed therefore for use as a field-diagnostic or in-low resource laboratories, for monitoring of CCHF outbreaks at the point-of-need, such as in remote rural regions in affected countries.

A DNA vaccine for Crimean-Congo hemorrhagic fever protects against disease and death in two lethal mouse models

Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne virus capable of causing a severe hemorrhagic fever disease in humans. There are currently no licensed vaccines to prevent CCHFV-associated disease. We developed a DNA vaccine expressing the M-segment glycoprotein precursor gene of CCHFV and assessed its immunogenicity and protective efficacy in two lethal mouse models of disease: type I interferon receptor knockout (IFNAR^-/-) mice; and a novel transiently immune suppressed (IS) mouse model. Vaccination of mice by muscle electroporation of the M-segment DNA vaccine elicited strong antigen-specific humoral immune responses with neutralizing titers after three vaccinations in both IFNAR^-/- and IS mouse models. To compare the protective efficacy of the vaccine in the two models, groups of vaccinated mice (7–10 per group) were intraperitoneally (IP) challenged with a lethal dose of CCHFV strain IbAr 10200. Weight loss was markedly reduced in CCHFV DNA-vaccinated mice as compared to controls. Furthermore, whereas all vector-control vaccinated mice succumbed to disease by day 5, the DNA vaccine protected >60% of the animals from lethal disease. Mice from both models developed comparable levels of antibodies, but the IS mice had a more balanced Th1/Th2 response to vaccination. There were no statistical differences in the protective efficacies of the vaccine in the two models. Our results provide the first comparison of these two mouse models for assessing a vaccine against CCHFV and offer supportive data indicating that a DNA vaccine expressing the glycoprotein genes of CCHFV elicits protective immunity against CCHFV.

Crimean-Congo hemorrhagic Fever Virus (CCHFV) is a tick-borne virus capable of causing lethal human disease against which there are currently no approved vaccines. In this study, we compared the immunogenicity and protective efficacy of a candidate DNA vaccine expressing the glycoprotein precursor gene of CCHFV in two mouse models. In addition to the recently established IFNAR^-/- mouse pathogenesis model, we also tested the vaccine in a novel murine system in which the interferon (IFN) α/β signaling response of immunocompetent mice is transiently suppressed. We found that the DNA vaccine elicited high humoral immune responses and provided significant protection against challenge with CCHFV in both mouse models. These findings further our understanding of the requirements for a CCHFV vaccine and provide a new mouse model for the development of CCHFV countermeasures.

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.

First serological evidence of Crimean-Congo haemorrhagic fever in febrile patients in Mozambique

OBJECTIVE

Despite its geographical spread, the epidemiology of Crimean-Congo haemorrhagic fever (CCHF) in Sub-Saharan Africa is incompletely understood and its occurrence in Mozambique is unknown. This study was conducted with the aim of investigating the occurrence of CCHF virus (CCHFV) among febrile patients attending an outpatient appointment clinic at three separate primary health care centres in Mozambique.

METHODS

Serum samples were collected from a total of 300 febrile patients aged >5 years who were recruited between March 2015 and March 2016 at three health centres in Mozambique. Each patient was screened for IgG antibodies against CCHFV using an ELISA.

RESULTS

Of the 300 patients enrolled, eight had samples that were positive for anti-CCHFV IgG antibodies, yielding a prevalence rate of 2.7%.

CONCLUSIONS

This study shows for the first time that humans are exposed to CCHFV in Mozambique. It highlights the need for further work to investigate the broader extent of circulating CCHFV in the country and its clinical implications.

Serosurvey for Crimean-Congo hemorrhagic fever virus infections in ruminants in Katanga province, Democratic Republic of the Congo

Crimean-Congo hemorrhagic fever virus (CCHFV) has been detected in many African countries. Unfortunately, little is known about the current CCHFV situation in most of those countries including the Democratic Republic of the Congo (DRC). In over 50 years, three human CCHF cases have been detected in DRC but no seroepidemiological investigation was performed so far. To determine the prevalence of CCHFV-specific antibodies we tested 838 serum samples of cattle, goat and sheep from the southern province Katanga, DRC. The detected seroprevalence in ruminants was 1.6% ranging from 0.4% to 3.4% between the two sampling sites, Kamina and Lubumbashi. The low prevalence indicates only sporadic introduction of CCHFV into this part of the country. DRC is a very large country and the study was performed only at two locations in one province; therefore, the investigations can be only a starting point for further epidemiological activities.

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.

Vector and Serologic Survey for Crimean-Congo Hemorrhagic Fever Virus in Poland

In contrast to animals, Crimean-Congo hemorrhagic fever (CCHF) causes a severe disease in humans with a high mortality rate. The etiological agent, CCHF virus (CCHFV), can be transmitted by argasid and ixodid ticks, but arachnids of the genus Hyalomma, followed by Rhipicephalus and Dermacentor serve as the major vectors of this virus. The goal of the study was to assess the epidemiological situation of CCHFV infection in cattle in south-east Poland, and survey for potential tick vector species. A total of 592 bovine blood samples from animals located in the southernmost region in Poland were tested by IgG sandwich enzyme-linked immunosorbent assay. Ticks (n = 993) from south-east Poland were collected from dogs, cats, cattle, and horses and tested by RT-PCR. All 592 serum samples were negative for IgG antibodies to CCHFV. Of the ticks collected, 125 were Dermacentor reticulatus and 868 represented Ixodes ricinus, both species are regarded as potential vectors of CCHFV. All tick samples were negative for the presence of CCHFV. Considering the zoonotic nature, public health importance, and the virus increasing spread, it was prudent to assess the seroprevalence of CCHFV in the south-east area of Poland, bordering with CCHFV endemic areas. It seems unlikely that CCHFV infection will suddenly spread in Poland, but considering the multiple possibilities of the virus introduction, serosurveys and vector biosurveillance should be conducted at regular intervals.

The reasons why Pakistan might be at high risk of Crimean Congo haemorrhagic fever epidemic; a scoping review of the literature

Pakistan has faced a number of significant healthcare challenges over the past decade. In 2000, one of these events - a deadly epidemic of Crimean Congo Haemorrhagic Fever (CCHF) - struck Pakistan. The people of Pakistan are at a very high risk of acquiring CCHF, due to a number of factors which emerge from a scoping review of the literature. First, the underdeveloped healthcare system of the country is currently not prepared to cope with challenges of this nature. Healthcare professionals and medical institutes are not sufficiently equipped to properly diagnose, manage and prevent CCHF. Second, a large percentage of the general public is unaware of the spread and control of the vector. The agricultural sector of Pakistan is vast and thus many people are involved in animal husbandry and the handling of livestock which can lead to the transmission of the CCHF virus. Even in urban areas the risk of transmission is significantly higher around the time of Eid-ul-Azha, when Muslims slaughter animals. Finally, the political upheavals faced by the country have also increased Pakistan's vulnerability because a large number of refugees from Afghanistan, a CCHF endemic country, have migrated to Pakistan as a result of the Afghan war. Most of the refugees and their animals settle in Baluchistan and Khyber Pakhtunkhwa provinces, which consequently have a higher prevalence of CCHF. This scoping review of the literature highlights the potential causes of high risk CCHF and draws conclusions and makes recommendations that policy-makers in Pakistan may wish to consider in-order to improve on the current situation.

Detection of Crimean-Congo hemorrhagic fever virus-specific IgG antibodies in ruminants residing in Central and Western Macedonia, Greece

Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne virus which causes lethal hemorrhagic fever in humans. Although, several reports regarding CCHFV antibody prevalence in humans exist in Greece, information about the current distribution is limited. The aim of the present study is to investigate the prevalence of CCHFV-specific IgG antibodies in cattle and sheep in Macedonia-Greece. The samplings were performed during spring 2013, in 5 regional units of Central Macedonia (Chalkidiki, Imathia, Kilkis, Pella and Thessaloniki) and in the 4 regional units of Western Macedonia (Grevena, Florina, Kastoria and Kozani). Specifically, sera from 538 cattle and 81 sheep underwent testing against CCHFV-specific IgG antibodies. Antiviral immune responses were observed in 31 cattle (6%, 95% CI: 4-8%) and in one sheep (1%, 95% CI: 0-8%). The total seroprevalence in the cattle sampled in Central Macedonia was 7% (28 out of 396, 95% CI: 5-10%). Within Central Macedonia, the highest seroprevalence was detected in Chalkidiki (38%, 95% CI: 23-56%), which was significantly higher (p<0.01) compared to the overall seroprevalence detected in cattle. In Western Macedonia, the total seroprevalence in cattle was 2% (3 out of 142, 95% CI: 1-7%). The 3 seropositive cattle were residing in the regional unit of Grevena. The one IgG-positive sheep serum was obtained from an animal residing in Thessaloniki. In this regional unit, the prevalence in sheep (2%, 95% CI: 0-10%) was much lower compared to the prevalence in cattle (12%, 95% CI: 6-22%), but significance was not achieved (p=0.03). The here presented seroepidemiological study demonstrates high transmission risk to human in specific geographical areas, which should be communicated to national and local public health authorities, so as to intensify preventive measures for public health protection.

Serological and Virological Evidence of Crimean-Congo Haemorrhagic Fever Virus Circulation in the Human Population of Borno State, Northeastern Nigeria

Background

Despite several studies on the seroprevalence of antibodies against Crimean-Congo Haemorrhagic Fever virus (CCHFV) from humans and cattle in Nigeria, detailed investigation looking at IgG and IgM have not been reported. Additionally, there have been no confirmed cases of human CCHFV infection reported from Nigeria.

Principal Findings

Samples from sera (n = 1189) collected from four Local Government Areas in Borno State (Askira/Uba, Damboa, Jere and Maiduguri) were assessed for the presence of IgG and IgM antibodies. The positivity rates for IgG and IgM were 10.6% and 3.5%, respectively. Additionally, sera from undiagnosed febrile patients (n = 380) were assessed by RT-PCR assay for the presence of CCHFV RNA. One positive sample was characterised by further by next generation sequencing (NGS) resulting in complete S, M and L segment sequences.

Conclusions

This article provides evidence for the continued exposure of the human population of Nigeria to CCHFV. The genomic analysis provides the first published evidence of a human case of CCHFV in Nigeria and its phylogenetic context.

Crimean-Congo haemorrhagic fever (CCHF) is an acute tick-borne zoonotic disease. The causative agent, CCHF virus (CCHFV), has the most extensive geographical distribution of the medically important tick-borne viral diseases with a distribution over much of Asia, the Middle East, Africa and expanding areas of south-eastern Europe. Whilst the main route of human infection with CCHFV is predominantly through tick bite, it can also be spread via bodily fluids and it has a reputation for causing nosocomial outbreaks in healthcare settings. Whilst CCHFV has been identified in ticks from Nigeria since 1970, there is scarce information on human infection. Within this report, the prevalence of CCHFV-reactive antibodies has been assessed in human sera providing evidence of continued circulation of the virus in the human population of Borno state, Nigeria. Additionally, in one sample the presence of viral RNA was detected which allowed a full sequence of the CCHFV to be obtained. This is the first report of CCHFV being associated in a human case from Nigeria and the full genetic characterisation of the virus being completed. The evidence within supports the hypothesis that CCHFV is endemic in Nigeria and should be considered as an aetiological agent in febrile patients.

A chronological review of experimental infection studies of the role of wild animals and livestock in the maintenance and transmission of Crimean-Congo hemorrhagic fever virus

This article provides a definitive review of experimental studies of the role of wild animals and livestock in the maintenance and transmission of Crimean-Congo hemorrhagic fever virus (CCHFV), the etiologic agent of Crimean-Congo hemorrhagic fever (CCHF), beginning with the first recognized outbreak of the human disease in Crimea in 1944. Published reports by researchers in the former Soviet Union, Bulgaria, South Africa, and other countries where CCHF has been observed show that CCHFV is maintained in nature in a tick-vertebrate-tick enzootic cycle. Human disease most commonly results from the bite of an infected tick, but may also follow crushing of infected ticks or exposure to the blood and tissues of infected animals during slaughter. Wild and domestic animals are susceptible to infection with CCHFV, but do not develop clinical illness. Vertebrates are important in CCHF epidemiology, as they provide blood meals to support tick populations, transport ticks across wide geographic areas, and transmit CCHFV to ticks and humans during the period of viremia. Many aspects of vertebrate involvement in the maintenance and spread of CCHFV are still poorly understood. Experimental investigations in wild animals and livestock provide important data to aid our understanding of CCHFV ecology. This article is the second in a series of reviews of more than 70 years of research on CCHF, summarizing important findings, identifying gaps in knowledge, and suggesting directions for future research.