Genetic monitoring of the Crimean-Congo Hemorrhagic Fever virus in Kazakhstan and Tajikistan in 2001-2003

Blood specimens obtained from 32 CCHF patients were tested for the presence of CCHF virus markers. In addition, 3210 ticks of the genera Hyalomma asiaticum, Hyalomma anatolicum, and Dermacentor niveus were examined to identify the CCHF virus antigen and RNA. This material was obtained during the 2001-2003 local outbreaks of CCHF in Kazakhstan and Tajikistan. The nucleotide sequence in the region 983-1282 of S segment of the CCHF virus for 12 wild type strains was determined. The phylogenetic relationships among the established biovariants of CCHF virus, and also between these biovariants and those from other regions of the world were identified. We were the first to demonstrate the presence of an African-like genotype of CCHF virus in the territory of Kazakhstan. The conclusion was made that two genotypes of CCHF virus were in circulation in Kazakhstan. It was also demonstrated that CCHF virus, circulating in the territories of Kazakhstan and Tajikistan, was genetically heterogeneous.     

Transmission of crimean-congo haemorrhagic fever virus from experimentally infected sheep to hyalomma truncatum ticks

Crimean-Congo haemorrhagic fever (CCHF) virus was inoculated into West African sheep that were simultaneously infested with adult Hyalomma truncatum ticks. Certain sheep developed a viraemia and antibodies, indicating virus infection and replication; however, the length and magnitude of the viraemia and serological responses corresponded to the animals' immunological status. Tick attachment and feeding was not influenced by sheep infection. CCHF virus infection was acquired by 11–33 % of female and 0–60 % of male ticks. Infection in the ticks did not influence their feeding success, as judged by weight at drop-off, and the weight of eggs produced by infected and non-infected ticks was similar. Transovarial transmission of CCHF virus was demonstrated in 2 of 12 (17 %) egg batches from infected female ticks, but in none of 19 egg batches from ticks that tested negative for CCHF virus. Our results suggest that under certain ecological conditions, sheep may serve to amplify CCHF virus in nature through horizontal transmission and that the maintenance cycle also may be influenced by transovarial transmission to the next generation of ticks.     

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

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne zoonosis with a high case fatality rate in humans. Although the disease is widely found in Africa, Europe, and Asia, the distribution and genetic diversity of CCHF virus (CCHFV) are poorly understood in African countries. To assess the risks of CCHF in Zambia, where CCHF has never been reported, epidemiologic studies in cattle and ticks were conducted. Through an indirect immunofluorescence assay, CCHFV nucleoprotein-specific serum IgG was detected in 8.4% (88/1,047) of cattle. Among 290 Hyalomma ticks, the principal vector of CCHFV, the viral genome was detected in 11 ticks. Phylogenetic analyses of the CCHFV S and M genome segments revealed that one of the detected viruses was a genetic reassortant between African and Asian strains. This study provides compelling evidence for the presence of CCHFV in Zambia and its transmission to vertebrate hosts.     

Tick survey and detection of Crimean-Congo hemorrhagic fever virus in tick species from a non-endemic area, South Marmara region, Turkey

Crimean-Congo hemorrhagic fever (CCHF) is an increasing health concern in Turkey since 2002. There were also some recent human cases from the South Marmara region of Turkey; thus, a tick survey was performed, and possible vector tick species for the CCHF virus were determined in the region. A total of 740 adult ticks were collected from infested livestock from five locations: Çanakkale-Biga, Bursa-Orhaneli, Bursa-Keles, Bal?kesir and Bilecik. Total of 11 tick species from the genera Hyalomma, Rhipicephalus, Dermacentor, Ixodes and Haemaphysalis were identified. Rhipicephalus ticks were dominant in the region; the most frequently observed tick species was R. turanicus, (53.1 %), and only 15.4 % of the identified ticks were H. marginatum. The occurrence of H. rufipes infestation in the region fort he first time. A total of 73 pools of adult ticks were tested with both an antigen-detecting ELISA and RT real-time PCR (RT rt PCR). The presence of the CCHF virus was demonstrated in 9 (12.3 %) of the tested tick pools. Although seven of the tick pools were positive for the CCHF virus with both of the methods, one pool was positive only with RT rt PCR and the other pool was only positive with the ELISA. Positive results were obtained from ticks collected from cattle, sheep and goats from two locations, Bursa-Orhaneli and Bilecik. The CCHF virus was detected in R. turanicus (n = 3), R. bursa (n = 2), H. marginatum (n = 2) and D. marginatus (n = 2) ticks. The results of this study confirm the presence of the CCHF virus and present preliminary data on the vector tick species in the southern Marmara region of Turkey.     

Synonymous codon usage pattern among the S,M, and L segments in Crimean-congo hemorrhagic fever virus

Crimean-Congo hemorrhagic fever (CCHF) virus is one among the major zoonosis viral diseases that use the Hyalomma ticks as their transmission vector to cause viral infection to the human and mammalian community. The fatality of infectious is high across the world especially in Africa, Asia, Middle East, and Europe. This study regarding codon usage bias of S, M, and L segments of the CCHF virus pertaining to the host Homo sapiens, reveals in-depth information about the evolutionary characteristics of CCHFV. Relative Synonymous Codon Usage (RSCU), Effective number of codons (ENC) were calculated, to determine the codon usage pattern in each segment. Correlation analysis between Codon adaptation index (CAI), GRAVY (Hydrophobicity), AROMO (Aromaticity), and nucleotide composition revealed bias in the codon usage pattern. There was no strong codon bias found among any segments of the CCHF virus, indicating both the factors i.e., natural selection and mutational pressure shapes the codon usage bias.     

Study of the circulation of Crimean hemorrhagic fever virus in Turkmenistan]

Final results of the virological and serological investigations of the circulation of the Crimean hemorrhagic fever virus in the Turkmenian SSR carried out in 1968-1976 are presented in this report. In the examination of 2294 blood serum samples of human beings complement binding antibodies against the Crimean hemorrhagic fever were revealed in 0.4% of cases. It was revealed that five species of ixodes ticks could he infected with this virus; for the first time its strains were also isolated from the Hyalomma dromedarii ticks. Isolation of the Crimean hemorrhagic fever virus from ticks and determination of the precipitating antibodies against this virus in agricultural animals--from 6.2 to 11.1%--in all the regions of the republic pointed out that the natural nidi zones were widespread at the territory of the Turkmenian SSR, and that it was necessary to carry out further study of the given focus.     

Characterization of the natural foci of Congo-Crimean hemorrhagic fever on the territory of Ukraine

The natural foci of the Congo-Crimean hemorrhagic fever (CCHF) in Ukraine were characterized by their geographical factors. The circulation of CCHF virus was found to occur mainly in forest and forest-steppe zones irrespective of the location of administrative regions. The territories found to be most favorable for the prolonged existence of the focus of CCHF were those having high humidity. The possibility of using geoinformation technologies for the correction of the boundaries of natural foci, the evaluation of the influence of geographical factors on the circulation of the virus was shown.     

Prevalence of Crimean-Congo Hemorrhagic Fever Virus in Healthy Population,Livestock and Ticks in Kosovo

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

Characterization of the glycoproteins of Crimean-Congo hemorrhagic fever virus

Crimean-Congo hemorrhagic fever (CCHF) virus is the cause of an important tick-borne disease of humans throughout regions of Africa, Europe, and Asia. Like other members of the genus Nairovirus, family Bunyaviridae, the CCHF virus M genome RNA segment encodes the virus glycoproteins. Sequence analysis of the CCHF virus (Matin strain) M RNA segment revealed one major open reading frame that potentially encodes a precursor polyprotein 1,689 amino acids (aa) in length. Comparison of the deduced amino acid sequences of the M-encoded polyproteins of Nigerian, Pakistani, and Chinese CCHF virus strains revealed two distinct protein regions. The carboxyl-terminal 1,441 aa are relatively highly conserved (up to 8.4% identity difference), whereas the amino-terminal 243 to 248 aa are highly variable (up to 56.4% identity difference) and have mucin-like features, including a high serine, threonine, and proline content (up to 47.3%) and a potential for extensive O-glycosylation. Analysis of released virus revealed two major structural glycoproteins, G2 (37 kDa) and G1 (75 kDa). Virus protein analysis by various techniques, including pulse-chase analysis and/or reactivity with CCHF virus-specific polyclonal and antipeptide antibodies, demonstrated that the 140-kDa (which contains the mucin-like region) and 85-kDa nonstructural proteins are the precursors of the mature G2 and G1 proteins, respectively. The amino termini of the CCHF virus (Matin strain) G2 and G1 proteins were established by microsequencing to be equivalent to aa 525 and 1046, respectively, of the encoded polyprotein precursor. The tetrapeptides RRLL and RKPL are immediately upstream of the cleavage site for mature G2 and G1, respectively. These are completely conserved among the predicted polyprotein sequences of all the CCHF virus strains and closely resemble the tetrapeptides that represent the major cleavage recognition sites present in the glycoprotein precursors of arenaviruses, such as Lassa fever virus (RRLL) and Pichinde virus (RKLL). These results strongly suggest that CCHF viruses (and other members of the genus Nairovirus) likely utilize the subtilase SKI-1/S1P-like cellular proteases for the major glycoprotein precursor cleavage events, as has recently been demonstrated for the arenaviruses.     

Experimental transmission of Crimean-Congo hemorrhagic fever virus: role of 3 vector species in the maintenance and transmission cycles in Senegal

In this article, we published the role of three species of ticks Amblyomma variegatum (Fabricius, 1974), Hyalomma marginatum rufipes (Koch, 1844) and Hyalomma truncatum (Koch, 1844) in the maintenance and transmission of the CCHF virus. The imagos of these species were infected by intracoelomic route. Vertical transmission (transtasial and transovarial) and horizontal transmission for different stases were studied by isolation on newborn mice, polymerase chain reaction, indirect immunofluorescence and ELISA. Our results proved that 15 days after inoculation, infection rates of 100% were noted with Hyalomma marginatum rufipes and Hyalomma truncatum. This rate is about 60% for Amblyomma variegatum. The imagos of the three species infected have transmitted the virus to their host during blood feeding (100%). A high transovarial transmission for Hyalomma marginatum rufipes and Hyalomma truncatum were observed (respectively 53 and 50%). This rate is about 12% for Amblyomma variegatum. The tick infection does not persist up to the first generation for the three species studied. Ticks are temporary reservoirs vectors but not permanent reservoirs of CCHF virus.     

Sequential determination of viral load,humoral responses and phylogenetic analysis in fatal and non-fatal cases of Crimean-Congo hemorrhagic fever patients from Gujarat,India, 2019

BackgroundThirty-four CCHF cases (17 fatal; 17 survived) were confirmed from Gujarat state, India during the year 2019. We aimed to find out the viral load, antibody kinetics, cytokine profile and phylogenetic analysis between fatal and non- fatal cases.MethodsThirty four cases were included in this study. Blood and urine samples were collected from all the cases on the day of admission to hospital. Non-fatal cases were followed weekly for understanding the profile of viral kinetics, anti-CCHFV IgM and IgG antibodies. We also quantified the cytokines in both fatal and non-fatal cases. For epidemiological correlation, livestock were screened for anti-CCHF IgG antibodies and the tick pool specimens were tested by real time RT-PCR. Virus isolation was attempted on tick pools and human specimens and phylogenetic analysis performed on human and ticks complete genome sequences.ResultsCCHF cases were detected throughout year in 2019 with the peak in August. Out of 34 cases, eight secondary CCHF cases were reported. Cases were predominantly detected in males and in 19–45 years age group (55.88%). The persistence of viremia was observed till 76^th POD (post onset date) in one case whereas anti-CCHFV IgM and IgG was detected amongst these cases from the 2^nd and 20^th POD respectively. Positivity observed amongst livestock and tick pools were was 21.57% and 7.4% respectively. The cytokine analysis revealed a significant increase in the level of serum IL-6, IL-10 and IFN-γ during the acute phase of the infection, but interestingly IL-10 lowered to normal upon clearance of the virus in the clinically recovered case. Fatal cases had high viral RNA copy numbers. Bleeding from one or two mucosal sites was significantly associated with fatality (OR-16.47;p-0.0034 at 95% CI). We could do CCHF virus isolation from two cases. Phylogenetic analysis revealed circulation of re-assortment of Asian-West African genotypes in humans and ticks.ConclusionsThe persistence of CCHF viral RNA was detected till 76^th POD in one of the survivors. The circulation of a re-assortment Asian-West African genotype in a CCHF case is also reported first time from India.     

A survey of ticks (Acari: Ixodidae) on dairy cattle on the island of Menorca in Spain

A survey of ticks affecting dairy cattle under extensive management on Menorca island (off the Spanish Mediterranean coast) was performed through 1999-2000 on seven farms. The species collected were Rhipicephalus bursa, R. turanicus, Hyalomma m. marginatum, H. lusitanicum and Boophilus annulatus. The most abundant species were R. bursa and H. m. marginatum, with peaks of 10.7 (in summer) and 7.5 (in spring) ticks/cow, respectively. R. turanicus was scarcely encountered, while B. annulatus and H. lusitanicum were abundant only in a few localities. The mild climate and adequate vegetation on the island provide satisfactory habitat for extended periods of tick activity, as compared with other regions where these ticks have been collected. The competence of the ticks as vectors for pathogens and the difficulty of using acaricide treatments in the region are discussed.     

Risk factors associated with exposure to Crimean-Congo haemorrhagic fever virus in animal workers and cattle,and molecular detection in ticks,South Africa

Crimean-Congo haemorrhagic fever (CCHF) is a severe tick-borne viral zoonosis endemic to parts of Africa, Europe, the Middle East and Central Asia. Human cases are reported annually in South Africa, with a 25% case fatality rate since the first case was recognized in 1981. We investigated CCHF virus (CCHFV) seroprevalence and risk factors associated with infection in cattle and humans, and the presence of CCHFV in Hyalomma spp. ticks in central South Africa in 2017–18. CCHFV IgG seroprevalence was 74.2% (95%CI: 64.2–82.1%) in 700 cattle and 3.9% (95%CI: 2.6–5.8%) in 541 farm and wildlife workers. No veterinary personnel (117) or abattoir workers (382) were seropositive. The prevalence of CCHFV RNA was significantly higher in Hyalomma truncatum (1.6%) than in H. rufipes (0.2%) (P = 0.002). Seroprevalence in cattle increased with age and was greater in animals on which ticks were found. Seroprevalence in cattle also showed significant geographic variation. Seroprevalence in humans increased with age and was greater in workers who handled livestock for injection and collection of samples. Our findings support previous evidence of widespread high CCHFV seroprevalence in cattle and show significant occupational exposure amongst farm and wildlife workers. Our seroprevalence estimate suggests that CCHFV infections are five times more frequent than the 215 confirmed CCHF cases diagnosed in South Africa in the last four decades (1981–2019). With many cases undiagnosed, the potential seriousness of CCHF in people, and the lack of an effective vaccine or treatment, there is a need to improve public health awareness, prevention and disease control.     

High seroprevalence for Crimean–Congo haemorrhagic fever virus in ruminants in the absence of reported human cases in many regions of Bulgaria

Crimean–Congo haemorrhagic fever (CCHF) is a severe tick-borne zoonotic disease in humans caused by CCHF virus. It has been observed in Bulgaria since 1952 and over the years more than 1600 cases have been reported in the country. Close contact with viraemic livestock was shown as one of the main causes of the infection. Detection of CCHF virus specific antibodies in livestock can be used as an indicator for virus circulation and risk assessment. CCHF seroprevalence was investigated in 843 cattle, 88 goats and 130 sheep, originating from all 28 districts of Bulgaria. CCHF virus-specific IgG antibodies were observed in 165 cattle (19.6, 95% CI 17.0–22.4%), in 20 goats (22.7, 95% CI 15.2–32.5%) and in 10 sheep (7.7, 95% CI 4.2–13.6%). The highest seroprevalence was detected in the district of Kardzhali, South Bulgaria (86.7, 95% CI 73.8–93.7%), a well-known focus of CCHF in humans. The other two districts with human CCHF cases, Blagoevgrad and Burgas, located in southwest and southeast Bulgaria, showed overall seroprevalences in livestock of 41.9% (95% CI 28.4–56.7%) and 31.3% (95% CI 22.2–42.1%), respectively. Seroprevalences in districts with no history of human CCHF cases varied between 55% (95% CI 39.8–69.3%) and 22.5% (95% CI 12.3–37.5%). These results suggest frequent CCHF virus infections even in regions without human CCHF cases and an enhanced risk of infection for humans in close contact with the infected livestock.     

Tick-borne encephalitis virus prevalence in Ixodes ricinus ticks collected in high risk habitats of the south-Bohemian region of the Czech Republic

A survey for tick-borne encephalitis virus in Ixodes ricinus ticks was conducted in May 2000 in two districts of the South-Bohemian region of the Czech Republic with a high occurrence of tick-borne encephalitis (TBE) in humans. Homogenized ticks were tested on PS cells, which were examined for any cytopathic effect, plaque assay and indirect fluorescent antibody test (IFT). The IFT has proved to be the most sensitive and most rapid test to demonstrate the virus in ticks. TBE virus was found in 17 of 187 pooled samples, consisting of a total of 2,968 ticks. The mean minimum infection rate was 0.6% for all tick stages combined. Infection rates in nymphs collected indifferent locations varied between 0.2 and 1.3% and between 5.9 and 11.1% in adult ticks. The observed TBE prevalence in ticks was compared with data obtained elsewhere in the Czech Republic. It is concluded that screening of ticks for TBE virus prevalence using IFT is a valuable indicator for the degree of risk to contract TBE in as particular habitat. This revised version was published online in July 2006 with corrections to the Cover Date.