Circulation of Crimean-Congo hemorrhagic fever virus in the Stavropol territory in the seasons of 1999-2000

After the prolonged (about 30 years) absence of Crimean-Congo hemorrhagic fever (CCHF) morbidity in the Stavropol territory cases of this infection were registered, and received laboratory confirmation, in summer of 1999-2000. At the end of the 1999 season antibodies to CCHF virus were detected among cattle-breeders in all 7 inspected regions of the territory. According to the data of the determination of virus contamination of Ixodes ticks (the season of 2000), the circulation of CCHF on the territory of 14 regions out of 24 expected was established. An essential factor of the exacerbation of the epidemic situation was a rise in the number of Hyalomma marginatum ticks, the main vector of the causative agent of CCHF in the south of Russia.     

Method for Accelerated Identification of Arboviruses After Inoculation of Mice

Sequential titration of infective virus and complement-fixing antigen in brain and liver of suckling mice infected with the following virus strains-Dugbe (a new arbovirus), Congo (related to Crimean hemorrhagic fever virus), yellow fever, dengue 1 and dengue 2-showed a progressive increase in titer after infection. High titers of both infective virus and complement-fixing antigen were demonstrated long before the mice showed clinical signs of infection. It is suggested that earlier isolation and identification of arboviruses from clinical and field specimens can be made if serological tests are done before mice are moribund.     

Detection and characteristics of foci of arbovirus infection in the Kazakh region

Complex studies carried out on the territory of Kazakhstan have allowed one to detect arboviruses, heretofore unknown in the republic, to determine their role in human infectious pathology and to obtain additional data on the ecology of viruses causing tick-borne encephalitis and Crimean hemorrhagic fever under the conditions of different geographical zones in the republic. On the basis of the results thus obtained the map indicating the spread of arbovirus infections and their causative agents on the territory of the Kazakh SSR has been drawn. This map may serve as a practical aid in organizing antiepidemic measures.     

Incidence of antibodies against human immunodeficiency virus, human T-cell lymphotropic virus type 1, hepatitis B virus, hemorrhagic fever with renal syndrome virus and Chlamydia in Tonga and western Samoa

Among the populations of Tonga and Western Samoa, serum antibodies against human immunodeficiency virus or hemorrhagic fever with renal syndrome virus were not detected (0/904 and 0/192). No serum samples were considered to be positive for antibody against human T-cell lymphotropic virus type 1 (0/527). Hepatitis B antigen and antibody were found in 4% (8/192) and 47% (90/192), respectively. Chlamydia trachomatis IgG and C. psittaci IgG antibodies were detected in 39% (75/192) and 47% (91/192), respectively. The possibilities of the spread of human immunodeficiency virus and hemorrhagic fever with renal syndrome virus on the islands when the viruses invade from abroad were discussed.     

Detection, isolation and confirmation of Crimean-Congo hemorrhagic fever virus in human, ticks and animals in Ahmadabad, India, 2010-2011

Background

In January 2011, human cases with hemorrhagic manifestations in the hospital staff were reported from a tertiary care hospital in Ahmadabad, India. This paper reports a detailed epidemiological investigation of nosocomial outbreak from the affected area of Ahmadabad, Gujarat, India.

Principal Findings

Samples from 3 suspected cases, 83 contacts, Hyalomma ticks and livestock were screened for Crimean-Congo hemorrhagic fever (CCHF) virus by qRT-PCR of which samples of two medical professionals (case C and E) and the husband of the index case (case D) were positive for CCHFV. The sensitivity and specificity of indigenous developed IgM ELISA to screen CCHFV specific antibodies in human serum was 75.0% and 97.5% respectively as compared to commercial kit. About 17.0% domestic animals from Kolat, Ahmadabad were positive for IgG antibodies while only two cattle and a goat showed positivity by qRT-PCR. Surprisingly, 43.0% domestic animals (Buffalo, cattle, sheep and goat) showed IgG antibodies in the adjoining village Jivanpara but only one of the buffalo was positive for CCHFV. The Hyalomma anatolicum anatolicum ticks were positive in PCR and virus isolation. CCHFV was isolated from the blood sample of case C, E in Vero E-6 cells and Swiss albino mice. In partial nucleocapsid gene phylogeny from CCHFV positive human samples of the years 2010 and 2011, livestock and ticks showed this virus was similar to Tajikistan (strain TAJ/{"type":"entrez-nucleotide","attrs":{"text":"H08966","term_id":"873788","term_text":"H08966"}}H08966), which belongs in the Asian/middle east genetic lineage IV.

Conclusions

The likely source of CCHFV was identified as virus infected Hyalomma ticks and livestock at the rural village residence of the primary case (case A). In addition, retrospective sample analysis revealed the existence of CCHFV in Gujarat and Rajasthan states before this outbreak. An indigenous developed IgM ELISA kit will be of great use for screening this virus in India.     

Lassa fever: implications of T-cell immunity for vaccine development.

Lassa fever is a re-emerging viral hemorrhagic fever, which causes significant human morbidity in endemic regions of West Africa. Attempts to vaccinate against this virus in animal models including non-human primates have revealed that eliciting a strong cellular immune response protects from clinical disease, but not infection, in the absence of measurable neutralizing antibodies. As there is renewed interest in developing a vaccine against Lassa fever for use in humans, several questions should be addressed in view of the scarce knowledge of the mechanisms of natural immunity against this disease. MHC-dependency of a vaccine relying mainly on the induction of T-cell immunity and its ability to cross-protect against different Lassa virus strains will be important issues. Furthermore, the question whether the vaccine can prevent human-to-human transmission of the virus should be discussed and the possibility that vaccination could predispose to immunopathology should be excluded. We are addressing some of the above mentioned problems concerning natural immunity through field studies in the Republic of Guinea, West Africa, and are presently studying the CD4 cell responses of Lassa antibody positive subjects on the basis of T-cell proliferation assays using recombinant Lassa virus proteins.     

Bayesian Phylogeography of Crimean-Congo Hemorrhagic Fever Virus in Europe

Crimean-Congo hemorrhagic fever (CCHF) is a zoonosis mainly transmitted by ticks that causes severe hemorrhagic fever and has a mortality rate of 5-60%. The first outbreak of CCHF occurred in the Crimean peninsula in 1944-45 and it has recently emerged in the Balkans and eastern Mediterranean. In order to reconstruct the origin and pathway of the worldwide dispersion of the virus at global and regional (eastern European) level, we investigated the phylogeography of the infection by analysing 121 publicly available CCHFV S gene sequences including two recently characterised Albanian isolates. The spatial and temporal phylogeny was reconstructed using a Bayesian Markov chain Monte Carlo approach, which estimated a mean evolutionary rate of 2.96 x 10^-4 (95%HPD=1.6 and 4.7 x 10^-4) substitutions/site/year for the analysed fragment. All of the isolates segregated into seven highly significant clades that correspond to the known geographical clades: in particular the two new isolates from northern Albania clustered significantly within the Europe 1 clade. Our phylogeographical reconstruction suggests that the global CCHFV clades originated about one thousand years ago from a common ancestor probably located in Africa. The virus then spread to Asia in the XV century and entered Europe on at least two occasions: the first in the early 1800s, when a still circulating but less or non-pathogenic virus emerged in Greece and Turkey, and the second in the early 1900s, when a pathogenic CCHFV strain began to spread in eastern Europe. The most probable location for the origin of this European clade 1 was Russia, but Turkey played a central role in spreading the virus throughout Europe. Given the close proximity of the infected areas, our data suggest that the movement of wild and domestic ungulates from endemic areas was probably the main cause of the dissemination of the virus in eastern Europe.     

A Multiplex PCR/LDR Assay for the Simultaneous Identification of Category A Infectious Pathogens: Agents of Viral Hemorrhagic Fever and Variola Virus

CDC designated category A infectious agents pose a major risk to national security and require special action for public health preparedness. They include viruses that cause viral hemorrhagic fever (VHF) syndrome as well as variola virus, the agent of smallpox. VHF is characterized by hemorrhage and fever with multi-organ failure leading to high morbidity and mortality. Smallpox, a prior scourge, has been eradicated for decades, making it a particularly serious threat if released nefariously in the essentially non-immune world population. Early detection of the causative agents, and the ability to distinguish them from other pathogens, is essential to contain outbreaks, implement proper control measures, and prevent morbidity and mortality. We have developed a multiplex detection assay that uses several species-specific PCR primers to generate amplicons from multiple pathogens; these are then targeted in a ligase detection reaction (LDR). The resultant fluorescently-labeled ligation products are detected on a universal array enabling simultaneous identification of the pathogens. The assay was evaluated on 32 different isolates associated with VHF (ebolavirus, marburgvirus, Crimean Congo hemorrhagic fever virus, Lassa fever virus, Rift Valley fever virus, Dengue virus, and Yellow fever virus) as well as variola virus and vaccinia virus (the agent of smallpox and its vaccine strain, respectively). The assay was able to detect all viruses tested, including 8 sequences representative of different variola virus strains from the CDC repository. It does not cross react with other emerging zoonoses such as monkeypox virus or cowpox virus, or six flaviviruses tested (St. Louis encephalitis virus, Murray Valley encephalitis virus, Powassan virus, Tick-borne encephalitis virus, West Nile virus and Japanese encephalitis virus).     

Hybridomas producing monoclonal antibodies to Crimean hemorrhagic fever virus

A series of hybridomas producing monoclonal antibodies to Crimean hemorrhagic fever virus was obtained and their cultural properties were characterized. HEMA-12 and HEMA-24 secreted monoclonal IgG2b antibodies, HEMA-101 secreted monoclonal IgG1 antibodies, HEMA-31, HEMA-9 and HEMA-11 secreted monoclonal IgG2 antibodies. According to the results of the indirect immunofluorescence test, the titer of specific immunoglobulins in the culture fluid was 1:16-1:32, but sometimes reached 1:64-1:128. The titer of antibodies in ascitic fluid amounted to dilutions of 10(4)-10(5). Hybridomas were cloned by the method of ultimate dilutions. The injection of 5-15 million HEMA cells into the abdominal cavity of BALB/c mice induced the formation of ascitic tumors in the animals within 7-11 days and the accumulation of ascitic fluid in a volume of 1-4 ml. Hybridomas, found to be capable of passage from mouse to mouse, underwent 5-16 passages during the term of observation.     

Passive transfer of antibodies protects immunocompetent and imunodeficient mice against lethal Ebola virus infection without complete inhibition of viral replication

Ebola hemorrhagic fever is a severe, usually fatal illness caused by Ebola virus, a member of the filovirus family. The use of nonhomologous immune serum in animal studies and blood from survivors in two anecdotal reports of Ebola hemorrhagic fever in humans has shown promise, but the efficacy of these treatments has not been demonstrated definitively. We have evaluated the protective efficacy of polyclonal immune serum in a mouse model of Ebola virus infection. Our results demonstrate that mice infected subcutaneously with live Ebola virus survive infection and generate high levels of anti-Ebola virus immunoglobulin G (IgG). Passive transfer of immune serum from these mice before challenge protected upto 100% of naive mice against lethal Ebola virus infection. Protection correlated with the level of anti-Ebola virus IgG titers, and passive treatment with high-titer antiserum was associated with a delay in the peak of viral replication. Transfer of immune serum to SCID mice resulted in 100% survival after lethal challenge with Ebola virus, indicating that antibodies alone can protect from lethal disease. Thus antibodies suppress or delay viral growth, provide protection against lethal Ebola virus infection, and may not require participation of other immune components for protection.     

Etiological relation between Korean hemorrhagic fever and epidemic hemorrhagic fever in Japan.

The first case of epidemic hemorrhagic fever in Japan was seen in Osaka in 1960. The etiologic agent of this disease has not yet been isolated, but a close etiologic relation between Korean hemorrhagic fever and epidemic hemorrhagic fever in Japan has been suspected because of similarities in the clinical and pathological pictures of the two diseases. This relation has now been confirmed serologically by demonstrating specific immunofluorescent antibodies to Korean hemorrhagic fever virus in 19 of 20 sera obtained from subjects 7 to 17 years after an acute attack of epidemic hemorrhagic fever.     

Expression of interferon-induced antiviral genes is delayed in a STAT1 knockout mouse model of Crimean-Congo hemorrhagic fever

ABSTRACT: Background Crimean Congo hemorrhagic fever (CCHF) is a tick-borne hemorrhagic zoonosis associated with high mortality. Pathogenesis studies and the development of vaccines and antivirals against CCHF have been severely hampered by the lack of suitable animal model. We recently developed and characterized a mature mouse model for CCHF using mice carrying STAT1 knockout (KO). Findings Given the importance of interferons in controlling viral infections, we investigated the expression of interferon pathway-associated genes in KO and wild-type (WT) mice challenged with CCHF virus. We expected that the absence of the STAT1 protein would result in minimal expression of IFN-related genes. Surprisingly, the KO mice showed high levels of IFN-stimulated gene expression, beginning on day 2 post-infection, while in WT mice challenged with virus the same genes were expressed at similar levels on day 1. Conclusions We conclude that CCHF virus induces similar type I IFN responses in STAT1 KO and WT mice, but the delayed and dysregulated response in the KO mice permits rapid viral dissemination and fatal illness.     

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.     

Successful topical respiratory tract immunization of primates against Ebola virus

Ebola virus causes outbreaks of severe viral hemorrhagic fever with high mortality in humans. The virus is highly contagious and can be transmitted by contact and by the aerosol route. These features make Ebola virus a potential weapon for bioterrorism and biological warfare. Therefore, a vaccine that induces both systemic and local immune responses in the respiratory tract would be highly beneficial. We evaluated a common pediatric respiratory pathogen, human parainfluenza virus type 3 (HPIV3), as a vaccine vector against Ebola virus. HPIV3 recombinants expressing the Ebola virus (Zaire species) surface glycoprotein (GP) alone or in combination with the nucleocapsid protein NP or with the cytokine adjuvant granulocyte-macrophage colony-stimulating factor were administered by the respiratory route to rhesus monkeys--in which HPIV3 infection is mild and asymptomatic--and were evaluated for immunogenicity and protective efficacy against a highly lethal intraperitoneal challenge with Ebola virus. A single immunization with any construct expressing GP was moderately immunogenic against Ebola virus and protected 88% of the animals against severe hemorrhagic fever and death caused by Ebola virus. Two doses were highly immunogenic, and all of the animals survived challenge and were free of signs of disease and of detectable Ebola virus challenge virus. These data illustrate the feasibility of immunization via the respiratory tract against the hemorrhagic fever caused by Ebola virus. To our knowledge, this is the first study in which topical immunization through respiratory tract achieved prevention of a viral hemorrhagic fever infection in a primate model.     

Evaluation of the European tick‐borne encephalitis vaccine against Omsk hemorrhagic fever virus

This study focused on the antigenic cross‐reactivity between tick‐borne encephalitis virus (TBEV) and Omsk hemorrhagic fever virus (OHFV) to assess the efficacy of the commercial TBE vaccine against OHFV infection. Neutralization tests performed on sera from OHFV‐ and TBEV‐infected mice showed that neutralizing antibodies are cross‐protective. The geometric mean titers of antibodies against TBEV and OHFV from TBEV‐infected mice were similar. However, the titers of anti‐TBEV antibodies in OHFV‐infected mice were significantly lower than those of anti‐OHFV antibodies in the same animals. In mouse vaccination and challenge tests, the TBE vaccine provided 100% protection against OHFV infection. Eighty‐six percent of vaccinees seroconverted against OHFV following complete vaccination, and the geometric mean titers of neutralizing antibodies against OHFV were comparable to those against TBEV. These data suggest that the TBE vaccine can prevent OHFV infection.     

Crimean-Congo hemorrhagic fever in Rostov Province: the epidemiological characteristics of an outbreak

The results of the epidemiological analysis of the outbreak of hemorrhagic fever which was caused by Crimean-Congo hemorrhagic fever virus and occurred during the period of July 3-19, 1999, in the Oblivskaya district of Rostov Province are presented. The specific epidemiological features of the outbreak have been determined. The possible versions of the appearance of the focus of infection and the role of Ixodes ticks in the circulation of the infective agent are discussed.     

Argentine hemorrhagic fever

Features of the Argentine hemorrhagic fever are described in the review. Epidemiology, etiology, clinical presentation and pathogenesis of the disease are examined. Special consideration is given to the features of the pathological agent of Argentine hemorrhagic fever--the Junin virus. Features of the disease diagnostics are indicated--virological and serological studies, immunochemical and molecular-biological methods of identification of the pathological agent and antibodies against it. Approaches to etiotropic therapy of this disease and vaccination are examined. Based on the foreign experience perspective guidance for the creation of the system of protection of the population of the Russian Federation against Argentine hemorrhagic fever are presented.     

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.     

Hyalomma ticks on northward migrating birds in southern Spain: Implications for the risk of entry of Crimean‐Congo haemorrhagic fever virus to Great Britain

Crimean‐Congo haemorrhagic fever virus (CCHFV) is a zoonotic virus transmitted by Hyalomma ticks, the immature stages of which may be carried by migratory birds. In this study, a total of 12 Hyalomma ticks were recovered from five of 228 migratory birds trapped in Spring, 2012 in southern Spain along the East Atlantic flyway. All collected ticks tested negative for CCHFV. While most birds had zero Hyalomma ticks, two individuals had four and five ticks each and the statistical distribution of Hyalomma tick counts per bird is over‐dispersed compared to the Poisson distribution, demonstrating the need for intensive sampling studies to avoid underestimating the total number of ticks. Rates of tick exchange on migratory birds during their northwards migration will affect the probability that a Hyalomma tick entering Great Britain is positive for CCHFV. Drawing on published data, evidence is presented that the latitude of a European country affects the probability of entry of Hyalomma ticks on wild birds. Further data on Hyalomma infestation rates and tick exchange rates are required along the East Atlantic flyway to further our understanding of the origin of Hyalomma ticks (i.e., Africa or southern Europe) and hence the probability of entry of CCHFV into GB.