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transmission of rift valley fever virus by the sand fly, phlebotomus duboscqi (diptera: psychodidae).studies were conducted to determine if the sand fly phlebotomus duboscqi could serve as a vector of rift valley fever (rvf) virus. when 145 p. duboscqi were fed on a hamster with rvf viremia (approximately 10(9) pfu/ml of blood), 72 (50%) became infected. of 5 with disseminated infections (i.e., virus recovered from their legs) 4 transmitted virus to hamsters by bite. sand flies were uniformly infected when rvf virus was inoculated by the intrathoracic route, and each of 31 sand flies so inocula ...19902316789
transmission of rift valley fever virus by adult mosquitoes after ingestion of virus as larvae.we studied the ability of culex pipiens, aedes circumluteolus, and ae. mcintoshi, exposed as larvae to liver tissue from a rift valley fever (rvf) virus-infected hamster, to become infected and transstadially transmit virus to the adult and for the adults to transmit virus by bite to hamsters. after exposure as larvae, 9% (5/54) of adult cx. pipiens and 8% (38/505) of the adult ae. (neomelaniconion) species were infected. all of the infected cx. pipiens and about half of the infected ae. circuml ...19902267972
establishment and characterization of a cell line from the mosquito culex (culex) theileri (diptera: culicidae) and its susceptibility to infection with arboviruses.the mosquito culex (culex) theileri theobald is probably the major vector of rift valley fever (rvf) virus during epizootics on the inland plateau of southern africa. a cell line was established from the tissues of this mosquito species to facilitate laboratory studies on rvf and other arboviruses. after temperature pretreatment, egg rafts from a laboratory colony were disinfected, mechanically disrupted, and grown in preconditioned eagles minimum essential medium supplemented with 10% fetal cal ...19902280394
expression strategy of a phlebovirus: biogenesis of proteins from the rift valley fever virus m segment.the middle (m) rna segment of rift valley fever virus (rvfv) encodes four proteins: the major viral glycoproteins g2 and g1, a 14-kilodalton (kda) protein, and a 78-kda protein. these proteins are derived from a single large open reading frame (orf) present in the virus-complementary m-segment mrna. we used recombinant vaccinia viruses in which sequences representing the m-segment orf were engineered as a surrogate system to study phlebovirus protein expression. to investigate the translational ...19902319645
use of reassortant viruses to map attenuating and temperature-sensitive mutations of the rift valley fever virus mp-12 vaccine.a live-attenuated vaccine for rift valley fever virus (rvfv), mp-12, has been developed recently by undirected, serial mutagenesis of a rvfv strain (zh548) isolated during the 1977 epidemic in egypt. in the present study, the mutations responsible for attenuation of this virus have been examined by analysis of reassortant viruses generated between the vaccine strain and a wild rvfv strain isolated in senegal. reassortant viruses were generated efficiently in multiply infected vero cells, and wer ...19902396475
prophylactic and therapeutic efficacy of poly(i,c)-lc against rift valley fever virus infection in mice.the prophylactic and therapeutic efficacy of polyriboinosinic-polyribocytidylic acid stabilized with poly-l-lysine and carboxymethylcellulose [poly(i,c)-lc] was evaluated in female swiss webster mice against a lethal infection of rift valley fever virus (rvfv). prophylactically, the best effect was obtained with 2-3 doses of 1-20 micrograms poly(i,c)-lc, which fully protected the mice in a schedule-dependent fashion against an ld100 rvfv challenge. multiple intermittent therapeutic administratio ...19852416883
use of bacterial expression cloning to define the amino acid sequences of antigenic determinants on the g2 glycoprotein of rift valley fever virus.four distinct antigenic determinants along the g2 glycoprotein encoded by the m segment rna of the phlebovirus rift valley fever virus were localized. these epitopes were defined by four monoclonal antibodies, three of which were capable of neutralizing virus infectivity; one was nonneutralizing. immunoprecipitation by these monoclonal antibodies of either denatured or native antigen characterized the epitopes as having linear or higher order structure. molecular cloning of g2 glycoprotein-codin ...19862422392
complement fixing antibodies against arboviruses in horses at lagos, nigeria.sixty-two sera horse collected from two stables at lagos, nigeria, were tested for complement fixing antibody to 8 arbovirus antigens; chikungunya, igbo-ora, yellow fever, wesselsbron, west nile, potiskum, uganda s and rift valley fever. ten per cent of the horse sera examined contained cf antibody to one or more of the test antigens and indicated considerable arbovirus activity in the two stables. reactions with flavivirus antigens were most common and the highest antibody titres were obtained ...19892485538
prophylaxis of rift valley fever with antiviral drugs, immune serum, an interferon inducer, and a macrophage activator.rift valley fever virus (rvfv), a member of the family bunyaviridae, extended its range from sub-saharan africa into egypt in 1977. its clinical spectrum is recognized to include severe manifestations such as hemorrhagic fever and encephalitis. for these reasons, as well as the limited knowledge of specific therapy for bunyaviridae infections, we investigated several prophylactic regimens for rvf in a mouse model. rimantadine, thiosemicarbazone, and inosiplex were ineffective. pretreatment with ...19862429616
genetic variation among geographic isolates of rift valley fever virus.the genetic variation of rift valley fever virus (rvfv) was estimated by sequencing a portion of the m segment rna of 22 isolates from a variety of host species collected over 34 years in 6 african countries. the m segment rna of the egyptian isolate, zh501, which has been molecularly cloned and sequenced, was used as a reference for these comparisons. specific gene regions, responsible for antigenic determinants presumed to play a role in protection against disease, were emphasized in these inv ...19882462795
antigenic and biological properties of rift valley fever virus isolated during the 1987 mauritanian epidemic.the antigenic and biological properties of three strains of rift valley fever virus (rvfv) isolated during the 1987 epidemic in mauritania were compared with those of strains isolated previously in west africa and with other selected african strains. neither the antigenic characteristics of the mauritanian isolates, as monitored by the binding of 59 monoclonal antibodies, nor the electrophoretic migration of the virus-specific structural and non-structural proteins were significantly different f ...19892474189
antibody prevalence against haemorrhagic fever viruses in randomized representative central african populations.between 1985 and 1987, 5,070 randomly selected persons living in 6 central african countries (cameroon, central african republic, chad, congo, equatorial guinea and gabon) were checked for serological evidence of haemorrhagic fever. rural and urban areas were studied, including ecoclimatic zones ranging from dry savana to tropical rain forest. virus-reactive antibodies were found with all antigens tested, and the global prevalence of positive sera was distributed as follows: crimean-congo haemor ...19892505350
toga-like virus as a cause of fulminant hepatitis attributed to sporadic non-a, non-b.virus-like particles (60-70 nm) with spiked surfaces budding into cell vacuoles and rod-shaped inclusions were detected in nuclei of hepatocytes from a british patient transplanted for sporadic non-a, non-b fulminant hepatitis (nanb-fhf), probably contracted in kenya. identical particles were seen in two successive grafts (days 2 and 10) at regrafting for recurrent fhf. ultrastructural features resembled those of the rna-containing arbovirus, rift valley fever virus, but serological markers agai ...19892502604
inhibition of crimean-congo hemorrhagic fever viral infectivity yields in vitro by ribavirin.ribavirin was evaluated as a potential therapeutic for crimean-congo hemorrhagic fever (cchf). viral yields for strains of cchf virus from europe, asia, and africa in african green monkey kidney (vero) cells were markedly reduced by this drug. some cchf viral strains appeared more sensitive than others, but in general, ribavirin doses as low as 5 micrograms/ml caused a transient reduction of viral yields. a further reduction in viral yields was induced by a dose of 25 micrograms/ml, and evidence ...19892510529
antibodies to haemorrhagic fever viruses in madagascar populations.sera of 381 adult people from 5 areas in madagascar were tested by the indirect immunofluorescence method for antibodies against congo-crimean haemorrhagic fever and rift valley fever viruses (bunyaviridae), ebola (strains zaire and sudan) and marburg viruses (filoviridae), and lassa virus (arenaviridae). the highest prevalence rate was that of ebola virus (4.5%). as no haemorrhagic syndrome has been found associated with this virus, the possible presence of a less pathogenic, antigenically rela ...19892515626
prevention of rift valley fever in rhesus monkeys with interferon-alpha.prophylactic and therapeutic efficacy of recombinant leukocyte a interferon (rifn-alpha a) and sendai virus-induced human leukocyte interferon (huifn-alpha) administered intramuscularly to rift valley fever virus (rvfv)-infected rhesus monkeys was studied. clinical, virologic, immunologic, and hemostatic parameters were monitored. five daily inoculations of 5 x 10(5) units of either interferon product per kilogram of body weight, initiated 24 hours before or 6 hours after rvfv infection, prevent ...19892546250
transmission of rift valley fever virus by different geographic strains of culex pipiens in egypt.previous investigations have delt with colonized cx. pipiens and rvf virus interactions. this study evaluated the vector competence of parental cx. pipiens populations for rvf virus and investigated variations in the vector competence among different geographic strains of this mosquito in egypt. cx. pipiens females were fed on viremic hamsters circulating 9.4-10.5 log10 smicld50 of virus. mosquito samples were freezed at different intervals extending between 0-12 days of extrinsic incubation (ei ...19892519963
prospects for treatment of viral hemorrhagic fevers with ribavirin, a broad-spectrum antiviral drug.ribavirin, a broad-spectrum antiviral drug, is active against hemorrhagic fever viruses (with the exception of ebola virus) in cell culture systems. in model infections with arenaviruses in guinea pigs and monkeys, ribavirin has demonstrated both prophylactic and therapeutic efficacy. in therapeutic studies it has not prevented late-onset neurologic disease. in human cases of lassa fever, it significantly reduces mortality when administered before day 7 of illness to persons at high risk. in rod ...19892546248
epidemiology of hemorrhagic fever viruses.twelve distinct viruses associated with hemorrhagic fever in humans are classified among four families: arenaviridae, which includes lassa, junin, and machupo viruses; bunyaviridae, which includes rift valley fever, crimean-congo hemorrhagic fever, and hantaan viruses; filoviridae, which includes marburg and ebola viruses; and flaviviridae, which includes yellow fever, dengue, kyasanur forest disease, and omsk viruses. most hemorrhagic fever viruses are zoonoses, with the possible exception of t ...19892546247
arbovirus infections and viral haemorrhagic fevers in uganda: a serological survey in karamoja district, 1984.sera collected in may 1984 from 132 adult residents of karamoja district, uganda, were examined by haemagglutination inhibition tests for antibodies against selected arboviruses, namely chikungunya and semliki forest alphaviruses (togaviridae); dengue type 2, wesselsbron, west nile, yellow fever and zika flaviviruses (flaviviridae); bunyamwera, ilesha and tahyna bunyaviruses (bunyaviridae); and sicilian sandfly fever phlebovirus (bunyaviridae); and by immunofluorescence tests against certain hae ...19892559514
arbovirus infections and viral haemorrhagic fevers in uganda: a serological survey in karamoja district, 1984.sera collected in may 1984 from 132 adult residents of karamoja district, uganda, were examined by haemagglutination inhibition tests for antibodies against selected arboviruses, namely chikungunya and semliki forest alphaviruses (togaviridae); dengue type 2, wesselsbron, west nile, yellow fever and zika flaviviruses (flaviviridae); bunyamwera, ilesha and tahyna bunyaviruses (bunyaviridae); and sicilian sandfly fever phlebovirus (bunyaviridae); and by immunofluorescence tests against certain hae ...19892559514
[transmission cycles of arboviruses in madagascar].some arboviruses are highly pathogenic for men or animals. arboviruses epidemiological patterns in madagascar were determined by entomological, serological, and virological surveys. we listed potentials arboviruses vectors in madagascar. entomological results generated by us during five years, as well as prior to, are shown. we caught more than 150,000 hematophagous arthropods, belonging to 107 species at least. 3 of these species were new. 4183 inoculation pools were done. we studied serollogic ...19892576622
baculovirus expression of the m genome segment of rift valley fever virus and examination of antigenic and immunogenic properties of the expressed proteins.autographa californica nuclear polyhedrosis viral recombinants containing coding information for the rift valley fever virus (rvfv) envelope glycoproteins (g1 and g2) and varying amounts of preglycoprotein coding sequences were prepared by using transfer vectors pac373 or pacym1. expression products were processed to yield proteins indistinguishable from authentic g1 and g2 by gel electrophoresis. the immunogenic properties of the expressed proteins were assessed by immunizing mice and challengi ...19892655274
efficacy of a sustained-release methoprene formulation on potential vectors of rift valley fever virus in field studies in kenya. 19892614412
biological and antigenic relationship between rift valley fever virus strains isolated in egypt and madagascar. 19892617635
serological evidence of dengue fever among refugees, hargeysa, somalia.epidemics of a malaria-like illness affected several thousand residents of the dam camp, a refugee camp near hargeysa in somalia, during 1985, 1986, and 1987. the disease was characterized by fever, chills, sweats, headache, back and joint pains for as long as 10 days in some patients. blood smears from acutely ill patients were negative for malaria. of 28 acute and 10 convalescent sera tested by the indirect fluorescent antibody (ifa) and by the hemagglutination inhibition (hi) tests, all were ...19892600591
pathogenesis of viral hemorrhagic fevers: rift valley fever and lassa fever contrasted.although many viral infections have on occasion been associated with hemorrhagic complications, infection with any of several rna viruses regularly results in vascular involvement and the syndrome called viral hemorrhagic fever (vhf). in spite of clinically useful similarities among various vhfs, there are significant differences in their pathogenesis and clinical evolution; these are often related to characteristics of their viral taxon. infection with rift valley fever (rvf) virus, a phlebovir ...19892665011
isolation of rift valley fever virus from human peripheral blood mononuclear cells: mauritanian epidemic.during the mauritanian rift valley fever (rvf) epidemic of 1987, peripheral blood mononuclear cells (pbmc) were studied from 78 sick patients. rvf virus (rvfv) was isolated in 5 cases, on aedes pseudoscutellaris ap61, from both pbmc and serum. among the 78 cases studied, rvf was proven in 19 cases (24.3%) by specific igm detection, and in 12 cases (15.3%) by virus isolation from serum, of which 3 also exhibited anti-rvf igm. among the 5 pbmc-positive rvfv cases, 2 strains were isolated in the pr ...19892667067
replication of hemorrhagic fever viruses in monocytic cells.monocytes play a central role in protection against many viruses. in some infections they are target cells for viral replication. there is increasing evidence that these cells may also be important in regulation of hemostasis. the part played by monocytic cells in the pathogenesis of hemorrhage in the viral hemorrhagic fevers is presently uncertain. monocytes and monocytic cell lines have been used to investigate the ability of viruses to infect these cells in vitro. several factors may affect t ...19892665010
diagnosis of a human case of rift valley fever by immunoperoxidase demonstration of antigen in fixed liver tissue. 19892667064
filter paper confetti in a serological rift valley fever survey.in order to collect epidemiological data about the rift valley fever epidemic in mauritania, we decided to use the filter paper method. the mean recovery level of specific antibodies from filter paper, tested using an immunoenzymatic method, is around one fourth. taking the mean haematocrit into account, we estimated the extract square with a 1/300 dilution. this method was very useful for epidemiological studies, we observed few patient refusals, but it is necessary to know the exact specificit ...19892667065
identification of mutations in the m rna of a candidate vaccine strain of rift valley fever virus.the m rna species of a candidate vaccine strain of rift valley fever virus (rvfv zh-548m12), derived by consecutive high level mutagenesis using 5-fluorouracil (h. caplen, c. j. peters, and d. h. l. bishop, j. gen. virol., 66, 2271-2277, 1985), has been cloned and the cdna sequenced. the data have been compared to those obtained for the parent virus strain rvfv zh-548 as well as the previously published data for rvfv zh-501 (m. s. collett, a. f. purchio, k. keegan, s. frazier, w. hays, d. k. and ...19892705307
assessment of an rdna probe filter hybridization assay for the detection of rift valley fever virus rna in human serum samples from the mauritanian epidemic.the rift valley fever virus (rvfv) epidemic that occurred in southern mauritania during the 1987 rainy season provided a unique opportunity to test and evaluate a recently developed, m-segment-specific, nucleic acid filter hybridization assay on a large collection of infected human serum samples. it afforded the opportunity to compare the procedure with two other methods for detecting virus: virus isolation and antigen detection by elisa. the filter hybridization procedure employed a polyethylen ...19892711045
rapid diagnosis of rift valley fever: a comparison of methods for the direct detection of viral antigen in human sera.human sera collected during the 1987 rift valley fever (rvf) epidemic in the senegal river basin were analysed using three enzyme immunoassays to establish the best method for rapid diagnosis of rvf. a biotin-avidin-enhanced antigen detection method utilizing monoclonal antibodies proved most sensitive. eighty-two viremic human sera were tested, and this assay detected antigen in 29.3% of the samples.19892711046
rift valley fever among domestic animals in the recent west african outbreak.severe haemorrhagic disease among the human population of the senegal river basin brought the rift valley fever virus (rvfv) outbreak of 1987 to the attention of science. as in previous rvfv outbreaks, local herdsmen reported a high incidence of abortion and disease in their livestock. serum samples were obtained from domestic animal populations from areas near rosso, the best studied focus of human infection, as well as other areas distant from known human disease. among animals from the area o ...19892711047
general aspects of the 1987 rift valley fever epidemic in mauritania. 19892711042
isolation of the rift valley fever virus by inoculation into aedes pseudoscutellaris cells: comparison with other diagnostic methods.the rift valley fever epidemic, which arose in the south of mauritania beginning on october 15, 1987, enabled a comparative study of different diagnostic methods among humans. during the first two weeks of the epidemic, four parallel methods were used: inoculation into aedes pseudoscutellaris cells, inoculation intracerebrally into suckling mice, tests by immunocapture of the circulating antigen and detection of type igm gammaglobulins. of 370 examined sera, 181 showed at least one marker of rec ...19892711043
rapid detection of rift valley fever antigen in the serum of infected lambs. 19892711044
rift valley fever virus m segment: phlebovirus expression strategy and protein glycosylation.the m segment rna of rift valley fever virus (rvfv) encodes four gene products: the two viral envelop glycoproteins g2 and g1, a glycosylated 78-kda protein, and a nonglycosylated 14-kda protein. these proteins are generated from a single open reading frame (orf) by a strategy involving independent translational initiations at both the first and second in-phase atg codons and co-translational processing of primary polyprotein products. the orf encodes six sites for n-linked glycosylation: one pr ...19892728348
ingestion of immune bloodmeals and infection of aedes fowleri, aedes mcintoshi, and culex pipiens with rift valley fever virus.rift valley fever (rvf) virus infection, dissemination, and transmission rates were determined for aedes fowleri, aedes mcintoshi and culex pipiens 7 or 10 days after sequentially feeding to repletion on rvf virus immune hamsters and rvf viremic hamsters, or after feeding on a mixture of rvf virus immune sheep serum and rvf viremic hamster blood through a pledget. no significant differences in infection or dissemination rates were detected among ae. fowleri and cx. pipiens feeding to repletion o ...19892729509
hemostatic derangement produced by rift valley fever virus in rhesus monkeys.rift valley fever (rvf) is an important cause of disease in animals and humans in sub-saharan africa. in a small percentage of human cases, the disease is complicated by hemorrhage, which often is associated with a fatal outcome. inoculation of rhesus monkeys with the zagazig hospital strain of rvf virus produced a clinical picture similar to illness in humans. ten of 17 monkeys developed clinical evidence of hemostatic impairment. when coagulation tests were performed, this group of monkeys had ...19892749112
effect of environmental temperature on the vector competence of aedes fowleri for rift valley fever virus.studies were conducted to determine the effect of environmental temperature on the ability of senegalese aedes fowleri to transmit rift valley fever (rvf) virus. temperatures tested included 17 degrees c, 28 degrees c and a cyclic (17-28 degrees c) regimen designed to mimic temperatures to which a mosquito might be exposed in october in southeastern senegal. after per oral exposure, infection rates were similar (ca. 93%) for all three groups. however, rvf virus disseminated to the haemocoel more ...19892756242
seroepidemiological survey on rift valley fever in zambia.this study was carried out to define the role of cattle as an amplifier of rift valley fever. three areas of different density of cattle population were surveyed. cattle do not seem to play a significant role as an amplifier of the virus in human beings.19892763763
[arbovirus transmission cycles in madagascar].some arboviruses are highly pathogenic for men or animals, arboviruses epidemiological patterns in madagascar were determined by entomological, serological, and virological surveys. we listed potentials arboviruses vectors in madagascar. entomological results generated by us during five years, as well as prior to, are shown. we caught more than 150,000 hematophagous arthropods, belonging to 107 species at least. 3 of these species were new. 4183 inoculation pools were done. we studied serologica ...19892751393
comparison of in vitro and in vivo systems for propagation of rift valley fever virus from clinical specimens.several cell cultures and animals were compared for their relative sensitivity as primary isolation systems for rift valley fever virus (rvfv) and to determine if virulence characteristics of the isolates were altered in these systems. eleven human sera from known cases of rift valley fever (rvf) were obtained from the 1987 epidemic in mauritania and served as the source of virus for these studies. sera were inoculated directly into cell cultures (vero, c6/36 and dbs-frhl-2) and animals (icr suc ...19892756240
rift valley fever infection of rhesus monkeys: implications for rapid diagnosis of human disease.rhesus monkeys inoculated with rift valley fever (rvf) virus provide a model in which serial observations of serum viral antigen and antibodies can be made. in 9 non-fatal and 3 fatal infections, either antigen or igm enzyme-linked immunosorbent assay (elisa) antibodies were detected in every serum sample during the acute phase. furthermore, viral nucleic acid could be detected by filter hybridization in most samples taken on days 1 to 3. circulation of significant quantities of viral rna provid ...19892756241
[epidemiology of rift valley fever in western africa. i. serologic survey in domestic ruminants of burkina faso].a serosurvey of rift valley fever virus infection has been conducted among 2,410 domestic ruminants (sheep, goats and cattle) from burkina faso in 1985, 1986 and 1987. an active circulation of virus was demonstrated and 26.7% of the total animal tested had rift valley fever virus reacting antibodies. an epizootic was demonstrated retrospectively for 1987 and appears to correspond to the rvf outbreak observed in the same type of sahelian environment during the same year in mauritania. analogous e ...19892766443
rift valley fever virus (family bunyaviridae, genus phlebovirus). isolations from diptera collected during an inter-epizootic period in kenya.a total of 134 876 diptera collected in kenya during a 3-year period were tested in 3383 pools for rift valley fever (rvf) virus. nineteen pools of unengorged mosquitoes were found positive for rvf. all isolations were made from specimens collected at or near the naturally or artificially flooded grassland depressions that serve as the developmental sites for the immature stages of many mosquito species. the isolation of virus from adult male and female a. lineatopennis which had been reared fro ...19852862206
analytical study of a rift valley fever epidemic.three epidemiological investigations were carried out during and after the 1987 rift valley fever (rvf) epidemic in south mauritania: a case control study, a cross-sectional study in the town of rosso and a cross-sectional study of villages and encampments around rosso. the case control study showed an association between epizootic and epidemic outbreaks. the study in rosso town showed housing and district effects. also, a medical survey of hospital staff showed the absence of interhuman contami ...19892787923
transstadial and horizontal transmission of rift valley fever virus in hyalomma truncatum.we exposed hyalomma truncatum and rhipicephalus appendiculatus to rift valley fever (rvf) virus in order to assess the possible role of these ticks as enzootic/epizootic rvf vectors. the virus replicated in h. truncatum after intracoelomic inoculation, and a minimum transmission rate of 17% was achieved after 15 days intrinsic incubation. the virus persisted at least 58 days in these ticks. virus was also shown to pass transstadially from inoculated h. truncatum nymphs to adults, with peak viral ...19892802027
crimean-congo haemorrhagic fever and rift valley fever in south-eastern mauritania. 19852857020
focus of rift valley fever virus transmission in southern mauritania. 19872881057
efficacy, toxicology and clinical applications of ribavirin against virulent rna viral infections. 19852867737
transmission studies in mosquitoes (diptera: culicidae) with disseminated rift valley fever virus infections. 19872880998
rift valley fever virus transmission by different egyptian mosquito species.4 egyptian mosquito species were tested for their ability to transmit the egyptian zh-501 strain of rift valley fever virus (rvfv) to golden syrian hamsters. culex (cx.) antennatus was the most efficient vector, showing a 37.5% transmission rate following a hamster blood meal containing 10 suckling mouse intracerebral 50% lethal doses (smild50) per ml. fully engorged mosquitoes of this species showed an infection rate of 85% with the mean viral titres of transmitting mosquitoes 100-fold higher t ...19872895516
epizootic of rift valley fever in zambia, 1985. 19872889285
vector potential of selected north american mosquito species for rift valley fever virus.selected north american mosquito species were evaluated as potential vectors of rift valley fever virus. field populations of aedes canadensis, ae. cantator, ae. excrucians, ae. sollicitans, ae. taeniorhynchus, ae. triseriatus, anopheles bradleyi-crucians, culex salinarius, cx. tarsalis, and cx. territans perorally exposed to 10(6.2)-10(7.2) plaque forming units of rift valley fever virus readily became infected. infection rates ranged from 51% (65/127) for cx. salinarius to 96% (64/67) for ae. ...19882895591
[arboviroses in the region of nosy-bé, madagascar. serologic and entomologic data].since 1977, the pasteur institute of madagascar has been studying, during six surveys, the arboviruses of nosy-be area, in the north-west of madagascar. 47.2% out of 271 human sera and 11.3% out of 151 sera of lemurs, tested for antibodies to 16 arboviruses by the haemagglutination inhibition test, are positive. the results show an important prevalence of flaviviruses. west nile and dengue 1 viruses were probably circulating some years before the surveys. antibodies against sindbis and rift vall ...19882900082
[sero-epidemiological study in mauritania (1985-1986): incidence of treponematosis, hepatitis b virus, hiv virus and viral hemorrhagic fevers].a serological serosurvey was made in different ethnic groups of mauritania in 1985. a very high prevalence of hepatitis b markers was found with more than 20% of hbs antigen carriers. treponema specific antibodies in low-age classes observed is a reflect of endemic syphilis. the seroprevalence of antibody against hiv and viral haemorrhagic fever viruses (rift valley fever, crimean-congo haemorrhagic fever and haemorrhagic fever with renal syndrome) was very low.19882900081
vector competence tests with rift valley fever virus and five south african species of mosquito.aedes juppi was readily infected by inoculation with virus but failed to transmit either horizontally or vertically. seventy-five to 90% of the other 4 mosquito species became infected after ingesting 6.8-9.8 log10cpd50/ml of virus. these species all transmitted virus at the following rates on the post-infection days indicated: aedes unidentatus (58%--day 11), aedes dentatus (32%--day 11, 50%--day 18), culex poicilipes (15%--day 15, 80%--day 30) and aedes argenteopunctatus (14% on day 30). on th ...19882903903
effects of ribamidine, a 3-carboxamidine derivative of ribavirin, on experimentally induced phlebovirus infections.ribamidine (1-beta-d-ribofuranosyl-1,2,4-triazole-3-carboxamidine) was inhibitory in rhesus monkey kidney (llc-mk2 derivative) cells to adames and balliet strains of punta toro virus (ptv), a phlebovirus related to rift valley fever and sandfly fever viruses. the 50% effective dose was 8 and 12 micrograms/ml against each respective virus strain; the 50% cytotoxic dose was 320 micrograms/ml, giving selectivity indices of 40 and 27 against each virus strain. the virus ratings were 1.2 and 1.0, res ...19882976263
complete nucleotide sequence of the m rna segment of rift valley fever virus.the entire m rna segment of the phlebovirus rift valley fever virus (rvfv) has been molecularly cloned and the complete nucleotide sequence determined. the rna is 3884 nucleotides in length, corresponding to a molecular weight of 1.38 x 10(6), having a base composition of 27.3% a, 25.4% g, 27.2% u, and 20.1% c. sequences present at the 3' and 5' termini of the molecule are largely complementary for some 51 residues and can form a stable duplex structure when the potential secondary structure of ...19852998042
complete sequences of the glycoproteins and m rna of punta toro phlebovirus compared to those of rift valley fever virus.the complete sequence of punta toro virus (phlebovirus, bunyaviridae) middle size (m), rna has been determined. the rna is 4330 nucleotides long (mol wt 1.46 x 10(6), base composition: 26.7% a, 33.6% u, 18.5% g, 21.2% c) and has 3'- and 5'-terminal sequences that, depending on the arrangement, are complementary for some 15 residues. the viral rna codes in its viral-complementary sequence for a single primary gene product (the viral glycoprotein precursor) that is comprised of 1313 amino acids (1 ...19852998043
panveld oviposition sites of floodwater aedes mosquitoes and attempts to detect transovarial transmission of rift valley fever virus in south africa.floodwater aedine mosquito eggs were recovered from soil samples taken from grassland depressions, called pans, in the orange free state province of south africa. a sedge, mariscus congestus (vahl) c.b.cl., was a useful indicator of aedes (ochlerotatus) juppi mcintosh oviposition areas. no transovarial transmission of virus was demonstrated by ae.juppi females reared from the eggs and allowed to feed shortly after eclosion on hamsters. no virus was recovered from 557 pools of 5425 adult ae.juppi ...19882980179
synthesis and biological activity of 5-thiobredinin and certain related 5-substituted imidazole-4-carboxamide ribonucleosides.a number of 5-substituted imidazole-4-carboxamide ribonucleosides were prepared and tested for their biological activity. treatment of 5-chloro-1-beta-d-ribofuranosylimidazole-4-carboxamide (2) with methanethiol provided 5-(methylthio)-1-beta-d-ribofuranosylimidazole-4-carboxamide (3a). similar treatment of 2 with ethanethiol or benzenemethanethiol gave the corresponding 5-ethylthio and 5-benzylthio derivatives 3b and 3c. oxidation of 3a and 3b with m-chloroperoxybenzoic acid furnished the corre ...19852993613
arthropod-borne virus zoonosis surveillance in the cape province: 1. prospective serological investigations for virus activity in the beaufort west and middelburg districts during 1981.in addition to the routine sero-epidemiological surveillance for arthropod-borne viral zoonoses in the cape province carried out by the department of medical microbiology and state health department of virology laboratory, we conducted a prospective serological investigation for virus activity during 1981 in two districts of the province, namely the beaufort west and middelburg districts, which experienced heavy rainfall during the first two months of that year. the approach used was to obtain p ...19852987499
rift valley fever virus m segment: cellular localization of m segment-encoded proteins.the phlebovirus rift valley fever virus (rvfv), like other members of the bunyaviridae family, matures intracellularly at the smooth-surfaced vesicles in the golgi region of infected cells. here we show that in cultured cells the rvfv glycoproteins g2 and g1 accumulate and are retained at this site. to investigate the parameters governing this subcellular localization, we have engineered portions of the cloned rvfv m segment (which encodes a 14- and a 78-kda protein, in addition to glycoproteins ...19883046119
[rift valley fever and phleboviroses in the central african republic].during 1984 and 1985, six rift valley fever virus strains (rvf) were isolated in central african republic, among them five from human samples. three strains were isolated in 1985 at the end of the rainy season, from sera of patients dead with severe jaundice with haemorrhagic syndrome, what could evoke a little outbreak. at this occasion, these rvf strains and the other strains of phleboviruses previously isolated in car, were antigenically compared by immuno-fluorescent assay (ifa) and compleme ...19883042177
solid-phase immunosorbent technique for rapid detection of rift valley fever virus immunoglobulin m by hemagglutination inhibition.a solid-phase immunosorbent technique (spit) was adapted to detect rift valley fever (rvf) virus-specific immunoglobulin m (igm) in serum samples from humans vaccinated with formalin-inactivated rvf vaccine. microdilution plates coated with goat anti-human igm were successively incubated with serum samples from human vaccinees, rvf virus hemagglutinating antigen, and goose erythrocytes. the rvf virus-specific igm in the serum samples from vaccinees bound to the rvf virus antigen and inhibited he ...19883053781
the gerbil, meriones unguiculatus, a model for rift valley fever viral encephalitis.the gerbil, meriones unguiculatus, was investigated as a model for the encephalitic form of rift valley fever. resistance to necrotizing encephalitis was age-dependent with 100% mortality at 3 weeks, decreasing to approximately 20% by 10 weeks of age in outbred gerbils inoculated subcutaneously. fatal encephalitis in the 10-week-old adults was dose-independent [1.0-7.0 log10 plaque forming units (pfu), subcutaneously]. viral replication and histological lesions were followed serially throughout ...19883060046
[serological study of the virus responsible for hemorrhagic fever in an urban population of cameroon].a sero-epidemiological study of hemorrhagic fever viruses in a urban population of cameroon. the authors report the results of a sero-epidemiological survey undertaken in a urban population of cameroon and concerning congo, rift (rvf), lassa, ebola, marburg and yellow fever viruses. on 375 human sera tested, 1.06% show antibodies against rvf virus and 1.87% are positive for anti-ebola antibodies thus yielding evidence that these two viruses are present in this area of cameroon. 33.75% have antib ...19883064937
viral hemorrhagic fever antibodies in nigerian populations.using the immunofluorescence test, a serosurvey for antibodies to five viral agents associated with hemorrhagic febrile infections was conducted with 1,677 human sera from different parts of nigeria. three hundred fifty-seven (21.3%) were positive for lassa virus antibody, while antibodies to rift valley fever virus were detected in 42 (2.5%) of the sera. testing for rift valley fever virus antibody was confirmed by plaque reduction neutralization test. antibodies to ebola and marburg viruses we ...19883128130
hemorrhagic fever virus infections in an isolated rainforest area of central liberia. limitations of the indirect immunofluorescence slide test for antibody screening in africa.serum samples from 119 healthy individuals and 106 epilepsy patients inhabiting grand bassa county, liberia, were tested for antibodies to hemorrhagic fever viruses (hfv) by indirect immunofluorescence. e6 vero cells infected with lassa fever virus (las), rift valley fever virus (rvf), congo hemorrhagic fever virus (con), marburg virus (mbg) and the ebola (ebo) virus strains mayinga (may) and boniface (bon) were used as antigen. to obtain reproducible and specific test results sera had to be abs ...19863092415
use of heat inactivated viral haemorrhagic fever antigens in serological assays.heating for 1 h at 60 degrees c completely destroyed the infectivity of sucrose-acetone-extracted antigen of rift valley (rvf) and congo crimean haemorrhagic fever (cchf), as well as of rvf- and cchf-infected mouse brain. these antigens could be successfully used, however, for complement fixation and igm-capturing enzyme immunoassay. vero e6 cell suspensions infected with hantaviruses such as hantaan 76-118, tchoupitoulas, sr 11, gb-b, cg 18-20, hällnäs, cg 13891, seoul and prospect hill, as wel ...19883146583
in vitro and in vivo phlebovirus inhibition by ribavirin.ribavirin (1-beta-d-ribofuranosyl-1,2,4-triazole-3-carboxamide) was markedly inhibitory in vitro to adames and balliet strains of punta toro virus (ptv), a phlebovirus related to rift valley fever and sandfly fever viruses. by using inhibition of viral cytopathic effect in llc-mk2 cells with both virus strains, the 50% effective dose was 4 to 10 micrograms/ml and the virus rating was 1.3. the adames strain of ptv infection in mice was established for evaluation of the in vivo antiviral efficacy ...19883129991
[current problems of arboviruses in central africa].19 arboviruses pathogenic for human are present in the central african republic (car) where serologic data indicate an active circulation in human population. in most cases the clinical picture of infection is mild. however 3 arbovirus were recently involved in fatal cases: in 1983 west-nile virus has been isolated in 4 patients with hepatitis. 2 fatal cases of yellow fever occurred in 1985 and 1986, and from 1983 to 1986 rift valley fever virus was isolated in patients who died from hemorrhagic ...19883180324
vector competence of a houston, texas strain of aedes albopictus for rift valley fever virus. 19883193106
reduced rift valley fever virus infection rates in mosquitoes associated with pledget feedings.infection rates were compared in culex pipiens and aedes taeniorhynchus after they fed on rift valley fever (rvf) viremic hamsters or ingested similar doses of rvf virus from blood-soaked pledgets. infection rates were significantly lower for mosquitoes that ingested virus from a pledget than for those that ingested similar doses from viremic hamsters. the method used to prevent normal clot formation for the pledget feedings (i.e., defibrination by shaking with glass beads or addition of heparin ...19883207178
[prevalence of antibodies against rift valley fever virus in sheep and goats in senegal].a total of 1,715 randomly selected sheep and goat sera from senegal were tested for antibodies against rift valley fever virus using an enzyme-linked immunosorbent assay. the results showed that rift valley fever is enzootic. the prevalence is highly heterogeneous, depending on the area. sheep and goats expressed comparable antibody prevalence, suggesting that both are involved equally in the virus cycle.19883214599
an rvf epidemic in southern mauritania. 19883207509
[arbovirus infections on the island of nosy-be; serologic and entomologic findings].since 1977, the pasteur institute of madagascar has been studying, during six surveys, the arboviruses of nosy-be area, in the north-west of madagascar. 47.2 p. 100 out of 271 human sera and 11.3 p. 100 out of 150 animal sera (mostly from lemurs), tested for antibodies to 16 arboviruses by the haemagglutination inhibition test, are positive. the results show an important prevalence of flaviviruses. west-nile and dengue 1 viruses were probably circulating some years before the surveys. antibodies ...19883242421
the horizontal distribution of aedes pupae and their subsequent adults within a flooded dambo in kenya: implications for rift valley fever virus control. 19883225577
mucosal priming alters pathogenesis of rift valley fever. 19883254072
newly recognized route of arbovirus dissemination from the mosquito (diptera: culicidae) midgut. 19873305948
viral determinants of virulence for rift valley fever (rvf) in rats.rift valley fever viral strains or variants (rvfv) were compared with respect to (a) virulence for wistar-furth rats; (b) in vitro sensitivity to rat and human interferon; (c) ability to form plaques in primary hepatocyte cultures from genetically resistant or susceptible rat strains, and (d) replicative potential in continuous rat cell lines. egyptian strains were highly virulent for wistar-furth rats; relatively resistant to rat interferon-alpha/beta; capable of producing plaques in primary he ...19883266284
morphology and development of rift valley fever virus in vero cell cultures.rift valley fever virus (rvfv) grown in vero cell cultures has a completed replication cycle within 13 hours. the first signs are the appearance of intranuclear fibrillar rods, followed by aggregations of precursor viral material in host cell cytoplasm and viral nucleocapsids budding into vacuoles associated with the golgi apparati. mature particles, liberated by the disintegration of vero cells, contained ribosomelike structures within the nucleocapsid, which was surrounded by a typical unit me ...19883280732
rift valley fever virus m segment: cell-free transcription and translation of virus-complementary rna.a cell-free system has been used to study gene expression of the m segment rna of the phlebovirus rift valley fever virus (rvfv). rvfv sequence-containing plasmids were used to synthesize m segment mrna-like transcripts. these transcripts were then translated in vitro in the absence or presence of microsomal membranes. cell-free translation of a transcript which closely resembled authentic m segment mrna (rna-7) yielded a primary translation product of 133 kilodaltons (kda), the size expected of ...19883285574
differentiation of a human monocytic cell line associated with increased production of rift valley fever virus by infected cells.rift valley fever (rvf) virus is a cause of significant human and animal disease in many parts of africa. in some cases, it causes a hemorrhagic fever, which is frequently fatal. prior studies have shown that rvf virus productively infects peritoneal macrophages from susceptible rat strains. the u937 human monocytic cell line was used to determine the effect of monocytic cell differentiation on the degree of viral production by cell cultures infected with rvf virus. differentiation of u937 cells ...19873323414
experimental rift valley fever in rhesus macaques.rift valley fever (rvf) is a major cause of human morbidity and mortality in endemic areas of sub-saharan africa and has the potential to cause epidemic disease in receptive areas world-wide. in this study, a rvf viral isolate from the 1977 egyptian epidemic (zh-501) inoculated intravenously into rhesus macaques caused a benign viremic infection in most, but resulted in the hemorrhagic fever syndrome in 20 per cent (3 of 15). serious disease of this type has not previously been observed in nonhu ...19883355374
rift valley fever virus m segment: use of recombinant vaccinia viruses to study phlebovirus gene expression.recombinant vaccinia viruses were constructed and used in conjunction with site-specific antisera to study the coding capacity and detailed expression strategy of the m segment of the phlebovirus rift valley fever virus (rvfv). the m segment could be completely and faithfully expressed in recombinant rvfv-vaccinia virus-infected cells, the gene products apparently being correctly processed and modified in the absence of the rvfv l and s genomic segments. the proteins encoded by the rvfv m segmen ...19883339714
vector competence of senegalese aedes fowleri (diptera: culicidae) for rift valley fever virus. 19883404545
characterization of attenuated strains of rift valley fever virus.the wild-type zh501 strain of rift valley fever (rvf) virus and two small-plaque strains (t1 and t46) derived from it were characterized by plaque size, pathogenicity for hamsters and ability to replicate in vero cells. additionally, a mutagenized, attenuated, large-plaque, vaccine-candidate strain of rvf virus (zh548-m12) was also studied. infections with either the zh501 or t46 strain were uniformly fatal to hamsters. in contrast, nearly all hamsters infected with either the t1 or zh548-m12 st ...19883356978
viral haemorrhagic fever survey in chobe (botswana). 19873445357
rift valley fever in egypt 1986. surveillance of sheep flocks grazing in the northeast nile delta.from october 1985 through november 1986, 1714 presumably unvaccinated sheep in 13 nomadic flocks located in four provinces in dakahliya governorate, in the northeast nile delta, were ear tagged and monitored for acquisition of rift valley fever virus (rvfv) antibodies. sheep were bled at approximately 3 month intervals and sera were tested for haemagglutination inhibition (hi) antibodies to rvfv. hi reactors were tested for rvfv specific igm antibody by enzyme-linked immunosorbent assay (elisa) ...19883404565
the distribution of rift valley fever virus in the mosquito culex pipiens as revealed by viral titration of dissected organs and tissues.distribution of rift valley fever virus (rvfv) was studied in the mosquito culex pipiens. mosquitoes were dissected on days 1-7 after an infectious bloodmeal, and rvfv plaque assays were performed on the legs, posterior midgut, ovaries, salivary glands, thoracic ganglia, and remaining organs and tissues (remnants). on days 7-12 and 14 following an infectious bloodmeal, mosquitoes were tested for their ability to transmit virus and then dissected. dissemination (systemic infection) rates averaged ...19883407841
studies on anti-viral mucosal immunity with the lipoidal amine adjuvant avridine. 19873425462
immunoelectron microscopy of rift valley fever viral morphogenesis in primary rat hepatocytes.the morphogenesis of the hepatotropic phlebovirus rift valley fever virus (rvfv) has been examined by immuno-electron microscopy in primary hepatocyte cultures derived from genetically susceptible and resistant rat strains. rvfv replicates in both cell types with growth kinetics comparable with those seen in other permissive cells. however, in contrast to that has been observed in other cell types, rvfv replication in hepatocytes is associated with maturation at cellular surface membranes in add ...19873499704
pathogenesis of rift valley fever virus (rvfv) in inbred rats.the pathogenesis of rift valley fever in adult rats from 3 inbred strains (lew, maxx, wf) was investigated. wf rats all died by day 2 postinoculation with viral tissue titers reaching 9 log10 pfu/g. lew and maxx rats were resistant to liver disease, but fatal necrotising encephalitis developed in 16 and 44% of the rats, respectively. detection of serum neutralising antibody on day 3 coincided with clearance of virus from serum and liver, although infectious virus was detected in spleen homogenat ...19873509859
evaluation of a new rift valley fever vaccine: safety and immunogenicity trials.a formalin-inactivated rift valley fever vaccine prepared in primary monkey kidney cells has been used to protect laboratory workers from disease since 1967. a similar but improved vaccine was prepared in 1978-1979 using well characterized diploid fetal rhesus lung cells. in initial clinical trials reported here, the new vaccine elicited high levels of plaque neutralizing antibodies and caused only minimal local reactions at the injection site. significant variability was observed in the geometr ...19863532605
use of the avidin-biotin-peroxidase complex immunocytochemical procedure for detection of rift valley fever virus in paraffin sections of mosquitoes.the avidin-biotin-peroxidase complex (abc) immunocytochemical procedure was used to locate rift valley fever (rvf) virus antigen in infected aedes albopictus c6/36 cultured cells and in serial paraffin sections of intrathoracically-injected egyptian culex pipiens. fixation of the cultured cells in formaldehyde or periodate-lysine-paraformaldehyde, and fixation of whole mosquitoes with formaldehyde resulted in good preservation of morphology and excellent differential staining between uninfected ...19863532843
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