arboviruses

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powerpoint presentation - mm 445 lecture 3 chair of microbiology, virology, and immunology arboviruses the arthropod-borne viruses, or arboviruses, are a group of infectious agents that are transmitted by blood-sucking arthropods from one vertebrate host to another. they can multiply in the tissues of the arthropod without evidence of disease or damage. the vector acquires a lifelong infection through the ingestion of blood from a viremic vertebrate. all arboviruses have an rna genome, and most have a lipid-containing envelope and consequently are inactivated by ether or sodium deoxycholate. there are more than 500 arboviruses, grouped according to their antigenic relationships. current taxonomic status of some arboviruses current taxonomic classification arbovirus members togaviridae genus alphavirus aura, chikungunya, eastern equine encephalitis, getah, maygro, mucambo, ndumu, o'nyong-nyong, ross river, semliki forest, sindbis, venezuelan and western equine encephalitis flaviviridae genus flavivirus dengue, israel turkey meningoencephalitis, japanese b encephalitis, kunjin, kyasanur forest disease, murray valley …

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y the arboviruses may be divided into 3 clinical syndromes: fevers of an undifferentiated type with or without a maculopapular rash and usually benign; encephalitis, often with a high case fatality rate; hemorrhagic fevers, also frequently severe and fatal. these categories are somewhat arbitrary, and some arboviruses may be associated with more than one syndrome, eg, dengue. togaviridae genera: alphavirus (typical virus – sindbis virus) rubivirus pestivirus togaviruses general properties small viruses, (+) ssrna, linear, м.w. 4,0 мd, icosahedral symmetry, envelope, virus-specific polypeptides, some of them – glycoproteins. unstable at room temperature, stable at —70 °c, and rapidly inactivated by ether or by 1:1000 sodium deoxycholate. this property separates them easily from enteroviruses alphavirus there are 30 alphaviruses, 13 of them can infect human virions are spherical, 60-70 nm in diameter, icosahedral nucleocapsid enclosed in a lipid-protein envelope. alphavirus rna is a single 42s strand of approximately 4x106 daltons virion …

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d to infect nerve cells. in natural infection of birds and mammals (and in experimental parenteral injection of the virus into animals), an inapparent infection develops in a majority. however, for several days there is viremia, and arthropod vectors acquire the virus by sucking blood during this period—the first step in its dissemination to other hosts. principal medically important alphaviruses virus antigenic clinical syndrome vector host distribution eastern equine encephalitis encephalitis (eee) mosquito birds americas western equine encephalitis encephalitis (wee) mosquito birds north america venezuelan equine encephalitis febrile illness, encephalitis (vee) mosquito rodents, horses americas principal medically important alphaviruses virus antigenic clinical syndrome vector host distribution chikunguny (chik) africa febrile illness, rash, arthralgia mosquito primates, humans india, southeast asia o’nyong-nyong (onn) febrile illness, rash, arthralgia mosquito primates africa sindbis (sin) febrile illness, rash, arthralgia mosquito birds nothern europe, africa, asia, australia semliki forest febrile illness, rare encephalitis mosquito birds africa …

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ription of the virion rna through a negative-strand rna intermediate produces a 26s positive-strand mrna (short) which encodes only the structural proteins, as well as additional 42s rna (long), which is incorporated into progeny virions. translation from the 26s mrna (which represents the 3' one-third of genomic rna) produces a polyprotein that is cleaved proteolytically into three proteins: c, pe2, and e1; pe2 is subsequently cleaved into e2 and e3. envelope proteins formed by posttranslational cleavage are glycosylated and translocated to the plasma membrane. virion formation occurs by budding of preformed icosahedral nucleocapsids through regionsof the plasma membrane containing e1 and e2 glycoproteins pathogenesis and clinical manifestations. human illness caused by alphaviruses is exemplified by agents that produce three markedly different disease patterns. chikungunya virus is the prototype for those causing an acute (3- to 7-day) febrile illness with malaise, rash, severe arthralgias, and sometimes arthritis. o'nyong'nyong, mayaro, and ross …

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on-specific defense mechanisms may be important. alphaviruses are efficient inducers of interferon, the production of which probably plays a role in modulating or resolving infections. antibodies are important in disease recovery and resistance. the appearance of neutralizing antibodies in serum coincides with viral clearance, and immune serum can diminish or prevent alphavirus infection. although their precise roles are not clearly established, t-cell responses are also demonstrable and may contribute substantially to immunity. diagnosis blood, cerebrospinal fluid examination, section material, blood serum to include viral cultures, is critical in differentiating bacterial from viral infections, and infectious from noninfectious etiologies. laboratory diagnosis can be established by isolating virus from the blood during the viremic phase or by antibody determination. express-methods: irhat, ift, elisa virological diagnosis: inoculation of laboratory animals (into the brain) – suckling mice, cell cultures, embryotaned eggs. identificarion: plaques formation, cpe, hit, cft, nt serology: paired sera (nt, cft, hit, …

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powerpoint presentation - mm 445 lecture 3 chair of microbiology, virology, and immunology arboviruses the arthropod-borne viruses, or arboviruses, are a group of infectious agents that are transmitted by blood-sucking arthropods from one vertebrate host to another. they can multiply in the tissues of the arthropod without evidence of disease or damage. the vector acquires a lifelong infection through the ingestion of blood from a viremic vertebrate. all arboviruses have an rna genome, and most have a lipid-containing envelope and consequently are inactivated by ether or sodium deoxycholate. there are more than 500 arboviruses, grouped according to their antigenic relationships. current taxonomic status of some arboviruses current taxonomic classification arbovirus members togaviridae genu...

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