Chapter 85 : Arboviruses

Abstract:

Although the laboratory diagnosis of arboviral infections still relies chiefly on serology, other approaches that directly detect viral antigen or genomic material and not antibodies are now routine. Assays that detect virus-elicited immunoglobulin M (IgM) are useful because they detect antibodies produced within days of a primary viral infection. IgG enzyme-linked immunosorbent assay (ELISA) has replaced the hemagglutination inhibition (HI) test for the diagnosis of some infections because the procedure is less cumbersome and titration curves for the two procedures are similar. The indirect immunofluorescence (IF) test for antibodies to most arboviruses is as specific as or less specific than the HI test. The major advantage of both the HI and the complement fixation (CF) test is that species-specific positive-control reagents are not necessary. The serum neutralization test is the most virus-specific test for serologic diagnosis and is used to confirm other serologic testing results. A variety of nucleic acid amplification platforms have been successfully utilized for the detection of arboviruses, including standard reverse transcriptase PCR (RT-PCR), real-time RT-PCR using fluorescent probes, and nucleic acid sequence-based amplification (NASBA). Each of these technologies is described; however, several important issues common to each approach are presented first. The isolation and identification of an arbovirus or its antigen or viral genomic sequences in a clinical sample generally are specific evidence of a recent infection. Three of these arboviruses (VEE, EEE, and WEE viruses) have been classified as possible biological threats. This designation has renewed interest in rapid and sensitive diagnosis of alphaviruses.