Dengue-morphology, control, fever, .pptx

Dengue-morphology, control, fever, .pptx

• 1.
  Dengue
• 2.
   Dengue virusis widely distributed throughout the tropics and subtropics  Dengue ranks as the most important vector-borne disease, with about 2.5 billion people in 200 countries at risk  The term ‘Break-bone fever’ was coined during the Philadelphia epidemic in 1780
• 3.
  Morphology  It isa mosquito-borne, single positive-stranded RNA virus of the family Flaviviridae; genus Flavivirus  Four types of Dengue virus exist: • DEN 1 – Hawaii (1944) • DEN 2 – New Guinea (1944) • DEN 3 – Philippines (1956) • DEN 4 - Philippines (1956)
• 4.
  Morphology  The DENVgenome is about 11000 bases of positive-sense, single-stranded RNA (ssRNA) that codes for three structural proteins (capsid protein C, membrane protein M, envelope protein E) and seven non-structural proteins (NS1, NS2a, NS2b, NS3, NS4a, NS4b, NS5)  The DENV E (envelope) protein, found as a dimer on the surface of the mature viral particle, is important in the initial attachment of this particle to the host cell  Each E protein monomer comprises three ectodomains, ED1 to ED3, and a transmembrane segment  The DENV prM (membrane) protein, which is important in the formation and maturation of the viral particle, consists of seven antiparallel β-strands stabilized by three disulfide bonds
• 5.
  Clinical Features  Denguevirus is transmitted from person to person by Aedes aegypti mosquitoes  The extrinsic incubation period is 8-10 days  No vertebrate hosts other than humans have been identified  There are mainly two phases for Dengue fever:
• 6.
  Clinical Features  Febrilephase  Patients typically develop a high-grade fever of sudden onset with headache, retrobulbar pain, photophobia, accompanied by facial flushing, skin erythema and pain in the back and limbs (break-bone fever) and maculopapular rash  The fever is typically biphasic
• 7.
  Clinical Features  Criticalphase  In this phase, the patients become worse around the time of defervescence, when the temperature drops to 37.5-38°C or less and remains below this level  Progressive leukopenia followed by a rapid decrease in platelet count usually precedes plasma leakage  An increasing haematocrit value above the baseline may be one of the earliest additional symptoms  Complications include Dengue hemorrhagic fever & Dengue Shock Syndrome
• 8.
  Distribution  Dengue wasinitially confined to the east coast of India and has caused epidemics  Subsequently, it spread westwards and in the 1990s, Surat and Delhi had major epidemics with deaths due to DHF and DSS
• 9.
  Laboratory Diagnosis  Mainstayof diagnosis – detection of non-structural viral protein antigen (NS1)  IgM ELISA test offers reliable diagnosis  A strip immunochromatographic test for IgM is available for rapid diagnosis, but has to be confirmed by ELISA
• 10.
  Prophylaxis and Treatment Control of Dengue is limited to vector control  No specific treatment available  Supportive management with cold tepid sponging  Paracetamol for fever should be avoided since it causes gastritis, vomiting and severe bleeding  Fluid and electrolyte replacement and platelet infusion can be done when counts are 10,000 and less