6. Dengue Fever


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6. Dengue Fever

  1. 1. Dengue fever Prof Dr Baqi Durrani
  2. 2. Epidemiology
  3. 4. Definition <ul><li>An Acute febrile illness </li></ul><ul><li>caused by dengue virus </li></ul><ul><li>Transmitted by aedes mosquito </li></ul><ul><li>Manifested by fever, bleeding,muscles and joints pain </li></ul>
  4. 5. Etymology <ul><li>The origins of the word dengue are not clear, but one theory is that it is derived from the Swahili phrase &quot;Ka-dinga pepo&quot;, which describes the disease as being caused by an evil spirit . The Swahili word &quot;dinga&quot; may possibly have its origin in the Spanish word &quot;dengue&quot; meaning fastidious or careful, which would describe the gait of a person suffering the bone pain of dengue fever </li></ul>
  5. 6. <ul><li>Slaves in the West Indies who contracted dengue were said to have the posture and gait of a dandy , and the disease was known as &quot;Dandy Fever&quot;. </li></ul><ul><li>The first record of a case of probable dengue fever is in a Chinese medical encyclopedia from the Jin Dynasty (265–420 AD) which referred to a “water poison” associated with flying insects. </li></ul><ul><li>The first confirmed case report dates from 1789 and is by Benjamin Rush , who coined the term &quot;breakbone fever&quot; because of the symptoms of myalgia and arthralgia </li></ul>
  6. 7. Transmission <ul><li>Dengue is transmitted to humans by the Aedes (Stegomyia) aegypti or more rarely the Aedes albopictus mosquito . The mosquitoes that spread dengue usually bite at dusk and dawn but may bite at any time during the day, especially indoors, in shady areas, or when the weather is cloudy </li></ul><ul><li>Blood transfusion </li></ul>
  7. 8. Etiology: <ul><li>Virus classification :Group IV ( (+) ssRNA ) </li></ul><ul><li>Family: Flaviviridae </li></ul><ul><li>Genus: Flavivirus </li></ul><ul><li>Species: Dengue virus </li></ul>
  8. 9. <ul><li>Unlike malaria , dengue is just as prevalent in the urban districts of its range as in rural areas </li></ul><ul><li>The WHO says some 2.5 billion people, two fifths of the world's population, are now at risk from dengue and estimates that there may be 50 million cases of dengue infection worldwide every year. The disease is now endemic in more than 100 countries </li></ul>
  9. 10. Clinical Features <ul><li>Fever like influenza </li></ul><ul><li>Myalgias </li></ul><ul><li>Arthralgias </li></ul><ul><li>Bleeding petechiae </li></ul><ul><li>Maculopapuler rash </li></ul><ul><li>Gastritis ,diarrhea, Abdominal pain </li></ul><ul><li>Thrombocytopenia Hemoconcentration </li></ul><ul><li>Dengue Shock Syndrome Neuro/ </li></ul>
  10. 11. <ul><li>may present unusually as liver dysfunction, renal impairment, meningo-encephalitis or gastroenteritis. </li></ul><ul><li>Fever, headaches, eye pain, severe dizziness and loss of appetite. </li></ul><ul><li>Hemorrhagic tendency (positive tourniquet test , spontaneous bruising, bleeding from mucosa , gingiva , injection sites, etc.; vomiting blood, or bloody diarrhea ) </li></ul><ul><li>Thrombocytopenia (<100,000 platelets per mm³ or estimated as less than 3 platelets per high power field) </li></ul><ul><li>Evidence of plasma leakage ( hematocrit more than 20% higher than expected, or drop in hematocrit of 20% or more </li></ul><ul><li>Encephalitic occurrences. </li></ul><ul><li>Dengue shock syndrome is defined as dengue hemorrhagic fever plus: </li></ul><ul><li>Weak rapid pulse, </li></ul><ul><li>Narrow pulse pressure (less than 20 mm Hg) </li></ul><ul><li>Cold, clammy skin and restlessness </li></ul>
  11. 12. Diagnosis <ul><li>Leukopenia </li></ul><ul><li>Thrombocytopenia </li></ul><ul><li>Rapid Diagnostic Test kits, which also differentiate between primary and secondary dengue infections. </li></ul><ul><li>Serology and polymerase chain reaction (PCR) studies are available to confirm the diagnosis of dengue if clinically indicated </li></ul>
  12. 13. Prevention <ul><li>No vaccine available at present </li></ul><ul><li>Thai researchers are testing a dengue fever vaccine on 3,000–5,000 human volunteers after having successfully conducted tests on animals and a small group of human volunteers </li></ul><ul><li>National Institutes of Health reported on </li></ul><ul><li>11 vaccins going on testing </li></ul>
  13. 14. Vaccine development <ul><li>In 1998, scientists from the Queensland Institute of Medical Research (QIMR) in Australia and Vietnam 's Ministry of Health introduced a scheme that encouraged children to place a water bug, the crustacean Mesocyclops , in water tanks and discarded containers where the Aedes aegypti mosquito was known to thrive </li></ul>
  14. 15. Treatment <ul><li>Timely supportive therapy </li></ul><ul><li>Rehydration, antipyretics </li></ul><ul><li>Transfusions </li></ul><ul><li>Platelets </li></ul><ul><li>Close monitoring of vital signs in the critical period (up to 2 days after defervescence - the departure or subsiding of a fever) is critical </li></ul>
  15. 16. ANTIVIRALAPPROACHE <ul><li>Dengue virus belongs to the family Flaviviridae , which includes the hepatitis C virus AND YELLOW FEVER among others. Possible laboratory modification of the yellow fever vaccine YF-17D to target the dengue virus via chimeric replacement has been discussed extensively in scientific literature, but as of 2009 no full scale studies have been conducted. </li></ul><ul><li>In 2006 a group of Argentine scientists discovered the molecular replication mechanism of the virus, which could be specifically attacked by disrupting the viral RNA polymerase In cell culture and murine experiments morpholino antisense oligomers have shown specific activity against Dengue virus. </li></ul>
  16. 17. Sterile insect technique <ul><li>The sterile insect technique , a form of biological control , has long proved difficult with mosquitos because of the fragility of the males. However, a transgenic strain of Aedes aegypti was announced in 2010 which might alleviate this problem: the strain produces females that are flightless due to a mis-development of their wings, and so can neither mate nor bite. The genetic defect only causes effects in females, so that males can act as silent carriers. </li></ul>
  17. 18. PREVENTION <ul><li>Singapore has managed to reduce the cases of not only dengue, but chikungunya and malaria by introducing an Integrated Vector Management System. Cases fell from 7,500 to 4,500 in 2008 </li></ul>
  18. 19. Prevention is better than cure