Introduction to DengueDengue is a mosquito-borne infection that in recentdecades has become a major international publichealth concern. Dengue is found in tropical and sub-tropical regions around the world, predominantly inurban and semi-urban areas. It is caused by a virus which is transmitted to the humans by mosquito known as ”Aedes aegypti & Aedes albopictus”
According to the WorldHealth Organization(WHO), Dengue is amosquito-borne infectionthat causes a severe flu-likeillness, and sometimes apotentially lethalcomplication called denguehemorrhagic fever. The incidence of dengue has grown dramaticallyaround the world in recent decades. Some 2.5 billionpeople – two fifths of the worlds population – are now atrisk from dengue. WHO currently estimates there may be50 million dengue infections worldwide every year.
Introduction to Dengue Virus Dengue virus is know as DENV. DENV is an single stranded RNA positive-strand virus of the family Flaviviridae, genus Flavivirus.DENV causes a wide range of diseasesin humans, from a self limited DengueFever (DF) to a life-threateningsyndrome called Dengue HemorrhagicFever (DHF) or Dengue ShockSyndrome (DSS)There are four antigenicallydifferent serotypes of the virus: a.DENV-1 b.DENV-2 c.DENV-3 d.DENV-4
AEDES AEGYPTI AEDES ALBOPICTUS Egyptian tiger mosquito Asian Tiger mosquito Origin: Africa Origin: Africa/S.E. Asia Primary vector for: Vector for: Yellow fever Same as aegypti Dengue fever Prefers to breed in trash Prefers to breed in water (out) storage containers (in Outdoor day biter and out) humans, livestock, amph Day biter humans ibians, reptiles, and birds
All in all, it takes 8-10 days. Two phases: terrestrial and aquatic Eggs are resistant to environmental stress. Eggs larva (feeder) in presence of water Larva pupa (non- feeder) Pupa young adult (still water)
Characteristics of theAedes Mosquito One distinct physical feature – black and white stripes on its body and legs. Bites during the day. Lays its eggs in clean, stagnant water Only the female Aedes mosquito feeds on blood. This is because they need the protein found in blood to produce eggs. Male mosquitoes feed only on plant nectar. On average, a female Aedes mosquito can lay about 300 eggs during her life span of 14 to 21 days.
How Do Aedes Mosquitoes TransmitDiseases... Mosquito bites and sucks And passes the virus blood containing the virus to healthy people from an infected person. when it bites them. Virus is carried in its body.
Mosquitoes sense the Body temperature presence of: Dark-colored materials Genetics – 85% clothings, garbage cans Chemicals Movement (respiratory, skin) Floral/fruity fragrances Carbon dioxide Moisture (activity, using candle) Lactic acid (exercise, after eating salty foods, high- potassium) Steroids Uric acid Cholesterol
Mosquitoes will practically breed anywherewhere there is a collection of water that stands longer than five to seven days. Some prefer lighted areas and some shady areas. Some prefer fresh water and some stagnant water.
Ponds Streams Swamps Common natural breeding groundsRock holes Ditches Tree holes 17
Rain barrel Cans Wells Common man-made breeding grounds VasesRoof gutter Old tires Road gutter
Where did the word “dengue” come from? Spanish, “dengue” for “fever” Swahili, “Ka-dinga pepo” for “sudden cramp-like illness caused by an evil spirit.”
Chronology 265-420 AD in China; called “water poison” Slaves in Caribbean, “Dandy fever” 1780 in Madras, India 1780, Benjamin Rush coined the term “breakbone fever” 1799 in Cairo and Alexandria, Egypt; Jakarta, Indonesia1943: Japanese scientists first identified the virus 1953: First report of Dengue Hemorrhagic Fever in Manila 1956: Four types of dengue 1994, Karachi , Pakistan Number of cases vs. number of countries 1955-2007
Dengue virus infection No Withsymptoms symptomsNo different Dengue Fever (DF) Dengue Hemorrhagefrom other Syndrome Fever (DHF) (plasma fever leakage) Symptoms: Sudden rise Without With unusual in temperature, facialhemorrhage hemorrhage flush, DF symptoms like Symptoms: high fever; vomiting, headache, etc., severe headache; pain sore throat, gum behind the eyes; bleeding, breathlessness, muscle, bone and joint elevated blood pains; hematocrit nausea, vomiting, and rash. Skin hemorrhage No Dengue Shock (tiny purplish-red spots shock Syndrome on skin) sometimes seen Symptoms: Occurs at the end of fever on 3rd to 7th day, skin becomes cool and blotchy, pulse weak and rapid, lethargy, restlessne ss, acute abdominal pain frequently felt just before onset of shock Dengue Dengue Hemorrhage Fever Fever 22
Signs and Symptoms of Dengue FeverRecognition of Dengue fever - Sudden onset of high fever - Severe headache (mostly in theforehead) - Pain behind the eyes which worsenswith eye movement - Body aches and joint pains - Nausea or vomiting
Diagnosis: Medical history Physical examination Tourniquet test Lab: Low platelet count (<150,000) Complete blood count/hematocrit Blood test for antibodies
WHAT TO DO WHAT NOT TO DO Bring the fever down. Avoid certain drugs like Sponge bath and aspirin, NSAIDs paracetamol. (ibuprofen, mefenamic Maintain hydration acid) using oral fluids. Avoid IV fluids. Use oral Keep mosquitoes away. fluids if child is able to Use mosquito nets. drink. Fluids in the lungs Water retention
Critical Period: Risk for DHF is high 5-7 days after fever subsides. Refuse fluids or Mottled skin vomiting. Sleepy or restless child. Gastrointestinal dehydration bleeding Abdominal pain Skin mottling, cold sweaty skin, cold hands and feet No urine for the past 6 hours. GI bleeding Abdominal pain
Odds of getting DHF? Causes of death DHF is a second Shock due to infection. dehydration 90% of DHF patients has Severe hemorrhage previous infection. Encephalitis Getting a second infection does not mean you’re Liver failure going to get DHF Risk of dying from DHF with inadequate treatment is 10%-15% Risk of dying from DHF with adequate treatment is < 1%
Barriers Against Mosquito Bites and Infection 28
DEET Natural Apply insect repellent Need frequent DEET (20-30%) application If repellent is Citronella, lemon aerosol, open air eucalyptus, castor If child, don’t apply to oil, peppermint oil. hands Multiple repellents tend Apply on clothing. to be more effective due Mosquito net if room is to mosquito differences. non-air-conditioned or screened
Change the water in vases and for aquatic plants at least once a week and Cover up tires before leave no water in the disposal to prevent water saucers underneath the from collecting. Keep drains free from plants blockage Cover watercontainers, wells, and water tanks tightly Check whether there is water collecting on the tray under an air- Dispose of unwanted conditioner and in the containers where water may drainage system, and collect such as lunch boxes Repair uneven surfaces of remove stagnant water and soft drink cans into covered bins the ground to prevent water from collecting Let’s Act to Prevent Dengue
Use mosquito nets or screens when the room is not air- conditioned Wear light-coloured and long-sleeved clothing and pants Apply mosquito repellents containing DEET to exposed parts of the body Install screens on windows and doors, or place mosquito coils /electric mosquito mats /anti-mosquito liquid near the windowsAvoid visitingscrubby areas
At present, there are no approved vaccines. At the US National Institute of Health, 11 vaccines are undergoing testing. Difficulties with vaccine development: Four serotypes with no cross- immunity. No good animal model for testing. Vaccines should be tetravalent against the DENV-1 to 4
ReferencesBooks Mandell’s Book of Infectious Disease, Seventh Edition Davidson’s Book Medicinewebsites www.medicinenet.com www.denguevirusnet.com www.drugbank.ca www.who.org
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