preventing dengue
DESCRIPTION
Presentation done last October 8, 2010 at Fairchild Semiconductor, EPZA 1, Lapu-Lapu City, Cebu, Philippines. Some data reflects regional situation. Data from statistics presented does not reflect current situation; however, links are provided for further information.TRANSCRIPT
Preventing Dengue
The Vector, The Virus, and The Fever
Prepared & Designed by:Raphael D. Fernandez, M.D.
Website: www.raphaelfernandez.com
10/12/2010 1
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Question
Why should we be concerned about Dengue?
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Dengue
• Worldwide, WHO estimates 2.5 billion people are at risk with 50 million cases annually.– Fatality rate: <1% to 20% depending
on health care– DHF develops in 1/100 cases
• Nationwide, 90,771 cases were recorded from January to Sept 29, 2010– Case fatality rate: 1%
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Dengue Update
• A total of 9,284 cases seen in Region 7 from January 1 to October 2, 2010– 65 deaths (CFR=0.7%)– 2009, 4,961/67 (CFR=1.4%)– Ages: 1-89 y.o. (↑6-10 y.o)– Sex: Male = Female
• Areas: Cebu City > Tagbilaran > Dumaguete > Lapulapu > Toledo
10/12/2010“Dengue Update,” 39th Morbidity Week
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Dengue Update, Central Visayas
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We Are Not AloneFrom 07 Sept to 07 Oct 2010
10/12/2010DengueMap, HealthMap.
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KNOW DO GOAL
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THE VECTORAedes aegypti and Aedes albopictus
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The Mozzies
3,500 mosquito species
Culex Anopheles Aedes
West Nile Virus Malaria Yellow FeverDengue
Chikungunya
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Question
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What does “aedes” mean?
“Unpleasant” (Greek) by Meigen in 1818
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Life Cycle
• 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)
“The Mosquito Life-cycle,” Centers for Disease Control and Prevention10/12/2010
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Feeding
• Mosquitoes sense the presence of:– Genetics – 85%– Chemicals (respiratory, skin)
• Carbon dioxide (activity, using candle)• Lactic acid (exercise, after eating salty
foods, high-potassium)• Steroids• Uric acid• Cholesterol
– Pregnancy– Body temperature– Dark-colored materials
• clothings, garbage cans
– Movement– Floral/fruity fragrances– Moisture
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Question
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Why do female mosquitoes need blood?
For egg development. The amino acid isoleucine is important.
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Breeding
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Mosquitoes will practically breed anywhere where 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.
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PondsStreams
Swamps
Rock holes
Ditches Tree holes
Common natural breeding grounds
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Common man-made breeding grounds
Wells
Rain barrel
Cans
Roof gutter
Old tires Road gutter
Vases
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ComparisonAedes aegypti Aedes albopictus
10/12/2010“Invasion biology of Aedes albopictus,” University of Florida.
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Aedes aegypti• Egyptian tiger mosquito• Origin: Africa• Primary vector for:
– Yellow fever– Dengue fever– Chikungunya fever
• Prefers to breed in water storage containers (in and out)
• Day biter humans
Aedes albopictus• Asian Tiger mosquito• Origin: Africa/S.E. Asia• Vector for:
– Same as aegypti
• Prefers to breed in trash (out)• Outdoor day biter humans,
livestock, amphibians, reptiles, and birds
“Larval habitats and distribution patterns of Aedes aegypti and Aedes albopictus in Thailand,” Chareonviriyaphap, et al., 2003. PDFAedes albopictus, Global Invasive Species Database.
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Question
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In the Philippines, which of the two is the predominant mosquito specie?
Aedes aegypti
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THE CAUSATIVE AGENTDengue Virus
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The Dengue Virus
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Dengue 1 Virus and Dengue Hemorrhagic Fever, French Polynesia, 2001, Hubert and Halstead, Emerging Infectious Diseases, August 2009
• Flavivirus (Yellow virus)• Only transmitted by
mosquito bites• It takes 8 days for a
mosquito to be a vector but remains infected for life.
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Historical
• Dengue viruses originally came from monkeys.
• It jumped to humans 100 to 800 years ago.
• It was a minor disease until World War 2
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Question
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Why has dengue became a significant health problem after World War 2?
Due to increased travel and active transport industry
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The Four Types
• Dengue has four closely related types or serotypes: DENV-1 to 4– Each serotype gives specific lifetime
immunity and short-term cross-immunity.
– A second, third or fourth infection results in a worse infection than the first.
– Infants can have a severe first infection if the mother has previous dengue infection.
10/12/2010 “Molecular Evolutionary Pathogenesis of Dengue Virus Infection,” Shannon Bennett
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Why is the next infection worse?When Good Antibodies Go Bad
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In ADE, two things will happen:1. The virus is still active and will
continue infecting cells and replicating in them.
2. The dengue virus will initiate a complement cascade activation that leads to blood vessel breakdown bleeding and shock
ADE can be found in:• Dengue patients with previous dengue
infections.• Infants and toddlers of mothers with
previous dengue infection.
Antibody-dependent Enhancement
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Dengue Spread
• Possible factors– Inadequate housing and
public health systems (water, sewage, waste management)
– Poor vector control– Climate change– Increased international
travel
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THE DISEASEDengue Fever, Dengue Hemorrhagic Fever
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Question
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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.”
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Historical Reports• Chronology
– 265-420 AD in China; called “water poison”– Slaves in Caribbean, “Dandy fever”– 1780 in Madras, India and Philadelphia,
USA– 1789, 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
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Number of cases vs. number of countries1955-2007
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Dengue virus infection
With symptoms
No symptoms
Dengue Fever (DF) Syndrome
No different from other fever
With unusual hemorrhageSymptoms: high fever; severe
headache; pain behind the eyes; muscle, bone and joint pains; nausea, vomiting, and rash. Skin hemorrhage (tiny purplish-red spots on skin)
sometimes seen
Without hemorrhage
Dengue Hemorrhage Fever (DHF) (plasma leakage)Symptoms: Sudden rise in
temperature, facial flush, DF symptoms like vomiting,
headache, etc., sore throat, gum bleeding, breathlessness,
elevated blood hematocrit
No shock Dengue Shock SyndromeSymptoms: Occurs at the end of fever on 3rd to 7th day, skin becomes cool and blotchy,
pulse weak and rapid, lethargy, restlessness, acute
abdominal pain frequently felt just before onset of shock
Dengue Fever Dengue Hemorrhage Fever
http://thestar.com.my/archives/2008/9/14/health/sf_pg06manifestation.jpg
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Dengue or not?
• Diagnosis:– Medical history– Physical examination– Tourniquet test
• Lab:– Low platelet count (<150,000)– Complete blood
count/hematocrit– Blood test for antibodies
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Managing DengueWhat to do• Bring the fever down. Sponge
bath and paracetamol. • Maintain hydration using oral
fluids.• Keep mosquitoes away. Use
mosquito nets.
What Not to do• Avoid certain drugs like aspirin,
NSAIDs (ibuprofen, mefenamic acid)
• Avoid IV fluids. Use oral fluids if child is able to drink.– Fluids in the lungs– Water retention
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Warning Signs of DHF
• Refuse fluids or vomiting.• Sleepy or restless child.• Gastrointestinal bleeding• Abdominal pain• Skin mottling, cold sweaty
skin, cold hands and feet• No urine for the past 6 hours.
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Critical Period: Risk for DHF is high 1-2 days after fever subsides.
Mottled skin
Abdominal pain
dehydration
GI bleeding
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Dengue Hemorrhagic Fever (DHF)
• Odds of getting DHF?– DHF is a second infection.
• 90% of DHF patients has previous infection.
• Getting a second infection does not mean you’re 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%
• Causes of death – Shock due to dehydration– Severe hemorrhage– Encephalitis– Liver failure
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Don’t get bitten again!
Advice to former dengue patients
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PREVENTING DENGUEBarriers Against Mosquito Bites and Infection
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Mosquito Repellents
• DEET– Apply insect repellent
• DEET (20-30%)• If repellent is aerosol, open air• If child, don’t apply to hands
– Apply on clothing.– Mosquito net if room is non-
air-conditioned or screened
• Natural– Need frequent application– Citronella, lemon eucalyptus,
castor oil, peppermint oil.– Multiple repellents tend to
be more effective due to mosquito differences.
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Prevent Breeding
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Cover water containers, wells, and water tanks tightly
Let’s Act to Prevent Dengue, Hong Kong Housing Authority
1 Keep drains free from blockage2
Change the water in vases and for aquatic plants at
least once a week and leave no water in the saucers underneath the plants
3Cover up tires before
disposal to prevent water from collecting.4
Dispose of unwanted containers where water may collect such as lunch boxes
and soft drink cans into covered bins
5 Repair uneven surfaces of the ground to prevent water
from collecting6Check whether there is
water collecting on the tray under an air-conditioner and in the drainage system, and
remove stagnant water
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Prevent Bites
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Wear light-coloured and long-sleeved clothing and
pants1Apply mosquito repellents
containing DEET to exposed parts of the body2
Use mosquito nets or screens when the room is
not air-conditioned3
Avoid visiting scrubby areas4
Install screens on windows and doors, or place mosquito coils /electric mosquito mats
/anti-mosquito liquid near the windows5
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Vaccines?
• 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
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Dengue Hemorrhagic Fever: Early Recognition, Diagnosis and Hospital ManagementClick the image below to view video from your browser.
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DENGUE REFERENCESWebsites of Interest
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Wikipedia
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http://en.wikipedia.org/wiki/Dengue_fever
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Centers for Disease Control and Prevention
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http://www.cdc.gov/Dengue/
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Dengue Map
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http://www.healthmap.org/dengue/index.php
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Center for Health DevelopmentCentral Visayas
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This Week in Virology
10/12/2010