preventing dengue

Preventing Dengue

The Vector, The Virus, and The Fever

Prepared & Designed by:Raphael D. Fernandez, M.D.

Website: www.raphaelfernandez.com

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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

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