Dengue

Junhel Dalanon, DDM, MAT

Contents1. What is dengue fever

2. Symptoms of dengue fever

3. Characteristics of the Aedes mosquito

4. Life cycle of the Aedes mosquito

5. How the Aedes mosquito transmit diseases

6. How to prevent the spread of dengue fever

7. The 10-Mininute Mozzie Wipe-out Exercise

8. Quiz

What is dengue fever?

Dengue Fever is an illness caused by infection with a virus transmitted by the

Aedes mosquito.

Symptoms of Dengue Fever

Example of a skin rash due to dengue fever

Do you know…

Dengue Fever (DF) and Dengue Haemorrhagic Fever (DHF) are the most common mosquito-borne viral disease in the world.

It can be fatal.

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.

Close-up of an Aedes mosquito

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.

Do you know…

1-2 days

Stagnant waterStagnant water

Pupae

4-5 days

Life cycle of the Aedes Mosquito

Larvae Eggs

2-3 days

How Do Aedes Mosquitoes Transmit Diseases...

Mosquito bites and sucks blood containing the virus from an infected person.

Virus is carried in its body.

And passes the virus to healthy people

when it bites them.

This is what you can do to help…

Prevent Aedes from Breeding!

Remove ALL sources of stagnant water.

Deny the Aedes mosquito of any chance

to breed.

10-Minute Mozzie Wipe-Out Exercise

Do the 10-Minute Mozzie Wipe-out Do the 10-Minute Mozzie Wipe-out everyday.everyday.

Change water in vases on alternate days.


Remove water from flowerpot plates on alternate days.


Turn over all pails and water storage containers.


Cover bamboo pole holders when not in use.


Clear blockages and put Bti insecticide in roof gutters monthly.

Unwanted itemsUnwanted items

Do not litter. Rubbish such as cups and bottles can collect

rain water and breed mosquitoes.

Before you leave for holidays…

• Cover all toilet bowls in your home.

• Seal off the overflow pipe of the flushing cistern.

• Cover all gully/floor traps.

• Add sand granular insecticide to places that mosquitoes could potentially breed, such as flower vases and places where stagnant water could not be removed.

Before you leave for holidays…Before you leave for holidays…

• Clear blockages and add Bti insecticide in roof gutters.

• Turn over all water storage containers.

•Ask a relative or close friend to check your home regularly for stagnant water if you are going away for a long period of time.

• Leave your contact with your neighbours or the neighbourhood police post/ centre so that you can be reached easily.

Before you leave for holidays…Before you leave for holidays…(Cont’d)(Cont’d)

Spread the dengue prevention message to others…

Let your family, friends and

neighbours know about the dangers

of breeding Mozzies!!

• Dengue is an arthropod-borne disease caused by any

one of four closely related viruses, (Arbovirus).

• Characterized by fever, severe headache, backache joint

pains nausea and vomiting, eye pain and rash

• Occasionally produces shock and hemorrhage, leading

to death.

• Also called breakbone fever, dandy fever or dengue

fever.

Dengue fever

Epidemiology• Globally, there are an estimated 50 to 100 million cases

of dengue fever (DF) and several hundred thousand

cases of dengue hemorrhagic fever (DHF) per year.

• 2.5 billion people are at risk world-wide

• In the last 20 years, dengue transmission and the

frequency of dengue epidemics has increased greatly in

most tropical countries

• It is a resurgent (re-emergent) disease worldwide in the

tropics

• Major global demographic changes (urbanization and

population growth)

• These demographic changes have resulted in sub-

standard environmental sanitation that facilitates

transmission of Ae. aegypti-borne disease; (Overcrowding

in cities with poor sanitation)

Factors contribute to the emergence and re-emergence of arthropod-borne diseases

• Increased travel by airplane resulting in a frequent

exchange of dengue viruses and other pathogens.

• Inadequate mosquito control services; the use of

insecticide space sprays for adult mosquito proved

ineffective approach for controlling Ae. aegypti. (Domestic

habitat)

• The emergence of resistance to insecticides linked to their

increased misuse.

Mean Annual Number of DHF CasesThailand, Indonesia and Vietnam, by Decade

* Provisional data through 1998

020406080

100120140160180200

Rep

orte

d C

ases

(T

hous

ands

)

1950s 1960s 1970s 1980s 1990s*

Reported Cases of DHF in the Americas, 1970 - 1999

* Provisional data through 1999

0

10

20

30

40

50

60

Rep

orte

d C

ases

(Tho

usan

ds)

1970s 1980s 1990s*

Distribution of suspected and confirmed Dengue fever in KSA

YearYear N. of suspected casesN. of suspected cases N. of confirmed N. of confirmed casescases

199419941995199519961996199719971998199819991999200020002001200120022002

6736731361365757626231312626171707071111

2892896622

1515000033000044

TotalTotal 10201020 319319

Dengue Viruses

• Four closely related single-stranded RNA Dengue

viruses (DEN-1, DEN-2, DEN-3 and DEN-4)

• Each serotype provides specific lifetime immunity,

and short-term cross-immunity (A person can be

infected as many as four times, once with each

serotype)

• All serotypes can cause severe and fatal disease

Transmission of Dengue Virusby Aedes aegypti

Viremia Viremia

Extrinsic incubation

period

DAYS0 5 8 12 16 20 24 28

Human #1 Human #2

Illness

Mosquito feeds /acquires virus

Mosquito refeeds /transmits virus

Intrinsic

incubation

period

Illness

Replication and Transmissionof Dengue Virus (Part 1)

1. Virus transmitted

to human in mosquito

saliva2. Virus replicates

in target organs3. Virus infects white

blood cells and

lymphatic tissues4. Virus released and

circulates in blood

3

4

1

2

Replication and Transmissionof Dengue Virus (Part 2)

5. Second mosquito

ingests virus with blood

6. Virus replicates

in mosquito midgut

and other organs,

infects salivary

glands

7. Virus replicates

in salivary glands

6

7

5

Aedes aegypti Mosquito

Aedes aegypti

• Dengue transmitted by infected female Aedes aegypti

mosquito

• Primarily, it is a daytime feeder

• Highly domesticated tropical mosquito, lives around

human habitation

• Lays eggs and produces larvae preferentially in

artificial water containers inside and around the

houses for example; plastic containers, flower vases,

buckets, used automobile tires,..

Dengue Clinical Syndromes

• Undifferentiated fever (87% of Patients are asymptomatic or mild fever)

• Classic dengue fever (DF)

• Dengue hemorrhagic fever (DHF)

• Dengue shock syndrome (DSS)

Clinical Characteristicsof Dengue Classic Fever

• Incubation period 3-14 days (commonly 4-7

days)

• Fever

• Headache

• Muscle and joint pain

• Nausea/vomiting

• Rash

• Hemorrhagic manifestations

Dengue Hemorrhagic Fever (DHF)

• Fever, or recent history of acute fever• Hemorrhagic manifestations• Low platelet count (100,000/mm3 or less)• Objective evidence of “leaky capillaries:”

– elevated hematocrit (20% or more over baseline)

– low albumin– pleural or other effusions

4 Necessary Criteria:4 Necessary Criteria:

Dengue Shock Syndrome (DSS)

• 4 criteria for DHF

• Evidence of circulatory failure.

Risk Factors Reported for DHF

• Virus serotype– DHF risk is greatest for DEN-2, followed by DEN-3, DEN-4 and

DEN-1• Pre-existing anti-dengue antibody

– previous infection– maternal antibodies in infants

• Host genetics

• Age (fatal cases are among children and young adult).• Higher risk in secondary infections• Higher risk in locations with two or more serotypes circulating

simultaneously at high levels (hyper-endemic transmission)

Increased Probability of DHF

Hyperendemicity

Increased circulation

of viruses

Increased probability

of secondary infection

Increased probability of

occurrence of virulent strains

Increased probability of

immune enhancement

Increased probability of DHFGubler & Trent, 1994

Common Misconceptions aboutDengue Hemorrhagic Fever

Dengue + bleeding = DHF Need 4 WHO criteria & capillary permeability

DHF kills only by hemorrhage Patient dies as a result of shock

Poor management turns dengue into DHF Poorly managed dengue can be more severe, but DHF is a distinct

condition, which even well-treated patients may develop DHF is a pediatric disease

All age groups are involved DHF is a problem of low income families

All socioeconomic groups are affected

Treatment of Dengue Fever • Antipyretics (Acetaminophen) preparations to manage

the pain and fever. • Avoid Aspirin and non-steroidal anti-inflammatory. • Rest and drink plenty of fluids• Monitor blood pressure, hematocrit, platelet count,...• Keep patient in screened sickroom or under a mosquito

net• Mosquito barriers are only needed until fever subsides,

to prevent Aedes aegypti mosquitoes from biting patients and acquiring virus.

Prognosis • Dramatic clinical response to aggressive fluids

and electrolytes.

• Convalescence may be prolonged, with weakness and mental depression

• Survival is related directly to early hospitalization and aggressive supportive care

• Treated DHF is associated with a 3% mortality rate

• Un-treated DHF is associated with a 50% mortality rate.

Prevention

• Personal protection against mosquito biting by:

– Screening doors and windows

– Protective clothing

– Application of mosquito repellents on exposed

skin

• However, the best preventive measure is vector

control.

Vector Control Methods:

• Biological control– Largely experimental

– Option: place fish in containers to eat larvae

• Environmental control– Elimination of larval habitats; Cover water holding

containers, Discard artificial containers,…

– It is the most likely method to be effective in the long

term.

Vector Control Methods:

• Chemical Control • Larvicides may be used to kill immature aquatic stages

• Ultra-low volume fumigation is ineffective against adult

mosquitoes as Aedes aegypti is fully domesticated

• Mosquitoes may have resistance to commercial aerosol

sprays.

Dengue Vaccine?

• No licensed vaccine at present

• Effective vaccine must be tetravalent

• Field testing of an attenuated tetravalent

vaccine currently underway

• Effective, safe and affordable vaccine will not

be available in the immediate future.

Community Participation

• Active community involvement and participation to

reduce larval breeding sources is the key for

prevention and control.

• Educate the public in the basics of dengue, such as:

– Where the mosquito lays her eggs

– The link between larvae and adult mosquitoes

– General information about dengue transmission,

symptoms and treatment

Public Education • Dengue fever is NOT contagious through person-to-

person contact

• Early hospitalization is important.

• Reduce A aegypti vector populations

• Reduce exposure to A aegypti.– Use insect repellent.

– Sleep under a mosquito net in affected areas.

– Wear protective clothing.

• Vaccine is NOT available.

Why is the Aedes mosquito dangerous to us?

ANSWER:

It can carry the dengue virus and infect a healthy person with dengue

fever.

Name the 5 steps in the 10-Minute Mozzie Wipe-

out Exercise

ANSWER:

1. Change water in vases on alternate.

2. Remove water from flowerpot plates on alternate days.

3. Turn over all pails and water storage containers.

4. Cover bamboo pole holders when not in use.

5. Clear blockages and put in Bti insecticide in roof gutters monthly.

What are the things that you should do before going for a

holiday?

ANSWER:• Cover all toilet bowls in your home.

• Seal off the overflow pipe of the flushing cistern.

• Cover all gully/floor traps.

• Add sand granular insecticide to places that mosquitoes could potentially breed, such as flower vases and places where stagnant water could not be removed.

•Clear blockages and add Bti insecticide in roof gutters.

• Turn over all pails and water storage containers.

•Ask a relative or close friend to check your home regularly for stagnant water if you are going away for a long period of time.

• Leave your contact with your neighbours or the neighbourhood police post/ centre so that you can be reached easily.

Dengue

Education

Transcript of Dengue