Dengue Fever Prevention and

Control

Saleem M. Rana, PhD

The Dengue Fever a Global Problem

• During epidemics of dengue, infection rates among those who have not been previously exposed to the virus are often 40% to 50%, but can reach 80% to 90%.

• An estimated 500 000 people with DHF require hospitalization each year, a very large proportion of whom are children. About 2.5% of those affected die.

• Without proper treatment, DHF fatality rates can exceed 20%.

• Wider access to medical care from health providers with knowledge about DHF - physicians and nurses who recognize its symptoms and know how to treat its effects can reduce death rates to less than 1%.

Aedes aegypti Aedes albopictus

Aedes aegypti

Aedes albopictus

Behavior

Day-time biter

Lives outside

But comes indoors

May lay eggs indoors

Lays eggs in artificial containers

Anything that can hold water

Rests in low, shaded areas.

Under tables, chairs

In machinery- if damp

More behavior

Day-time biter – also in lighted rooms at night.

Silent flier – no buzz in your ear.

Very gentle on skin and not easily felt biting.

Adults not active under 15-16 degrees.

Adults not killed by cold, just go inactive.

Eggs laid containers of water

Egg to Larva to Adult in one week or less.

Movies

Comparison of Aedes (Larvae)

Characters Ae. aegypti Ae.albopictus

ANTENNAE single hair near middle single hair near saddle

HEAD upper & lower hairs

single

upper & lower hairs

single

THORAX heavy hooks on sides weak or no hooks on side

COMB SCALES pitchfork-shaped; 7-12 in

1 row

thorn-like; in 1 row

SIPHON index 2.0; pectin evenly

spaced

pectin evenly spaced

GILLS all the same length,

rounded; longer than anal

segment

all the same length,

rounded; longer than anal

segment

Comparison of Aedes (Adult)

Characters Ae. aegypti Ae.albopictus

PALPS dark with white tip;

clypeus white

dark with white tip;

clypeus black

PROBOSCIS dark dark

SCUTUM dark with white lyre-

shaped pattern

dark with white median

stripe

THORAX dark with patches of

white scales

dark with patches of

white scales

WINGS dark dark

ABDOMEN dark with narrow white

basal bands

dark with narrow white

basal bands

HIND LEGS dark with white basal

bands

dark with white basal

bands

Possible Weapons to Fight Dengue

Fever

• Drugs that kill the virus in humans

• Insecticides that kill the mosquito vector

• Vaccines

1. Drugs

• No specific anti viral

• Symptomatic treatment

2. Insecticides:

Mosquitoes Quickly Acquire Resistance

Before During After

Biologic niche intact Mosquitoes return

3. Vaccine

Does not exist (yet)

Mosquito Breeding

No comments

Before sunrise

Near sunset

Symptoms

Dengue fever is a flu-like illness with varying characteristics: Infants and youths often experience an undifferentiated febrile disease

with rash.

Older children and adults may have a mild febrile syndrome but more typically experience: high fever,

severe headache,

pain behind the eyes,

muscle and joint pains and

rash.

Typically, a person will develop dengue fever as a result of initial exposure to one serotype. Upon recovery, a patient develops immunity to this single serotype.

SYMPTOMS

Upon second infection with a different serotype:

the patient stands a greater risk of developing dengue haemorrhagic

fever (DHF), a more serious and potentially fatal disease.

DHF is characterized by:

o High fever, haemorrhagic phenomena, enlarged liver and

circulatory failure.

o A sudden onset of fever is the first indication of DHF,

accompanied by facial flush and other symptoms of

dengue fever.

o The fever persists for 2-7 days and can reach 41° C,

followed by febrile convulsions and haemorrhagic phenomena.

SYMPTOMS

The patient may recover and symptoms abate. But if left untreated, the patient may go into shock (DSS) with a rapid, weak pulse, followed by signs of circulatory failure such as cool, blotchy skin. Without proper treatment, the patient may die within 12-24 hours.

Strategies for Dengue Control

National Strategy.

SOLID WASTE

MANAGEMENT

CASE

MANAGEMENT

CAPACITY

BUILDING

ACSM

SURVEILLANCE

VECTOR

CONTROL

DENGUE

CELL

Control Strategy

Selective integrated vector control, with community and

intersectoral participation

Active disease surveillance based on a strong health information system-involves clinical and laboratory-based

vector surveillance for monitoring and evaluation of control

programmes.

Control Strategy

Emergency preparedness for development of emergency and contingency plans, including education of the medical community, hospitalization plans, case management and emergency vector control.

Capacity building and training for surveillance, laboratory diagnosis, case management and vector control at professional, supervisory, technical and field levels.

Vector control research including studies on vector biology and control, disease relationships, design and management of control programmes (including social and economic approaches) and cost benefit analyses. The relative impact of the components of integrated vector control require further elucidation.

Problems And Challenges

• demographic changes ▫ uncontrolled population growth

▫ Mobility

▫ unplanned urbanization.

▫ man-made larval habitats e.g. household water storage

containers, discarded solid waste items, such as plastics, glass containers and used automobile tyres.

NEW APPROACH:

GENETIC MODIFICATION OF MOSQUITOES

1) GENETICALLY ENGINEER MOSQUITOES

TO MAKE THEM RESISTANT TO VIRUS

2 ) INTRODUCE THE REFRACTORY GENE(S)

INTO MOSQUITO POPULATIONS

LESS TRANSMISSION LESS DENGUE FEVER

Monthly Temperature, Rainfall and DF 2008 in Lahore

100 88

27 31 40

33 27 24

33

19 7

12

80 71 67

60

80 86

93 96

40

57 60

36

20 24 27 20

1st week 2nd week 3rd week 4th week

DF +ve cases Aedes egypti Aedes albopictus

larvae Fogging larvicide

IRS

Correlation between dengue fever prevalence, vector density and control activities 2008 in Lahore

Annual correlation between dengue fever, temperature and rainfall 2008 in Lahore

Message Start

Active disease surveillance based on :

a strong health information system to involves the

clinical and laboratory-based dengue surveillance

for early detection of epidemics, and

Develop a quick reporting system from:

FLCF ----EDOH---DGHS

vector surveillance for monitoring and evaluation of

control programmes.

Aware the Community

Thanks