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Prevention of Mosquito-borne Diseases. Central Health Education Unit June 2007. Mosquito-borne diseases. Common mosquito-borne diseases Prevention of mosquito-borne diseases • Work of the Government • Personal Protection • Elimination of Mosquitoes. Common mosquito-borne diseases.

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prevention of mosquito borne diseases
Prevention of Mosquito-borne Diseases

Central Health Education Unit

June 2007

mosquito borne diseases
Mosquito-borne diseases
  • Common mosquito-borne diseases
  • Prevention of mosquito-borne diseases

•Work of the Government

•Personal Protection

•Elimination of Mosquitoes

common mosquito borne diseases
Common mosquito-borne diseases
  • Dengue Fever
  • Japanese Encephalitis
  • Malaria

Dengue Fever – statistical data

Note: Dengue Fever became a notifiable disease since

March 1994

dengue fever introduction
Dengue Fever - Introduction
  • Etiological agent
    • Dengue viruses (DEN-1, DEN-2, DEN-3 and DEN-4) - flaviviruses
  • Principal vector
    • Aedes albopictus
    • Aedes aegypti

Source of photo: Food and Environmental Department

dengue fever habitual behaviour of aedes albopictus
Dengue Fever – Habitual Behaviour of Aedes Albopictus
  • Usually breed in stagnant water
  • Usually active in dark or shaded places outdoors, but indoor activity is also possible
  • Distance of flight:less than 100 meter
  • Most active: 2 hours before sunset (5-6pm) and morning (8-9am)

Source of photo: Food and Environmental Department

dengue fever mode of transmission

Infected mosquito

Incubation Period: 3 to 14 daysMost commonly 4 to 7 days

Healthy person

Dengue Fever – Mode of Transmission

Infected person

Dengue fever is not spread by contact with

infected persons.

dengue fever symptoms
Dengue Fever - Symptoms
  • Fever: continuous for 3 to 7 days
  • Severe headache
  • Joint pain, muscle pain, pain behind eyeballs
  • Nausea, vomiting, and rash
  • In very rare cases, the condition may worsen into dengue haemorrhagic fever, leading to internal bleeding, shock, or even death.
dengue fever treatment
Dengue Fever - Treatment
  • At present, no specific drug that can treat dengue fever effectively.
  • Patient should be isolated in a mosquito-free environment to prevent the spread of disease

Treatment (1)

  • Patients infected with classical dengue usually recovers in 1 to 2 weeks
  • For serious cases, supportive treatments are provided by hospitals
  • If you suspect that you have dengue fever, you should seek medical treatment promptly

Treatment (2)

  • For high fever, wipe the body with warm water and proper use of anti-fever drugs can relieve the fever
  • Don’t take aspirin-containing drugs because they worsen the haemorrhage

Dengue fever patient’s immunity

  • Immunity is gained against that serotype after recovery from its infection. However, no effective protection is conferred against infection by the other three serotypes.
  • If the patient is infected with the other three different serotypes, it will increase the risk of getting haemorrhagic fever.
j apanese encephalitis s tatistical data
Japanese Encephalitis – statistical data

Note: Voluntary reporting before 2004, JE became a notifiable disease since 16 July 2004

j apanese encephalitis introduction
Japanese Encephalitis –Introduction
  • Etiological agent
    • Japanese encephalitis virus
  • Principal vector
    • Culex tritaeniorhynchus
j apanese encephalitis mode of transmission
Japanese Encephalitis – Mode of Transmission
  • Spread by Culex tritaeniorhynchus
  • The mosquitoes infected by feeding on pigs and wild birds infected with the Japanese encephalitis virus

within 4-14 days

  • The disease is not directly transmitted from person to person or from animal to human.
j apanese encephalitis signs and symptoms
Japanese Encephalitis- Signs and symptoms
  • Majority are asymptomatic
  • Low grade fever with headache
  • More severe infection:quick onset of headache, high feverneck stiffness, impaired mental state, coma, tremors, occasional convulsions and paralysis.
  • Death rates may range from 5% to 35%.Patients who survive may have neurological consequences.
j apanese encephalitis treatment
Japanese Encephalitis- Treatment
  • Seek medical treatment promptly
  • The mainstay of treatment is supportive
j apanese encephalitis vaccination
Japanese Encephalitis - Vaccination
  • WHO recommendation:vaccination for the whole country is indicated when there are 10 to 100 cases for every 100,000 population.
  • Provide 80-100% immunity, but may have adverse reactions.
  • Immunity may last for about 3 years.
  • Should consult medical officer for vaccination.
j apanese encephalitis do i need to have vaccination
Japanese Encephalitis– Do I need to have vaccination?
  • WHO recommendation
    • Travellers going to endemic areas particularly in rural areas and

staying over 30 days are

recommended for vaccination.

  • Where can I get the vaccination?
    • Travel Health Centres of the Port Health Office of the Department of Health
    • Enquiry No:2150 7235

Malaria- Introduction

  • Etiological agent
    • A group of malaria parasites
  • Principle vector
    • female Anopheline mosquito

Malaria– Mode of Transmission

  • When the mosquito bites a malaria patient, the mosquito

becomes infected and will pass on the disease when it

bites another person.

  • Malaria is not transmitted from person to person.
  • Malaria can be transmitted through contaminated blood

transfusion, organ transplant, or shared needles or


  • It may also be transmitted from a mother to her

foetus/newborn baby before or during delivery.

7-30 days later

Infected mosquito

Healthy person

Infected person


Malaria– Signs and symptoms

  • Intermittent fever, chills, sweating, headache, tiredness, poor appetite and muscle pain.
  • In typical cases, the fever comes, then subsides for 1 to 3 days and then comes again in a cyclical pattern.
  • Complications include anaemia, liver and kidney failure, seizures, mental confusion, coma, and death if the disease is not treated promptly.

Malaria– Treatment

  • Consult a doctor for early diagnosis is crucial.
  • The doctor would prescribe a course of anti-malarial drugs with other supportive measures.
  • The patient should complete the whole course of medication to ensure clearance of the malaria parasites.

Malaria– Prevention

  • Recommendation from WHO:

If you travel to areas where malaria is

common, you should start taking the

anti-malarial drugs two to three weeks

before the trip, continue for four more

weeks after leaving the malarious area.

  • From where I can obtain the anti-malarial drugs?
    • Travel Health Centre, Department of Health
    • For Enquiries:2150 7235

Malaria– Vaccination

  • There are no vaccines against malaria.
prevention of mosquito borne diseases30
Prevention of mosquito-borne diseases

Work of the Government

  • To prevent mosquito-borne diseases effectively relies on the support and co-operation of both public and private sectors with the government.

Work of the Government

Publicity and Health Education

  • Provide health education on personal protection against mosquito-borne diseases for general public.
  • Publicize personal protection against mosquito-borne diseases for travellers.
  • Latest updates on dengue fever for healthcare workers through periodicals, mails and internet.
disease surveillance
Disease surveillance
  • Dengue fever, Japanese encephalitis and Malaria have been brought into one of the statutory notifiable diseases.
  • web-based Central Notification Office (CENO On-line)

Disease surveillance

  • Contact tracing, epidemiological investigations on disease outbreaks.
  • Liaise with relevant department, e.g. Food and Environmental Department for following up control measures.
  • Collaborate with other departments and Hospital Authority in formulating response measures to prevent local spread of Dengue fever.
disease surveillance34
Disease surveillance
  • Maintain close liaison with nearby regions and oversea countries.
  • Make announcement to general public on reported cases and disease situation of nearby regions and remind public of preventive measures.

Personal Protection

The best protection is to avoid being

bitten by mosquitoes by paying

attention to the following:

  • Avoid staying in dark, outdoor

places such as brushwood, pavilions,

or the shade of a tree during the

hours when Aedes albopictus is



Personal Protection

  • Avoid going out in the hours when Aedes albopicuts feed or wear light-coloured, long-sleeves clothing and trousers.

Personal Protection

  • Install mosquito nets to doors and windows so that mosquitoes can’t get in.

Personal Protection

  • Accommodation should have air-conditioners or mosquito nets
  • Hang mosquito screens around your bed
  • Use of mosquito coil

Personal ProtectionChoosing the insect repellents

  • DEET containing products, such as repellents, anti-mosquito patches and spray are generally most effective to avoid mosquito bites.
  • Citronella, Soybean oil and 3-[N-Butyl-N-acetyl]-aminopropionic acid containing products also have mosquito repellent effects.
  • Portable ultrasonic devices are less reliable when compared with DEET.

Safety tips on using repellents that contain DEET (1)

  • Avoid applying high DEET

concentration products (i.e. >35%)

  • Always read and follow the

instruction label carefully

before using repellents.

safety tips on using repellents that contain deet 2
Safety tips on using repellents that contain DEET (2)
  • As rare reports about application of repellents with DEET associated with seizures in young children, therefore the low concentration product (10%DEET) should be used on children.
  • DEET is not recommended for use on infants less than 2 months of age. They should use mosquito net for health protection (e.g. infant carrier draped with elastic edge mosquito net).

Safety tips on using repellents that contain DEET (3)

  • Never use repellents over wounds or irritated skin.
  • Apply the repellent on exposed skin surfaces only

or on top of clothing. Do not use under clothing.

Do not attach the anti-mosquito patches directly

on the skin if it is specifically for clothing.

  • Wash repellent-treated skin with soap and water

when you come indoors.

  • When using sprays, do not spray directly on face

spray on hands first and then apply to face. Do

not apply to eyes or mouth.


Prevention of mosquito-borne diseasesElimination of Mosquitoes

The most effective way to eliminate mosquitoes is to:

  • Keep the environment clean.
  • Remove stagnant water so that mosquitoes can’t breed.

Possible Breeding Grounds of Aedes Albopictus (1)

  • Artificial containers:
    • Vases, saucers underneath flower pots, trays underneath air-conditioners, buckets jars and jugs of earthenware, cement troughs, dumped tyres and solid wastes such as cans, disposable cups and bowls, and plastic bags.

Possible Breeding Grounds of Aedes Albopictus (2)

Natural containers:

The hollow space inside a bamboo, hollows of a tree and the rachis of a leaf.


Elimination of Mosquitoes

  • Cover water containers

tightly so that

mosquitoes can’t get in

to lay eggs.


Elimination of Mosquitoes

  • Dispose of domestic wastes, empty bottles, cans and lunch boxes properly into a covered binto prevent the accumulation of stagnant water.

Elimination of Mosquitoes

  • Change water for vases

and aquatic plants at

least once a week,

leaving no water under

the pots or in the

bottom saucers.

  • Scrub the container

surfaces thoroughly to

prevent mosquito eggs

sticking on them.


Elimination of Mosquitoes

  • Remove or puncture any dumped tyres to prevent the accumulation of stagnant water.

Elimination of Mosquitoes

Keep ditches free from blockage.


Elimination of Mosquitoes

Fill up uneven ground surfaces to prevent the accumulation of stagnant water.


Elimination of Mosquitoes

  • Remove stagnant water immediately if mosquitoes are found to be breeding. Use environmentally friendly insecticides such as lavicidal oil if necessary.

Elimination of Mosquitoes

  • In cultivation ponds, water tanks or large containers, biological controls such as keeping fishes to eat mosquito larvae would be a good option.

Mosquito Elimination Checklist (1)

  • Are containers and other items where water could accumulate disposed of properly? (For example, throwing empty cans, foam rubber boxes, cups and bottles into a covered bin)
  • Are water containers covered properly?

Mosquito Elimination Checklist (2)

  • Are ditches free from blockage?
  • Are containers with stagnant water cleaned regularly?(For example, vases, saucers underneath flower pots, water storage device of an air-conditioner, water tanks and pools)
  • Are uneven ground surfaces filled to prevent the accumulation of stagnant water?

Seek medical consultation immediately

  • Having been bitten by a

mosquito and displaying

symptoms afterwards

  • Falling ill, especially having

a fever within one month

after you have returned

from abroad



  • Centre for Health Protection,

Department of Health (

  • Hong Kong Traveller’s Health Service, Department of Health (
  • 24-Hour Health Education Hotline, Department of Health (2833 0111)
  • Food and Environmental Hygiene Department Hotline: 2868 0000


elimination of mosquito is the most effective prevention strategy
Elimination of mosquito is the most effective prevention strategy

Let’s remove stagnant water and eliminate mosquitoes