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Dengue Fever

Local Vector Biology

Aedes albopictus

  1. Eggs can withstand drought very well
  2. Breed in small containers such as cans, discarded tyres, tree holes, rock pools and bamboo ends holding small amount of water
  3. Adults rest in shrubby area
  4. Adult has a white stripe on the dorsal surface of thorax and bands on legs.
  5. Although exophilic, adults may also enter into houses
  6. Day biter (Peak : within 2 hours after dawn and before sunset)
  7. Weak flier (about 100m)
  8. Vector of dengue fever

Vector Surveillance

Since 2000, we have been using Oviposition Trap (Ovitrap) to detect the presence of adult Aedine mosquitoes in selected areas. The Ovitrap is a simple device made of a black plastic container of approximately 200ml with a brownish oviposition paddle placed diagonally. It is covered by a black lid with openings and a raised grey cover.

Oviposition Trap (Ovitrap)

Note: Please do not tamper with the ovitrap set by the Food and Environmental Hygiene Department.

An Ovitrap Index for Aedes albopictus will be enumerated by the formula :

Ovitrap Index for Aedes albopictus = No. of Aedes-positive ovitraps / No. of ovitraps collected from the specific area x 100%

Starting from October 2015, there are a total of 52 locations selected for the vector surveillance.  Two different indices, namely Area Ovitrap Index for Aedes albopictus (AOI), and Monthly Ovitrap Index for Aedes albopictus (MOI), would be enumerated.  AOI indicates the extensiveness of the distribution of Aedine mosquitoes in that particular area surveyed while the MOI is the average of all AOIs within the same month, which reflects the territory-wide situation of Aedes albopictus.

Survey of Aedes albopictus has been carrying out in Hong Kong International Airport since 1998. Starting from 2004, dengue vector surveillance work would be extended to other port areas. Two different indices, namely Port Ovitrap Index for Aedes albopictus (POI), and Port Monthly Ovitrap Index for Aedes albopictus (PMOI), would be enumerated. POI indicates the extensiveness of the distribution of Aedine mosquitoes in particular group of surveyed port areas while the PMOI is the average of all POIs within the same month, which reflects the overall situation of Aedes albopictus in port areas.

Ovitrap only detects activities of Aedine mosquitoes in the area where the ovitrap is set and it cannot be used for detecting the activities of other species of mosquitoes (such as Culex and Anopheline mosquitoes). The ovitrap index for Aedes albopictus of an area reflects only the extensiveness of the distribution of Aedes albopictus but not its density or quantity in the relevant surveillance area during the week of surveillance. Apart from making reference to the relevant ovitrap index for Aedes albopictus, parties concerned should take into account other factors such as their findings and reports on mosquito problem they received in planning and implementing their mosquito prevention and control work.

The Ovitrap Index for Aedes albopictus can be classified into 4 levels. Specific preventive and control measures will be initiated accordingly. Management of housing estates, hospitals, schools, construction sites and other venues or properties are also advised to take specific measures to contain mosquito problems in their own properties. The 4 levels of Ovitrap Index for Aedes albopictus and actions to be taken by the management are listed in the following table.

The ovitrap index for Aedes albopictus is divided into four levels, reflecting the infestation level of the Aedes albopictus. Level 1 (< 5 per cent) indicates that infestation of the mosquito is not extensive in the area surveyed. Level 2 (5 per cent - < 20 per cent) indicates that infestation of the mosquito is slightly more extensive in the area surveyed. Level 3 (20 per cent - < 40 per cent) indicates that infestation of the mosquito exceeds one-fifth of the area surveyed. Level 4 (>/= 40 per cent) indicates that almost half of the surveyed area is infested with the mosquito.

Classification Ovitrap Index for Aedes albopictus Action to be taken
Level 1 O.I. < 5%

- Closely monitor the hygienic condition to prevent breeding of mosquitoes;

- Conduct weekly inspection to identify breeding / potential breeding places and eliminate such places as far as possible.

- Public are advised to check and eliminate any possible breeding places within their premises at a frequency not less than once a week (Please go to Advice to Public for details)

Level 2 5% £ O.I. < 20%
Level 3 20% £ O.I. < 40%

- To conduct special operations in addition to the regular weekly program to eliminate all breeding / potential breeding places;

- Private pest control contractor might be employed to control the mosquito problem.  Other control measures by using larvicides or adulticides might be feasible.

Level 4 O.I. ³ 40%

The following graph shows the comparison of Monthly Ovitrap Index for Aedes albopictus between 2016 and average of 2000 to 2015.

Monthly Ovitrap Index

  • Please click here for graphical information on the ovitrap indices for Aedes albopictus of the year from 2004 to 2015.
  • Please click here for monthly data on the ovitrap indices for Aedes albopictus of the year from 2003 to 2015.
  • Please click here for port monthly data on the ovitrap indices for Aedes albopictus of the year from 2004 to 2015.

The Monthly Ovitrap Index for Aedes albopictus for May 2016 is 9.3%.

The Monthly Ovitrap Index for Aedes albopictus for June 2016 is not yet available.

The Port Monthly Ovitrap Index for Aedes albopictus for May 2016 is 3.6%.

The Port Monthly Ovitrap Index for Aedes albopictus for June 2016 is not yet available.

Area Ovitrap Index for Aedes albopictus for all the 52 locations are shown in the following maps :

Hong Kong
Location Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Chai Wan West 0.0 0.0 0.0 0.0 3.7 5.3            
Tin Hau 0.0 0.0 0.0 0.0 13.7 20.8            
Shau Kei Wan & Sai Wan Ho 0.0 0.0 0.0 0.0 0.0 25.9            
North Point 0.0 0.0 0.0 0.0 3.6 9.1            
Wan Chai North 0.0 0.0 0.0 0.0 0.0 7.5            
Happy Valley 0.0 0.0 0.0 1.8 7.0 19.6            
Central,Sheung Wan and Sai Ying Pun 0.0 0.0 0.0 0.0 7.7              
Sai Wan 0.0 0.0 0.0 0.0 9.1              
Aberdeen and Ap Lei Chau 0.0 0.0 0.0 3.8 12.2              
Pokfulam 0.0 0.0 0.0 2.2 14.0              
Deep Water Bay & Repulse Bay 0.0 0.0 0.0 5.5 3.7 21.8            
Islands
Cheung Chau 0.0 0.0 0.0 0.0 11.4 8.8            
Tung Chung 0.0 0.0 0.0 8.1 18.4              
Kowloon
Location Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Tsim Sha Tsui 0.0 0.0 0.0 0.0 14.8              
Tsim Sha Tsui East 0.0 0.0 0.0 0.0 3.7              
Mong Kok 0.0 0.0 0.0 0.0 0.0              
Cheung Sha Wan 0.0 0.0 0.0 1.9 7.4              
Lai Chi Kok 0.0 0.0 0.0 2.0 8.0              
Ho Man Tin 0.0 0.0 0.0 0.0 1.9              
Kowloon City North 0.0 0.0 0.0 1.8 5.5              
Hung Hom 0.0 0.0 0.0 0.0 0.0              
Lok Fu West 0.0 0.0 0.0 1.7 8.3              
Kai Tak North 0.0 0.0 0.0 0.0 2.7              
Sham Shui Po East 0.0 0.0 0.0 2.0 9.3              
Wong Tai Sin Central 0.0 0.0 0.0 1.6 11.1              
Diamond Hill 0.0 0.0 0.0 0.0 8.0              
Ngau Chi Wan 0.0 0.0 0.0 1.9 16.7 18.5            
Kwun Tong Central 0.0 0.0 0.0 9.8 16.9              
Lam Tin 0.0 0.0 0.0 3.7 7.3              
Kowloon Bay 0.0 0.0 0.0 1.9 13.8              
The New Territories
Location Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Tseung Kwan O South
(Formerly Tseung Kwan O)
0.0 0.0 0.0 3.5 20.7              
Tseung Kwan O North 0.0 0.0 0.0 6.7 31.7              
Sai Kung Town 0.0 0.0 0.0 0.0 6.3              
Tai Wai 0.0 0.0 0.0 0.0 8.9 5.6            
Yuen Chau Kok 0.0 0.0 0.0 1.8 13.8 22.4            
Ma On Shan 0.0 0.0 0.0 0.0 8.5 11.9            
Tai Po 0.0 0.0 0.0 0.0 9.8              
Fanling 0.0 0.0 0.0 0.0 5.6              
Sheung Shui 0.0 0.0 0.0 0.0 9.4              
Tin Shui Wai 0.0 0.0 0.0 0.0 1.8              
Yuen Kong 0.0 0.0 0.0 4.0 28.0              
Yuen Long Town 0.0 0.0 0.0 0.0 7.5              
Tuen Mun North 0.0 0.0 0.0 0.0 13.8              
Tuen Mun South 0.0 0.0 0.0 0.0 7.4              
So Kwun Wat 0.0 0.0 0.0 0.0 13.0              
Tsuen Wan Town 0.0 0.0 0.0 0.0 5.7              
Ma Wan 0.0 0.0 0.0 0.0 0.0              
Sheung Kwai Chung 0.0 0.0 0.0 0.0 13.5              
Kwai Chung 0.0 0.0 0.0 0.0 7.3              
Lai King 0.0 0.0 0.0 0.0 7.4              
Tsing Yi South
(Formerly Tsing Yi)
0.0 0.0 0.0 7.0 12.3              
Tsing Yi North 0.0 0.0 0.0 5.5 12.7              
Port areas
Location Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Hong Kong International Airport 0.0 0.0

0.0

0.9 2.4              
Cross Boundary Check Points on Land 0.0 0.0 0.0 1.2 11.9              
Private Cargoes Working Areas 0.0 0.0 0.0 0.0 10.1              
Cross Boundary Ferry Piers 0.0 0.0 0.0 0.0 0.8              
Container Terminals 0.0 0.0 0.0 0.0 0.3              
Public Cargoes Working Areas 0.0 0.0 0.0 0.0 9.3              

 

Preventive Measures

Advice on mosquito control and prevention

Aedes albopictus (白紋伊蚊) is highly prevalent in Hong Kong. It breeds both in urban and rural areas and their breeding sites can be artificial receptacles like cans, lunch boxes, discarded tyres, clogged surface channels, containers; and naturally occurring tree holes, bamboo stumps and leaf axils.

Killing of mosquito larvae

Prevention is better than cure. As the mosquitoes have to breed in water, it is more effective and efficient to control mosquito at source at its aquatic stage. Pesticide should only be used for killing of mosquito in its breeding place or preventing its breeding if the breeding sources or potential breeding grounds are inaccessible or could not be eliminated for the time being. The followings must be noted for killing mosquito larvae:

  1. Larvicidal oil or larvicide (such as temephos, Bacillus thuringiensis subspecies israelensis etc.) can be applied to stagnant water directly with dosage according to the label instructions.
  2. Higher than required concentration of larvicide or excessive amount of larvicidal oil would not give better result on killing the mosquito larvae.
  3. The pesticides used must have been registered with the Agriculture, Fisheries and Conservation Department.
  4. Depending on the product, larvicide may be applied weekly into the stagnant water until the water has been removed.
  5. Larvicidal oil need not be applied into the stagnant water again if the oil is still present in the water.
  6. Pesticide applicator should put on protective gears including face mask and rubber gloves during pesticide application.

Killing of adult mosquito

Elimination of adult mosquitoes is relatively difficult as compared with that of the larvae. Adult mosquitoes usually disperse from their breeding place and hide in inconspicuous sites. The followings must be noted for killing adult mosquitoes:

  • Adult mosquito can be killed by using household pesticides against flying insect with dosage according to the label instructions.
  • The pesticides may be applied in form of aerosol, liquid spray, smoke (traditional mosquito coil) or vapour (electric mosquito mat/liquid).
  • Do not spray the pesticides directly against functioning electrical appliances or flame to avoid explosion.
  • Aerosol and liquid spray has to be applied directly to the adult mosquito for effective killing.
  • Spraying of pesticide excessively on adult mosquito is not necessary for killing the insect.
  • Mosquito coil and electric mosquito mat/liquid has to be placed near possible entrance, such as window, for mosquito.
  • Care must be taken to ensure good ventilation and to avoid fire hazard on using mosquito coil.

Protection against adult mosquitoes

Adult mosquito attacks people for getting blood for laying eggs. The followings have to be noted for getting protection against adult mosquitoes:

  1. Windows and doors could be screened.
  2. Wear long-sleeved clothes and long trousers when going outdoors.
  3. Mosquito bednet could be used when the room is not air-conditioned.
  4. Bodies could be protected from mosquito bite by applying mosquito repellent on the clothes or skin according to label instructions.
  5. Some people may be allergic to insect repellent. Apply small amount of insect repellent to small area of the body to check for any allergic response before using the repellent.

Note: Always read and follow label instructions when using pesticides. Please also refer to the leaflet on Safe Use of Household Pesticides produced by Agriculture, Fisheries and Conservation Department for further information. (Tel. No. 2150 7010, Fax: 2314 2622, e-mail: afcdenq@afcd.gov.hk, Web-site: http://www.afcd.gov.hk). The public can also call the telephone hotline of Food and Environmental Hygiene Department at Tel. No. 2868 0000 for more information on mosquito prevention and control.

Remark on mosquito control

Integrated pest management approach has to be adopted for the prevention and control of mosquito. Elimination of stagnant or/and slow running water is the fundamental and most effective mosquito prevention and control method. Application of chemical including pesticide should be the last resort and temporary measure for killing mosquito larvae. Space spraying against adult mosquitoes by using pesticide should only be carried out when there is an urgent need to reduce the number of adult mosquito such as preventing transmission of mosquito-borne diseases. Ecological impacts have to be taken into consideration for selecting the method(s) for mosquito control.

Advice to Public:

  1. To tidy up their premises and check for any accumulation of water inside their premises;
  2. To remove all unnecessary water collection and eliminate the sources;
  3. To change at least every week the water in flower vases and saucers of potted plants to prevent breeding of mosquitoes. The use of saucers should be avoided whenever possible;
  4. To properly cover all containers that hold water to prevent mosquito from accessing the water;
  5. To properly dispose articles that are able to contain water such as empty lunch boxes, cans and tyres;
  6. To stop storing water along morning walk trails or Government land for irrigation;
  7. To make large holes on tyres used as anti-bumping measure in garage to prevent water trapping or use mark(s) on the parking space to prevent bumping instead.
  8. To contact the district pest control offices or PCAS of FEHD, or pest control companies for assistance in mosquito control or prevention.

Anti-mosquito Measures

*Anti-mosquito Measures - Advice for Construction Sites
*Prevention of Dengue Fever (Advice for Housing Estates)
*Prevention of Dengue Fever (Advice for Schools)
*Prevention of Dengue Fever (Advice for Social Service Hostels / Homes)
*Prevention of Dengue Fever (Advice to Picnickers and Hikers)
*Anti-mosquito Measures - Advice for Hospitals / Clinics
*Anti-mosquito Measures - Advice for Ports
*Anti-mosquito Measures - Advice for Ferry
*Anti-mosquito Measures - Advice for Household (Chinese / English / Thai / Sinhalese / Indonesian / Japanese / Pakistani / Philippino / Nepali)

Weekly Mosquito Inspection Program

  PDF format Richtext format
* Weekly Mosquito Inspection Program for Schools pdf txt
* Weekly Mosquito Inspection Program for Construction Sites pdf txt
* Weekly Mosquito Inspection Program for Housing Estates pdf txt
* Weekly Mosquito Inspection Program for Domestic Premises (English) pdf txt
* Weekly Mosquito Inspection Program for Domestic Premises (Thai) pdf  
* Weekly Mosquito Inspection Program for Domestic Premises (Sinhalese) pdf  
* Weekly Mosquito Inspection Program for Domestic Premises (Indonesian) pdf  
* Weekly Mosquito Inspection Program for Domestic Premises (Japanese) pdf  
* Weekly Mosquito Inspection Program for Domestic Premises (Pakistani) pdf  
* Weekly Mosquito Inspection Program for Domestic Premises (Philippino) pdf  
* Weekly Mosquito Inspection Program for Domestic Premises (Nepali) pdf  
* Weekly Mosquito Inspection Program for Port Facilities pdf txt
* Weekly Mosquito Inspection Program for Social Service Centers pdf txt
* Weekly Mosquito Inspection Program for Hospitals and Clinics pdf txt

Internet Knowing Aedes albopictu Quiz Game

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