Breed in small containers such as cans, discarded tyres, tree holes, rock pools and bamboo ends holding small amount of water
Adults rest in shrubby area
Adult has a white stripe on the dorsal surface of thorax and bands on legs.
Although exophilic, adults may also enter into houses
Day biter (Peak : within 2 hours after dawn and before sunset)
Weak flier (about 100m)
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.
Note: Please do not tamper with the ovitrap set by the Food and Environmental Hygiene Department.
An Ovitrap Index will be enumerated by the formula :
Ovitrap Index = No. of Aedes-positive ovitraps / No. of ovitraps collected from the specific area x 100%
Starting from 2003, there are a total of 38 locations selected for the vector surveillance. Two different indices, namely Area Ovitrap Index (AOI), and Monthly Ovitrap Index (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 (POI), and Port Monthly Ovitrap Index (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.
The Ovitrap Index 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 and actions to be taken by the management are listed in the following table.
Classification
Ovitrap Index
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 between 2010 and average of 2000 to 2009.
Please click here for graphical information on the ovitrap indices of the year from 2003 to 2009.
Please click here for monthly data on the ovitrap indices of the year from 2003 to 2009.
Please click here for port monthly data on the ovitrap indices of the year from 2004 to 2009.
The Monthly Ovitrap Index forJuly 2010 is 13.0%.
The Port Monthly Ovitrap Index forJuly 2010 is0.8%.
Area Ovitrap Index for all the 38 locations are shown in the following maps :
Aedes albopictus (¥Õ¯¾¥ì°A) 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:
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.
Higher than required concentration of larvicide or excessive amount of larvicidal oil would not give better result on killing the mosquito larvae.
The pesticides used must have been registered with the Agriculture, Fisheries and Conservation Department.
Depending on the product, larvicide may be applied weekly into the stagnant water until the water has been removed.
Larvicidal oil need not be applied into the stagnant water again if the oil is still present in the water.
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:
Windows and doors could be screened.
Wear long-sleeved clothes and long trousers when going outdoors.
Mosquito bednet could be used when the room is not air-conditioned.
Bodies could be protected from mosquito bite by applying insect repellent (containing DEET) on the clothes.
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:
To tidy up their premises and check for any accumulation of water inside their premises;
To remove all unnecessary water collection and eliminate the sources;
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;
To properly cover all containers that hold water to prevent mosquito from accessing the water;
To properly dispose articles that are able to contain water such as empty lunch boxes, cans and tyres;
To stop storing water along morning walk trails or Government land for irrigation;
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.
To contact the district pest control offices or PCAS of FEHD, or pest control companies for assistance in mosquito control or prevention.
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