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 2008 and average
of 2000 to 2007.
Please
click
here for graphical information on the ovitrap indices of the
year from 2003 to 2007.
Please click
here for monthly data on the ovitrap indices of the
year from 2003 to 2007.
Please click
here for port monthly data on the ovitrap indices of the
year from 2004 to 2007.
The Monthly Ovitrap
Index for
July 2008 is 13.1%.
The Port
Monthly Ovitrap Index forJuly 2008 is0.8%.
Area Ovitrap Index for
all the 38 locations are shown in the following maps :
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:
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 and exposed part of the body.
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.
Last revision date: 13-08-2008