mosquito pests and their control

Biology of mosquito

Characteristics of mosquito:

Life cycle: complete metamorphosis with 4 stages (egg, larva, pupa and adult)

Egg:

Larva:

Pupa:

Adult:

Behaviour :

  1. Mating: Female mosquito of many species mate 1 to 2 days after hatching. Female adults normally mate only once in its life.
  2. Feeding: Normally only female adults feed on animal blood. Male adults feed on plant juice. Some species are anthropophilic and some are zoophilic.
  3. Egg laying: Female mosquito of most species has to get blood meal for the development of eggs. Breeding place can be permanent stagnant water, flowing water, temporary stagnant water or containers.
  4. Resting: Adult mosquito rests near breeding site for a few hours after hatching. Exophilic mosquito also rests indoors for a short period of time before and after feeding.
  5. Dispersion: Adult mosquito disperses for feeding, finding suitable resting sites, mating and laying eggs. It can disperse through flight, air current or vehicles.
  6. Hibernation: Some mosquitoes (for example most species of Anopheles and Culex) hibernate in winter at adult stage. Aedes over winter at egg stage.
  7. Longevity: Generally male mosquitoes only survive one week but the females can live for two to three weeks.

Mosquitoes commonly found in Hong Kong

Among the more than 3000 species found around the World, more than 70 species have been found locally. Some 10 species such as Anopheles sinensis, Anopheles maculatus, Aedes albopictus Culex quinquefasciatus and Culex tritaeniorhynchus are commonly found. The mosquito-borne disease vectors found locally are:

  1. Anopheles jeyporiensis (Photo)
    • Breed in paddy field, waterlogged field and stream
    • Female adults are most active during 23.00p.m. to 2.00a.m.
    • Anthropophilic although it also feeds on animals
    • Local malaria vector
  2. Anopheles minimus (Photo)
    • Breed along slow running, unpolluted stream with diffused sunlight and marginal vegetation
    • Greater larval density in periods from March to April and September to October
    • Feed on human and animals at night but viciously at midnight
    • Adults stay indoors before dawn after feeding
    • Local malaria vector
  3. Aedes togoi (Photo)
    • Breed in large number in pools with semi-saline water along seacoasts
    • Vicious night biter
    • Strong flier
    • Vector of filariasis
  4. Aedes albopictus (Photo)
    • Eggs can withstand drought very well
    • 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
    • Weak flier (about 100m)
    • Vector of dengue fever
  5. Culex quinquefasciatus (Photo)
    • Breed in large number in practically all types of water collections from rainwater holding artificial containers to polluted river
    • Always found in construction sites
    • Each egg raft has about 300 eggs
    • Female adults feed viciously on animals or human at night
    • Strong flier
    • Vector of filariasis
  6. Culex tritaeniorhynchus (Photo)
    • Breed in pool, fishpond, water lodged grass field, slow running stream and ditch
    • Adults are active at night with peak of activities one hour after dark
    • Exophilic but stay indoors before and after feeding on blood
    • Mainly zoophagous but also feed on human
    • Vector of Japanese encephalitis and filariasis

Common local mosquito-borne diseases

New information on Gravidtrap Index for Aedes albopictus

Mosquito survey

Malaria vector

To study the distribution of Anopheles. A larval and an adult survey have been conducted locally in order to have detailed information about the growth patterns and distribution of the local malaria vectors.

Dengue fever vector

To study the distribution of Aedes albopictus, gravidtraps are set in selected areas throughout the territory for monitoring the breeding of these mosquitoes. The percentage of the gravidtraps found positive with breeding of these mosquitoes gives the Gravidtrap Index for Aedes albopictus. The value of Gravidtrap Index for Aedes albopictus indicates the extensiveness of the breeding of the vectors.

Gravidtrap index for Acdes albopictus is the percentage of the number of Aedes-positive gravidtraps divided by total number of gravidtraps retrieved from a particular area. Density index for Aedes albopictus is the total number of adult Aedes albopicutus collected divided by total number of Aedes-positive gravidtraps retrieved from a particular area

The period for setting gravidtraps in the survey areas is two weeks. During the survey period, the gravidtraps are collected on a weekly basis. At the end of the first week of surveillance, all the gravidtraps are retrieved and another batch of gravidtraps is set at the same location for surveillance for the second week. The glue boards inside the retrieved gravidtraps are immediately examined for the presence of adult Aedine mosquitoes (“Aedes-positive”) for the purpose of compiling the Gravidtrap Index (First Phase) and Density Index (First Phase). At the end of the second week of surveillance, all the gravidtraps are retrieved and instantly checked for the presence of adult Aedine mosquitoes (“Aedes-positive”) on the glue boards. Data of the two weeks’ surveillance will be combined to obtain the Area Gravidtrap Index (AGI) and Area Density Index (ADI).

FEHD will notify its District Environmental Hygiene Offices and other relevant government departments of the Gravidtrap Indices and Density Indices of various phases once the figures are available, so that they can promptly carry out targeted mosquito prevention and control work. To facilitate public access to the latest survey data, FEHD will announce the phased indices for Aedes albopictus for each of the surveyed areas on the FEHD webpage. Corresponding mosquito prevention and control measures can be taken by the public in a more expeditious manner so as to prevent the spread of dengue fever.

The Gravidtrap Index and Density Index for Aedes albopictus of each surveyed area are released in two phases. Figures released in the first phases are phased indices and the second phase indices represent the AGI and ADI of the surveyed area in that month.

1st Phase GI is the percentage of number of Aedes positive gravidtraps for the first week divided by total number of gravidtraps retrieved for the first week. AGI is the percentage of number of Aedes positive gravidtraps for the 2 weeks divided by the total number of gravidtraps retrieved for the 2 weeks. 1st Phase DI is number of adults of Aedes collected for the 1st week divided by the total number of Aedes positive gravidtraps for the 1st week. ADI is number of adults of Aedes collected for the two weeks divided by the total number of Aedes positive gravidtraps for the 2 weeks

Please click here for the phased Gravidtrap Index in September 2020.

Area Gravidtrap Indices and Density Indices for Aedes albopictus for the 62 survey areas in 2020 are provided below:

Hong Kong Island (Map)
District Location Apr May Jun Jul Aug Sep Oct Nov Dec
Central/Western Central and Admiralty AGI 1.0% 2.0% 9.5% 4.1% 2.0% 3.1%
ADI 1.0 1.0 1.3 1.3 1.0 1.0
Sheung Wan & Sai Ying Pun AGI 3.4% 12.5% 15.0% 5.0% 1.7% 5.9%
ADI 1.0 1.3 1.4 1.0 1.0 1.0
Sai Wan AGI 3.7% 4.7% 22.4% 7.5% 7.3% 7.4%
ADI 1.3 1.4 1.8 1.1 1.6 1.0
Eastern Chai Wan West AGI 0.0% 2.7% 16.1% 3.5% 0.9% 3.5%
ADI N/A 1.0 1.1 1.0 1.0 1.5

Shau Kei Wan
& Sai Wan Ho

AGI 1.8% 17.1% 26.8% 19.4% 11.6% 2.8%
ADI 1.5 1.3 1.4 1.9 1.0 1.0
North Point AGI 0.0% 12.0% 30.4% 13.4% 3.8% 4.6%
ADI N/A 1.3 1.5 1.3 1.3 1.0
Southern Aberdeen and Ap Lei Chau AGI 2.8% 18.3% 17.3% 12.7% 4.5% 5.5%
ADI 1.0 1.4 1.1 1.5 1.0 1.0
Pokfulam AGI 3.5% 5.3% 26.4% 10.6% 8.1% 11.0%
ADI 1.0 1.0 1.6 1.3 1.0 1.0
Deep Water Bay & Repulse Bay AGI 3.4% 11.5% 20.7% 9.4% 7.0% 5.9%
ADI 1.0 1.0 1.0 1.0 1.0 1.0
Wanchai Tin Hau AGI 7.0% 11.3% 12.6% 12.0% 18.9% 19.3%
ADI 1.4 2.4 2.0 1.3 1.6 2.0
Wan Chai North AGI 0.0% 2.7% 0.9% 0.0% 3.7% 2.7%
ADI N/A 1.0 2.0 N/A 1.0 1.0
Happy Valley AGI 3.6% 1.9% 20.2% 5.6% 4.7% 1.9%
ADI 1.0 1.0 1.2 1.2 1.0 1.0
Islands (Map)
District Location Apr May Jun Jul Aug Sep Oct Nov Dec
Islands Cheung Chau South
(Formerly: Cheung Chau)
AGI 25.6% 15.8% 15.7% 1.4% 4.3%
ADI 1.4 1.7 1.5 1.0 1.0
Cheung Chau North AGI N/A N/A 20.9% 5.7% 8.8%
ADI N/A N/A 2.4 1.5 1.8
Tung Chung AGI 8.1% 10.0% 11.0% 7.0% 7.0%
ADI 1.5 1.3 1.5 1.3 1.1
Kowloon (Map)
District Location Apr May Jun Jul Aug Sep Oct Nov Dec
Yau Tsim Tsim Sha Tsui AGI 4.9% 12.8% 9.4% 3.2% 0.8% 2.4%
ADI 1.0 1.8 1.0 1.0 1.0 1.0
Tsim Sha Tsui East AGI 0.0% 3.9% 24.5% 4.8% 6.0% 2.9%
ADI N/A 1.3 1.5 1.0 1.2 1.0
Mong Kok Mong Kok AGI 1.7% 5.0% 6.7% 4.2% 0.0% 2.5%
ADI 1.0 1.0 1.1 1.6 N/A 1.0
Sham Shui Po Cheung Sha Wan AGI 2.9% 9.5% 10.4% 5.3% 7.9%
ADI 1.0 1.0 1.4 1.0 1.1
Lai Chi Kok AGI 7.1% 8.9% 11.6% 5.4% 1.8%
ADI 2.5 1.0 2.0 1.2 1.0
Sham Shui Po East AGI 0.9% 10.2% 18.3% 3.8% 2.8%
ADI 1.0 1.3 1.2 1.0 1.0
Kowloon City Ho Man Tin AGI 1.9% 8.5% 19.4% 6.5% 5.5% 3.6%
ADI 1.0 1.2 1.3 1.7 1.0 1.0
Kowloon City North AGI 3.6% 5.5% 7.4% 0.9% 2.8%
ADI 1.0 1.0 1.0 1.0 1.0
Hung Hom AGI 1.8% 7.9% 18.8% 10.9% 1.8% 6.3%
ADI 1.0 1.1 1.2 1.1 1.0 1.0
Lok Fu West AGI 5.2% 5.8% 26.3% 7.6% 16.7% 32.2%
ADI 1.3% 1.1 1.4 1.1 1.4 1.5
Kai Tak North AGI 8.6% 11.1% 26.6% 10.3% 4.9% 6.1%
ADI 1.1 1.7 1.7 1.3 1.3 1.4
Wong Tai Sin Wong Tai Sin Central AGI 6.7% 10.5% 19.4% 13.6% 11.9% 8.3%
ADI 1.0 1.3 1.7 1.6 1.6 1.0
Wong Tai Sin West AGI N/A N/A 25.0% 7.5% 6.5% 5.6%
ADI N/A N/A 1.0 1.1 1.0 1.0
Diamond Hill AGI 0.0% 0.9% 15.5% 9.6% 4.4% 2.6%
ADI N/A 2.0 1.0 1.2 1.0 1.0
Ngau Chi Wan AGI 1.0% 5.7% 23.6% 11.7% 15.7% 22.6%
ADI 1.0 1.0 1.6 1.2 1.2 1.3
Kwun Tong Kwun Tong Central AGI 10.2% 18.8% 17.1% 4.0% 7.1%
ADI 1.4 1.2 1.4 1.0 1.0
Lam Tin AGI 8.4% 10.9% 21.8% 10.8% 7.5%
ADI 1.1 1.1 1.6 1.3 1.1
Yau Tong AGI 1.4% 12.2% 7.1% 9.5% 4.3% 5.6%
ADI 1.0 1.1 1.0 1.0 1.0 1.0
Kowloon Bay AGI 4.2% 9.8% 17.5% 10.7% 7.4%
ADI 1.0 1.3 1.1 1.1 1.2
New Territories (Map)
District Location Apr May Jun Jul Aug Sep Oct Nov Dec
Sai Kung

Tseung Kwan O West
(Formerly: Tseung Kwan O South)

AGI 6.3% 5.6% 10.4% 2.8% 3.6%
ADI 1.1 1.0 1.2 1.0 1.0
Tseung Kwan O East AGI N/A N/A 23.5% 8.7% 7.7% 7.5%
ADI N/A N/A 2.0 1.1 1.9 1.6
Tseung Kwan O North AGI 7.7% 15.2% 32.0% 9.9% 20.8%
ADI 1.3 1.2 1.6 1.0 1.4
Sai Kung Town AGI 13.9% 21.3% 19.4% 8.4% 1.9%
ADI 1.1 1.2 1.3 1.1 1.0
Ngau Liu & Muk Min Shan AGI N/A N/A 32.7% 16.3% 10.2% 14.0%
ADI N/A N/A 1.9 1.8 1.2 1.1
Sha Tin Tai Wai AGI 10.5% 10.4% 18.5% 10.7% 7.1% 3.2%
ADI 1.2 1.2 1.1 1.2 1.7 1.3
Sha Tin East AGI 1.6% 20.2% 14.5% 6.6% 4.1% 8.0%
ADI 1.0 2.0 2.2 1.3 1.4 1.8
Ma On Shan AGI 8.1% 12.1% 28.1% 8.6% 8.1% 5.6%
ADI 1.2 1.9 2.0 1.2 1.5 1.0
Sha Tin Town Centre and Fo Tan AGI 6.0% 6.5% 21.0% 17.0% 7.7% 6.4%
ADI 1.3 1.1 1.8 1.8 1.1 1.0
Tai Po Tai Po North AGI 1.7% 5.0% 19.2% 1.7% 5.9% 5.2%
ADI 1.0 1.0 1.0 4.5 1.0 1.0
North Fanling AGI 5.2% 4.3% 17.4% 5.4% 7.8% 5.2%
ADI 1.5 1.0 1.6 1.3 1.1 1.0
Sheung Shui AGI 3.5% 10.5% 34.2% 13.8% 5.4% 2.6%
ADI 1.0 1.1 1.8 1.4 1.0 1.3
Yuen Long Tin Shui Wai AGI 8.0% 6.4% 5.6% 2.4% 2.4% 4.8%
ADI 1.0 1.0 1.1 1.0 1.0 1.0
Yuen Kong AGI 2.0% 2.0% 8.0% 0.0% 6.1% 4.1%
ADI 1.0 1.0 1.0 N/A 1.0 1.0
Yuen Long Town AGI 3.6% 6.5% 15.2% 10.5% 2.7% 4.5%
ADI 1.0 1.1 1.1 1.5 1.0 1.0
Ki Lun Shan AGI N/A N/A 29.2% 6.4% 4.0% 2.0%
ADI N/A N/A 2.6 1.0 1.0 1.0
Tuen Mun Tuen Mun North AGI 2.3% 18.5% 11.5% 5.4% 0.8% 1.5%
ADI 1.0 1.9 1.3 1.1 1.0 1.0
Tuen Mun South AGI 0.9% 18.2% 14.7% 9.1% 1.8% 2.8%
ADI 1.0 1.3 1.3 1.0 1.5 1.0
Tuen Mun West AGI 3.1% 15.6% 21.9% 6.1% 6.4% 4.3%
ADI 1.0 2.1 1.9 1.0 1.3 1.0
So Kwun Wat AGI 2.6% 12.1% 21.6% 7.8% 4.4% 1.0%
ADI 1.3 1.1 1.4 1.1 1.0 1.0
Tsuen Wan Tsuen Wan Town AGI 0.8% 4.2% 17.6% 5.0% 1.7% 2.5%
ADI 1.0 1.4 1.7 1.0 1.0 1.7
Tsuen Wan West AGI 9.0% 12.0% 23.8% 2.9% 4.7%
ADI 1.3 1.1 1.7 1.0 1.0
Ma Wan AGI 6.1% 27.1% 32.0% 12.2% 10.0% 2.0%
ADI 1.0 1.2 1.6 1.2 1.0 1.0
Sheung Kwai Chung AGI 3.7% 5.6% 5.7% 0.0% 4.6%
ADI 1.0 1.2 1.3 N/A 1.2
Kwai Tsing Kwai Chung AGI 5.4% 9.6% 5.4% 2.7% 4.3%
ADI 1.0 1.0 1.0 1.0 1.0
Lai King AGI 17.1% 21.0% 25.0% 13.7% 10.5% 8.5%
ADI 1.3 1.2 2.0 1.1 1.0 1.1
Tsing Yi South AGI 5.2% 12.1% 23.5% 5.2% 0.9%
ADI 1.3 1.4 1.6 1.3 2.0
Tsing Yi North AGI 1.8% 5.6% 18.4% 7.6% 15.4% 38.0%
ADI 1.0 1.2 2.0 1.0 1.4 1.4
Port areas (Map)
Port Area Apr May Jun Jul Aug Sep Oct Nov Dec
Hong Kong International Airport PGI 0.2% 0.8% 1.4% 0.4% 0.3%
PDI 1.2 1.2 1.1 1.0 1.0
Cross Boundary Check Points on Land PGI 0.9% 4.7% 7.2% 2.3% 1.6%
PDI 1.0 1.5 1.5 1.0 1.4
Private Cargo Working Areas PGI 1.3% 7.3% 11.3% 1.5% 3.5%
PDI 1.0 1.1 1.3 1.2 1.1
Cross Boundary Ferry Piers PGI 0.5% 3.6% 2.5% 1.1% 1.4%
PDI 1.0 1.2 1.0 1.2 1.2
Container Terminals PGI 0.1% 0.9% 0.8% 0.5% 0.3%
PDI 1.0 1.1 1.0 1.0 1.0
Public Cargo Working Areas PGI 0.3% 4.9% 10.2% 3.2% 2.0%
PDI 1.0 1.1 1.1 1.2 1.0

Mosquito prevention

Advice

To the public

The public is advised:

To the management of construction sites

The management of construction sites is advised:

Mosquito control

Adult Control

Larval Control