July’s monthly ovitrap index for Aedes albopictus rises

     The Food and Environmental Hygiene Department (FEHD) today (August 21) announced that the monthly ovitrap index for Aedes albopictus for July rose to 15.7 per cent from 11.3 per cent in June, indicating that mosquito infestation was slightly more extensive in the areas surveyed. Coupled with the 16 confirmed local dengue fever (DF) cases recorded so far this month, the FEHD reminded the public to heighten vigilance and keep up effective prevention and control measures against mosquitoes, as well as to take personal protective measures to reduce the risk of contracting mosquito-borne diseases through mosquito bites. The Government is actively studying the proposal to announce the ovitrap index for Aedes albopictus in a more timely manner.

     "Aedes albopictus is a kind of mosquito that can transmit DF and Zika virus. The hot and rainy weather of summer is favourable for massive mosquito breeding. In view of the fact that DF is still highly prevalent in neighbouring areas, and Hong Kong recorded 16 local DF cases so far this month, the community must work with the Government to continue to carry out effective mosquito prevention and control measures," an FEHD spokesman said.

     In order to strengthen dengue vector surveillance, the FEHD has increased the number of survey areas from 52 to 57 last month, and the survey period has also been extended from one week to two weeks every month. Among the 57 areas surveyed last month, the Area Ovitrap Index (AOI) in 15 areas reached or exceeded the alert level of 20 per cent. They were Yau Tong (45.1 per cent), Wo Che (42.6 per cent), Tseung Kwan O North (33.3 per cent), Tsuen Wan West (29.8 per cent), Tuen Mun West (28.7 per cent), Kowloon Bay (28.7 per cent), Kowloon City North (24.5 per cent), Central and Admiralty (24.5 per cent), Yuen Kong (24 per cent), Tai Wai (22.8 per cent), Wong Tai Sin Central (21.8 per cent), Ma On Shan (21.8 per cent), Lam Tin (20.8 per cent), Tsim Sha Tsui (20.2 per cent) and Ngau Chi Wan (20.2 per cent).

     As for the port areas, the monthly ovitrap index for Aedes albopictus for July also slightly rose to 2.7 per cent from 2.4 per cent in June.

     The spokesman said, "The FEHD is very concerned about mosquito infestation, and an inter-departmental anti-mosquito response mechanism has been activated in the above-mentioned areas for co-ordinating relevant departments and stakeholders to carry out effective mosquito prevention and control measures. In response to the ten odd DF cases recorded in Hong Kong recently, the FEHD has stepped up targeted mosquito prevention and control work at the relevant districts, including conducting fogging operations to reduce the number of adult mosquitoes; and applying larvicides and clearing stagnant water and disused articles to prevent mosquito breeding in areas within a 500-metre radius of the residences of the patients and the places visited by them after illness onset. The FEHD also collected samples of Aedes albopictus at the places concerned for dengue virus testing.

     “The FEHD has earlier commenced the third phase of the territory-wide anti-mosquito campaign and enhanced the mosquito control work by conducting the territory-wide all-out anti-mosquito operations for 10 weeks to concentrate on killing adult mosquitoes with a view to reducing the risk of the spread of DF. During the period, relevant departments and the Hospital Authority will also carry out the all-out anti-mosquito operations in areas under their purview, including conducting fogging operations in the scrubby areas within 200-metre radius of the residences every week to kill adult mosquitoes; carrying out inspection of venues, removing stagnant water, applying insecticide and disposing of abandoned water containers every week to prevent mosquito breeding; and trimming of grass to remove the potential habitat of adult mosquitoes and facilitate mosquito control work."

     In addition, relevant departments have individually notified the groups that had voluntarily subscribed to the ovitrap rapid alert system when the AOI reached the alert level of 20 per cent. Subscribers have been invited to post specially designed alert notices in the common parts of their premises to urge occupants and staff to carry out mosquito prevention and control measures promptly.

     The FEHD has also swiftly handled mosquito complaints and taken out prosecutions against mosquito breeding under the relevant ordinance. The FEHD set up four Pest Control Inspection Teams in May last year to step up inspection of construction sites and enforcement action against mosquito breeding. This year (as at August 19), the FEHD had instituted 139 prosecutions for mosquito breeding found in relevant premises under the Public Health and Municipal Services Ordinance (Cap 132), comprising 133 cases involving construction sites and six cases involving other premises.

     The FEHD and relevant government departments will continue to intensify their mosquito prevention and control work covering areas under their purview, and strengthen publicity and education campaigns, including closely liaising with local organisations and widely disseminating anti-mosquito messages through their community network. In addition, the district offices of the FEHD will target areas which have drawn particular concern, such as public markets, cooked food centres and hawker bazaars, single-block buildings, streets and back lanes, common parts of buildings, village houses, construction sites, vacant sites and road works sites to intensify mosquito prevention and control work. The FEHD will, immediately after each phase of the campaign, conduct special territory-wide thematic mosquito prevention and control operations so as to enhance the effectiveness of the campaign.

     As Aedes albopictus breeds in small water bodies, the spokesman reminded members of the public to continue to carry out effective mosquito prevention and control measures, including inspecting their homes and surroundings to remove potential breeding grounds, scrubbing vases and pot plant saucers at least once a week, properly disposal of containers such as soft drink cans and lunch boxes, and drilling large holes in unused tyres. He also advised the public and estate management bodies to keep drains free of blockage and fill up all depressions to prevent puddles from forming. They should also scrub all drains and surface sewers with an alkaline detergent compound at least once a week to remove any mosquito eggs.

     In addition, rural areas and the vicinity of shrubby areas are the natural habitats for mosquitoes, other insects and animals. Members of the public living in rural areas may install mosquito screens on windows and doors if necessary. Those staying in the natural environment should follow appropriate personal protective measures against mosquitoes, such as avoiding staying in the vicinity of shrubby areas for a long time, wearing light-coloured long-sleeved clothes and trousers and applying DEET-containing insect repellent. Members of the public are reminded to make reports to the government departments via 1823 if mosquito problems are detected.

     The spokesman reiterated that effective mosquito control requires the sustained effort of all parties concerned. The community must work together with the Government to carry out effective mosquito control measures.

     The ovitrap index is divided into four levels, reflecting the infestation level of 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. The Government will step up the scale of anti-mosquito operations according to the level of infestation as well as reports from front-line staff and the public.

     As Aedes albopictus can transmit DF and Zika virus, oviposition traps are set in 57 areas in Hong Kong for monitoring the breeding of Aedes albopictus, which is only one of the mosquito species commonly found in Hong Kong and is active only in the daytime. The index does not capture the activity of Aedes albopictus outside the 57 areas and it also does not measure the prevalence of other kinds of mosquitoes.

     The ovitrap indices for Aedes albopictus in different areas and information on mosquito prevention and control measures are available on the department website at www.fehd.gov.hk.