Drop recorded in August’s monthly ovitrap index for Aedes albopictus
The Food and Environmental Hygiene Department (FEHD) today (September 14) announced that the monthly ovitrap index for Aedes albopictus for August dropped to 7.3 per cent from 15.7 per cent in July. Though there was a decrease in the ovitrap index, the mosquito infestation was still slightly more extensive in the areas surveyed. Coupled with the 29 local dengue fever (DF) cases recorded so far, the FEHD reminded the public to remain vigilant 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.
"Aedes albopictus is a kind of mosquito that can transmit DF and Zika virus. In view of the 29 local DF cases recorded in Hong Kong since mid-August, and that the weather in Hong Kong remains hot and rainy even though autumn has arrived, which is favourable for the breeding of mosquitoes, as well as DF is still highly prevalent in neighbouring areas, the public must stay alert and work with the Government to continue to carry out effective mosquito prevention and control measures," an FEHD spokesman said.
Among the 57 areas surveyed last month, only the Area Ovitrap Index (AOI) in Yau Tong (34.7 per cent) exceeded the alert level of 20 per cent. As for the port areas, the monthly ovitrap index for Aedes albopictus for August also dropped to 2.2 per cent from 2.7 per cent in July.
The spokesman said, "The FEHD is very concerned about mosquito problems. In response to the local DF cases, the FEHD commenced the third phase of the territory-wide anti-mosquito campaign from mid-August and has enhanced the territory-wide all-out anti-mosquito operations 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 have also carried 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. The decrease in August’s monthly index showed that we started seeing the results of the aforementioned operations."
In addition, an inter-departmental anti-mosquito response mechanism has been activated in the area with the AOI reaching the alert level of 20 per cent for co-ordinating relevant departments and stakeholders to carry out effective mosquito prevention and control measures. Relevant departments have individually notified the groups that had voluntarily subscribed to the ovitrap rapid alert system in that area. 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 September 9), the FEHD had instituted 155 prosecutions for mosquito breeding found in relevant premises under the Public Health and Municipal Services Ordinance (Cap 132), comprising 147 cases involving construction sites and eight cases involving other premises.
The spokesman added, "In order to keep the public abreast of the latest situation of mosquito infestation and facilitate them to take timely mosquito prevention and control measures, the FEHD has released additional AOI for Aedes albopictus at two more stages starting from September, apart from the announcement of the monthly AOI and the monthly ovitrap index for Aedes albopictus. The FEHD will follow the established practice of notifying relevant government departments of the aforementioned indices so that they can carry out targeted mosquito prevention and control work promptly to strengthen the anti-mosquito efforts."
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 disposing 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.