Monthly gravidtrap index for Aedes albopictus of December 2020 remains at lowest level
The Food and Environmental Hygiene Department (FEHD) today (January 25) announced that the monthly gravidtrap index for Aedes albopictus (MGI) for December 2020 dropped further to 0.7 per cent from 1.9 per cent in November last year. The index in December remains lowest at Level 1, indicating that mosquito infestation in the areas surveyed was not extensive.
　　Among the 62 survey areas, no area was recorded with gravidtrap indices exceeding the alert level of 20 per cent. Moreover, the monthly density index for Aedes albopictus (MDI) in December 2020 slightly dropped to 1.0 from 1.1 in November, which represented that an average of one Aedes albopictus adult was found in the Aedes-positive gravidtraps, indicating that the number of adult Aedes albopictus was not high in the areas surveyed. The FEHD reminded the public that despite the fact that the index has further dropped and remained at a low level, the breeding and activities of mosquitoes will continue in winter and the community must remain vigilant and continue to carry out effective mosquito prevention and control measures.
As for the port areas, the port monthly gravidtrap index in December rose slightly to 0.1 per cent from 0.03 per cent in November last year, while the port monthly density index in December is 1 as in November.
Looking back, progress has been made in the Government's mosquito prevention and control work in 2020. There was only one local dengue fever case recorded in Hong Kong last year. The monthly local gravidtrap index for Aedes albopictus during the past rainy season from May to September was at a similar level to that of previous years, and the recent indices have even dropped to the lowest level at Level 1. Since April 2020, the FEHD has introduced newly designed gravidtraps to replace ovitraps previously used to directly count the number of adult mosquitoes, so as to enumerate the gravidtrap index and the new density index, which reflect the extensiveness of distribution and the density of Aedes albopictus respectively. The relevant indices have been launched and widely used.
The FEHD launched its year-end clean-up operation on January 18 this year, during which mosquito preventive and control work will be enhanced, including carrying out inspections, removing stagnant water, applying insecticide and disposing of abandoned water containers weekly to prevent mosquito breeding, and trimming of grass to discourage resting of adult mosquitoes on the site. The FEHD and relevant government departments will continue the above mosquito prevention and control work in areas under their purview and strengthen publicity and education campaigns.
The area gravidtrap index (AGI) and the area density index (ADI) indicate the extensiveness of distribution and the density of Aedine mosquitoes respectively in that particular survey area, while the MGI and the MDI are enumerated by pooling together all AGIs and ADIs of the same month, which reflect the general situation of Aedes albopictus in all survey areas. The gravidtrap and density indices for Aedes albopictus in different areas and information on mosquito prevention and control measures are available on the department's website at www.fehd.gov.hk.
The spokesman said, "Aedes albopictus is a kind of mosquito that can transmit dengue fever (DF) as well as Zika virus infection. DF is commonly found in tropical and subtropical regions of the world, and has become endemic in many countries in Southeast Asia. The World Health Organization also issued warnings that the number of DF cases recorded in Asia last year was higher than before. As Hong Kong has recorded one local DF case last year and the dengue activity in neighbouring areas has remained high, as well as the breeding and activities of mosquitoes will continue in winter, we hope that the public would continue to work with the Government to carry out effective mosquito prevention and control measures."
The spokesman added that as Aedes albopictus breeds in small water bodies, members of the public should carry out effective mosquito prevention and control measures including inspecting their homes and surroundings to remove potential breeding grounds, changing the water in vases and scrubbing the inner surfaces, removing the water in saucers under potted plants 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 level all defective ground surfaces to prevent accumulation of water. They should also scrub all drains and surface sewers with an alkaline detergent at least once a week to remove any mosquito eggs.
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.