July’s monthly gravidtrap index for Aedes albopictus drops

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     The Food and Environmental Hygiene Department (FEHD) today (August 19) announced that the monthly gravidtrap index for Aedes albopictus (MGI) in July dropped to 7.4 per cent from 14.8 per cent in June, which was at Level 2, indicating that distribution of Aedes albopictus in the areas surveyed was fairly extensive but maintained at a relatively low level.

     Among the 64 survey areas, only Ma On Shan was recorded with the area gravidtrap index (AGI) (22.8 per cent) exceeding the alert level of 20 per cent. The gravidtraps concerned were mostly located in the vicinity of public and private residential areas, schools, recreational and sports facilities and public places. The FEHD has collaborated with relevant government departments, including the Housing Department, the Education Bureau and the Leisure and Cultural Services Department, by taking immediate action to strengthen mosquito prevention and control work in the areas concerned. Moreover, the monthly density index for Aedes albopictus (MDI) in July was 1.2, which represented that an average of 1.2 Aedes albopictus adults were found in the Aedes-positive gravidtraps, indicating that the number of adult Aedes albopictus was not high in the areas surveyed. As for the port areas, the port monthly gravidtrap index in July was 1.5 per cent, while the port monthly density index in July was 1.2, both remaining at a low level.

     The FEHD reminded that, although the indexes have declined, members of the public should continue to take effective prevention and control measures against mosquitoes to reduce the risk of the spread of mosquito-borne diseases in the territory as the hot and rainy weather of summer is favourable for proliferation of mosquitoes.

     "Relevant government departments will continue to intensify mosquito prevention and control work covering venues under their purview. Apart from strengthening publicity and education, the FEHD is conducting a three-phase territory-wide Anti-mosquito Campaign this year. The second phase of the Campaign ended in mid-June and the third phase has been launched on August 9 and will run until October 29. During the period, the FEHD and relevant government departments will enhance the mosquito prevention and control work and target areas which have drawn particular concern, such as locations in close proximity to human residences, parks, schools, construction sites, public housing estates, hospitals, illegal cultivation sites, waterfront public and private cargo working areas, cross-boundary checkpoints, typhoon shelters and cross-boundary ferry terminals, to remove the accumulation of water and to carry out mosquito prevention and control work," a spokesman for the FEHD said.

     The 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 dengue activity in neighbouring areas has remained high and Hong Kong has recorded one imported DF case so far this year. Also, Hong Kong's hot and rainy summer is conducive to the proliferation of mosquitoes, so the community should stay vigilant and continue 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 public and estate management bodies to keep drains free of blockage and level all defective ground surfaces to prevent the 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.

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