Following is a question by the Hon Leung Che-cheung and a reply by the Secretary for Food and Health, Professor Sophia Chan, in the Legislative Council today (November 1):

Question:

     Japanese encephalitis (JE) is a mosquito-borne disease.  Most people infected with JE virus have symptoms that are comparatively mild or not apparent. Since January this year, there have been five JE cases in Hong Kong, all of which being locally acquired cases.  The patients in two of the aforesaid cases live in Tin Shui Wai and in another case, which is the world's first case of JE being transmitted by blood transfusion, the blood donor concerned also lives in Tin Shui Wai. Some members of the public suspect that quite a number of Tin Shui Wai residents have been infected with JE virus.  Besides, it has been reported that there is a serious mosquito problem in Tin Shui Wai and the reasons for that include the failure of the Food and Environmental Hygiene Department officers to gain access to private farmlands in the district to carry out anti-mosquito work.  In this connection, will the Government inform this Council:

(1) apart from deploying additional manpower to carry out anti-mosquito work in Tin Shui Wai, whether the authorities have, since January this year, targeted the pig farms near the district in carrying out anti-mosquito work; if so, of the details;

(2) given that the findings of a survey conducted by me earlier have revealed that the level of awareness of JE vaccines among Tin Shui Wai residents was rather low, and a number of JE cases have occurred in the district, of the reasons why the authorities have not considered providing vaccination for residents in the district and stepping up publicity in this respect; and

(3) whether the Government monitored in the past three years the anti-mosquito work carried out at private places (particularly on private lands in Tin Shui Wai); if so, of the details?

Reply:

President,

     The Hong Kong Special Administrative Region Government has all along attached importance to pest, rodent and mosquito control. The Food and Environmental Hygiene Department (FEHD) set up four Pest Control Inspection Teams in May this year to step up inspections of construction sites and potential sites for mosquito breeding and enforcement actions against mosquito breeding. Among the five local Japanese encephalitis (JE) cases this year, two patients live in Tin Shui Wai and the blood donor involved in a case of JE being transmitted by blood transfusion also lives in Tin Shui Wai. Against this background, the Government has strengthened anti-mosquito work in Tin Shui Wai. Where the circumstances so warranted, the Government may consider exercising its authority under section 27 of the Public Health and Municipal Services Ordinance (Cap 132) to enter private premises (including private land) for carrying out anti-mosquito work. 

     My reply to various parts of the question raised by Hon Leung is as follows:

(1) In view of the above JE cases, the FEHD has carried out targeted anti-mosquito work, including conducting entomological surveys and carrying out anti-mosquito work in areas within a two-kilometre radius of the residence of the patients and the places visited by them during the incubation period. District task force meetings have also been conducted to liaise with relevant Government departments and organisations to step up anti-mosquito work in areas within their purview. In response to the above local JE cases, the FEHD has collected and tested 53 mosquito samples. All samples were found negative for JE virus.

     The relevant Government departments have also stepped up their anti-mosquito work accordingly. Apart from strengthening the anti-mosquito work in Tin Shui Estate and other relevant housing estates in Tin Shui Wai, the Housing Department has installed six additional mosquito trapping devices in Tin Shui Estate with a view to reducing the number of adult mosquitoes at public areas and lowering the risk of contact between mosquitoes and humans.

      In August and September this year, the FEHD increased the number of pest control roving teams in Yuen Long district by two teams to 22 teams under the current contract under the Home Affairs Department's District-led Actions Scheme, so as to step up the anti-mosquito work at the public areas in the vicinity of Tin Shui Wai Open Nullah, Tin Heng Estate, Tin Chak Estate, Tin Yan Estate, Tin Wah Estate and Tin Shui Estate.

      The FEHD has also conducted joint site visits with the Agriculture, Fisheries and Conservation Department (AFCD) to the Wetland Park and the pig farms situated within the two-kilometre radius of Tin Shui Estate to offer technical advice on mosquito prevention and elimination. Other actions taken are as follows:

(i) Notices have been issued by the AFCD to advise pig farmers to take anti-mosquito measures, such as installing mosquito trapping devices in their pig farms to lower the risk of contact between mosquitoes and pigs;
(ii) Health talks on anti-mosquito work have been organised for the pig farmers; and
(iii) Concerted efforts have been made by relevant bureaux and departments to step up anti-mosquito work in the vicinity of pig farms.

      After conducting inspections on the pig farms, the two departments considered the measures implemented by the pig farmers to be effective.

      On top of the above, the FEHD has also strengthened the surveillance of JE vectors since October 2015. In the period between January and August this year, a total of 251 mosquito samples were collected and tested, all of which were found negative for the JE virus.

(2) In general, when determining whether to provide vaccination to a specific population, the Government must take into account well-established scientific criteria and a number of public health considerations, including the efficacy and side effects of the vaccine, the availability of other effective preventive measures, cost-effectiveness, the administrative arrangements for vaccination and adequacy of vaccine supply.

     The Scientific Committee on Vector-borne Diseases (the Committee) under the Centre for Health Protection of the Department of Health has discussed the use of JE vaccination in Hong Kong as a measure to prevent JE at several meetings. The Committee considered the territory-wide incidence rate of local JE cases in Hong Kong to be low. Even in high-risk areas such as those near pig farms, the incidence rate was comparable to the incidence rates in countries and areas where JE vaccination has been used to prevent JE after incorporation of the JE vaccine into the immunisation programmes in those countries and areas. The Committee considered that although serious side effects are uncommon with modern JE vaccines, the number of such serious side effects is directly proportional to the number of people vaccinated. The Committee estimated that the number of serious side effects due to the JE vaccine far outweighs the protective benefits of the vaccine in preventing JE in areas where JE occurs infrequently such as Tin Shui Wai. The Committee has thus concluded that the risks of using JE vaccine in the Hong Kong population, including the population living within a two-kilometer radius of pig farms, to prevent JE outweigh its benefits. The Committee also recommended other measures, such as mosquito control and personal protection against mosquito bites, to prevent JE.

(3) To effectively prevent and control the breeding of mosquitoes, the Government's efforts alone are not enough. We need the participation of various sectors and the community.  The most effective way is for the public to start at individual level and at home by removing stagnant water in their premises and taking personal protective measures against mosquitoes.  If the owners of private properties have difficulties in conducting the mosquito prevention work, the FEHD will be ready to offer appropriate assistance. The FEHD may also consider exercising the authority to enter private premises, including private land, to carry out anti-mosquito work if necessary. For example, the FEHD has been installing mosquito screens at vent pipes of septic tanks in private village houses, including private village houses in more than 150 villages in Yuen Long District, since March 2016 to prevent the breeding of mosquitoes in the tanks.

Ends/Wednesday, November 1, 2017
Issued at HKT 16:12

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