LCQ17: Prevention of diseases caused by amoebae
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Question:
It is learnt that amoebae will appear in warm freshwater rivers and streams or swimming pool water with an insufficient chlorine content, and may cause serious illness and death if they invade the human body. Regarding the prevention of diseases caused by amoebae, will the Government inform this Council:
(1) of the number of cases of patients seeking consultation which involved diseases caused by amoebae (including amoebic dysentery, Acanthamoeba keratitis and amoebic meningoencephalitis) in the past decade and, among them, the number of death cases;
(2) whether it has regularly taken water samples from public and private swimming pools or leisure pools for testing, so as to check for the presence of lethal pathogens such as amoebae; if so, of the details; if not, the reasons for that;
(3) of the number of cases of an insufficient chlorine content in swimming pools or leisure pools in Hong Kong in each of the past decade, and how the authorities followed up such cases;
(4) as it is learnt that in recent years, more and more members of the public went to the countryside for river tracing, and they even drank mountain water directly on the way, whether it knows the number of cases of invasion of the human body by amoebae in the past five years as a result of coming into contact with stream water or drinking mountain water; and
(5) whether it will step up publicity efforts or formulate action plans for the prevention of diseases caused by amoebae; if so, of the details and timetable; if not, the reasons for that?
Reply:
President,
In consultation with the Department of Health (DH), the Food and Environmental Hygiene Department (FEHD) and the Leisure and Cultural Services Department (LCSD), the reply to various parts of the question raised by the Hon Chan Hoi-yan is as follows:
(1) and (4) Amoeba is a type of unicellular organism with over 2 000 different known species. It is very common in nature environment around the world, including soil and fresh water. Very few free living amoebae in the environment are known as agents of human infections and related invasive infections are rare.
Different species of amoeba may cause different diseases, including amoebic dysentery, keratitis, meningoencephalitis, etc. Among them, amoebic dysentery is a statutorily notifiable infectious disease. In accordance with the Prevention and Control of Disease Ordinance (Cap. 599), all registered medical practitioners are required to notify the Centre for Health Protection (CHP) of the DH all suspected or confirmed cases of notifiable infectious diseases.
Amoebic dysentery is an intestinal infection caused by a protozoan parasite called Entamoeba histolytica. Transmission of amoebic dysentery occurs mainly through the faecal-oral route, including eating and consumption of contaminated food or water. Amoebic dysentery is more common in developing countries and tropical areas with poor sanitary conditions.
In the past decade, the CHP recorded a total of 89 cases of amoebic dysentery (including 67 local cases), including one fatal case in early 2020. The patient concerned had a travel history in late 2019. The CHP does not keep any statistics regarding cases arising from contacting with stream water or drinking mountain water. The breakdown of the aforesaid 89 cases by year is as follows:
| Year | Number of cases of amoebic dysentery |
| 2012 | 7 |
| 2013 | 4 |
| 2014 | 11 |
| 2015 | 5 |
| 2016 | 3 |
| 2017 | 10 |
| 2018 | 5 |
| 2019 | 15 |
| 2020 | 9 |
| 2021 | 9 |
| 2022 (Note) | 11 |
| Total | 89 |
(2) At present, the LCSD is responsible for the management of public swimming pools while the FEHD is responsible for the licensing and regulatory work of private swimming pools.
The LCSD attaches great importance to the cleanliness and hygiene of public swimming pools and has drawn up parameters for monitoring the water quality of its public swimming pools. Such parameters, which are drawn up with reference to the guidelines issued by the World Health Organization and in consultation with the DH, include the free residual chlorine, pH value, total bacteria count and turbidity of pool water. The public swimming pools under the LCSD are well equipped with filtration and disinfection systems. Water of the swimming pools is continuously filtered and disinfected throughout the opening hours. Dedicated LCSD staff members are deployed to take water samples from swimming pools on an hourly basis for testing to ensure that the level of free residual chlorine and pH value of the pool water is up to standard. In addition, the LCSD has also commissioned accredited laboratories to conduct testing on the pool water of its swimming pools on a weekly basis to ascertain that the water quality is up to the relevant standard. To maintain proper functioning of the filtration and disinfection systems of swimming pools, the works departments concerned will conduct regular checking for the systems, and carry out comprehensive inspections and maintenance works during annual maintenance to ensure that the systems can maximise their effectiveness.
Regarding private swimming pools, the FEHD issues Swimming Pool Licences under the Swimming Pools Regulation (Cap. 132CA), so as to ensure that the water quality of these swimming pools will not affect public health when they are open for use. Cap. 132CA sets standards for water quality, including bacteriological quality, clarity, pH value, etc. Monthly inspections and pool water sampling for bacteriological examinations are conducted by the FEHD staff members during the opening time of swimming pools, while pool water sampling for chemical analysis for water clarity is conducted annually. Besides, as required by the licensing conditions, licensees shall arrange tests on pH value of pool water at least once every day. Cap. 132CA also stipulates that the swimming pool be equipped with a water filtration system or renewing new water from the source, and the number of times of changing the pool water to ensure that the pool water meets the standards of water quality. In addition, the licensing conditions for the Swimming Pool Licence include requirements for the ratio of free residual chlorine content.
Under normal circumstances, amoeba cannot survive in properly maintained and chlorinated pool water, as such, it is currently outside the scope of water quality monitoring for public and private swimming pool. Members of the public are also advised by the CHP to avoid swallowing water while swimming, and not to swim for at least two weeks after diarrhoea stops.
(3) To ensure the cleanliness and hygiene of the public swimming pool water, the LCSD has drawn up guidelines under which the fee residual chlorine level must be maintained within the range of one to three parts per million (ppm). If deviation from the parameters is found in the daily testing of pool water, such as a drop in the level of free residual chlorine, venue staff will immediately rectify the situation according to the established guidelines. No cases of inadequate level of free residual chlorine in public swimming pool water have been recorded by the LCSD in the past ten years.
In addition, according to the licensing conditions of the Swimming Pool Licence of the FEHD, the free residual chlorine content of the pool water shall be maintained at a level of not less than one ppm (where chlorine compounds are used for disinfecting the pool water) or 0.5 ppm (where chlorine compounds are used to supplement disinfection by ozone of the pool water) at any time during which the private pool is in use by bathers. The licensees should have a set of testing kit for daily testing of the concentration of free residual chlorine in the pool water. They are required to test the pool water not less than once per day for its free residual chlorine content. The results of such tests shall be properly recorded for inspection by the FEHD officers. In the past ten years, no case about insufficient amount of free residual chlorine in licensed swimming pools has been received by the FEHD.
(5) Currently, the website of CHP has set out health information on amoebic dysentery for public's reference (www.chp.gov.hk/en/healthtopics/content/24/11.html). Depending on the local situation and the need, publicity will be strengthened (including Facebook page, YouTube channel, television, radio station, health education infolines, newspapers, media interviews, etc.).
Note: as of October 12, 2022
Ends/Wednesday, October 26, 2022
Issued at HKT 16:15
Issued at HKT 16:15
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