ANTI-MOSQUITO CONTROL

Dr Chew Chin Han asked the Minister for Health whether the present methods used in anti-mosquito control are also effective in the extermination of the Aedes Aegypti mosquito which is responsible for the transmission of haemorrhagic fever and which is resistant to D.D.T.

Mr Yong Nyuk Lin: Mr Speaker, Sir, present methods of anti-mosquito control are aimed primarily against the malaria mosquito (the type known as Anopheles maculatus and Anopheles sundaicus). (I am afraid I have not done my Latin; so the accent may not be quite right.) As the mosquitoes which transmit haemorrhagic fever are different, namely, Aedes species, other methods will have to be adopted.

These methods are mainly against the larval stages of these mosquitoes. A one-year pilot project, which was carried out in the Geylang area bounded by Sims Avenue, Paya Lebar Road, Sungei Kallang and Sungei Geylang since September last year, demonstrated the effectiveness of simple measures by elimination of breeding places and public education through television, radio and pamphlets, and by personal contacts with the residents. The mosquito index fell within five weeks from an original 10 per cent to about 2 per cent.

As complete eradication of the mosquito vectors may not be a practical possibility, what is aimed at is effective control, in order to bring the mosquito index down to insignificant numbers. For the present, D.D.T. appears to be effective against the local strains of mosquitoes, although resistance has already been reported in most parts of South East Asia.

We are also making determined efforts to improve environmental sanitation in urban constituencies by clearing blocked drains, which are the cause for stagnant water and thus become excellent breeding grounds for mosquitoes. This involves many aspects of public health, especially licensing and control of hawkers (who are chief culprits for irresponsible dumping of refuse into drains), better drainage and unslabbing of roadside drains, as well.

It may be of interest to the Member for Tampines to know that a W.H.O. Consultant on haemorrhagic fever will be visiting the following countries in the Western Pacific Region, namely, the Philippines, Vietnam, Malaysia and Singapore, next month (October). The purpose of the consultant's visit will be to hold preliminary discussions with clinicians and scientists on (a) criteria for the establishment of common definitions for reporting cases of haemorrhagic fever, and (b) some technical aspects of haemorrhagic fever surveillance and control.