ENG-1968 — Page 156

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HEALTH

Malaria continues to occur on a very limited scale, being restricted to certain uncontrolled rural areas of the Colony. Most of the cases during the year were reported from isolated parts of the Tai Po district of the New Territories. The important carriers of malaria are Anopheles minimus, found breeding in hill streams, seepages and irrigation ditches, and A. jeyporiensis var. candidiensis, which breeds in rice cultivation, fallow rice fields, pools in rice stubble and water flowing through grass. Other anopheline species found in the Colony play little or no part in malaria transmission. Plasmodium vivax is the predominant parasite.

Malaria prevention in the urban areas is based chiefly on anti- larval measures consisting of draining and clearing streams, ditching and oiling. Areas under active control are the populated portions of the whole of Hong Kong Island, Kowloon and New Kowloon, extending from Kwai Chung, in the west, to Lei Yue Mun in the east, in addition, Cheung Chau Island and Rennie's Mill Village, in the New Territories, are similarly protected. Larvicidal oil con- tinues to be employed as the main larvicide, but malathion, diazinon and gamma-BHC were used on a limited scale in areas where the application of oil was not suitable. These anti-larval operations against anopheline breeding afford protection from malaria to approximately 80 per cent of the colony's population. None of the few cases appearing in the urban areas during the year could be attributed to breakdown of these control measures. In the greater part of the New Territories where the background is essentially rural, the adoption of anti-malarial mosquito measures described above is not feasible at present and screening of buildings, use of mosquito nets and chemoprophylaxis constitute the main protection against malaria. All anti-mosquito measures for the prevention of malaria are carried out by the Pest Control Section of the Urban Services Department. Clinical aspects of malaria control such as malaria surveys and chemotherapy are the responsibility of the Medical and Health Department.

Diphtheria continued to occur mainly among children under 10 years of age, predominantly within the 'pre-school' age-group. An intensive immunization campaign which has been in progress since 1959 has brought the disease under control and it is pleasant to report that for the first time a four week period was recorded