HEALTH
149
Epidemiological control is based on contact investigation, the follow-up of defaulters from treatment and the vaccination of child contacts with BCG. The main difficulty encountered is the un- willingness of many contacts to return for further examination after a year because they neither see nor feel any sign of the disease. A further problem is the resettlement of cured patients in suitable employment, and this is the subject of continuing effort. Dermatology. Treatment is given free at a number of out-patient sessions for the diagnosis and treatment of skin conditions. This has the valuable incidental advantage of assisting in the detection of leprotic and syphilitic lesions.
Malaria. Malaria continues to be endemic but is largely restricted to certain parts of the uncontrolled rural areas. About 90 per cent of notified cases came from these uncontrolled areas, Sai Kung accounting for about two-thirds of the total. None of the few cases appearing in the urban areas during the year could be traced to infection contracted there. The important carriers of malaria are A. minimus found breeding in certain 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.
Malaria control in the urban areas is based chiefly on anti- larval measures consisting of draining and clean-weeding streams, ditching and oiling. Anti-malaria oil continued to be employed as the main larvicide, although Gammexane Dispersible Powder and Diazinon are also used on a limited scale in areas where the application of oil is not suitable. These anti-larval operations against anopheline breeding afford protection to over 2,500,000 people living within the urban areas of Hong Kong, Kowloon and New Kowloon and in certain circumscribed zones in the New Territories. In the remainder of the New Territories control by anti-larval measures is not at present practicable.
Paludrine prophylaxis continues as the main line of defence against malaria for disciplined groups stationed in the New Territories. Malariometric surveys were carried out from time to time. These showed that spleen and parasite rates in children aged two and nine ranged from zero to 14.9 per cent and zero to 7.8 per cent respectively. Throughout the year blood smears were