X1000307-1952-53_Part01 — Page 17

CONTROL

Imagocides

112. Residual spraying by DDT was made use of in the following circumstances:

() As a supplementary barrier check in Chinese villages on the perimeter of the larval controlled areas. This was done at three-monthly intervals. (ii) The perimeter villages surrounding five Army Camps in the New Territories, in an attempt to minimize the number of latent Benign Tertian infections among the troops taking paludrine prophylactically.

(iii) All Government quarters in the New Territories.

Control of Breeding.

118. Control was effected by spraying with water miscible Gammexane. Excellent results were obtained with this insec- ticide, and after two years use, no larval resistance appears to have developed as has been the case here with regard to the common house fly.

114. In addition to this routine work, the area of control was extended for one mile round the Airport in connexion with the resettlement of squatters in the neighbouring area of Ngau Tau Kok. Further, in the New Territories, many miles of drainage, stream training, etc., was carried out to protect the personnel engaged in the construction of the Tai Lam Chung Dam. These areas are also under routine spraying with Gammexane.

Result of Control.

115, Numerous checking catches and surveys were made by anti-malarial staff in the controlled area. Except in two isolated instances on private property, no anophelines, either larvæ or adults, could be found. Incoming aircraft were similarly searched with negative results.

116. This does not mean that the larval control programme can be relaxed in any way. A sharp reminder of this fact occurred on three occasions during the year when, outbreaks

of malaria occurred in three areas on the Island. Further, checks have shown that heavy vehicular traffic from the New Territories, the Railway, and some 400 juuks, are daily pouring their quota of mosquitoes into the controlled area.

Malaria Incidence.

117. The civilian European population at risk is approxi- mately 25,000 and from these 15 cases of malaria were notified during the year as compared with 12 cases in the previous year. From the 2,250,000 Chinese in Hong Kong and Kowloon, 951 cases were reported as compared with 526 in the previous year.

118. Forty-six deaths were attributed to malaria in the Colony as a whole, constituting .23 per cent of all deaths. In 1932, 454 deaths were attributed to malaria accounting for 2.28 per cent of all deaths.

Insecticides.

119. W.H.O. has asked for the active co-operation of Govern- ments and field workers in the development of insecticides for malaria control. Following reports from Malaya of the success of emulsion concentrates and high spread DDT in oil, as larvi- cides, experiments were carried out in the New Territories by a combined team from the Malaria Bureau, the Army Hygiene Unit from Malaya, and the Asiatic Petroleum Co.

120. The results were inconclusive and did not determine the most important point, namely the phytocytic effect of the concentrate on growing rice. The Malaria Bureau has agreed to continue experimenting, using the concentrate emulsion on selected areas of paddy in the New Territories for the control of both first and second crops i.e. from April to the end of November.

Laboratory.

121. In addition to the routine checking, much work was done on two intimately connected problems, namely the possible use of residual spraying of DDT or Gammexane as a method of malaria control in the New Territories, and the investigation

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