127. The basis of anti-malaria work in Hong Kong is by Jarval control throughout the urban area, the main vectors being A. minimas and A. jeyporiensis. This work continued steadily, water miscible Gammexane being used with good results, but residual spraying of DDT as a supplementary anti- adult measure was carried out in villages on the perimeter of the area in which larval control was alone undertaken. This spraying was carried out at Intervals of 3 months. However, observations made in the New Territories ou the control of A. mínímus, A, jeyporiensis, A. kyreanus and A. maculatus by residual spraying have not shown good results, perhaps, because of the type of construction of the village huts, which consist of local bricks containing a large amount of laterite, the surface being rendered with earth. On such a surface the insecticide ia very rapidly absorbed. There are also indications that the mosquitues in question do not rest long enough indoors for the insecticides to be effective. Be that as it may, it was observed that after spraying, morning catches of mosquitoes had returned to the pre-spraying level after only 7 days.
128. In addition to the control measures exercised within the urban districts, similar measures were instituted in a limited area in the New Territories in the vicinity of the construction work which has commenced on the new dam at Tai Lam Chung, The average monthly labour population engaged on this project throughout the year was 600 and no cases of malaria were recorded. This is of Interest in view of the fact that exactly 20 years ago when the Shing Mun Dam was being constructed in exactly similar circumstances in the New Territories there was an average monthly population of 595 and the total number of malaria cases treated in 1933 at the dam camp was 1,096.
129. The Malaria Bureau, under the direction of the Malariologist, is responsible for anti-malaria measures through- out the Colony. The staff available to the Malariologist were 11 Malaria Inspectors and some 230 daily paid overseers and labourers. In addition the Bureau, at the request of the World Health Organization, conducted a series of experiments to deter-
30
mine the resistance, if any, of the local species of body lice to DDT, Gammexane and the Pyrenthrins. Some 1,000 lice were tested against standard concentrations of these substances, and no appreciable resistance to them was observed.
Tuberculosis Control
130, It has been stated that tuberculusis constitutes the Colony's major public health problem. Notified cases during 1963 numbered 11,900 and the 2,989 deaths from this causé constituted 16% of all deaths. Tuberculin testing with a view to Instituting a mass RCG campaign revealed that nearly 95% of the population above the age of 14 years had already incurred some infection as evidenced by positive teata. In the face of prevailing social and economic conditions with increasing unemployment and a definite trade recession one cannot hope that a great and rapid improvement in the situation with regard to an infection which flourishes in such circumstances. Never- theless, it is interesting to note that during 1953 there was a substantial decline in the number of cases notified. The tuble below, which sets forth the death rate from tuberculosis per hundred thousand of the population and the percentage of deaths from tuberculosis in relation to deaths from all other causes for the past 6 years, shows a steady rise in both figures until the year 1951 and a continuing fall since then. The meaning of this is not fully understood but it cannot be due to environ- mental factors as these appear to have remained unchanged throughout the whole period.
TABLE G
Year
$% of death from Luberondonia
D/A per 100,000
1948
14.6
108.9
1949
16.0
1950
[7.7
144.0
1951
208.0
1952 1953
1.
16.4
130.6
מווימ
30
140.6
158.4