T
147
134
the Anophelines. The question of Anopheline infection by monkeys does not arise as there are no monkeys at large on the Island and no captive monkeys in this locality. This point has been raised by Dr. R, Green in the Transactions of the Royal Society of Hygiene and Tropical Medicine Vol. XXV, No. 6. The question also arises as to the mosquito infection being derived from birds (Mayne, Indian Journal Medical Research, 1928). None of the oocysts seen had the appearance described as the result of bird infection. The experiments of Russell in the Philippines do not lend support to this view as regards the local A. minimus (American Journal of Tropical Medicine, Vol. XI, No. 2, 1931).
The catching of such Anophelines as were obtained in this neighbourhood required a considerable expenditure of time and energy.
(2) Hong Kong Volunteer Defence Corps Camp.
Members of the staff who were under canvas during six week ends in November and December obtained 43 Anophelines from tents between dusk and 10 p.m., 28 were A. hyrcanus, 7 A. jeyporiensis, 6 A. minimus, 1 A. maculatus, 1 A. tesselatus. None of these were found infected on dissection.
There was swampy land adjacent likely to harbour A. hyrcanus.
(3) Woo Li Hop l'illage, and the adjacent matshed for road-making coolies.
The coolies were engaged in making a road to the Shing Mun Dam site, and were housed in a building composed of bamboo poles and palm leaf thatch known as a matshed. There has been a good deal of malaria amongst them and amongst the villagers. Searches were made at various times in the matshed, houses, cowhouses, and pigsties of the village, and the results are indicated in Table IX. The cowhouses are substantially built and dimly lighted, a torch light being required for the search. One investigator complained of having been bitten on three occasions in one morning. In some instances the cowhouses form part of the owners' dwelling, in others they are separate. The pigsties have walls reaching to the roof and are dark within. This has been the first opportunity of search- ing such buildings, and future results are likely to be interesting owing to the conditions of shelter different from the Wong Chuk Hang area. Infected mosquitoes were found in cowhouses but none so far in pigsties. The results of the dissections are found in Table XI.
(4) Kowloon Tong, Shaukiwan, Pokfulam, Ngau Tau Kok and Shek 0.
During visits to above places झ few Anophelines were obtained in brief searches, but none were found infected.
135
(d) INVESTIGATIONS AS TO PREVALENCE OF MALARIA IN
CERTAIN AREAS.
These were continued at Kowloon Tong, others were com- menced at Shek 0, Lai Chi Kok Gaol, and Shing Mun Dam. Areas previously dealt with were again investigated with the object of obtaining certain information, namely the Ravine above Pokfulam Reservoir, Wong Chuk Hang locality between Aberdeen and Shouson Hill, the surroundings of the site for the new Government Civil Hospital, and a Ravine at Repulse Bay. Minor investigations were inade at Barker Road where breeding places of A. maculatus were found; at Ngau Tau Kok where spleen rates were taken and a larval survey done; at Deep Water Bay where the blood of eleven servants at the Golf Club was examined and no malaria parasites were found, although hill streams are close by, however mosquito nets were in use and quinine was being issued.
Kowloon Tong.
The area investigated at Kowloon Tong extended half a mile outwards from the periphery of this Garden City and required as much time as would be needed for several ordinary surveys, owing to its extent. Kowloon Tong is approximately rectangular in shape, its long border being perpendicular to a range of hills which is parallel to and adjacent to a short border. Several streams flow down from these hills, and the majority soon finds their way into trained channels. Numerous larvae of A. maculatus and A. minimus have been found in these streams. Whilst little evidence of the prevalence of malaria was forthcoming from the portion remote from the hills, this was not the case in the neighbourhood of the hills. A spleen rate of 3.45% was obtained amongst the children of the cultivators in the neighbourhood, these, as a rule, resided at some distance from the hills as the narrow heads of the valleys do not afford much scope for growing crops. For blood examinations servants were considered to be the best material owing to their being less careful, as a rule, as to the use of mosquito nets and attention to adequate treatment of malaria when contracted. Thick blood films were taken from 187 servants living within quarter mile from the hill foot, 14 of these contained malarial parasites or 7.49%. Out of 160 films taken from those living half mile and more from the hill foot, only 1 was found positive or 0.63%. In the blood films of 103 servants living between quarter mile and half mile from the hill foot, 5 infections were found or 4.85%.
Shek O.
Owing to complaints of malaria received, visits were paid to Shek O towards the end of the year and arrangements made for the making of a map of the area concerned. Larval surveys have been done and spleen rates taken of the village children
148
*