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The places where the children resided are indicated by fractions with arrows leading from them. The denominator of the fraction indicates the number of children examined at the place, the numerator the number with enlarged spleens. If a line be drawn on the map from Sandy Bay to R.B.L. 2380, it will divide the circle into a small and a large sector, in the small sector 26 children were examined, 19 had enlarged spleens or 73.08%. In the large section 124 children were examined 3 of which had enlarged spleens or 2.43%. In 1932 a complete survey of the area was done during the period April 25th- May 20th: partial surveys were done in June, and in September, and a complete survey during December. 3878 A. maculatus larvae. 33 A. hyrcanus, 1 A. minimus, were found in the April and May survey; 245 A. maculatus in the June; 869 A. maculatus, 2 A. minimus in the September one, but at the end of the year 1615 A. maculatus larvae, 274 A. minimus. Practically all the larvae of A. minimus were found within the smaller sector of the circle (where the children with enlarged spleens were) one adjacent to it, elsewhere they occurred in small numbers. From this it would appear that A. maculatus is of no great importance as a carrier of malaria in comparision with A. minimus.
There does not appear to be any very obvious reason as to why A. minimus larvae should be found in one sector in comparative abundance and not in the other. From their origin as far as Pokfulam Road, the streams are of the usual type, boulder strewn, with rocky beds, flowing between the spurs of the ridge in their courses towards the sea, with bushes. shrubs and trees growing on the banks but as is usually in this Colony, in only a few places, providing sufficient shade to inhibit A. maculatus or A. minimus laying their eggs in the water. Between Pokfulam Road and the sea other factors come into play, as regards B and the tributaries on its left bank an distreans C, D, E. In the lower part of B next to Sandy Bay the stream is used by laundry men for the daily washing of clothes, no larvae were found there, no doubt owing to the action of the soap on the water. Just above Victoria Road the branches on the left bank contain washing places, with the same results. From hence onward as far as stream E most of the land is cultivated by the Dairy Farm. On the slopes are several cattle byres and pig yards the drainage from these usually finds its way into a sump and is delivered daily into a system of irrigation ditches for the purposes of enriching the soil and only occasionally finds its way directly into the hill streams. The manure is stored in shelters with cement floors and is used for fertilizing purposes. Guinea grass (Panicum maximum) is grown for the use of the cattle. Very few A. minimus were found in these portions of the streams within the cultivated areas, but neither were they found in abundance above the Pokfulam Road except in a branch on the right bank of stream A. Below this road they were found in a branch
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on the left bank of A, and in most abundance in B. It is possible that A. maculatus can tolerate a higher degree of pollution than A. minimus and can flourish in pools and streams with a swifter current than A minimus can exist in.
Repetition of Repulse Bay area Survey.
A survey was made in a ravine at Repulse Bay during April, there had been a previous spell of dry weather and in this instance as many larvae of A. minimus were collected as of A. maculatus. Similar results were obtained in a previous survey done in 1930 after the rains,
(e) MOSQUITO NUISANCES.
Complaints as to above were investigated at Lai Chi Kok Gaol (female), the Peak District, Stubb's Road, Shek O, St. John's Cathedral. Aedes albopictus was the culprit at the Cathedral, C. fatigans in the other localities. At the Peak the larvae of C. fatigans were found in abundance in the water in gully traps. There had previously been a prolonged spell of dry weather and consequently no flushing out of the gully traps by showers, At Shek O the larvae were found in the aerobic compartment of a septic tank, other septic tanks examined in the locality were found to have both compartments covered with a thick scum and no larvae were found.
Mosquitoes captured and sent in by residents of Pokfulam were identified as C. fatigans although numerous breeding places of A. maculatus were in the vicinity, none of these figured in the catch. In this connection a complaint regarding biting insects was made by the Principal of Victoria Home, Kowloon. These were considered to belong to the Gamasidae and to be derived from birds nesting in the roof. Recommendations for dealing with the nuisance were made accordingly in all instances.
(f) INSTRUCTION OF PROBATIONERS AND TEACHING OF MOSQUITOLOGY.
The instruction of the probationers was continued during the year.
As no local infections were forthcoming from the dissections made in the early months, material was obtained from Dr. Walch. Java, and Dr. Manalang of the Philippines for the purposes of demonstration. The probationers have now had considerable practice in the diagnosis of infected midguts and salivary glands. They can make permanent mounts and stained preparations of such. They can recognize microfilaria and malarial parasites in thick blood films. They can under- take permanent preparations of the hypopygia. They have had considerable experience in obtaining Anophelines for dissecting and in keeping them alive in the Laboratory until required. in the rearing of mosquitoes from larvae and in association of any particular larva and with the corresponding mosquito.
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