X1000307-1950-51_Part02 — Page 28

ANNEXURE N.

ANNUAL REPORT OF MALARIA BUREAU,

APPENDIX A. (FLY CONTROL).

1. Field Trial of Gammexane Dispersible Powder P320 as a Fly Larvicide in Control of Sumps.

The efficacy of "Gammexane" Dispersible P520 was further tested for a period of about three months in large scale field trials for the eradication of fly larvæ bred in manure sumps. The tests were carried out in a half mile area of which Fanling Military Camp and Police Training School were the centre in the months of October, November and December, 1950. The incidence of fly breeding is the heaviest of the year during these months.

About 150 fly-larvæ infected sumps were chosen for the tests. The sumps were of varying size. The largest was 9 ft. by 10 ft. The smallest was 5 ft. by 4 ft. The manure in the selected sumps was of different consistency. The nature of the manure varied from sump to sump.

The size of the sumps selected for this experiment was observed, to determine the quantity of "Gammexane" Powder required for the treat- ment of each (2 oz. per 10 sq. ft.).

ment.

The same spraying technique was used throughout the experi-

All the selected sumps were treated with "Gammexate" suspen- sion on the 10th October, and again on the 17th October, 1950, at a dosage of 2 oz. per 10 sq. ft. As the sumps had never been treated previously with insecticide or larvicide of any kind, fly breeding recommenced on the 4th or 5th day after treatment. It appeared that these sumps had not received an adequate dose, and a twice-weekly spraying was therefore adopted on the 24th October, 1950. After the introduction of this method of treatment, the fly breeding of the sumps was brought under complete control.

As the results of the dosage of P520 used in these twice-weekly treatment was so successful, trials were carried out using a comparatively lower rate. On the 7th November, 1960 a lower dosage (1 oz. per 10 sq. ft.) was used. The same good results were achieved in these tests as in the first tests in which a higher dosage was used.

Weekly observation of the fly population was made in three places, the Police Headquarters, the Military Camps and the bazaar at

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the Fanling cross roads, prior to the beginning of, and throughout the trial. Literally thousands of Musca vicina were to be found in the kitchens, and on the food in these three centres. This high level was maintained in these three places for two weeks after the first treatment. but was then progressively reduced, and after the first month remained at a level of 5 to 18 flies per centre per inspection up to the end of December, 1950.

1.

2.

The results of the tests indicated.

that treatment carried out twice a week achieves an adequate control.

that the quantity of P620 can be reduced in subsequent treatments when control has been attained.

3.

that a small dosage (1 oz. per 10 sq. ft.) proves to be effective as a continuous treatment.

4.

that it requires a big labour force to carry out a mass control.

In conclusion no cases of dysentery during the control period were reported either from the Military Camp or Police Training School, although there were a number from the neighbouring Camps.

The cost of the Gammexane (350 lbs.) used for the three months period was $550.- on the basis of 160 sumps, this works out at $1.10 per sump per month. The treatment of these 150 sumps was a day's work for 4 coolies. Thus the cost of labour is approximate $4.- per month per sump-making a total cost (unless Army personnel are used) of $5.- per sump per month.

2. Experiments in the Prevention of Fly Breeding in Raw Nightsoil by Gammexane Dispersible Powder P 520.

Two sites were chosen for the experiment, one at the com- positing station at Taun Wan where there is heavy Musca vicina breeding, and one at the San Hui maturing plant where the species Chrysomyia and Lucilia predominate.

Six concrete cells holding approximately 40 catties of nightsoil each were constructed. One was used as a control, and to the nightsoil in each of the others was admixed Gammexane in the following pro- portions: 1/800, 1/400, 1/200, 1/100 and 1/50. As no previous work had been done on this subject, the dilutions of necessity had to be on the high side.

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