115
was dispelled in 1937 when they cut the aqueduct which carried water into
Razmak and even more rudely shattered when in 1938 they poisoned the water
in Asad Khel reservoir with picric acid.
Once again in 1939 they interfered with our water supplies by unsuccess
-fully attempting to poison with picric acid the drinking water reservoir at
Dizh Narai.
All water since May 1938 has been tested daily for poisons at Razani,
Damdil and Thal, and occasionally at Mir Ali, a special attention being paid
to tests for arsenic. By means of surprise tests it is ensured that all medical
officers, assistant surgeons and sub-assistant surgeons in Waziristan are tho
-roughly familiar with the use of the "Case, water testing, poisons".
K. Sandfly fever enquiry.
The field and part of the laboratory work of this enquiry was carried
out by an officer of the R. A. M. C. with a small staff at Peshawar under the
direction and pay of the Director, King Institute, Guindy, Madras.
Field Work.
Systematic trapping of sandflies showed that P. minutus and P. papatassi
were not present either at the beginning of the season or in the autumn below
maximum temperatures of about 75—80° F. and minimum of 45° F. with a
relative humidity of 40—45 per cent.
It was noted that as temperatures rise or fall so the period required for
complete metamorphosis shortens or lengthens; this is in July—August egg
4—6 days, larva 14—17 days, pupa 5—10 days, and average total 26—30
days: in September—October egg 6 days, larva 17 days, pupa 19 days;
average total 42 days; the variation being chiefly in the pupal stage.
The application of coal-tar to the footings of all buildings for a distance
of 2 feet upwards and outward from the junction of walls with ground was
tried out. Surveys over a period of 10 weeks showed no appreciable reduc
-tion in sandfly population of the buildings until the coal-tar applications were
extended to the interior wall-floor junctions when a reduction of 25 per cent
to 50 per cent in sandflies was produced.
Investigations of insecticidal spray solutions an sandflies was carried out.
Of the "kerosine base" solutions "Lethane" and three pyrethrum extracts,
viz., "Stafford Allen's Liquid Extract (Pyefly)", "Pyrocide 20" and "Pyra
-cetone" were successful. "Lethane" appeared to be the most economical
and the dosage required appeared to be constant, thus: in a closed room
sprayed either with an atomiser or hand spray an atmospheric concentration
equivalent to 7.0 cc. of pure solution per 1,000 c.ft. of air will kill all sand-
flies present, and concentrations as low as 0.8 or 1.0 cc. per 1,000 c.ft. will
reduce sandflies present by 50—60 per cent. Pyrethrum extracts are costly,
the dosage appears to vary at different dilutions and there is little residuary
repellant effect so that evening spraying gives the most satisfactory results.
All these solutions can be used with success in much weaker strengths
than the official dilutions. For example "Lethane" effective at 1 in 66
instead of 1 in 33 and Pyefly at 1 in 100 instead of 1 in 64.
NOTE.—Since these trials were carried out we have completed arrangements for the
manufacture of pyrethrum extract sprays at the Medical Store Depots of Madras and
Bombay. This spray solution is now in use and is most effective at a much less cost than
proprietary solutions.