174 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [I, II
found effective. Unfortunately, the only wash available for these tests failed to give more than 75
per cent. kill under ordinary farm conditions. It was at first thought that the frothy nature of the
wash on application prevented the entrance of the solution; but a second sample was received which
had been prepared on a less frothy base and showed no greater efficiency.
COST OF APPLICATION.
Derris powder, highly toxic to warble fly larvæ, was obtained last season at a retail price of 3s.
per lb. This was sufficient to make 1 gallon of wash. The number of cattle that can be treated
with 1 gallon of wash obviously varies with the degree of infestation with warbles, the care taken in
application, etc. In the general tests (Division 2) above, with a heavy infestation, 1 gallon was
sufficient to dress 50-60 cattle once. This was the initial dressing and naturally less wash would be
required at subsequent dressings.
It is estimated, from the work in the Demonstration Scheme where small herds were involved,
that 1 lb. of derris powder is sufficient to provide wash for four-monthly dressings on a farm with
20-25 infested cattle. On this basis, the cost for four-monthly treatments should not exceed 2 d. per
animal.
DISCUSSION.
From the preceding trials, it is evident that the farmer has at his disposal materials which,
with ordinary care, are highly efficient in the destruction of warble-fly larvæ when applied under
ordinary farm conditions. Derris powder wash is particularly suitable for this purpose, but, where-
as most of the derris available to the farmers is highly toxic, the farmer must beware lest he obtains
derris which is valueless for the destruction of warbles. Although, last season, few firms could give
a guarantee of toxicity it should be possible in future to obtain such guarantee provided the firm can
state that the derris was obtained from the same source or that it has been subsequently tested.
With the existence of an efficient and inexpensive insecticide, the control of the warble-fly now
depends very largely upon the co-operation of farmers in organized anti-warble-fly campaigns. The
advantage of treating cattle over large areas is obvious. During a period of agricultural depression,
however, no additional expenditure upon insecticides will be undertaken unless prospects of a quick
return are forthcoming. The farmer will receive the immediate benefit through the better condition
of his treated cattle and he will also reduce the losses resulting from the " gadding" caused by the
fly. The monetary value of these factors, unfortunately, is difficult to estimate, but several farmers
who dressed their cattle for the first time this season have expressed the opinion that there was a
decided improvement in the condition of the cattle after treatment. Further, there is evidence that
the local butchers and dealers are fully alive to the situation and are prepared to pay 10 s. to 20 s.
more for a non-warbled beast. These factors should encourage farmers to join in an anti-warble-fly
campaign.
Experiments on the Mechanical Transmission of West African Strains of
Trypanosoma Brucei and T. Gambiense by Glossina and other Biting Flies.—A. W.
TAYLOR, B. SC., Entomologist, Tsetse Investigation, Northern Nigeria. (Transactions of
the Royal Society of Tropical Medicine and Hygiene, Vol. XXIV, No. 3, 1930.)
SUMMARY.
1. Four strains of T. brucei have been successfully transmitted by the direct method, using
G. tachinoides as mechanical vector.
2. Direct transmissions of T. brucci by G. tachinoides have only been carried out where the
interval between the break in the infecting feed and the resumption of the flies' meal on a clean
animal does not exceed ten minutes.