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ABSTRACTS
quality was found to be good even under adverse conditions of storage. For pro
duction of this new vaccine, seeded Roux flasks of bovine meat extract broth at
pH 7.6 containing 0.1 per cent haemolysed bovine blood were incubated at 37.5°C
for a period of 7 days. Further particulars of its method of preparation and biolo
gical standards prescribed for its use in the field were described. Earlier investiga
tions by the author on other methods of prophylaxis showed chick embryo vaccine
and aggressin to be of limited value, while immune serum and saponin vaccine
were of 'doubtful efficacy '. (P.)
Spraying to control warble fly. D. STEWART MACLAGAN. (1957). Agriculture (Lond.)
LXIII (12), 564-67
T HE author reviews briefly the present methods adopted for the control and
eradication of warble fly and gives the results of some of the experiments
carried out on this problem in different parts of the world in recent years. He states
that, though the practice of dressing warble fly affected cattle with derris wash has
proved to be of considerable success in Great Britain, on the continent of Europe
and in America the progress in reducing the infestation is still disappointingly slow.
The latest approach to the problem is by way of internal medication using the
organo-phosphate insecticides such as Diazinon, Chlorthion and ET-57, with the
object of killing the migrating larvae before or as soon as they arrive in the subdermal
tissues on the back of the affected animal. Some good results have been obtained
in America by this method as regards the killing of the larvae inside the cattle is
concerned, but a systemic insecticide of sufficiently low mammalian toxicity to
allow an adequate margin of safety in general use by farmers has not yet been found
and until such a chemical is found a supplementary method of hastening the eradica
tion of Hypoderma would be by preventive spraying.
The author thinks that the diversity of opinion concerning the effectiveness of
the sprays arises from differences in formulation, concentration and toxic ingredients
of the various preparations used, and in a few instances from injudicious timing of
the application. In a number of trials, good results have been achieved by spraying
with DDT and BHC. The protective action of DDT is found to be superior to
that of BHC. In a pilot trial with an emulsion of 3 per cent DDT the author got
66 per cent reduction in the number of animals infested with more than two warbles
and a 70 per cent reduction in the average number of warbles per animal. Each
treated animal received ⅔ pint of fluid in the form of a mist-like spray on its flank,
belly, legs and escutcheon. Application was made only once but the results show
that two applications at half the concentration would do better. Modern sprays
based on micro-crystalline ingredients and cationic wetters ensuring a heavy deposit
of the toxicant on hair and the advent of highly persistent insecticides such as
Dieldrin and Ciazinon, are heralding a new era in preventive spraying, and the
possibility of other methods, particularly the preventive spraying supplementing
or even replacing the existing method of treating cattle with rotenone-containing
washes, has increased. (R.P.C.)