Abstract
IN an interesting report on pébrine in silkworms in A India (Memoirs Dept. Agric. in India, Bacteriological Series, vol. 1, No. 8, November, 1920, pp. 75, 26 plates), Mr. C. M. Hutchinson gives an account of experimental work on methods of infection. He found infected ova in the pupal ovary, and the infection is traced in the egg, larva, and pupa—and recounts the life-history of the causal organism, Nosetna bombycis. The Pasteur method of searching for the organism, devised more than fifty years ago, consists in crushing the body of the moth in a mortar, and examining, under a magnification of about 600, a small fraction of the resulting powder in a drop of water, to ascertain if the characteristic spores of Nosema are present. This method, according to the author, has not been attended in India with any approach to the measure of success which has been attained in Europe. The chances of non-detection of infected moths, and the risk of spreading the spores (due to careless application of the method) in the rooms used for examining the moths, are considerable—the author states that he has seldom failed to find Nosema spores in the floor dust from these rooms, even in cases where the floors were of concrete. In Europe a period of several months elapses between oviposition by the moth and hatching of the eggs, so that the examination of the moths can be undertaken when they have undergone natural desiccation, and the Nosema, if present, is likely to be in the form of the readily recognisable spores. In India the eggs hatch out within eight days after they are laid, and during this period all the moths must be examined, Rapid desiccation prevents the Nosema forming spores, and the number of spores present in a rapidly dried moth may be so small as to escape detection by the Pasteur method. The author's revised method, depending on the fact that infection is chiefly in the chyle stomach, is to remove with needles a portion of this organ to a slide, rub it up in water, and examine it microscopically. Incidentally he remarks on the inefficiency of the copper sulphate solutions usually employed for sterilising rearing houses and appliances in Bengal, but he found that formaldehyde, employed as vapour or in i per cent, solution, completely destroyed the infective power of Nosema spores. A hopeful line of inquiry seems to be opened up by experiments which indicate that resistance to infection Is increased by hill rearing.
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Pébrine in Silkworms. Nature 109, 253–254 (1922). https://doi.org/10.1038/109253b0
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DOI: https://doi.org/10.1038/109253b0