The prevalence of Trichocephalus dispar / by H.S. French and A.E. Boycott.

  • French, Herbert Stanley, 1875-1951.
Date:
1905
Catalogue details

Licence: In copyright

Credit: The prevalence of Trichocephalus dispar / by H.S. French and A.E. Boycott. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    The results have indeed no pathological interest; they indicate rather the extent to which the general population in London comes into contact with human faeces. The life-history of Tricliocephalus dispar is not elucidated in all detail, but the essential facts seem to be fully established. The eggs measure about 55 by 25 /a, and as they leave the host in the stools contain an undifferentiated ovum; further development is very slow and many months are occupied in the growth of the larva within the egg. This growth is to some extent independent of temperature and will take place at “ room-temperature ” in this country. The thick egg-shell is very resistant; in consequence the embryo can survive great vicissitudes of temperature and moisture, and may remain capable of development for a long time (up to five years— Davaine) after leaving the body. The larva does not escape from the egg outside the body, but only on being taken into the alimentary canal. Eggs which do not contain a developed larva are not infective. As far as is known, infection can only take place per os. The length of life of the adult worm in the human intestine is, we believe, quite unknown; analogy would lead us to suppose that it may extend to several years. Monkeys and lemurs are said to be often infected with T. dispar; in this country, however, this is of no moment in the present connection. Closely allied, but distinct, species are found in several of the domestic animals—notably T. crenatus in the pig and T. affinis in the sheep. The eggs of these other species very closely resemble those of T. dispar, but the specificity of worm infections practically precludes the suggestion that the eggs which we have found in human stools are other than those of T. dispar, and that the infections with this worm had their origin in faeces other than human1. It follows from this that infection arises by the ingestion of material contaminated with stale human faeces. Immediate personal infection or reinfection is excluded by the fact that the eggs must go through a lengthy period of development outside the body before they become infective. Any interest which our result may have lies in the demon- stration—which is we believe unequivocal—that all the precautions which are taken in this country to secure the safe disposal of human excreta have not been adequate to prevent a purely faecal infection being present in at least 8 p.c. of the population2. 1 It is possible, though hardly credible, that the eggs found might have been the eggs of some other species of Tricliocephalus which had been swallowed and passed through the body as such. In any case, the infection must be faecal whether it be human or animal. 2 It follows from the long duration of the infection that this figure is to some extent an accumulated result, and possibly also partly the result of conditions now past.
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