Some Bearings of Zoology on Human Welfare

Abstract

THE bearings of zoology on human welfare-as illustrated by the relation of insects, protozoa, and helminthes to the spread or causation of disease in man-have become increasingly evident in these later years, and are familiar to every student of zoology or of medicine. At the time of the last meeting of the British Association in Liverpool (1896), insects were suspected of acting as transmitters of certain pathogenic organisms to man, but these cases were few, and in no single instance had the life-cycle of the organism been worked out and the mode of its transmission from insect to man ascertained. The late Sir Patrick Manson, working in Amoy, had shown (1878) that the larvae of Filaria bancrofti undergo growth and metamorphosis in mosquitoes, but the mode of transference of the metamorphosed larvae was not determined until 1900. Nearly two years after the last meeting in Liverpool the part played by the mosquito as host and transmitter of the parasite of malaria was made known by Ross. In addition to these two cases, at least eight important examples can now be cited of arthropods proved to act as carriers of pathogenic organisms to man e.g. Stegomyia-yellow fever; Phlebotomus- sandfly fever; tsetse-flies-sleeping sickness; Cono-rhinus-South American trypanosomiasis (Chagas' disease); Chrysops-Filaria (Loo) loa; the flea Xeno-psylla cheopis-plague; the body-louse-trench fever, relapsing fever, and typhus; and the tick Ornithodorus -African relapsing fever.