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A Consideration of the Relation of Host-specificity of Helminths and other Metazoan Parasites to the Phenomena of Age Resistance and Acquired Immunity
Published online by Cambridge University Press: 06 April 2009
Extract
1. The relation of host-parasite specificity to age resistance.
Conclusive demonstration of a substantial resistance developing concomitantly with the ageing of the host has been made with reference to four helminths, namely: Ancylostoma duodenale and A. caninum in the dog and Ascaridia lineata and Syngamus trachea in the chicken. A. duodenale in the dog and S. trachea in the chicken are manifestly in abnormal hosts. In contrast with this, it is to be noted that the normal hosts of these parasites, respectively man and the turkey, exhibit no appreciable age resistance. With regard to the remaining two cases, those of Ancylostoma caninum and Ascaridia lineata, the association of age resistance and a specific host-parasite mal-adjustment is not nearly so clear. In nature, both parasites enjoy a polyxenous distribution, neither having acquired the need for strictly specific host conditions for development. As a result of recent researches with A. caninum it has been brought out that the species is comprised of strains better adapted to one species of host than to another, and it has been demonstrated that a higher degree of age resistance is exhibited in the host parasitised with a foreign strain. Although no information on the matter is available, it is quite possible that age resistance will be found to be less markedly expressed in other species or races of suitable hosts, when the bionomics of both Ancylostoma caninum and Ascaridia lineata are further investigated.
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- Copyright © Cambridge University Press 1929
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