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Predisposition to ascariasis: patterns, mechanisms and implications

Published online by Cambridge University Press:  19 May 2009

C. V. HOLLAND
C. V. HOLLAND*
Affiliation:
Department of Zoology, School of Natural Sciences, Trinity College Dublin, Dublin 2, Ireland
*
*Corresponding author. Tel: +353 1-8961096. E-mail: cholland@tcd.ie
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Summary

Ascaris lumbricoides, the human roundworm, is a remarkably infectious and persistent parasite. It is a member of the soil-transmitted helminths or geohelminths and infects in the order of 1472 million people worldwide. Despite, its high prevalence and wide distribution it remains along with its geohelminth counterparts, a neglected disease. Ascariasis is associated with both chronic and acute morbidity, particularly in growing children, and the level of morbidity assessed as disability-adjusted life years is about 10·5 million. Like other macroparasite infections, the frequency distribution of A. lumbricoides is aggregated or overdispersed with most hosts harbouring few or no worms and a small proportion harbouring very heavy infections. Furthermore, after chemotherapeutic treatment, individuals demonstrate consistency in the pattern of re-infection with ascariasis, described as predisposition. These epidemiological phenomena have been identified, in a consistent manner, from a range of geographical locations in both children and adults. However, what has proved to be much more refractory to investigation has been the mechanisms that contribute to the observed epidemiological patterns. Parallel observations utilizing human subjects and appropriate animal model systems are essential to our understanding of the mechanisms underlying susceptibility/resistance to ascariasis. Furthermore, these patterns of Ascaris intensity and re-infection have broader implications with respect to helminth control and interactions with other important bystander infections.

Keywords

Ascaris lumbricoidesepidemiologyaggregationpredispositionsusceptibilityresistancemechanismcontrol
Type
Research Article
Information
Parasitology , Volume 136 , Special Issue 12: Special Centenary Issue – Parasitology 1908–2008 , October 2009 , pp. 1537 - 1547
Copyright
Copyright © Cambridge University Press 2009

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