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The course of infection in rats given small primary doses of Strongyloides ratti and S. venezuelensis

Published online by Cambridge University Press:  05 June 2009

K. Christine Carter  and
P. A. G. Wilson
K. Christine Carter
Affiliation:
Department of Zoology, Edinburgh University, West Mains Road, Edinburgh EH9 3JT, UK
P. A. G. Wilson*
Affiliation:
Department of Zoology, Edinburgh University, West Mains Road, Edinburgh EH9 3JT, UK
*
*Author for correspondence.
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Abstract

Development of exact doses (<100) of Strongyloides venezuelensis third-stage larvae in adult Wistar rats was insignificant (mean proportion of 0·076 of the dose at day 8, n = 16) compared with a homogonic strain of S. ratti (0·538, n = 6; 0·726, n = 6) and heterogonic S. ratti (0·681, n = 6). Newly-weaned Wistars allowed development of a mean proportion of S. venezuelensis of 0·298 (n = 4) compared with 0·013 (n = 4) of the same sample of larvae in adult hosts. Experiments with 75Se-labelled larvae established that S. venezuelensis effectively failed to migrate from skin to intestine in adult animals, while mean proportions of 0·141 (n = 5) and 0·138 (n = 4) of the label was found in the intestines of newly-weaned rats 72 h after skin application. Labelled larvae of homogonic S. ratti migrated equally well in both age groups of host (0·350 and 0·358 in 12- and 3-week-olds respectively). Adult S. venezuelensis transferred surgically to the intestines of previously uninfected full-grown Wistars survived over a 21-day period to the same extent as either strain of S. ratti. Resistance of Wistar rats to S. venezuelensis therefore appears to affect the migratory stage preferentially. S. venezuelensis developed better in mature PVG inbred rats (mean = 0·301, n = 20). Studies of S. ratti showed that infections of both strains initiated by exact (<100) doses in Wistar rats had decayed to insignificance between days 26 and 32. The rate of loss of adults of the heterogonic strain was significantly greater than that for the homogonic. The egg content of worms declined as infection progressed and rats were idiosyncratic in their influence on parasite reproduction from the earliest time of sampling (8 d). It was established that ‘autoinfection’ was an unlikely feature of the biology of homogonic S. ratti following the surgical transfer of 450 first-stage larvae to the intestines of 8 adult Wistar rats. No evidence of infection appeared in the guts of these animals 8 days post-transfer. The significance of these results in terms of the biology of Strongyloides spp. naturally occurring in the rat is discussed.

Keywords

Strongyloides rattiStrongyloides venezuelensisratsmall doseprimary infectionsurgical transferautoinfectionradioactive labelling
Type
Research Article
Information
Journal of Helminthology , Volume 63 , Issue 2 , June 1989 , pp. 107 - 114
Copyright
Copyright © Cambridge University Press 1989

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