Abstract
The distributions of the nematode parasites Heligmosomoides polygyrus and Syphacia stroma were quantified in three equal-length sections along the intestine of wood mice (Apodemus sylvaticus) trapped in three different locations in the south of England. The distribution of H. polygyrus did not change in the presence of S. stroma, this species being largely confined to the anterior third of the intestine, whether S. stroma was or was not present. However, while in single infections with S. stroma, worms were equally distributed in the anterior and middle sections of the intestine, in the presence of H. polygyrus, a higher percentage of worms was located in the middle section. This was a dose-dependent response by S. stroma to increasing worm burdens with H. polygyrus, and even relatively low intensities of infection with H. polygyrus (e.g. ≤10 worms) were sufficient to cause a posterior redistribution of S. stroma into the middle section. A similar posterior shift in the percentage distribution of S. stroma in the intestine was evident in juvenile and mature mice of both sexes, and in mice from all three study sites. The ecological significance of these results is discussed.
Highlights
The survival of parasites within hosts requires intimate fine-tuning to conditions in the site where they reside
The extent of the redistribution of S. stroma was highly dependent on the intensity of the H. polygyrus infection, with relatively fewer S. stroma persisting in the anterior intestinal section as the intensity of H. polygyrus
1.6 ± 0.73 0 3.3 ± 1.93 increased. This pattern of redistribution of S. stroma into the middle section in concurrent infections with H. polygyrus was evident in both age classes and sexes of mice, and in all three trapping sites
Summary
The survival of parasites within hosts requires intimate fine-tuning to conditions in the site where they reside. In helminths this ranges from morphological structures required to maintain position (e.g. scoleces of cestodes, probosces of acanthocephalans (Smyth, 1976) and the intricate surface ridges of nematodes, called crêtes (Durette-Desset, 1985)), host enzymeblocking factors (Hawley et al, 1994; Zang & Maizels, 2001) to an array of molecules that interfere with host immune effector mechanisms (Hewitson et al, 2011; Whelan et al, 2012). The long coil-like shape of this species (previously known as Nematospiroides dubius; Behnke et al, 1991) enables worms to coil around and between the villi especially those located in the duodenum and the anterior jejunum of the small intestine (Bansemir & Sukhdeo, 1996). The worms feed on enterocytes of the villi (Bansemir & Sukhdeo, 1994)
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