The distribution of <i>Nematospiroides dubius</i> within the small intestine of laboratory mice

Analyses of primary infections of Nematospiroides dubius in male and female laboratory mice show that on days 4--6 post-infection worms occupy up to 50% of the small intestine but as the age of the infection increases worm populations are highly aggregated in relation to the anterior sections of the small intestine. Individual worms are also shown to be aggregated with respect to each other. Between days 42 and 60 post-infection, although the pattern of distribution of N. dubius along the small intestine does not significantly change, survival of worms is influenced by both age and sex of ASH/CSI S.P.F. mice, reasons for which are discussed in the light of previous work on primary infections of N. dubius in other strains of laboratory mice.