The course of infection and egg production ofPolymorphus minutus(Acanthocephala) in domestic ducks

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Abstract
Laboratory infections ofPolymorphus minutusin domestic ducks have been studied, and the parasites have been found to move posteriorly for a distance of about 4% of the host's intestinal length during the course of the infection.No evidence has been found for male and female worms having different attachment zones.Worms which had become attached anterior to a position 60% along the intestinal length were considered to be more likely to move or be expelled from the host before other worms in the population.Growth of male and female worms was studied by weight measurements. The growth rates of worms of both sexes are similar during the first week of the infection, but by the third week the weight of female worms is more than twice that of male worms.Mature eggs were first found in the host's faeces from 22 to 25 days after the beginning of the infection. Egg release continued for a variable period depending on the number of female worms present in the host.The average peak rates of egg production were 1700, 2000 and 700 eggs/day/ worm for the three cases studied.Eggs were estimated to remain for 50–100 min in the duck's intestine after being released by the worms but before being passed out of the host.The introduction of a Perspex cannula into the small intestine of a domestic duck does not disturb the environment ofP. minutus.We are most grateful to Dr R. C. Campbell, School of Agriculture, University of Cambridge, for all his help and advice about the statistical analysis employed in this work, to Mr J. A. F. Fozzard, Department of Anatomy, for taking the radiograph, to Dr P. Tate for helpful discussions, and to the S.R.C. for a grant for P.J.W.