Effect of Ascaris suum on growth and expulsion of Hymenolepis diminuta in mice

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Abstract
SUMMARY: Mice inoculated with 2000 Ascaris suum eggs 7 days before an infection with 2 cysticercoids of Hymenolepis diminuta harboured significantly fewer and/or smaller tapeworms than control mice by day 7 post-infection. When the interval between the infections was increased, the effect on H. diminuta decreased and no effect was found 21 days after the A. suum infection or if the infections were given simultaneously in ńaive or in mice immune to A. suum. Two possible explanations for the rejection and/or stunting of H. diminuta in mice infected 7 days earlier with A. suum are suggested; either a host reaction in the small intestine stimulated by the returning larvae of A. suum after their hepato–pulmonary migration or an indirect effect of decreased food intake of the host caused by this migration. It is concluded that experiments on possible immunodepressive or immunostimulating effects of parasites ought to include studies on living agents and that they should not rely on measurements of immune responses only.