Flow cytometric DNA analysis of the haematopoietic tissue of carp Cyprinus carpio during experimental infection with the haemoflagellate Trypanoplasma borreli

Common carp Cyprinus carpio L. were experimentally infected with the haemoflagellate Trypanoplasma borreli Laveran & Mesnil, 1901. During parasitemia, proliferation rates of anterior and trunk kidney, spleen and thymus were investigated by flow cytometry using 4,6-diamidino-2-phenylindole (DAPI) as DNA dye. It was demonstrated that flow cytometric DNA analysis is a helpful tool for investigating the proliferation behaviour of haematopoietic tissue from infected carp. At the maximum and during the chronic phase of the parasitemia, infected carp showed an increased percentage of S-phase cells in anterior kidney, trunk kidney and thymus compared to non-infected fish. The results indicate that T. borreli stimulates poiesis of haematological/immunological tissues in vivo.