Histopathological study of mice infected with <i>Trypanosoma vivax</i>.

<p>8-week-old Outbred mice were injected i.p. with 10² bloodstream forms of <i>T. vivax</i> and different lymphoid and non lymphoid organs were harvested for histopathological examination 20 days post-infection. Spleen (A–D): (A) Diffuse lesions characterized by large necrotic foci in the red pulp (black star), associated with lymphoid tissue disorganization in the white pulp (white star). (B) Infiltration of a necrotic focus by activated macrophages (top of the Fig., arrows) and trypanosomes (arrowhead shows very small basophilic points in the inset depicting a higher magnification). (C) Presence of lower density hematopoiesis compared to non-infected mice. (D) Infiltration of the white pulp by activated macrophages and presence of a Mott cell (arrow). Liver (E–G): (E) Multifocal inflammatory lesions centered on portal tracts/centrilobular veins (arrows), and focal necrotic focus (star). (F) Peri-venous inflammatory infiltrate composed of plasma cells (mostly), but also lymphocytes and macrophages. In the inset depicting a higher magnification, arrowhead points to trypanosomes in the vascular spaces. (G) Foci of extramedullary hematopoiesis. Kidney (H–J): (H) Interstitial inflammatory infiltrates (I) mostly composed of plasma cells. (J) Trypanosomes in an arcuate artery (star); in the inset depicting a higher magnification, arrowhead points to trypanosomes in the vascular spaces. Cerebellum (K–M): (K) Multifocal lesions centered on blood vessels (arrows). (L) Blood vessel lumen filled by trypanosomes, proteins and erythrocytes (star), with perivascular edema (arrow) and ischemic neurons (arrowheads). (M) Trypanosomes in a meningeal blood vessel. Hematoxylin-eosin staining, scale bars are indicated at the bottom of each photograph. In the inset depicting a higher magnification, the arrowhead points to trypanosomes.