Figure 1

C. parvum oocyst excretion, lesions and lymphocyte infiltration during infection. (A) C. parvum oocyst excretion: mean/gram of faeces ± standard error (10 to 15 animals). (B) C. parvum parasitic stages immunolabelled in brown in a 3 dpi ileal Peyer’s patch (IPP): on the brush border of absorptive epithelium (AE) (arrow) and follicle-associated epithelium (fae/FAE) (arrowhead) covering the lamina propria (lp/LP) and dome (d). Lymphoid follicle (f). (C) Trophozoites and meronts at 6 dpi, in the JPP AE (arrowhead) observed by transmission EM (C1, C2) and scanning EM of meronts in infected FAE (C3; arrowhead) and merozoite leaving a meront (C4; arrowhead). (D-G) PPs representative changes during infection (HE staining). JPPs of control (D) and 6 dpi inoculated lambs (E) with villous atrophy and fusion (*) and lymphocyte infiltration in lp. (F-G) Attenuation, lymphocyte infiltration, detachment of fae (arrowhead) and absorptive epithelium (AE) (arrow) in an infected IPP. (H) Semi quantitative scoring of histopathological changes in IPP during infection. Sections from control lambs were used as a baseline and each change was rated according to severity on a 0 to 100 visual analogue scale (VAS). Values represent mean with 95% confidence intervals for 4 to 8 animals. (I-K) Cells extracted of spleen (Sp), mesenteric lymph nodes (MLN), JPPs and jejunum from matched pairs of lambs were purified on density gradients and mononuclear cell (MNC) and lymphocyte percentages were determined by flow cytometry on morphology parameters. (I) Plots show the gating of lymphocytes (black gate) and MNC (white gate) in the jejunum. In this example, lymphocytes represented 11 and 38% of MNC (88 and 84% of the cells analyzed) in control versus matched inoculated lamb, respectively. (J) The MNC absolute number ratio and (K) the lymphocyte percentage ratio were determined for each pair of lambs at 3 or 6 dpi. The red bars indicate the median values. Mann–Whitney statistic test: significance * p < 0.05, ** for p < 0.01.