Table 1. Experimental cryptosporidiosis in SCID mice: influence of inoculum size on infectivity and histopathological findings.
| Group of mice | Intended infective oocyst dose | Mean of infective oocysts after verification of prepared doses (SD) | Number of infected mice/total mice per groupe (%) | Histopathological findings: score of severitya | |
| Stomach | Ileo-caecal area | ||||
| 1 | 1 | 3.6+1.8 | 2/7 (28.5)d | 2 to 5 | 2 to 3 |
| 2 | 10 | 11.6+3.6 | 6/8 (75) | 2 to 4 | 2 to 3 |
| 3 | 100 | 47.2+25 | 7/7 (100)e | 3 to 5 | 3 |
| 4 | 100,000 | ND | 4/4 (100) | 3to 5 | 3 to 4 |
| 5b | 0 | ND | 0/3 (0)f | 0 | 0 |
| 6c | 0 | ND | 0/3 (0)f | 0 | 0 |
Euthanasia was done 45 to 100 days P.I.
a
0, no lesion; 1, inflammation and/or regenerative changes; 2, low grade intraepithelial neoplasia (LGIEN); 3, high grade intraepithelial neoplasia (HGIEN), carcinoma in situ (limited to the epithelium) or intramucosal adenocarcinoma (invasion into the lamina propria through the basement membrane of glands). 4, submucosal adenocarcinoma when glands penetrate through the muscularis mucosa; 5, invasive adenocarcinoma with the invasion through the muscularis into the subserosa.
b
Inoculation with PBS.
c
Inoculation with 105 heat-inactivated oocysts.
d
One mouse found dead on day 2 P.I.
e
One mouse found dead on day 5 P.I.
f
One mouse found dead on day 1 P.I.
ND: Note done.