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Abstract Mice were immunosuppressed by oral administration of synthetic corticosteroid (Dexazone tablets 0.5 mg, Al Kahira Pharmaceutical and Chemical Industries Company, Egypt ) at a dose of 25μg/ gm body weight /day for 14 successive days before oral inoculation with Cryptosporidium oocysts. Treatment with NTZ, AZB or both were given to prophylactic and theraputic groups. Fresh faecal pellets were collected from each mouse separately and examined by MZN staining method to calculate Cryptosporidium oocyst shedding on the last day of the experiment (30th dpi). Mice were sacrificed at 30th dpi. The peripheral blood was aseptically collected and the serum was separated after centrifugation and stored at -20 ºC for immunological analysis. The terminal one cm of the ileum and the whole lung tissues were taken from each mouse, then fixed in 10% neutral formalin for histopathological examination and immunohistochemical staining of CD3 and iNOS. Parasitological results The lowest mean number of oocyst shedding in mice stool (310± 7.45) was observed in the prophylactic subgroup GIIc (received AZB+NTZ) in comparison with control positive subgroup GIb (8008.571± 7.48) (P>0.001). In the therapeutic subgroup GIIIc (received AZB+NTZ), reduction was recorded with a mean of 1508±7.15, then therapeutic subgroup GIIIb (NTZ treated) with a mean of 2007.78±5.65. In the therapeutic GIIIa (AZB treated) mean number of oocyst shedding (4508.13± 5.94) was not as low as in the other groups. In desending order, the reduction percent of oocyst was 96.13%, 89.89%, 81.17%, 74.93, 62.45% in GIIc, GIIb, GIIIc, GIIIb and GIIa, respectively. while the lowest reduction percent of oocyst was 43.71% in the therapeutic subgroup GIIIa (AZB treated). Histopathological results: Intestine Histopathological examination of ileal sections from mice of GIa (control - ve) showed normal structure with average length and width of villi without any pathological changes in the mucosa or the lamina propria, while GI b (control + ve) showed loss of villous architecture, shortening, broadening of the villi and even villous atrophy. Additionally, there were mucosal ulceration, edema, low-grade dysplasia, and goblet cells depletion in the covering epithelium and inflammatory cellular infiltrate observed mainly in the core of the villi and extending into the submucosa. Cryptosporidum oocysts appeared along the brush border of the villi and in the intestinal lumen as rounded to oval bodies and purple-stained. Improvement of ileal tissue samples appeared in groups GIIc and GIIIc (receive combined treatment with AZB and NTZ either prophylactic or therapeutic), in the form of mild inflammation with intact mucosa, intestinal villi, and crypts. In addition, Cryptosporidium endogenous developmental stages have hardly been seen and the epithelium of these groups showed preserved polarity and were devoid of any cytological atypia. While GIIa, GIIb, and GIIIb showed partial improvement in the histopathological changes with mild to moderate inflammatory infiltrate in the core of villi with intact mucosa and mild blunting, shortening and ulceration of villi. Summary |