الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Cyptosporidium is a protozoan parasite that causes diarrhc£al disease in both animals and humans. Infection may be present in both immunocompetent and immunodeficient hosts with differences in the outcome of the disease in these two groups. In healthy individuals, cryptosporidial infection is self limited, whereas immunocompromized patients may recover from the infection only after restoration of their immune functions. These observations are highly suggestive that active immunity is necessary for resistance to the parasite. In the past, it was difficult to identify Cyptosporidium parvum in routine stool preparations. No,,’, the use of modified parasitological techniques for the detection of this parasite in stool specimens, revealed that it is both widespread and common in humans. In. the present study, Cyptosporidium oocysts were isolated fronl the stools of infected children having diarrhc£a. The oocysts were counted and orally inoculated in neonatal suckling mice (to study primary infection), and in weaned mice (to study reinfection). Mice used in the present work were di\’ided into the following groups: Group-I: Neonatal mice used to study pattern of oocyst shedding, histopathological and serological changes after primary infection. Group-II: Uninfected mice (control of Group-I). Group-Ill: ~!Iice were used for a skin test after two and three months of primary infection. Group-N: Control mice of Group-Ill. Group-V: Mice that were infected as neonates were reinfected after weaning to study the pattern of oocyst shedding, histopathological and serological changes and skin test after reinfection. Group-VI: Control mice of Group-V, they were infected for the first time at the same age of reinfection. For the study of primary cryptosporidial infection, 3-4 mice from Group-I were sacrificed daily to obtain stools, and tissue samples from the stomach, duodenum, jejunum, ileum and c(£cum. A drop of blood was also taken on Whatma:n no.3 filter paper for the serological study. Sacrifaction was daily done till maximum shedding, then mice were followed up by stool examination. Smears of stool samples were stained via modified Z-N technique and oocysts were counted. Tissue samples were stained with H&E and examined for any changes. Antigen was prepared from Cyptosporidium oocysts for: a- IFAT which was used to detect IgG antibody in the serum of examined mice. b-Skin test which was used to detect the presence of specific T-lymphocytes responsible for cell mediated immunity. For the study of cryptosporidial reinfection, group-V was reinfected with the same oocyst inoculum dose, as that used in the primary infection, two weeks after the stop of oocyst shedding in stools (following primary infection). tI Stool pellets were obtained daily and were examined with the modified Z-N technique. Random sacrifaction of mice was done on the second and ninth days post reinfection to obtain tissue samples and blood drops for histopathological and serological studies respectively. The skin test was also performed on the same two days. Samples .. were studied with the same methods used for primary infection. Results of the present work revealed that when primary infection was initiated in neonatal suckling mice, shedding of oocysts began on the first day post infection in small numbers. Then, it increased gradually to a peak on the eighth day post infection. It then decreased on the following days and stopped nineteen days post infection. No histopathological changes could be observed on the first day post infection. Sloughing of epithelial cells, blunting of villi and inflammatory cellular infiltration of the lamina I propria were apparent from the second day to the tenth i. 1 day post infection in the ileum. 1 ! On the thirtieth day post infection, and after the shedding of oocysts had stopped, the ilea of the examined mice appeared within normal configuration, with a small number of scattered organisms in the mucosa.