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Giardiasis is one of the most frequent entero-parasites worldwide; its prevalence is more common in developing countries. Giardia lamblia is considered one of the opportunistic parasites and aits clinical manifestations represent the expression of host resistance and parasite viri lence. As of chronic giardiasis cases were expected to worsen in immunosuppressed patients with development of various complications. This work assessed the histolopathological and the possible immunological effects of infection with G. lamblia in an immunosuppressed experimental animal model in comparison to immunocompetent one. Mice were divided into 4 groups;. group I: simmunocompetent (IC) mice infected with G. lamblia cysts, group II: immunosup pressed (S) mice infected with cysts, group III: uninfected immunocompetent mice and group. IV: uninfected immunosuppressed mice. From each group, small intestine was. removed for histopathological and molecular studies. Also, cyst counting in the stool of infected mice was estimated. We found that the number of G. lamblia cysts in the stool of IS mice was significantly higher than that from IC ones. Shortening of the villi was more pronounced in the IS than in IC group. Furthermore, intraepithelial lymphocytic count, goblet cell count and mast cell count were significantly decreased in the IS infected group as compared to IC ones. Expression of interleukin.6 mRNA showed high expression in IC infected mice while it was weak in IS mice. In conclusicn, the present study revealed the importance of the innate immunity presented by goblet cells, mast cells and other adaptive immunity responses; in the clearance of Giardia.

This work studied the effect of sub-chronic DDT exposure on the course of experimental giardiasis and efficacy of its treatment. A total of 160 mice were divided into six groups: G1: 30 mice received DDT and infected with Giardia lamblia. G2: 30 mice received DDT, infected and treated with tinidazole (TNZ). G3: 30 mice infected with Giardia. G4: 30 mice infected and treated with TNZ. G5: 30 mice received DDT only. G6: 10 mice served as normal control. Mice were sacrificed at 7, 14, 21 & 28 days P.I. All groups were subjected to cyst count/2 hours collected stool, trophozoite count in intestine, histopathological examination of small intestinal section and avidin biotin peroxidase technique for local IgA staining. Also, IFN-gamma was measured in sera. DDT caused early shedding of many cysts and increase in trophozoite counts for a long time, decreased intra epithelial lymphocytes, low levels of IgA & IFN-gamma and severe histopathological changes in intestinal sections in G1 as compared to G3. Also, DDT reduced the efficacy of TNZ treatment in G2 as compared to G4. The results strongly support the immunomodulating effect of DDT on experimental giardiasis that might be responsible for persistence of infection, resistance to treatment and re-infection in DDT exposed persons.

Propolis, a honey bee product, gained popularity in alternative medicine. Its prophylactic and therapeutic effects were experimentally evaluated. One hundred and fifty immunocompetent mice were orally infected by 5 x 10(5) axenically cultivated Giardia lamblia trophozoites. The trophozoite count in intestine, interferon-gamma serum level, histopathological examination of duodenal and jejunal sections were assessed for evaluation of propolis and metronidazole (MTZ) effect after 6 & 12 days post infection (p.i). Also, T-lymphocyte profile in blood was investigated 12 days p.i using flow cytometry (FCM). Propolis as prophylaxis showed a significant decrease in intensity of infection, together with a significant increase in IF-gamma serum level and increase in CD4+: CD8+T-cell ratio. In treatment it gave a highly significant decrease in trophozoite count than that obtained by MTZ 6 days after infection but the efficacy was almost equal after 12 days. The mice treated with propolis alone showed a reversed CD4+: CD8+ T-lymphocyte ratio, such strong immune enhancing effect resulted in an undesirable increase in inflammatory response at intestinal level. The combined therapy showed a stronger efficacy in reducing the parasite count than that gained by each drug alone. Their combined use caused an immunological balance as shown by the T-lymphocyte profile that saved the intestinal homeostasis and histological architecture.

The role of adhesion molecules; the intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) as mediators in development of skin allergy caused by giardiasis and the controlling role of the cytokine interleukin (IL)-6 over these adhesion molecules were studied. The work included 25 symptomatic giardiasis patients with skin allergy manifested by diffuse urticaria, pruritus, wheal and erythema, and had positive serum anti-Giardia immunoglobulin (Ig) E measured as mean optical density (OD) value by enzyme linked immunosorbent assay (ELISA), employed as an evidence of allergic sensitization (G.I). They were compared with 30 symptomatic giardiasis patients (G.II) and 20 apparently healthy control subjects (G.III), both latter groups had negative serum anti-Giardia IgE. The mean OD value of anti-Giardia IgE was significantly increased in G.I (P < 0.01) & insignificantly different in GIII (P > 0.05) compared with G.III. Serum levels of soluble forms of adhesion molecules; sICAM-1 & sVCAM-1, and IL-6 were determined by ELISA. sICAM-1 & sVCAM-1 serum levels were significantly increased (P < 0.001) in G.I compared with G.III and showed insignificant difference (P > 0.05) between Gs. II & III. Serum IL-6 significantly increased in G.I (P < 0.001) & G.II (P < 0.05) compared with G.III, and was significantly higher (P < 0.001) in G.I than G.II. Serum IL-6 correlated positively with serum sICAM-1 (P < 0.01) and sVCAM-1 (P < 0.001) in G.I. The results are discussed.

Comparative study between the prevalence of pathological grading and Giardia genotypes revealed that, in patients infected with Giardia group I and II, out of patients having Giardia genotype I the prevalence of grade 0 was 13.16%, grade I was 21.05%, grade II was 47.37%, grade III was 13.16% and grade IV was 2.26% in comparison to 0%, 30.77%, 46.15%, 7.69% and 15.38% in genotype II (13 patients) and 10%, 40%, 20%, 20% and 10% in group III (10 patients) also in relation to 25%, 43.75%, 18.75%, 6.25% and 6.25% in mixed genotype infections group (16 patients) and 25%, 25%, 35.71%, 10.71% and 3.57% in undetermined infection group (28 patients) for grade 0, I, II, III & IV pathology respectively. There was no statistically significant difference regarding the prevalence of pathological grading in different Giardia genotypes in Gs I & II (P > 0.05). The mean OD of anti-Giardia secretory IgA in relation to Giardia genotypes in patients infected with Giardia Gs I & II was significantly different in the mean OD values of anti-Giardia secretory IgA in patients with different Giardia genotypes which were 1.091 +/- 0.377, 1.079 +/- 0.474, 1.524 +/- 0.503, 1.292 +/- 0.472 & 1.004 +/- 0.31 groups of genotype I, II, III, mixed genotypes infection and undetermined infection group respecttively (P > 0.05), being more increased in patients infected with Giardia genotype III and in mixed genotype infection.

There was statistically significant difference between all groups of giardiasis patients regarding the grade of CD4 lymphocyte infiltration (P<0.001), being more marked in symptomatic group. The prevalence of flatulence, anorexia and vomiting were more frequent in patients with heavy CD4 lymphocyte infiltration in duodenum. A high statistical significant increase was in the mean OD values of anti-Giardia duodenal secretory IgA in patients with marked CD4 infiltration in duodenum. But, a statistical insignificant difference in mean OD values of anti-Giardia total serum Ig in patients with different grades of CD4 infiltration in symptomatic group. There was statistically significant increased in the mean OD values of anti-Giardia total serum Ig in patients with marked intraepithelial CD8 lymphocyte Infiltration in the duodenum In the asymptomatic group, there was statistically insignificant difference in the mean OD values of anti-Giardia total serum Ig in patients with different grade of intra-epithelial CD8 infiltration in symptomatic group. There is statistically significant increased in the mean OD values of anti-Giardia total serum Ig in patients with marked intra-epithelial CD8 lymphocyte infiltration in the duodenum regarding immunohistochemical staining of Giardia antigen in duodenal biopsies. All the 61 symptomatic giardiasis patients revealed Giardia antigen stains in their duodenal biopsies with a sensitivity of 100% while asymptomatic group a sensitivity of 93.181%. None in the controls showed positive Giardia antigen in the duodenal biopsies with 100% specificity.

Hundred immunosuppressed patients and 50 apparently healthy individuals as control were subjected to stool examination for parasitic infections by the direct smear method and the merthiolate iodine formal-dehyde (MIF) concentration technique. The modified Ziehl-Neelson stain and the aniline carbol methyl violet stain were used to detect Cryptosporidium oocysts. 27 Patients were found positive using the MIF technique while only 13 of them were positive by the direct smear method. Cryptosporidium oocysts were detected in 7 cases using the aniline carbol methl violet stain while only 5 of them were positive by the modified Ziehl-Neelson stain.

This study was carried out on sixty mice which were allocated in two group. Group I: included thirty mice which were splenectomized and orally inoculated with Giardia lamblia cysts. Group II: thirty intact infected mice which served as a control group. The mice in group I captured G. lamblia infection and demonstrated trophozoites in their intestinal sections when PAS (periodic acid Schiff) and IIF (indirect immunofluorescence) stains. On the other hand, intestinal sections stained with hematoxyline and eosin showed a spectrum of pathological changes with shortened fused villi, heavy lymphocytic infiltration in the lamina propria and atrophy in musculosa and ganglion cells which showed decrease in number per base of villus. The levels of antibody response measured with IIF-test showed significant decrease in group I compared with the control group. This study demonstrated the role of humoral immunity in infection with G. lamblia.

Chronic diarrhoea accompanied by weight loss is a common and often debilitating problem in immunocompromized patients, receiving chemotherapeutic agents. In these patients, the intestinal opportunistic parasites probably played a major role in causing this clinical manifestation. The present work, aims to search for these parasites. Special stains for each parasite were used to differentiate it easily from the fecal elements, obviating the need for diagnostic invasive techniques especially used in microsporidial infection. The detected parasites were, Giardia lamblia (17.7%) best seen by iron haematoxylin stain. Coccidian oocysts (Cryptosporidia; 13.3% Isospora belli; 2.2%) were clearly seen by using Ziehl-Neelsen and Chromotrope-based stains. The Gram positive spores of Enterocytozoon bieneusi were (4.4%) and best seen by using chromotrope-based stain, where as Giemsa failed in their diagnosis.

The present study was designed to find out the prevalence of different intestinal opportunistic parasites in different groups of immunocompromised hosts; patients suffering from malignancy with or without immuno-suppressive drugs, or with chronic renal failure, or diabetes mellitus, or subjects under cortisone therapy. Examination of stool samples collected from 427 immunocompromised hosts revealed the detection of intestinal opportunistic parasites in 98 samples, with a prevalence of 23%. Infection with opportunistic parasites was higher in males than in females (32.6% versus 12.9%). There was statistically significant association of infection with G. lamblia and Cryptosoporidium in the mixed infection detected. The highest group affected with the opportunistic parasites was the group of patients under corticosteroid therapy (31.7%), followed by patients suffering from renal failure (28.8%) and malignancy (25.7%), while the least group affected were the diabetic patients (8%). The highest prevalence rate was 10.3% for G. lamblia, being followed by E. histolytica (7%), C. parvum (6.3%), Microsporidia (2.3%) and the least one was for Strongyloides (0.7%). No cases of Isospora belli infection was detected. Relation between presence of opportunistic parasites and risk factors was discussed and evaluated.

A total of 455 children were chosen randomly and surveyed for giardiasis by stool examination using several techniques. A case control study design was adopted where 91 cases of giardiasis (symptomatic and asymptomatic) and 101 children giardiasis free were examined. ABO blood groups and HLA typing were investigated. It was concluded that blood group A was more susceptible to giardiasis especially asymptomatic form, while blood group B was less susceptible to giardiasis. On the other hand, there was no association between AB or O and giardiasis. But, there was a strong association between HLA A10, A11, B5, B7 and B17 phenotypes and symptomatic giardiasis and an association as well between HLA B7, B17, Bw14 and Bw40 and asymptomatic giardiasis.

This study was done to evaluate the pathological effects of Giardia lamblia cysts obtained from immunosuppressed host on the small intestine and liver of immunocompetent hosts. Thirty mice, subdivided into two groups, were infected with G. lamblia cysts in a dose of 5000 cysts/mouse. The first group (10 mice) was inoculated with Giardia cysts obtained from immunocompetent patients and the second group (20 mice) was inoculated with Giardia cysts obtained from already immunosuppressed mice (injected with cyclophosphamide). Stool examination revealed that mice in both groups passed cysts on day 6 +/- 1 after infection. The pathological changes of small intestine in both groups were more or less similar. The changes were in the form of shortening and widening of the villi with cellular inflammatory infiltrate in the lamina propria. The liver of both groups showed no pathological changes. It can be concluded that, although immunosuppression affects the immune system and the defensive mechanism of the host, yet it has no effects on the virulence of the excreted Giardia lamblia cysts.

No significant sex-related difference was observed in immunocompetent mice. Sexually mature mice of both sexes excreted large numbers of Giardia cysts over a longer period than did immature ones. Cyclosporin A has compromised the immunological response of the primary Giardia infection. However, it does not affect the ability of the immune host to resist challenge infection. The use of this drug may cause fulmination of giardiasis.

Giardia-spontaneously cured mice were rendered resistant to challenge infection. This was documented by the decreased cyst excretion rate comparable to the control ones. Endoxan and irradiation treatment caused a breakdown in both humoral and cellular immunity. Immune-depressed mice were more susceptible to Giardia infection, thus proving the active role of antibodies and cell-mediated immune response in giardiasis.

The ultrastructure of penetrating Giardia lamblia trophozoites in immunosuppressed albino rats is described for the first time. Recorded changes in the general contour of the parasite; loss of flagellae, and suction disc, disappearance of the endoplasmic reticulum, appearance of abundant electron dense coarse granules as well as large sized vacuoles opening to outside, are probably modifications associated with penetration and accommodation to the new environment. Penetration appears to be due to activity of the trophozoite rather than passive transfer by tissue macrophages.