الفهرس 
acknowledgementOnly 14 pages are availabe for public view
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Abstract
Giardia Lamblia has been recognized as a human pathogen once outbreaks of giardiasis were first described in 1960s and 1970s. Factors that influence susceptibility, pathogenicity and development of symptoms have not been clearly identified. Giardiasis presents with variable clinical manifestations mging from asymptomatic or transient intestinal complaints that ~solve spontaneously to severe long standing disease with 1I1alabsorption and debilitation. In Egypt, it is considered to be one of te common causes of acute or persistent diarrhoea in children. The present work was designed to study some of the factors related to the development of symptoms in children infected with iardia Lamblia. Biological and biochemical differences among ’ifferent isolates have been noted. The biological differences include: the infective dose, drug ponse, viral infection of the pa-rasite and endosymbionts. iochemical differences include: differences in DNA and antigenic nation. These differences among the isolates could alter the basic lost-parasite relation and might result in varying immune responses or lstance of the host. . Out of 500 examined children, 45 were found to excrete Giardia lamblia cysts in their stools. Those children were examined dinically, and data regarding age, sex, socio-economic level, weight _aId height were taken. As regards age, the development of symptoms was found to ~ higher in lower age groups, while asymptomatic children were in t older age groups. Yet, this relation was not statistically significant. When sex was considered, male were found to have a higher intensity of infection which was not statistically significant, while females had a m~nificant higher percentage in development of symptoms. Socio~onomic level of the cyst excreting children was insignificant ~garding intensity of infection. In the present work, neither the development of sYmptoms .tJr the intensity of infection affected the general nutritional status of :tte children infected with Giardia Lamblia. Also no significant ’fferences in stunting or wasting occurred between sYmptomatic and iymptomatic children. Biological differences between the isolated strains of Giardia mblia were noted in the present study. Cysts were isolated from ols of the children and then inoculated into mice that were oratory bread and were free from infection. After 11 days of ulation, mice stools were examined for Giardia Lamblia cysts and men mice were sacrificed and their intestines were examined for IfOphozoites. Cysts in stools and trophozoites in intestines of mice were counted to study the effect of various Giardia Lamblia isolates and the virulence of the organism. Giardia isolates were divided into 2 groups according to the ~resence or absence of symptoms in the examined children. ~ymptomatic isolates were further subdivided into symptomatic non diarrhoeic and symptomatic diarrhoeic isolates. It was found that the mean cyst count obtained from mice inoculated with symptomatic ~olates with diarrhoea was significantly higher than that obtained from asymptomatic isolates. Trophozoite counts obtained from symptomatic isolates were lrigher than those obtained from asymptomatic isolates. This indicates iliat there is a difference in virulence of various isolates with more virulence of symptomatic isolates. Giardia Lamblia elicits both humoral and cellular antibody responses. Circulating antibodies against Giardia lam~lia were demonstrated in cases of giardiasis associated with malabsorption. However, low levels of immunoglobulin A has been noticed in patients with persistent giardiasis.