Immunological and Environmental Studies On Giardia Duodenalis

Giardia duodenalis (synonyms G. lamblia or G. intestinalis), the only species belonging to the genus Giardia found in humans, is a pathogenic protozoan with a worldwide distribution having a more relevant prevalence in warm climate and in children. G. duodinalis is a water-borne flagellated parasite that causes giardiasis in humans. In addition, giardiasis affects domestic and wild mammals “e.g., cats, dogs, cattle, deer, and beavers” (Thompson, 2000). Host-to-host transference of Giardia cysts takes place via the fecal-oral route. This allows the protozoan to infect the next generation of hosts through a diverse range of mechanisms: person to person, animal to human or by contact with contaminated water and food. Outbreaks commonly occur in areas with inadequate water treatment, especially developing countries, where infection rates can be higher than 50% of the total population. It is well documented that in developing countries, infections are associated with poor sanitary conditions, poor water quality and overcrowding. Giardia is one of the leading protozoan causes of gastrointestinal illness worldwide and has joined the ranks of the WHO Neglected Diseases Initiative. Giardiasis constitutes an important public health problem in Egyptian children. Contamination of the Nile River with fecal materials including viruses and pathogenic protozoa still represents an environmental health hazard in Egypt, especially in rural areas. The clinical features of giardiasis range from acute or chronic diarrhea, abdominal pain, nausea, flatulence, vomiting, weight loss, to absence of symptoms and signs.
In the diagnosis of Giardia, stool examination is the traditional, safest and easiest method. Microscopy of Giardia cysts and trophozoites is more straightforward, and there is little risk of confusion with other parasites. Moreover, only “ghost” cysts with an empty appearance are sometimes not recognized as Giardia parasites. However, the sensitivity of microscopy is quite low due to the intermittent excretion of Giardia cysts, the microscopical examination of a single stool specimen has a low sensitivity and may therefore miss up to 50% of Giardia infections. And thus, it is recommended that at least three samples be examined in order to rule out giardiasis which is time consuming and delay the diagnosis.