Giardia lamblia ELISA (REF. 610001)
apDia Giardia lamblia ELISA is an In Vitro Diagnostic (IVD) immunoassay for the qualitative determination of Giardia specific antigens in faecal specimens.
Giardiasis is a common cause of gastroenteritis in humans and known to affect at least 200 million people worldwide with 2 % of adults and 6-8 % of children in developing countries getting infected each year. Nearly 33 % of the population in developing countries has contracted the disease at least once in their life. In the USA and other industrialized countries it is also by far the most common intestinal parasitic disease found in humans. Giardiasis is caused by a flagellated protozoan parasite, Giardia lamblia. The life cycle of the parasite begins with ingestion of cysts by the host.
Following excystation, active trophozoites emerge which colonize the lumen of the small intestine to feed. After the feeding stage, the parasites replicate asexually through longitudinal binary fission. During their passage through the digestive system, some parasites are converted to cysts. Both cysts and trophozoites are then excreted with the faeces but only the hardy, resistant cysts can persist for weeks to months outside the host, in soils, on surfaces or in stagnant water systems like ponds, swimming pools, water reservoirs.
Humans usually become infected by the parasite in several ways:
- Transmission by waterborne sources: swallowing of dormant cysts present in contaminated water or food.
- Transmission by faecal-oral route in situations with poor hygienic practice, e.g. in day-care centres.
- Close contact with infected persons.
- Since domestic animals like cats, dogs, cattle, birds but also wild mammals (e.g. deer, beaver) act as reservoir hosts for Giardia, a zoonotic transmission is also a possibility.
Upon infection, trophozoites colonizing the small intestine induce inflammation, apoptosis of intestinal epithelial cells, morphological changes to the microvilli and villar atrophy, causing problems with the small intestine’s absorption system (failure to absorb fat, lactose, vitamin A and B12). Parasites do not enter the bloodstream however and do not spread to other parts of the gastrointestinal tract. Symptoms of acute giardiasis typically set in one to two weeks after exposure to the parasite and may include diarrhea, hematuria, flatulence, nausea, greasy stool, stomach and abdominal cramps, intestinal malabsorption, dehydration and weight loss.
Up to 50-60 % of cases seem to be asymptomatic.
The disease normally resolves by itself after a mere six weeks if left untreated but may persist for longer periods in immunocompromised patients. Severe giardiasis might delay physical and mental growth and cause malnutrition in children. In some people, particularly those with a lack of IgA antibodies, recurring infections can develop into a chronic state of giardiasis.
Diagnosis of giardiasis is not always straightforward due to a lack of symptoms in many cases.
Useful diagnostic methods are:
Invasive techniques:
- Duodenal biopsy to detect presence of trophozoites.
- String test or entero-test: a gelatin capsule with a string attached is swallowed by the patient. When it passes into the small intestine, trophozoites get stuck to the string. The string is then withdrawn from the patient and examined microscopically for parasites.
Non-invasive techniques:
- Stool microscopy: examination of stool samples for presence of trophozoites or cysts. Because parasites are shed intermittently, multiple stool collections are necessary. This method relies on experienced lab technicians for a correct diagnosis because infections are often difficult to demonstrate.
- ELISA to detect Giardia antigens in stool samples. Faecal immunoassays offer comparable or even better sensitivity and specificity to microscopic examination and are fairly simple to perform.
- Molecular testing (PCR).
Of the non-invasive techniques, microscopic examination of stools has been the most common but this method relies on the expertise of the technician. Because of the historically low proficiency of correct microscopic examinations and intermittent excretion of organisms, alternative diagnostic methods have been investigated. It has been shown that by using the ELISA method, a comparable sensitivity can be achieved.
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GIARDIA LAMBLIA KIT 96 TESTS, REF. 610001
The ELISA kits offered by apDia are validated on open ELISA automates such as the Dynex Instruments.
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