الفهرس 
Disease and distribution
TrophozoiteOnly 14 pages are availabe for public view
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Abstract
Giardiasis is a global public health problem, with 300 million
people infected each year. Giardia lamblia, a flagellated
protozoan, is among the most common intestinal protozoa and is
the most frequent parasitic agent of gastroenteritis worldwide. It is
considered to be one of the most common nonviral nonbacterial
cause of diarrhea worldwide.
The world health organization (WHO) considers diarrheal
disease the second most common cause of morbidity and mortality
in children in the developing world.
Giardiasis is endemic in all regions of the world with a
prevalence range from 2-7% in developed countries to 20-30% in
most developing countries. It constitutes a significant public health
problem in Egypt especially in rural areas.
Giardia has a simple life cycle that comprises a resistant
infectious cyst stage and a mobile disease-causing trophozoite,
both forms are found in faeces. Giardia cyst can be transmitted
directly, through the faecal-oral route, or indirectly, by ingestion of
contaminated water or food.
The clinical features of giardiasis range from acute or chronic
diarrhea, abdominal pain, vomiting, flatulence, nausea, weight
loss, to absence of symptoms and signs.Because of the increased risk of side effects and the possible
emergence of antibiotic-resistant organisms, the most beneficial
way in treating giardiasis naturally may be through a combination
of both nutritional interventions and phytotherapeutic agents.
Microscopic examination of stool specimens is generally
accepted as the gold standard for the diagnosis of parasitic
diseases, in comparison with new tests, and it has the advantage
of being inexpensive compared to antigen detection tests.
Although microscopy has the advantage of low cost and ability to
simultaneously detect other gastrointestinal parasite, the
disadvantages of this method is that G. lamblia cysts are small and
similar in appearance to many pseudoparasites such as yeast. Also,
the trophozoites break up rapidly in the stool, so cannot be used to
measure the severity of infection and the sensitivity of microscopy
is quite low due to the intermittent excretion of Giardia cysts so
two or three specimens collected on different days should be
analyzed.
Recently, ELISA has been considered as cost effective
diagnostic method that can detect small quantities of coproantigens
of parasite, even in mild infection, and diagnosed even if the live
parasite is absent in the feacal sample. It can also detect soluble
antigens in the faeces and can detect Giardia antigens in the stool
even during periods of absent cysts by direct microscopy.The present study aimed at developing pAb-based antigen
detection assay through paramagnetic nanoparticles conjugation in
order to increase sensitivity of antigen detection assays, hence early
and light Giardia infections could be easily detected. The large
surface area of nano-materials enables attachment of large number
of target-specific molecules of interest for ultra-sensitive detection.
In the current study, stool samples were collected to obtain,
purify and analyze Giardia antigen. It was purified from stool
samples using Parasep (Midi Faecal Parasite Concentrator). It
improves the parasitic yield in faecal specimens.
Then the total protein content of G. lamblia antigens was
estimated, the crude antigen obtained from positive Giardia stool
samples found to be 8 mg/ml as measured by Bio-Rad Protein
assay while it was 4.5 mg/ml after purification by Parasep. By
using 12.5% SDS-PAGE technique under reducing condition, the
purified Giardia antigen showed four major bands at 47.5, 17.0,
14.0 and 12.5 kDa. Then the antigenicity was tested by indirect
ELISA.
Giardia antigen was used for immunization of rabbit for
preparation of rabbit anti-G. lamblia IgG pAb. In the present study,
the purified anti-G. lamblia IgG pAb was labeled with HRP andwas used for the detection of Giardia antigen in stool of infected
patients by sandwich ELISA.
This study was conducted on 25 G. lamblia infected patients in
addition to 30 other parasites infected patients and 20 healthy
controls. Parasitological examinations by both direct smear and
MIFC gave 100% specificity and positive predictive value (PPV).
The MIFC method showed a sensitivity of 84% and NPV was 92.5%,
whereas, direct smear method achieved sensitivity of 72 % and
NPV was 87.7%.
The rabbit IgG pAb raised against purified Giardia antigen and
was successfully detected by sandwich ELISA with sensitivity 88%
and specifity 92%. PPV and NPV were 84.61%, 93.87%
respectively.
The current work has demonstrated that the immune magnetic
beads ELISA with paramagnetic nanoparticles conferred a higher
sensitivity (92%) in detecting G. lamblia in stool samples. Also, it
gave higher specificity, PPV and NPV 94%, 88.64 % and 95.91 %,
respectively
It can be concluded that the sandwich ELISA with
paramagnetic nanoparticles technique appear to be sufficiently
sensitive assays for the detection of human giardiasis than
sandwich ELISA.