الفهرس 
Schistosoma mansoniOnly 14 pages are availabe for public view
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Abstract
Schistosomiasis is the second most prevalent parasitic disease in the world after malaria, Egypt’s share of the burden is about 7.2 million patients. Although transmission has been greatly reduced in Egypt, evidence indicated that a non-integrated intervention strategy is still used and transmission of infection in high-risk areas in the Nile Delta remains uninterrupted calling for improved, more comprehensive control strategies.
The use of NPs in medical field has been increased due to their properties as ultra-small size, large surface area to mass ratio and being highly reactive. In this aspect, AgNPs were found the most effective against bacteria, viruses and eukaryotic microorganisms, while AuNPs can destroy cancer cells and bacteria like MRSA. They also proved potent effect on selected parasites.
Prevention of schistosomiasis is more important than treatment itself. There is an urge to search for a new drug which can be safer and more effective than previous ones.
The present study aimed to evaluate the potential effect of Ag and Au NPs on B. alexandrina snails and S. mansoni cercariae in vitro and to assess their effect on the infectivity of cercariae in vivo.
For serving the in vitro study, B. alexandrina snails, S. mansoni miracidia and cercariae were obtained from Medical Malacology Laboratory at TBRI.
The in vitro study included, dose-response studies for detection of the mortality for each of B. alexandrina snails and cercariae of S. mansoni and detection of infection rate of the snails.
B. alexandrina snails were subjected to different concentrations of AgNPs (100, 50, 40, 30, 25, 10, 5 and 3 ppm) and AuNPs (200, 180, 160, 140, 120 and 100 ppm). Results were compared to controls. The snails were kept for 3 days and then monitored for detection of mortality rate. After that, the calculated LC50 of each drug was used to detect the infection rate of the snails.
AgNPs at concentrations of 100, 50, 40 and 30 ppm led to death of 100% of snails while at concentrations of 25, 10, 5 and 3 ppm led to 80%, 60%, 40% and 20% snail death respectively. AuNPs at concentrations of 200, 180 and 160 ppm led to death of 100% of snails while at concentrations of 140, 120 and 100 ppm led to 60%, 20% and 0% snail death respectively. Results of the effect of LC50 of Ag and Au NPs on B. alexandrina snails with S. mansoni miracidia revealed absence of cercarial shedding by both drugs in comparison to the control ones.
S. mansoni cercariae were exposed to different concentrations of AgNPs (50, 25, 10, 5 and 3 ppm) and AuNPs (100, 75, 50, 10 and 5 ppm). Results were compared to control. The cercariae were observed under a dissecting microscope at successive intervals of 15, 30, 45 and 60 mins for detection of any behavioral or morphological changes. The mortality rate was determined. A number of the treated cercariae as well as control ones were examined under electron microscope to detect any ultrastructural changes.
AgNPs showed 100% lethality at all time intervals from 30 min up to 60 min with concentrations (50, 25 and 10) ppm. While AuNPs showed 100% lethality, at 60 min with concentrations (100, 75 and 50) ppm and at 45 min with concentrations (100 and 75) ppm.
Both drugs led to ultrastructural thinning of tegument with focal loss of spines, edematous swelling of the muscle layer and deeper parenchyma with external protrusion and focal breach of continuity of the tegument.
For serving the in vivo study, experimentally Swiss Albino mice were infected with S. mansoni cercariae (60 ± 10 cercariae) which were either treated pre-infection with individual NP or were given the NP 1 h PI, by either TI or SC injection. Mice were categorized into 7 groups and sacrified 6 wks PI.
The parameters used to assess the in vivo study included, parasitological parameters with assessing of total worm burden, tissue egg count/gm intestine and liver and oogram pattern and histopathological parameter including detection of egg-induced granulomatous cellular reaction and measurement of hepatic granulomas number and size.
AgNPs prevented the occurrence of infection when cercariae were treated before the infection by either TI or SC routes as shown by the parasitological parameters and also by absence of granuloma formation in hepatic tissue. But, when the treatment was given 1 h PI it led to decrease in egg count/gm intestine and liver in TI infected group unlike SC infected group. As regard oogarm pattern and granuloma formation, approaching results to infection control were shown.
AuNPs led to decrease in TWB in all tested groups. While egg count/gm intestine and liver were decreased in TI infected groups either with pre-treated or post-treated cercariae in contrast to SC infected groups. The oogram pattern and granuloma formation showed approaching results to infection control.
This study highlighted that, Ag and Au NPs proved to have a promising potential as molluscicides and cercaricides in vitro and can prevent or modulate the infectivity of cercariae in vivo.