Abstract
The present study was done using two concentrations of the photosensitizer Hematoporphyrin coated Gold Nanoparticles (HpdGNP3) (5x10–6 , 5x10–5 mole/dicemeter–3), to evaluate their efficacy on survival rate, egg-laying capacity of Biomphalaria alexandrina snails and on histological deteriorations in their hermaphrodite gland. B. alexandrina snails were incubated for 12 hours at each tested concentration in the dark, thereafter they were exposed to direct sunlight (336.2 W/m2) for either 2 or 4 hours followed by 24 hours of recovery. Control snails were treated with these concentrations without exposure to light irradiance. Another experiment was carried out simultaneously and the snails were left for 4 weeks of recovery to evaluate their egg-laying capacity (Mx). The results indicate that 5x10–5 Mdm–3 (HpdGNPs) with 4 hours of exposure sunlight suppressed the survival rate of B. alexandrina snails by 50%. Meanwhile, control snails incubated with 5x10–5 Mdm–3 HpdGNPs were not affected and still alive (100%). For snail’s fecundity (Mx), treated snails laid low number of eggs throughout the recov-ery period (4 weeks), in comparison with that of control ones. The highest value of Mx for snails treated with 5x10–5 Mdm–3 Hpd coated GNPs was recorded at the 3rd week of recovery period, being 6.7 eggs/snail, compared to 37.6 eggs/control snail. This has a negative reflect on the reproductive rate (Ro) of treated snails as it was reduced under these conditions by 76.6% and 86.1%, respectively.Histological tests re-vealed injuries in spermatocytes, oocytes, several degenerations of B.alexandrina hermaphrodite gland then evacuations in many gonad’s cells which severely suppressed their capacity for egg-laying. It is concluded from the present work that exposing B. alexandrina snails to sublethal concentrations of the photosensiter Hpd coated GNPs (12 hours incubation, 4 hours exposure to 336.2 W/m2) significantly reduced their reproductive capacity that may have a negative reflect on schistosomiasis transmis-sion.
Highlights
Schistosomiasis is an important public health prblem in Egypt and several developing countries (Pasvol and Hoffman, 2001)
Biomphalaria alexandrina snails (6 - 9 mm) were laboratory produced in Medical Malacology Department at Theodor Bilharz Research Institute (TBRI), Giza, Egypt
Control snails incubated with 5 × 10–5 Mdm–3 HpdGNPs were not affected and still alive (100%)
Summary
Schistosomiasis is an important public health prblem in Egypt and several developing countries (Pasvol and Hoffman, 2001). Control of this parasitic disease could be through treatment of infected persons, health education, sanitation and snail control. Snail control strategies are considered a priority for preventing or minimizing schistosomiasis transmission (Lardans and Dissous, 1998). These strategies have been based upon elimination of the snail intermediate hosts chemically, biologically or environmentaly. Phtosensitizing compounds could be evaluating for controlling noxious water parasites, since sunlight activated dyes characterized by a high efficiency, lack of mutagenic activity and negligible toxicological risk to humans and other mammalian species (Ben Amor et al, 1998)
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