In vitro efficacy of new synthetic benzimidazole-related compounds against Schistosoma mansoni adult worms

Objective: To evaluate the in vitro antischistosomal activity of two new synthetic benzimidazole-related compounds: NBTP-OH and NBTP-F. Methods: Schistosoma adult worms were recovered from mice infected with Schistosoma mansoni cercaria, washed and then incubated in the culture media with different concentrations of compounds NBTP-OH and NBTP-F up to 72 h. Scanning electron microscopy was conducted to report morphological changes. Results: Incubation of adult Schistosoma mansoni with 10 µg/mL of NBTP-OH for 48 h killed 81.25% of worms. The calculated LC50 and LC90 72 h post-incubation were 6.8 µg/mL and 9.8 µg/ mL, respectively. Exposure of worms to 10 µg/mL of NBTP-F killed 89.5% of worms after 48 h, mostly males (83.3%), the LC50 and LC90 after 72 h of incubation were 4.8 µg/mL and 6.9 µg/mL, respectively. Worms incubated for 72 h with these compounds revealed swelling and deformity of oral sucker, disorganization and erosion of the tegument when examined with scanning electron microscopy. Conclusions: NBTP-OH and NBTP-F possess in vitro antischistosomal activities; however, in vivo studies should be conducted to examine their antischistosomal effects.

Experimental evaluation of Candonocypris novaezelandiae (Crustacea: Ostracoda) in the biocontrol of Schistosomiasis mansoni transmission

<p><b>OBJECTIVE</b>To test Candonocypris novaezelandiae (Baird) (C. novaezelandiae), sub-class Ostracoda, obtained from the Nile, Egypt for its predatory activity on snail, Biomphalaria alexandrina (B. alexandrina), intermediate host of Schistosoma mansoni (S. mansoni) and on the free-living larval stages of this parasite (miracidia and cercariae).</p><p><b>METHODS</b>The predatory activity of C. novaezelandiae was determined on B. alexandrina snail (several densities of eggs, newly hatched and juveniles). This activity was also determined on S. mansoni miracidia and cercariae using different volumes of water and different numbers of larvae. C. novaezelandiae was also tested for its effect on infection of snails and on the cercarial production.</p><p><b>RESULTS</b>C. novaezelandiae was found to feed on the eggs, newly hatched and juvenile snails, but with significant reduction in the consumption in the presence of other diet like the blue green algae (Nostoc muscorum). This ostracod also showed considerable predatory activity on the free-living larval stages of S. mansoni which was affected by certain environmental factors such as volume of water, density of C. novaezelandiae and number of larvae of the parasite.</p><p><b>CONCLUSIONS</b>The presence of this ostracod in the aquatic habitat led to significant reduction of snail population, infection rate of snails with schistosme miracidia as well as of cercarial production from the infected snails. This may suggest that introducing C. novaezelandiae into the habitat at schistosome risky sites could suppress the transmission of the disease.</p>