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.

Description of two new cercariae [an echinostome cercaria and a xiphidiocercaria] procured from biomphalaria pfeifferi [Krauss] from Nigeria

During parasitological examination of Biomphalaria pfeifferi snails obtained from Niger state [Nigeria], 2 new types of cercariae were found. They are identified to the level of referring to the major group and described here for the first time. They were examined viable and stained with vital stains as well as fixed in 70% alcohol. They were drawn with a camera lucida and photographed. They are identified as an echinostome cercaria and a xiphidiocercaria. The echinostome is characterized by having a ventral sucker almost double in size the oral one. It has a semicircular structure located beyond the oral sucker. Three pairs of penetration glands are found at the anterior portion of the body. The number of collar spines is relatively large [44-46]. The flame cells are 17x2 in number. Two main lateral excretory ducts extend anteriorly, form two typical echinostome loops then pass posteriorly to open together in a diverticulat-ed excretory vesicle. Its tail is relatively long and flattened with 3 fin folds. The tail [640 microm] is longer than the body [475microm].The xiphidiocercaria belongs to the [ornatae] group. It is relatively small [180.5x110microm] with a long stylet [3'0nm]. Its oral sucker is one and half times the size of the ventral sucker. Two excretory ducts extend posteriorly in both sides and become dilated and unite to open in a circular excretory vesicle. Tail is slender shorter than the body and has a dorso-ventral fin fold. Key words: Echinostome cercaria, xixphidiocercaria, Biomphalaria pfeifferi

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>

Experimental studies of effect of chaetogaster limnaei [oligochaeta: annelida] on Schistosoma mansoni transmission in aquatic habitats

This study assessed the effect of association between the oligochaete Chaetogaster limnaei and the snail Biomphalaria alexandrina on schistosomiasis transmission in aquatic habitats. This experimental study included factors affecting the oligochaete / snail association such as water volume and snail species and size. The effect of Chaetogaster on snail survivorship, growth and reproduction, life of the free - living larval stages of Schistosorna mansoni and on infection of the snail with miracidia were also studied. Results show that there was a positive correlation between snail size and infestation intensity of the oligochaete. The infestation of B. alexandrina by Chaetogaster had no effect on the survival and growth of snails, but led to a remarkable reduction in egg production. Chaetogaszer proved to have predatory activity on S. mansoni miracidia and cercariae and the number of predated organisms increased with the increase of prey density. Introducing one Chaetogaster per snail after exposure to S. mansoni miracidia showed no effect on infection rate of snails and length of incubation and shedding periods but reduced significantly the total periodic cercarial production of the parasite. This study gives indication that Chaetogaster may play a significant role in reducing the population of the medically important snail B. alexandrina via suppressing its productivity, as well as reducing schistosome transmission

Differentiation between Biomphalaria alexandrina, B. glabrata and their hybrid existing in freshwater habitats in Egypt

Biomphalaria alexandrina, .B. glabrata and their hybrid were previously found separately or associated with each other in natural habitats in Egypt. This paper reports on distinguishing these snails from each other, which might be of practical help for malacologists and epidemiologists concerned with schistosomiasis transmission and control in Egypt. Differentiation between these snails utilizes certain conchological and anatomical criteri a for some organs of taxonomic importance.Thus, from the present study, the shell diameter for B. alexandrina, B. glabrata and the hybrid is maximally13 mm, 28 mm and 19 mm respectively. In case of B. glabrata, the headfoot appears faint greenish yellow in colour, while it is dark grey in both of B. alexandrina and the hybrid snails. Both of the latter snails show dense black pigmentation on the mantle surface, while B. glabrata has a patchy pigmentation especially close to the mantle edge. In median sized snails [12 mm in shell diameter], the radular pattern in B. alexandrina has the teeth numbers [133-151x49] for transverse and longitudinal raws, while i n both B. glabrata and the hybrid snails it has [133-146x43]. The mesocone of the lateral tooth is simply triangular in B. alexandrina while it is arrowhead-shaped in B. glabrata and the hybrid snail. The renal ridge seems to be the main anatomical criterion distinguishing the present snails. In case of B. alexandrina, it is totally missing, while in B. glabrata it is thin, projecting with pointed edge and in the hybrid snail, it appears thick and lower, with a blunt edge. In case of both B. alexandrina and the hybrid snails, the vergic sheath length is equal to the preputium, while in B. glabrata, it is 20% longer than the preputium