Efficacy of artemisinin-naphthoquine phosphate against Schistosoma haematobium adult flukes: dose-effect relationship and tegumental alterations.

Schistosoma haematobium and Schistosoma mansoni infections have broadly overlapping geographical distributions. Praziquantel is the only treatment for human schistosomiasis, so drug tolerance and/or resistance are major concerns. Artemisinin-naphthoquine phosphate (CO-ArNp), an artemisinin-based combination therapy endorsed by the World Health Organization as a gold standard therapy for malaria, has also been identified as a promising treatment for S. mansoni. In this in vitro study, we tested the effect of 1-40 µg/ml CO-ArNp on S. haematobium worms, and inspected tegumental changes by using scanning electron microscopy (SEM), aiming to determine if this combination therapy has a broad-spectrum antischistosomal activity. Incubation of S. haematobium adults with 20 or 30 µg/ml CO-ArNp caused 100% mortality of worms within 72 or 48 h, respectively. SEM examination showed extensive tegumental alterations such as oedema, constriction, shortening and loss of spines, fissuring, sloughing and perforation, resulting in exposure of the underlying basal lamina, mainly in treated male schistosomes. Besides the well-established potent efficacy, bioavailability, tolerability and safety of the antimalarial artemisinin-naphthoquine phosphate combined therapy, these results may also suggest its possible utilization as a new broad-spectrum antischistosomal agent.

The first record of Centrocestus formosanus (Nishigori, 1924) (Digenea: Heterophyidae) in Egypt.

The life cycle of Centrocestus formosanus (Digenea: Heterophyidae) was to be successfully completed in the laboratory in the present study. Hundreds of the thiarid snail, Melanoides tuberculata, were collected from the main water course Mansouriya Canal, Giza Governorate, Egypt. The snails were individually exposed to artificial light to determine possible infection with trematode larvae. Fifteen snails were found infected with opthalmopleurolophocercous cercariae (infection index of 1.97). These opthalmopleurolophocercous cercariae shedded from snails were collected and placed in an aquarium with fish intermediate host, Gambusia affinis, to obtain metacercariae encysted in the gills. The gills with metacercariae were fed to albino rats, Rattus norvegicus, to obtain the adult worms. Adult worms were recovered in the small intestine of rats at 7 days after infection and they were identified as Centrocestus formosanus based on the morphological characteristics and the comparison with the previous descriptions in the literature. They were small, 518 × 324 µm in average size and had characteristic 32 circumoral spines around the oral sucker. The morphological characteristics of the developmental stages, from cercariae to adults, of this heterophyid fluke were given here. Therefore, the presence of this fluke is to be confirmed for the first time in Egypt by the present study.

On the pathogenicity of attenuated Schistosoma mansoni cercariae released from metabolically disturbed Biomphalaria alexandrina.

Biomphalaria alexandrina were treated with sublethal concentrations (LC10) of dry powdered leaves Solanum nigrum or whole dry Ambrosia maritima. The two plants affected the development of schistosome parasite within snails by disturbing the glycolytic flux, the most important metabolic pathway for schistosome-infected snails. Attenuated cercariae released from treated snails were used to infect male albino mice to evaluate their pathogenicity compared to control cercariae shed from untreated snails. The mean number of worms established declined from about 70 +/- 17.6 worms/mouse infected with control cercariae to 23.4 +/- 20.33 and 14.18 +/- 10.06 worms/mouse infected with S. nigrum and A. maritima-attenuated cercariae respectively. Most males and females detected in these animals measured 0.4-0.6 and 0.6-1.2 mm respectively compared to 1.2-1.4 and 1.4-1.7 mm in males and females released from mice infected with normal cercariae. Egg count in the liver and intestine of mice infected with attenuated cercariae was remarkably lower showing reduced fecundity of worms developed from attenuated cercariae. Number and size of granulomatous reactions showed remarkable reduction in attenuated cercariae-infected mice. Biochemical analyses for pathogenicity achieved with attenuated cercariae showed that while serum aspartate and alanine aminotransferases (AST &ALT) were more or less similar, depleted glycogen and elevated lipid peroxides were normalized when compared to those infected with normal cercariae.

Sublethal concentration of Ambrosia maritima(Damsissa) affecting compatibility of Biomphalaria alexandrina snails to infection with Schistosoma mansoni through disturbing the glycolytic pathway.

High glycolytic flux as an emergency pathway for generating ATP was recorded as the most important metabolic pathway required for the success of Biomphalaria-Schistosome sporocyst interaction. Effect of LC25 of dry powdered Ambrosia maritima (Damsissa) as plant molluscicide on hexokinase (HK), pyruvate kinase(PK), glucose phosphate isomerase(GPI) was tested. It resulted in a significant inhibition of the three investigated enzymes. Treatment of snails with LC10 concentrations of A. maritima reduced considerably the infection rate of Biomphalaria alexandrina with Schistosoma mansoni to be 34% compared to an infection rate of 80% in control non-treated snails. Longer prepatent period and remarkable decrease in cercarial production was also recorded in snails treated with the sublethal concentrations of this molluscicide.

Invasion of the Nile Valley in Egypt by a hybrid of Biomphalaria glabrata and Biomphalaria alexandrina, snail vectors of Schistosoma mansoni.

Two years (1996-1997) of systematic survey showed that a hybrid of Biomphalaria glabrata and Biomphalaria alexandrina has invaded the irrigation and drainage systems in the Nile Delta and the Valley nor the of El-Menya. However, the infestation of water courses by and the population density of this snail were variable in various localities. The infestation rate ranged between 7.1% in El-Fayoum Governorate and 52.6% in El-Dakahliya Governorate and the snail density from 2 snails/site to 69.7 snails/site in the same governorates, respectively. Comparing the survey results of the two study years in the sampling sites indicated that the hybrid snail has relatively increased in population density than B. alexandrina. The hybrid snail of B. glabrata and B. alexandrina was found alone in some sites, but was mostly associated with B. alexandrina. The results showed also that both Biomphalaria have almost the same major physicochemical requirements. However, the hybrid snails and B. alexandrina were found differently associated with aquatic snails and plants. The hybrid snail was found naturally infected with S. mansoni thus giving indication that it is presently participating in schistosomiasis mansoni transmission in Egypt.

Compatibility of Biomphalaria alexandrina, Biomphalaria glabrata and a hybrid of both to seven strains of Schistosoma mansoni from Egypt.

The susceptibility of Biomphalaria alexandrina, Biomphalaria glabrata and a hybrid snail of both, all obtained from natural habitats in Egypt, to infection with six human local strains of Schistosoma mansoni and a laboratory strain of human origin was determined. The infection rate, prepatent period, periodic cercarial production and duration of cercarial shedding were compared in all cases. The results showed that each of the three studied Biomphalaria snails had different rates of infection and different values of total periodic cercarial production with various strains of S. mansoni. However, the mean infection rate of all local S. mansoni strains was significantly much higher in B. alexandrina than each of B. glabrata and the hybrid snail, being 66%, 7.2% and 8.5%, respectively. Considering the mean of results of all local S. mansoni strains used, the longevity of cercariae-shedding B. glabrata and the hybrid snails was much longer than that of B. alexandrina, with high significant difference between them (P < 0.01), being 94.5, 103.3 & 69.1 days, respectively. The mean prepatent period of various S. mansoni strains showed no significant difference in the three Biomphalaria snails studied. The hybrid snail produced periodically (1 h stimulant twice weekly) more schistosome cercariae/snail (4,784.2) than B. glabrata (2,913.4 cercariae/snail) and the least production was in the case of B. alexandrina (1,397.2 cercariae/snail) (P < 0.05). The diurnal pattern of S. mansoni cercarial shedding was found to be similar for B. glabrata, B. alexandrina and the hybrid snail showing a peak of cercariae at the same time (9-10 a.m.).

Biomphalaria glabrata: a new threat for schistosomiasis transmission in Egypt.

This is the first report on the infestation of irrigation and drainage systems at Giza, Qalyoubiya and Kafr El Shiekh Governorates, with Biomphalaria glabrata (the snail host of Schistosoma mansoni in the new world). Identification of this snail species was based on morphometry of the shell, shape of the radular lateral teeth and presence of the characteristic renal ridge. B. glabrata snails collected from natural water courses in Egypt proved to be susceptible to a local strain of S. mansoni. These snails were infected by 52% versus 75% for Biomphalaria alexandrina (the only local host) under the same laboratory conditions. Meanwhile the periodic total cercarial production was higher in B. glabrata than in B. alexandrina (252 +/- 110 cercariae/snail versus 203 +/- 86 cercariae/snail, respectively). Differences in infection rate, length of schistosome incubation period, duration of cercarial shedding and cercarial production in various sizes of the two snail species are reported and discussed.