Historical record of heavy metals in the mollusk shells of the Nile Delta

Identifying the baseline status and the timing of ecosystem disturbances are essential for restoration programs. The historical bioaccumulation of heavy metals was assessed from an 80-cm-long core from the Manzala Lagoon (Nile Delta). The heavy metal concentrations increased slightly upward and peaked around 1964, after the completion of Aswan High Dam. The metal concentrations of shells are 2-3 times less than those of bulk sediment. The topmost sediments are enriched in Cd, Cu, and Pb above USEPA. Sediment type and sediment grain size have a minor effect on the heavy metal concentration in mollusk shells, suggesting a priority over bulk sediments. Although correlated, the shells of the grazer gastropod Melanoides tuberculata have the highest concentration of all metals relative to the suspension-feeder bivalves Cerastoderma glaucum and Saccostrea cuculata. This was attributed to the influences of the eco-physiological traits, which exert a similar influence on the bioaccumulation process of all metals.

New perspectives for fascioliasis in Upper Egypt's new endemic region: Sociodemographic characteristics and phylogenetic analysis of Fasciola in humans, animals, and lymnaeid vectors

BACKGROUND

Fascioliasis is a significant vector-borne disease that has emerged in numerous tropical and subtropical countries causing severe health problems. Egypt is one of the fascioliasis endemic regions; however, the current situation in Upper Egypt is understudied, with only sporadic human cases or outbreaks. This study aims to highlight the sociodemographic characteristics of human fascioliasis in a newly emerged endemic area in Upper Egypt, along with risk factors analysis and the molecular characteristics of the fasciolid population in humans, animals, and lymnaeid snails.

METHODOLOGY/PRINCIPAL FINDINGS

The study reported Fasciola infection in patients and their close relatives by analyzing the risk of human infection. Morphological and molecular characterization was performed on lymnaeid snails. Multigene sequencing was also used to characterize fasciolids from human cases, cattle, and pooled snail samples. The study identified asymptomatic Fasciola infection among family members and identified the presence of peridomestic animals as a significant risk factor for infection. This is the first genetic evidence that Radix auricularia exists as the snail intermediate host in Egypt.

CONCLUSIONS/SIGNIFICANCE

This study revealed that Assiut Governorate in Upper Egypt is a high-risk area for human fascioliasis that requires additional control measures. Fasciola hepatica was the main causative agent infecting humans and snail vectors in this newly emerged endemic area. In addition, this is the first report of R. auricularia as the snail intermediate host transmitting fascioliasis in Upper Egypt. Further research is required to clarify the widespread distribution of Fasciola in Egypt's various animal hosts. This provides insight into the mode of transmission, epidemiological criteria, and genetic diversity of fasciolid populations in Upper Egypt.\.

Assessment of schistosomiasis transmission in the River Nile at Greater Cairo using malacological surveys and cercariometry

Continuous field studies on the abundance and distribution of freshwater snails and cercarial populations are important for schistosomiasis control programs. In the present work, snail surveys and cercariometry were conducted for four successive seasons at 12 sites on the Nile River banks in the area of Greater Cairo to identify potential transmission foci for schistosomiasis. In addition, water physicochemical parameters were recorded. The results showed that the electrical conductivity, total dissolved solids, dissolved oxygen, and pH were within the permissible levels, except that the water temperature increased, especially in the spring season. Malacological surveys identified 10 native snail species at the studied sites of the Nile River, namely Bulinus truncatus, Biomphalaria alexandrina, Lymnaea natalensis, Lanistes carinatus, Cleopatra bulimoides, Melanoides tuberculata, Helisoma duryi, Bellamya unicolor, Physa acuta, Thedoxus niloticus, and one invasive snail species, Thiara scabra. The calculated diversity index indicated that the structure of snails' habitats was poor, while Evenness index indicated that the individuals were not distributed equally. Natural infection results identified no schistosome cercariae in B. truncatus and B. alexandrina. However, the cercariometry recovered Schistosoma cercariae in all the surveyed sites during all seasons with variable distribution. The preceding data suggest that there are still some active transmission foci for schistosomiasis infection in the Nile River. Moreover, the present finding highlights the importance of cercariomety as a complementary approach to snail samplings for identifying the transmission foci for schistosomiasis.

Geography and ecology of invasive Pseudosuccinea columella (Gastropoda: Lymnaeidae) and implications in the transmission of Fasciola species (Digenea: Fasciolidae) - a review

Pseudosuccinea columella is considered invasive and has become an important intermediate host of both Fasciola species in many regions of the world. This systematic review assessed the geographical distribution of P. columella, and its implications in the transmission of Fasciola hepatica and Fasciola gigantica, globally. A literature search was conducted on Google Scholar, JSTOR and PubMed databases using Boolean operators in combination with predetermined search terms for thematic analysis. Results show that P. columella has been documented in 22 countries from Europe (3), Africa (8), Oceania (2), North America (3) and South America (6). Furthermore, this snail species has shown to adapt to and inhabit a vast array of freshwater bodies including thermal lakes and ditches with acidic soils. Studies showed that P. columella transmits F. hepatica, with natural and experimental infections documented in sub-Saharan Africa, Europe, South America and North America. Experimental infection studies in Cuba showed the presence of P. columella populations resistant to F. hepatica infection. Furthermore, some populations of this invasive snail collected from F. hepatica endemic locations in Brazil, Venezuela, Australia, South Africa, Colombia and Argentina were found without Fasciola infection. As a result, the role played by this snail in the transmission of Fasciola spp. in these endemic areas is still uncertain. Therefore, further studies to detect natural infections are needed in regions/countries where the snail is deemed invasive to better understand the veterinary and public health importance of this snail species in Fasciola-endemic areas and determine the global dispersion of resistant populations of P. columella.

Abundance and Annual Distribution of Freshwater Snails and Some Trematode Cercariae at Damietta Governorate, Egypt

In addition to being a good food source, freshwater snails are considered one of the positively and negatively influencing invertebrates on the environment. Several biotic and abiotic factors are thought to affect the distribution and the dynamics of these snails. Freshwater snails are the most dominant and conspicuous individuals of the freshwater biota in Damietta Governorate. In this study, freshwater snails were collected monthly from 5 geographically and environmentally different sites at Damietta Governorate at the north of Egypt during June 2017-May 2018. Seven snail species; Lanistes carinatus, Lanistes varicus, Pila wernei, Segmentorbis angustus, Melanoides tuberculata, Biomphalaria alexandrina, and Gabbiella senoriansis, were identified. Lanistes carinatus was the most abundant species (56.4%) in the collection sites. Besides, Al-Inaniyyah village had the highest snail species abundance and variety. The abundance of the most recorded species varied seasonally; the highest abundance was recorded during summer while the lowest was during winter. The abundance of some snail species correlated positively or negatively with some physico-chemical parameters; water temperature, dissolved oxygen, conductivity, total dissolved salts, and electrical conductivity. Two types of trematode cercariae; gymnocephalus cercariae and xiphidiocercariae, were harvested from Lanistes carinatus. The highest prevalence of both cercarial types was detected during summer. The correlation between the prevalence of both cercarial types and the physico-chemical parameters were determined. Xiphidiocercariae were the most predominant cercarial type in Damietta Governorate. Our findings suggest that the invasion of some freshwater snails is likely to be the cause of the low prevalence or complete absence of some medically important intermediate snail hosts. We recommend further characterization of the distribution of freshwater snails and the interrelationships among them in Egypt, and suggest a controlled use of selected snail species to combat their medically important analogues.

Preliminary Study on Survey and Population Dynamic of the Terrestrial Snail Monacha obstructa (Pfeiffer) (Hygromiidae, Mollusca) at Crop Fields in Fayoum Governorate, Egypt

<b>Background and Objective:</b> <i>Monacha obstructa</i> has a serious harmful impact as agricultural pest infested field crops, fruits, vegetables and ornamental plants nurseries in multiple Egyptian governorates. The objective of this research was estimating the population dynamic of the terrestrial gastropod species <i>Monacha obstructa</i> (Pfeiffer) (Hygromiidae) on two economic crop fields and its correlation with temperature degree and relative humidity, the level of infestation on other economic crops had been estimated as well. <b>Materials and Methods:</b> This study was conducted in three sites in Fayoum governorate, 1) Forkous village at Tamiya District, 2) Dar Ramadsite including the Experimental farm and research station of the Faculty of Agriculture, Fayoum University, Fayoum District and 3) Feedimeen village at Sannoris District. The distribution and population dynamics of <i>Monacha obstructa</i> were assessed as one of dominant species on two field crops Egyptian clover <i>Trifolium alexandrinum </i>L. and wheat <i>Triticum aestivum</i> L. at Forkous village, Tamiya District and Dar Ramad site, Fayoum District, during two successive seasons 2016/2017 and 2017/2018. <b>Results:</b> Majority of the examined crops in the sites were found with heavy infestation of this species, while the two species <i>Cochlicella acuta</i> (Müller) (Geomitridae) and <i>Massylaea vermiculata </i>(Müller) (Helicidae) recorded in December, 2017 and in January, 2018, respectively, on mango trees in Feedimeen at Sannoris district for only one time. High density of <i>M. obstructa</i> recorded on Egyptian clover more than wheat at Forkous village and Dar Ramad site for the both seasons in this study. <b>Conclusion:</b> Results concluded that <i>Monacha obstructa</i> has a serious harmful impact as agricultural pest infested field crops, fruits, vegetables and ornamental plants nurseries in Forkous village and Dar Ramad site, respectively.

Taxonomic assessment of genetically-delineated species of radicine snails (Mollusca, Gastropoda, Lymnaeidae)

The article represents an overview of 29 biological species of the radicine snails (generaAmpullaceanaServain, 1882,BullastraBergh, 1901,RacesinaVinarski & Bolotov, 2018,KamtschaticanaKruglov & Starobogatov, 1984,MyxasG.B. Sowerby I, 1822,OrientogalbaKruglov & Starobogatov, 1985;PeregrianaServain, 1882,RadixMontfort, 1810, andTibetoradixBolotov, Vinarski & Aksenova, 2018) recovered during our previous molecular taxonomic study (Aksenova et al. 2018a; Scientific Reports, 8: 11199). For each species, the following information is provided: scientific name, a (non-exhaustive) list of synonyms, type locality, type materials, shell and copulative apparatus morphology, distribution, and nomenclatural and taxonomic remarks. The colour images of shell(s) of each species are also given as well as illustrations of the copulatory apparatuses. We revealed a great conchological variation in the radicines, both intra- and interspecific, alongside with striking uniformity in the structure of their copulatory apparatuses. The latter was once thought to be a reliable tool for species delineation and identification in this snail group. The total of 29 species characterised here represents, probably, only a subset of the global taxonomic richness of the radicine snails, which approaches 50 species.

Phenotypic plasticity of the gastropod Melanoides tuberculata in the Nile Delta: A pollution-induced stabilizing selection

To understand the effect of metal pollution on the speciation process, we conducted comparative analyses of six populations of the gastropod Melanoides tuberculata, which dominated the Manzala lagoon (Nile Delta, Egypt). Geometric morphometric analysis was implemented to quantify the phenotypic plasticity of the species. The results from both Canonical Variate Analysis and Relative Warp indicated an overall decrease in the morphological breadth of M. tuberculata in the polluted sites. The favored phenotypes in the polluted sites have moderate whorl section, moderate ovate aperture, less-prominent radial ornament, and overall moderate-spired shells. Lack of morphological variations and dominance of intermediate phenotypes in the polluted sites indicate that stabilizing selection is driving the morphological pattern of this species. Moreover, analysis by using the partial least square model confirmed that metal pollution is the major predictor of the observed shape variations, whereas other biotic/abiotic traits are a minor predictor.

Galba robusta sp. nov. from Yemen (Gastropoda: Lymnaeidae)

Mollusks of the genus Galba Schrank, 1803, inhabiting north-east Africa and the Arabian Peninsula, are separated into two morphologically distinct groups. The first group contains two conchologically indistinguishable species, G. truncatula (O.F. Müller, 1774) and G. schirazensis (Küster, 1862). The second group includes one species characterized by significantly larger size and different shell proportions as compared to G. truncatula and G. schirazensis. This species is new one and described here as G. robusta sp. nov. with type locality situated in Yemen. It is hypothesized that G. robusta sp. nov. has a vast distribution, ranging from Central Iran southwards to East Africa. A comparison of the new taxon with two nominal species of Galba, G. mweruensis (Connolly, 1929) and G. umlaasianus (Küster, 1862) described from East and South Africa, as well as some data on conchological variation of African representatives of this genus are given.

Population genetics of the Schistosoma snail host Bulinus truncatus in Egypt

The tropical freshwater snail Bulinus truncatus serves as an important intermediate host of several human and cattle Schistosoma species in many African regions. Despite some ecological and malacological studies, there is no information on the genetic diversity of B. truncatus in Egypt. Here, we sampled 70-100 snails in ten localities in Upper Egypt and the Nile Delta. Per locality, we sequenced 10 snails at a partial fragment of the cytochrome c oxidase subunit 1 gene (cox1) and we genotyped 25-30 snails at six microsatellite markers. A total of nine mitochondrial haplotypes were detected, of which five were unique to the Nile Delta and three were unique to Upper Egypt, indicating that snail populations may have evolved independently in both regions. Bayesian clustering and hierarchical F-statistics using microsatellite markers further revealed strong population genetic structure at the level of locality. Observed heterozygosity was much lower compared to what is expected under random mating, which could be explained by high selfing rates, population size reductions and to a lesser extent by the Wahlund effect. Despite these observations, we found signatures of gene flow and cross-fertilization, even between snails from the Nile Delta and Upper Egypt, indicating that B. truncatus can travel across large distances in Egypt. These observations could have serious consequences for disease epidemiology, as it means that infected snails from one region could rapidly and unexpectedly spark a new epidemic in another distant region. This could be one of the factors explaining the rebound of human Schistosoma infections in the Nile Delta, despite decades of sustained schistosomiasis control.