Iman Fathy Abou-El-Naga

Biomphalaria alexandrina in Egypt: Past, present and future

The African species of Biomphalaria appeared as a result of the relatively recent west-to-east trans-Atlantic dispersal of the Biomphalaria glabrata-like taxon. In Egypt, Biomphalaria alexandrina is the intermediate host for Schistosoma mansoni. Biomphalaria alexandrina originated in the area between Alexandria and Rosetta and has historically been confined to the Nile Delta. Schistosoma mansoni reached Egypt via infected slaves and baboons from the Land of Punt through migrations that occurred as early as the Vth Dynasty. The suggestion of the presence of Schistosoma mansoni infection in Lower Egypt during Pharaonic times is discussed despite the fact that that there is no evidence of such infection in Egyptian mummies. It is only recently that Biomphalaria alexandrina colonized the Egyptian Nile from the Delta to Lake Nasser. This change was likely due to the construction of huge water projects, the development of new water resources essential for land reclamation projects and the movement of refugees from the Suez Canal zone to the Delta and vice versa. The situation with respect to Biomphalaria in Egypt has become complicated in recent years by the detection of Biomphalaria glabrata and a hybrid between both species; however, follow-up studies have demonstrated the disappearance of such species within Egypt. The National Schistosoma Control Program has made great strides with respect to the eradication of schistosoma; however, there has unfortunately been a reemergence of Schistosoma mansoni resistant to praziquantel. There are numerous factors that may influence the prevalence of snails in Egypt, including the construction of water projects, the increase in reclaimed areas, global climate change and pollution. Thus, continued field studies in addition to the cooperation of several scientists are needed to obtain an accurate representation of the status of this species. In addition, the determination of the genome sequence for Biomphalaria alexandrina and the use of modern technology will allow for the study of the host–parasite relationship at a molecular level.

Biomphalaria species in Alexandria water channels.

Of the several species of Biomphalaria snails worldwide that serve as the intermediate host for Schistosoma mansoni, Biomphalaria alexandrina is a species that is indigenous to Egypt. Recently, there has been much debate concerning the presence of Biomphalaria glabrata and the hybrid of the species with Biomphalaria alexandrina. Due to this debate, the absence of a clear explanation for the presence of B. glabrata in Egyptian water channels and the probability that they may be reintroduced, we conducted this field study to identify Biomphalaria species present in Alexandria water channels. Laboratory-adapted susceptible snails to Schistosoma mansoni of the following species were used as a reference; Biomphalaria alexandrina, Biomphalaria glabrata and their hybrid. These snails were used to perpetuate the Schistosoma life cycle at the Theodor Bilharz Research Institute (TBRI), Cairo, Egypt. Morphological and molecular studies were conducted on these reference snails as well as on the first generation of Biomphalaria snails from two areas in the Alexandria governorate. The morphological study included both external shell morphology and internal anatomy of the renal ridge. The molecular study used a species-specific PCR technique. The results demonstrated that there was an absence of Biomphalaria glabrata and the hybrid from Alexandria water channels. Moreover, the susceptibility patterns of these reference snails were studied by measuring the different parasitological parameters. It was found that Biomphalaria glabrata and the hybrid were significantly more susceptible than Biomphalaria alexandrina to the Egyptian strain of Schistosoma mansoni. The results demonstrated that if Biomphalaria glabrata was reintroduced and adapted to the local environment in Egypt, it would have important epidemiologic impacts that would have a serious effect on the health of Egyptian people.

Demographic, socioeconomic and environmental changes affecting circulation of neglected tropical diseases in Egypt.

Egypt has been plagued by many neglected tropical diseases since Pharaonic time. These diseases are Schistosomiasis, soil-transmitted helminthiasis, lymphatic filariasis, leishmaniasis and fascioliasis beside the epidermal parasitic skin diseases. Indeed, theses diseases still persist as public health problem in the country by the influence of demographic, socioeconomic and environmental obstacles. This study seeks for understanding the contribution of each factor in each obstacle in neglected tropical diseases perpetuation which in turn could help the governorate in planning integrated control strategies. It was found that poverty, unregulated urbanization and inadequate sanitation are important socioeconomic factors that have great effect on the transmission dynamics of the diseases. The environmental factors which affect the epidemiology of these diseases in the country are scarcity of water, construction of dams, land reclamation for agriculture beside the climate factors. Unfortunately, the panic increase in the population growth rate minimizes the efforts done by the governorate to elevate the public health services. These conditions also affect the transmission of epidermal parasitic skin diseases including scabies, head lice and hookworm-related cutaneous larva migrans. The control programs and the recommendations to combat the diseases were discussed. The present study showed that the ecological factors affecting each neglected tropical disease in Egypt are somewhat similar which makes it worthy to develop an integrated control approaches aiming at improving the leading factors of neglected tropical diseases circulation in the country.

Genetic Variation between Biomphalaria alexandrina Snails Susceptible and Resistant to Schistosoma mansoni Infection

Much effort has been made to control schistosomiasis infection in Egypt. However, enduring effects from such strategies have not yet been achieved. In this study, we sought to determine the genetic variability related to the interaction between Biomphalaria alexandrina snails and Schistosoma mansoni. Using RAPD-PCR with eight (10 mers) random primers, we were able to determine the polymorphic markers that differed between snails susceptible and resistant to Schistosoma mansoni infection using five primers out of the eight. Our results suggest that the RAPD-PCR technique is an efficient means by which to compare genomes and to detect genetic variations between schistosomiasis intermediate hosts. The RAPD technique with the above-noted primers can identify genomic markers that are specifically related to the Biomphalaria alexandrina/Schistosoma mansoni relationship in the absence of specific nucleotide sequence information. This approach could be used in epidemiologic surveys to investigate genetic diversity among Biomphalaria alexandrina snails. The ability to determine resistant markers in Biomphalaria alexandrina snails could potentially lead to further studies that use refractory snails as agents to control the spread of schistosomiasis.

Impact of the age of Biomphalaria alexandrina snails on Schistosoma mansoni transmission: modulation of the genetic outcome and the internal defence system of the snail

Of the approximately 34 identified Biomphalaria species,Biomphalaria alexandrina represents the intermediate host of Schistosoma mansoni in Egypt. Using parasitological and SOD1 enzyme assay, this study aimed to elucidate the impact of the age of B. alexandrina snails on their genetic variability and internal defence against S. mansoni infection. Susceptible and resistant snails were reared individually for self-reproduction; four subgroups of their progeny were used in experiment. The young susceptible subgroup showed the highest infection rate, the shortest pre-patent period, the highest total cercarial production, the highest mortality rate and the lowest SOD1 activity. Among the young and adult susceptible subgroups, 8% and 26% were found to be resistant, indicating the inheritance of resistance alleles from parents. The adult resistant subgroup, however, contained only resistant snails and showed the highest enzyme activity. The complex interaction between snail age, genetic background and internal defence resulted in great variability in compatibility patterns, with the highest significant difference between young susceptible and adult resistant snails. The results demonstrate that resistance alleles function to a greater degree in adults, with higher SOD1 activity and provide potential implications for Biomphalaria control. The identification of the most susceptible snail age enables determination of the best timing for applying molluscicides. Moreover, adult resistant snails could be beneficial in biological snail control.

Meta-analysis indicates lack of local adaptation of Schistosoma mansoni to Biomphalaria alexandrina in Egypt

In Egypt, reclaiming portions of the desert using water from the Nile has resulted in large-scale invasion of Biomphalaria alexandrina in these regions. Studies exploring the local adaptation of Schistosoma mansoni to its snail host have been carried out to predict the extension of schistosomiasis to newly reclaimed areas. A meta-analysis of the relevant reports was conducted to compare the different biological characteristics of sympatric and allopatric Schistosoma mansoni and Biomphalaria alexandrina using different experimental designs. The results showed that there were no significant differences in the biological characteristics of sympatric and allopatric populations. The experimental design of some of the studies analyzed was found to affect the total cercarial production. The distance between the origin of the parasite and that of the snail did not affect any of the biological characteristics. The results showed that there is no evidence of local adaptation between Schistosoma mansoni and Biomphalaria alexandrina; however, the parasite is adapted to its intermediate host throughout the water bodies located in Egypt. The absence of local adaptation between Schistosoma mansoni and Biomphalaria alexandrina is likely of critical importance in predicting public health risks engendered by future reclaimed agriculture projects. Indeed, these results could assist in determining the appropriate balance between the development of water resource projects and schistosomiasis control in Egypt.

The effect of lopinavir/ritonavir and lopinavir/ritonavir loaded PLGA nanoparticles on experimental toxoplasmosis

A marked reduction has been achieved in the incidence and clinical course of toxoplasmic encephalitis after the introduction of protease inhibitors within the treatment regimen of HIV (HIV-PIs). This work was undertaken to study for the first time, the efficacy of HIV-PIs, lopinavir/ritonavir (L/R), as a therapeutic agent in acute experimental toxoplasmosis. Lopinavir/ritonavir (L/R) were used in the same ratio present in aluvia, a known HIV-PIs drug used in the developing countries in the treatment regimens of AIDs patient. Poly lactic-co-glycolic acid (PLGA) nanoparticles were used as a delivery system to L/R therapy. L/R alone or after its encapsulation on PLGA were given to Swiss strain albino mice that were infected with RH virulent toxoplasma strain. Both forms caused parasitological improvement in both mortality rate and parasite count. The higher efficacy was achieved by using L/R PLGA together with minimizing the effective dose. There was significant reduction in the parasite count in the peritoneal fluid and the liver. Parasite viability and infectivity were also significantly reduced. The anti-toxoplasma effect of the drug was attributed to the morphological distortion of the tachyzoites as evident by the ultrastructure examination and suppressed the egress of tachyzoites. L/R also induced changes that suggest apoptosis and autophagy of tachyzoites. The parasitophorous vacuole membrane was disrupted and vesiculated. The nanotubular networks inside the parasitophorous vacuole were disrupted. Therefore, the present work opens a new possible way for the approved HIV-PIs as an alternative treatment against acute toxoplasmosis. Furthermore, it increases the list of the opportunistic parasites that can be treated by this drug. The successful in vivo effect of HIV-PIs against Toxoplasma gondii suggests that this parasite may be a target in HIV treated patients, thus decrease the possibility of toxoplasmic encephalitis development.

In vitro interactions between the defense systems of resistant and susceptible Biomphalaria alexandrina and sporocysts of Schistosoma mansoni.

Biomphalaria species that act as an intermediate host for Schistosoma mansoni have different degrees of susceptibility and different internal defense system responses against parasites. Of these species, Biomphalaria alexandrina represents the only intermediate host in Egypt. Given the limited data on the efficacy of the B. alexandrina internal defense system in comparison to that of other species, we sought to better understand its defense against S. mansoni. We performed in vitro hemocyte adherence assay using whole hemolymph and in vitro reaction using the hemocyte-free hemolymph of susceptible and resistant snails against transformed mother sporocysts. The results demonstrated that the interacting factors between the parasite and the hemolymph of the resistant and susceptible snails do not act in a similar manner. Destruction of the parasite was a restricted function of the hemocytes among resistant snails only. This study demonstrates the key role played by snail hemocytes as a first line of defense against the parasite. The incubation of the hemocyte-free hemolymph of both susceptible and resistant snails with the sporocysts did not lead to any changes in the sporocysts shape or integrity. This immunological variance demonstrated between susceptible and resistant snails could be useful to differentiate between susceptible and resistant snails in future field studies. In addition, the results may help further studies to explain the process of attraction, encapsulation and subsequent killing of S. mansoni in its intermediate host.

Desarrollo y viabilidad de huevos de Toxocara canis

INTRODUCTION Toxocariasis is a soil-transmitted zoonotic disease caused mainly by ingestion of larvated eggs of Toxocara canis. OBJECTIVES To study the morphology of the intraovular developmental stages of Toxocara canis in culture, characterize non-viable eggs and the sequences of larval molting and compare the viability of eggs at the early stages of division and at reaching full maturation. MATERIAL AND METHODS Observation of developing embryos and characterization of non-viable eggs were done using light microscope. The proportions of viable eggs during embryonation were compared to the proportions of viable mature eggs. RESULTS Cell division commenced after 24 hours of cultivation. Early stages were found to be present over a period of 3-5 days. The developmental stages identified were eggs with: One cell, two cells, three cells, four cells, early morula, late morula, blastula, gastrula, tadpole, pre-larva, first, second and third stage larva. Two larval molts occurred. Non-viable eggs had degenerated cytoplasm, thin or collapsed shell and the larvae did not move after exposure to light. No significant differences were found between the proportions of viable eggs from day five to day 21 as compared to viability of fully mature eggs (30 days). CONCLUSION Developing embryos in the environment may be considered as a potential threat to the public health. The precise identification of developmental stages and the clear differentiation of viable and non-viable eggs can help in determining an accurate baseline rate of development that could be used in studies of ovicidal compounds.

Towards elimination of schistosomiasis after 5000 years of endemicity in Egypt

Schistosomiasis is a snail-transmitted infectious disease caused by a long lasting infection with a blood fluke of the genus Schistosoma. S. haematobium and S. mansoni are the species endemic in Egypt. The country has been plagued and seriously suffered from schistosomiasis over the past 5000 years. Great strides had been done in controlling the disease since 1922. The history, epidemiology and the different control approaches were reviewed. Currently, Egypt is preparing towards schistosomiasis elimination by 2020. The new strategy depends on four main axes; large scale treatment in all areas of residual transmission by targeting entire populations with PZQ, intensified snail control, heath education and behavioral changes and expansion of the complementary public health interventions. While on the road towards elimination, we addressed here the important challenges, lessons and the key issues from the different control strategies to help the achievement of our goal. Notably, frangibility of the drug based control, emergence of resistance against PZQ, persistence of some hot spots areas, the need of further control efforts to the high risk individuals and community involvement in the control programs, reconsideration of diagnostic tests used in surveillance, and continous monitoring of the field to detect changes in the snail intermediate host. Importantly, the adaptation between the parasite and its intermediate snail host throughout water bodies in Egypt merits attention as Schistosoma infection can be introduced to the new reclaimed areas. This review may help supplying information for the policy makers to tailor control measures suitable to the local context that could help in the transfer from control to elimination.