Physiological studies on Biomphalaria alexandrina and Bulinus truncatus, the snail vectors of Schistosommiasis (original) (raw)
Related papers
Comparative Biochemistry and Physiology Part B: Comparative Biochemistry, 1975
Schistosorae infection of the snails Biomphalaria alexandrina and Bulinus truncatus affected their citric acid cycle pathways; especially those concerned with succinic and cytochrome oxidases. 2. The rate of gluconeogenesis was decreased in schistosome-infected snails to 62 per cent for Bulinus truncatus and to 45 per cent for Biomphalaria alexandrina. 3. Lactic acid production was increased in schistosome-infected snails to 52 and 73 per cent that of uninfected B. alexandrina and B. truncatus respectively. 4. Schistosome infection caused a marked decrease in the glycogen content of the tissues of both snail species. 5. The effect of schistosome infection on the intermediary metabolism of both snails is discussed.
Experimental Parasitology, 2011
Snails' susceptibilities to infection with Schistosoma mansoni were determined through observation of infection rates, total cercarial production and tissue responses of the first generation (F1) of Biomphalaria alexandrina snails, originally collected from different Egyptian governorates (Giza, Fayoum, Kafr El-Sheikh, Ismailia and Damietta) and responses were compared between groups. The emergence of cercariae for a 3-month period and the calculation of survival and infection rates, in control (Schistosome Biological Supply Center; SBSC) and infected snails were evaluated. SBSC and Giza snails showed greater susceptibilities to infection and lower mortality rates. In addition, at 6 and 72 h post-exposure to miracidia all the snail groups showed no difference in the anatomical locations of sporocysts. The larvae were found in the head-foot, the mantle collar and the tentacles of the snails. Sporocysts showed normal development with low tissue reactions in SBSC and Giza snail groups infected with S. mansoni miracidia (SBSC). However, in Fayoum, Kafr El-Sheikh, Ismailia and Damietta snail groups, variable tissue responses were observed in which numerous hemocytes made direct contact with S. mansoni larvae forming capsules. The results suggested that, different responses of B. alexandrina snail's hemocytes towards S. mansoni are related to the degree of susceptibility of these snails. So this is important in planning the strategy of schistosomiasis control.
Acta Tropica, 1996
Alterations in physiology of snail host induced by larval trematodes are generally interpreted like the results of a nutrient deprivation similar to starvation . However, few studies ) have been made on the nutritional physiology of snail hosts to assess the impact of trematode infection on nutrient assimilation and energy conversion. For Schistosoma mansoni pluri-infected Biomphalaria glabrata, have shown that during patent period food consumption and assimilation per unit snail weight were unaffected but gross conversion efficiency was sharply reduced. According to these authors, the decreased conversion efficiency of parasitized snails indicates that a significant portion of the food energy consumed by the host is utilized by the parasite for development and reproduction.
2007
Schistosomiasis is an important parasitic disease that infects humans. Among the main species of schistosomes infecting humans is Schistosoma mansoni and S. haematobium. Snails of various genera, such as Biomphalaria alexandrina and Bulinus truncates, act as intermediate hosts and play a major role in the transmission of schistosomes. Transmission from human to snail is under the influence of the ciliated miracidium larvae that hatch from the eggs of the parasite voided in the faeces or urine. After a period of asexual multiplication in the snail, a second aquatic larval stage, the cercaria, emerges and infects human by direct penetration of the skin. The present work was carried out on Biomphalaria alexandrina snails, the intermediate host of Schistosoma mansoni. Snails were collected from various sites in south western Saudi Arabia. Their progeny were reared in the laboratory under standard conditions. Different biological experiments were carried out to determine the susceptibility level in the various populations of snail. The miracidia were obtained by isolating viable ova of the hatching parasite from faeces of infected individuals (human and mice). Different sets of regulated experimental infection of snails with the miracidia of Schistosoma mansoni were preformed. The effect of miracidial density, water temperature, miracidial age, size of snails, as well as light and darkness were investigated. The study revealed that the infection rate increased as the number of miracidia used increased (1, 60%; 2, 60%; 3, 70%; 5, 80%; 15, 90%; and 20, 90%). No significant increase of infection rate was achieved at higher water temperatures (at 15°C: 65% with newly hatched miracidia; 75%, with 15 minutes miracidia; 85% with 30 minutes miracidia; 95% with 45 minutes miracidia and 100% with 60 minutes miracidia. At 20°C: 75% with newly hatched miracidia; 80%, with 15 minutes miracidia; 90%, with 30 minutes miracidia; 95% with 45 minutes miracidia and 100% with 60 minutes miracidia). Similar results were obtained at 25°C and 30°C. However, the infection rate decreased in relation to snail size increase. At snail size 2-4 mm the infection rate was 90%, the rate decreased to 85% at 4-6 mm and 6-8 mm size, while at 8-10 mm size the rate was 80%. At 10-12 mm and 13-15 mm size the rate dropped to 75%. Light and dark conditions had a significant difference on the infection rate (40% in darkness and 90% in light). Laboratory observations also indicated that some of the snails exposed to infection with miracidia of the respective parasite developed infection and produced cercariae, while the rest remained uninfected.
Journal of Parasitology Research
Only a fraction of the Biomphalaria and Bulinus snail community shows patent infection with schistosomes despite continuous exposure to the parasite, indicating that a substantial proportion of snails may resist infection. Accordingly, exterminating the schistosome intermediate snail hosts in transmission foci in habitats that may extend to kilometres is cost-prohibitive and damaging to the ecological equilibrium and quality of water and may be superfluous. It may be more cost effective with risk less ecological damage to focus on discovering the parameters governing snail susceptibility and resistance to schistosome infection. Therefore, laboratory bred Biomphalaria alexandrina and Bulinus truncatus snails were exposed to miracidia of laboratory-maintained Schistosoma mansoni and S. haematobium, respectively. Snails were examined for presence or lack of infection association with soft tissue and hemolymph content of proteins, cholesterol, and triglycerides, evaluated using standard...
The Compatibility Between Biomphalaria glabrata Snails and Schistosoma mansoni
Elsevier eBooks, 2017
This review reexamines the results obtained in recent decades regarding the compatibility polymorphism between the snail, Biomphalaria glabrata, and the pathogen, Schistosoma mansoni, which is one of the agents responsible for human schistosomiasis. Some results point to the snail's resistance as explaining the incompatibility, while others support a "matching hypothesis" between the snail's immune receptors and the schistosome's antigens. We propose here that the two hypotheses are not exclusive, and that the compatible/incompatible status of a particular host/parasite couple probably reflects the balance of multiple molecular determinants that support one hypothesis or the other. Because these genes are involved in a coevolutionary arms race, we also propose that the underlying mechanisms can vary. Finally, some recent results show that environmental factors could influence compatibility. Together, these results make the compatibility between B. glabrata and S. mansoni an increasingly complex puzzle. We need to develop more integrative approaches in order to find targets that could potentially be manipulated to control the transmission of schistosomiasis. 2 THE GENETIC DETERMINISM OF THE COMPATIBILITY/INCOMPATIBILITY OF BIOMPHALARIA GLABRATA AND SCHISTOSOMA MANSONI The low prevalence of snails with patent schistosome infection, which is usually observed in transmission foci (Anderson and May 1979; Sire et al., 1999), was first believed to be explained by the low probability of an encounter between the partners. This hypothesis cannot be excluded in the interaction between B. glabrata and S. mansoni. However, a molecular screening approach yielded interesting results regarding the interaction between Schistosoma haematobium and Bulinus globosus snails. This work showed that although patency was often very low (less than 4% shed cercariae), more than 40% of the snails were exposed to the parasite in the field (Allan et al., 2013). Thus, snails experienced high levels of parasitic exposure, but only a small proportion of infected snails reached the stage of cercarial shedding. Moreover, even if snails were penetrated by miracidia, the infections often failed to develop to patency (Allan et al., 2013). These results suggest that nonsusceptibility or incompatibility of a particular host and parasite combination is a major factor in the low prevalence observed in the field. This nonsusceptibility/incompatibility can also reflect a biochemically unfavourable intramolluscan environment for the parasite, which is termed "unsuitability" (Lie and Heyneman, 1977; Sullivan and Richards, 1981). However, the most frequently involved mechanism consists of the recognition, encapsulation and killing of the parasite by immune cells (haemocytes) of the snail (Fig. 1 A). Numerous infection-based experiments have been performed
2016
Schistosomiasis, the most important parasitic disease in Egypt, has plagued its people since ancient times. Two species of Biomphalaria are reported from Egypt, the indigenous Biomphalaria alexandrina and Biomphalaria glabrata, the latter is believed to be introduced during the past few decades. Both are known to be excellent hosts of Schistosoma mansoni, in Egypt. SDS-PAGE was used to separate tissue proteins of control and Schistosoma-infected Biomphalaria alexandrina and B.glabrata snails. Also total protein of these groups was measured using Bradford assay method. The present data showed that there is a variation in the protein profiles under the effect of infection, and the days of infections can also affect total and protein profiles pattern. There was a significant decrease in B.alexandrina total protein, in contrary, total protein of B.glabrata groups exhibited significant and insignificant increase under the effect of infection. The electrophoretic pattern showed that there...