Direct and delayed effects of low temperature on the freshwater snail Indoplanorbis exustus (Deshayes, 1934), intermediate host of schistosomias

The direct and delayed effect of short-term exposure to low temperature (17.5 °C) on growth, reproduction and longevity of adolescent and mature freshwater Indoplanorbis exustus Deshyaes (Mollusca: Gastropoda) was studied in the laboratory. We found that growth and reproduction were retarded, but were enhanced when later they were returned to ambient temperature.     

LacdiNAc- and LacNAc-containing glycans induce granulomas in an in vivo model for schistosome egg-induced hepatic granuloma formation

Schistosomes, major parasitic helminths, express numerous glycoconjugatesthat provoke humoral and cellular immune responses in the infectedhuman host. The main pathology in schistosomiasis is due tothe formation of granulomas around tissue-trapped eggs and theresulting organ damage. By using a mouse model of inductionof granulomas by hepatic implantation of antigen-coated beads,it has been determined that the glycan part of schistosomalsoluble egg antigens (SEA) initiates granulomogenesis. To identifywhich individual glycan elements in this complex SEA mixtureare granulomogenic, we have tested in the same mouse model conjugatesof various synthetic oligosaccharides characteristic for schistosomeeggs, including GalNAcß1-4GlcNAc (LacdiNAc, LDN),Galß1-4(Fuc1-3)GlcNAc (Lewis^x), Fuc1-2Fuc1-3GlcNAc(DF-Gn), and Fuc1-3GalNAcß1-4(Fuc1-3)GlcNAc (F-LDN-F).Ribonuclease (RNase) A and B, and different fetuin glycoformswere included as controls. Only beads that carry glycoconjugateswith terminal LacdiNAc or Galß1-4GlcNAc (LacNAc, LN)elements gave rise to granulomas, with macrophage, lymphocyte,and eosinophil levels similar to the granulomatous lesions causedby schistosome eggs in a natural infection. Uncoated beads,and beads coated with fucosylated glycoconjugates or glycoconjugateslacking terminally exposed Gal or GalNAc, only attracted a monolayerof macrophages. These results indicate that the formation ofhepatic granulomas is triggered specifically by glycoconjugateswhich carry terminal LacNAc or LacdiNAc, both constituents ofthe schistosome egg.     

Low genetic diversity in a snail intermediate host (Biomphalaria pfeifferi Krass, 1848) and schistosomiasis transmission in the Senegal River Basin

Population genetic perturbations of intermediate hosts, often a consequence of human pressure on environmental resources, can precipitate unexpectedly severe disease outbreaks. Such disturbances are set to become increasingly common following range changes concomitant with climate shifts, dwindling natural resources and major infrastructure changes such as hydroprojects. Construction of the Diama dam in the Senegal River Basin (SRB) reduced river salinity, enabling the freshwater snail intermediate host Biomphalaria pfeifferi to rapidly expand its distribution. A serious public health problem ensued, with an epidemic of intestinal schistosomiasis occurring in the previously schistosome‐free Richard‐Toll region within 2 years. The current study aimed to assess the population variability of B. pfeifferi in the SRB, and speculate upon its subsequent impact on host‐parasite interactions following such engineered ecological change. Genetic variation at nine polymorphic microsatellite loci revealed little population differentiation in SRB snails compared with those from natural habitats in Zimbabwe, where Schistosoma mansoni transmission is much lower. ‘Open’ SRB habitats are associated with greater water contact, smaller population sizes and less genetic diversity, with sites downstream of Richard‐Toll showing greater inter‐ and intrapopulation variation, concomitant with less frequent human contact. These observations may be explained by rapid expansion into pristine habitat selecting for high fecundity genotypes at the expense of schistosome resistance, presenting S. mansoni with genetically homogenous highly fecund susceptible populations around the focal point, promoting development of a highly compatible host‐parasite relationship. Longitudinal study of such systems may prove important in predicting public health risks engendered by future environmental engineering projects.     

Freshwater snails of Oman,South Eastern Arabia

A systematic account is given of the extant freshwater snail fauna of Oman, based on recent collections made in Dhofar and in the northern mountainous areas. Also included are certain species found in brackish coastal localities. A total of 8 freshwater species is regarded as belonging to the fauna of normal freshwater; 7 have been found alive (Thiara scabra, Melanoides tuberculata, Lymnaea natalensis, Gyraulus piscinarum, Biomphalaria arabica, Bulinus wrighti and Indoplanorbis exustus) and one is known only as shells (Paludestrina glaucovirens). This report of G. piscinarum is the first for Oman and may be the first reliable identification for Arabia. Three taxa from brackish water, Gangetia miliacea, Iravadia quadrasi and Melanoides sp., are new for the fauna of Oman and of the whole Arabian peninsula. The finding of G. miliacea provides the first instance of any member of the Stenothyridae living west of the Gulf of Oman and identified from whole snails rather than empty shells. I. quadrasi is the first member of its genus to be found alive west of the Gulf of Oman.     

Integrated Schistosomiasis and Soil-Transmitted Helminthiasis Control over Five Years on Kome Island,Tanzania

Integrated control strategies are important for sustainable control of schistosomiasis and soil-transmitted helminthiasis, despite their challenges for their effective implementation. With the support of Good Neighbors International in collaboration with National Institute of Medical Research, Mwanza, Tanzania, integrated control applying mass drug administration (MDA), health education using PHAST, and improved safe water supply has been implemented on Kome Island over 5 years for controlling schistosomiasis and soil-transmitted helminths (STHs). Baseline surveys for schistosomiasis and STHs was conducted before implementation of any integrated control strategies, followed by 4 cross-sectional follow-up surveys on randomly selected samples of schoolchildren and adults in 10 primary schools and 8 villages, respectively, on Kome islands. Those follow-up surveys were conducted for impact evaluation after introduction of control strategies interventions in the study area. Five rounds of MDA have been implemented from 2009 along with PHAST and improved water supply with pumped wells as other control strategies for complementing MDA. A remarkable steady decline of schistosomiasis and STHs was observed from 2009 to 2012 with significant trends in their prevalence decline, and thereafter infection rate has remained at a low sustainable control. By the third follow-up survey in 2012, Schistosoma mansoni infection prevalence was reduced by 90.5% and hookworm by 93.3% among schoolchildren while in adults the corresponding reduction was 83.2% and 56.9%, respectively. Integrated control strategies have successfully reduced S. mansoni and STH infection status to a lower level. This study further suggests that monitoring and evaluation is a crucial component of any large-scale STH and schistosomiasis intervention.     

Surface antigens on cercariae,schistosomula and adult worms of Schistosoma mansoni

Shah J. and Ramasamy R. 1982. Surface antigens on cercariae, schistosomula and adult worms of Schistosoma mansoni. International Journal for Parasitology12: 451–461. The surface protein antigens of Schistosoma mansoni were radiolabelled by lactoperoxidase catalysed I¹²⁵-iodination and analysed by immune-precipitation and polyacrylamide gel electrophoresis. The results showed that regularly labelled surface antigens of mol. wts >150,000, 78,000, 45,000 and 22,000 were present on adult worms. Common surface antigens were observed on the cercariae, schistosomula and adult worms. It is suggested that surface antigens released from living adult worms can sensitise a host to react against the invading schistosomula of a secondary infection. However, the failure to vaccinate mice using material containing adult worm surface antigens suggests that the induction of protective immunity is a complex phenomenon.     

Preliminary observation on the role of conditioning and mechanical Interference with egg masses and Juveniles in the competitive relationships Between Helisoma Durvi (Wetherby) and the Intermediate host of Schistosoma Mansoni Sambon: Biomphalaria Camerunensis (Boettger).

Biological control of the intermediate hosts of schistosomiasis by means of the introduction oa a competitor snail Helisoma duryi has been suggested. The effect of conditioning by Biomphalaria camerunensis and H. duryi respectively on growth and egg laying capacity of B. camerunensis and on the hatchability of B. camerunensis egg masses was compared. No differences were found besides an indication of a growth promoting effect of B. camerunensis conditioning. B. camerunensis egg masses were found to be much more sensitive to mechanical interference from snails than were H. duryi egg masses. Both juvenile and adult H. duryi caused a great reduction in the number of B. camerunensis egg masses and adult B. camerunensis showed a great tendency to destroy its own egg masses. Newly hatched B. camerunensis appeared to be destroyed to a greater extent by adult H. duryi than by adult B. camerunensis.     

Signalling pathways and the host-parasite relationship: putative targets for control interventions against schistosomiasis: signalling pathways and future anti-schistosome therapies

A better understanding of how schistosomes exploit host nutrients, neuro-endocrine hormones and signalling pathways for growth, development and maturation may provide new insights for improved interventions in the control of schistosomiasis. This paper describes recent advances in the identification and characterisation of schistosome tyrosine kinase and signalling pathways. It discusses the potential intervention value of insulin signalling, which may play an important role in glucose uptake and carbohydrate metabolism in schistosomes, providing the nutrients essential for parasite growth, development and, notably, female fecundity. Significant progress has also been made in the characterisation of other schistosome growth factor receptors, such as transforming growth factor beta receptor and epidermal growth factor receptor, and in our understanding of their roles in the host-parasite molecular dialogue and parasite development. The use of parasite signal transduction components as novel vaccine or drug targets may prove invaluable in prevention, treatment and control strategies to combat schistosomiasis.     

Evaluation of transient elastography in assessing liver fibrosis in patients with advanced schistosomiasis japonica

Schistosomiasis remains an important public health issue. The presence and extent of liver fibrosis are associated with disease progression and prognosis. The study is aimed at exploring the value of liver stiffness measurement (LSM) by transient elastography in assessing liver fibrosis in patients with advanced schistosomiasis japonica. Seventy-three patients were consecutively recruited for the purpose of this study. The correlation between noninvasive parameters and histological fibrosis stages was analyzed and an area under receiver operating characteristic curve (AUROC) was used to assess diagnostic efficacy. Our results demonstrated that there are significant differences between LSM values of patients with different stages of fibrosis (F1 vs. F2, F2 vs. F3 and F3 vs. F4, P < 0.01). The AUROC values of LSM in detecting significant fibrosis (F ≥ 2), advanced fibrosis (F ≥ 3) and cirrhosis (F = 4) were 0.96, 0.90, and 0.92 respectively. The optimal cut-off LSM values were 8.0 kPa, 9.5 kPa, and 18.0 kPa for significant fibrosis, advanced fibrosis and cirrhosis. Based on differences between AUROC values, LSM was proven to be superior to several serum models in detecting advanced fibrosis and cirrhosis. In conclusion, our study demonstrates that LSM is a reliable parameter for assessing risk of liver fibrosis in patients with advanced schistosomiasis japonica.