Blood Fluke Resistance: The larval stages of the blood fluke Schistosoma mansoni are disseminated via a replicative cycle in freshwater snails. When people come into contact with contaminated water, the larvae attach to and penetrate the skin. The resulting disease, bilharzia or schistosomiasis, afflicts approximately 67 million people in Africa and South America. Unfortunately, the parasite is showing resistance to one of the available therapeutic drugs, oxamniquine, which means that schistosome control relies on a single drug, praziquantel. Valentim et al. (p. 1385 , published online 21 November) analyzed the genetic and molecular basis of resistance to oxamniquine through a combination of genetic linkage mapping, genome sequencing, functional genomics analysis, and x-ray crystallography.

The Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) was funded in 2008 to conduct research that would support country schistosomiasis control programs. As schistosomiasis prevalence decreases in many places and elimination is increasingly within reach, a sensitive and specific test to detect infection with Schistosoma mansoni and Schistosoma haematobium has become a pressing need. After obtaining broad input, SCORE supported Leiden University Medical Center (LUMC) to modify the serum-based antigen assay for use with urine, simplify the assay, and improve its sensitivity. The urine assay eventually contributed to several of the larger SCORE studies. For example, in Zanzibar, we demonstrated that urine filtration, the standard parasite egg detection diagnostic test for S. haematobium, greatly underestimated prevalence in low-prevalence settings. In Burundi and Rwanda, the circulating anodic antigen (CAA) assay provided critical information about the limitations of the stool-based Kato–Katz parasite egg-detection assay for S. mansoni in low-prevalence settings. Other SCORE-supported CAA work demonstrated that frozen, banked urine specimens yielded similar results to fresh ones; pooling of specimens may be a useful, cost-effective approach for surveillance in some settings; and the assay can be performed in local laboratories equipped with adequate centrifuge capacity. These improvements in the assay continue to be of use to researchers around the world. However, additional work will be needed if widespread dissemination of the CAA assay is to occur, for example, by building capacity in places besides LUMC and commercialization of the assay. Here, we review the evolution of the CAA assay format during the SCORE period with emphasis on urine-based applications.

Background: Schistosoma mansoni is a blood fluke that infects approximately 90 million people. The complete life cycle of this parasite can be maintained in the laboratory, making this one of the few experimentally tractable human helminth infections, and a rich literature reveals heritable variation in important biomedical traits such as virulence, host-specificity, transmission and drug resistance. However, there is a current lack of tools needed to study S. mansoni's molecular, quantitative, and population genetics. Our goal was to construct a genetic linkage map for S. mansoni, and thus provide a new resource that will help stimulate research on this neglected pathogen. Results: We genotyped grandparents, parents and 88 progeny to construct a 5.6 cM linkage map containing 243 microsatellites positioned on 203 of the largest scaffolds in the genome sequence. The map allows 70% of the estimated 300 Mb genome to be ordered on chromosomes, and highlights where scaffolds have been incorrectly assembled. The markers fall into eight main linkage groups, consistent with seven pairs of autosomes and one pair of sex chromosomes, and we were able to anchor linkage groups to chromosomes using fluorescent in situ hybridization. The genome measures 1,228.6 cM. Marker segregation reveals higher female recombination, confirms ZW inheritance patterns, and identifies recombination hotspots and regions of segregation distortion. Conclusions: The genetic linkage map presented here is the first for S. mansoni and the first for a species in the phylum Platyhelminthes. The map provides the critical tool necessary for quantitative genetic analysis, aids genome assembly, and furnishes a framework for comparative flatworm genomics and field-based molecular epidemiological studies.

Background: MicroRNAs (miRNAs) constitute a class of single-stranded RNAs which play a crucial role in regulating development and controlling gene expression by targeting mRNAs and triggering either translation repression or messenger RNA (mRNA) degradation. miRNAs are widespread in eukaryotes and to date over 14,000 miRNAs have been identified by computational and experimental approaches. Several miRNAs are highly conserved across species. In Schistosoma, the full set of miRNAs and their expression patterns during development remain poorly understood. Here we report on the development and implementation of a homology-based detection strategy to search for miRNA genes in Schistosoma mansoni. In addition, we report results on the experimental detection of miRNAs by means of cDNA cloning and sequencing of size-fractionated RNA samples. Results: Homology search using the high-throughput pipeline was performed with all known miRNAs in miRBase. A total of 6,211 mature miRNAs were used as reference sequences and 110 unique S. mansoni sequences were returned by BLASTn analysis. The existing mature miRNAs that produced these hits are reported, as well as the locations of the homologous sequences in the S. mansoni genome. All BLAST hits aligned with at least 95% of the miRNA sequence, resulting in alignment lengths of 19-24 nt. Following several filtering steps, 15 potential miRNA candidates were identified using this approach. By sequencing small RNA cDNA libraries from adult worm pairs, we identified 211 novel miRNA candidates in the S. mansoni genome. Northern blot analysis was used to detect the expression of the 30 most frequent sequenced miRNAs and to compare the expression level of these miRNAs between the lung stage schistosomula and adult worm stages. Expression of 11 novel miRNAs was confirmed by northern blot analysis and some presented a stage-regulated expression pattern. Three miRNAs previously identified from S. japonicum were also present in S. mansoni. Conclusion: Evidence for the presence of miRNAs in S. mansoni is presented. The number of miRNAs detected by homology-based computational methods in S. mansoni is limited due to the lack of close relatives in the miRNA repository. In spite of this, the computational approach described here can likely be applied to the identification of pre-miRNA hairpins in other organisms. Construction and analysis of a small RNA library led to the experimental identification of 14 novel miRNAs from S. mansoni through a combination of molecular cloning, DNA sequencing and expression studies. Our results significantly expand the set of known miRNAs in multicellular parasites and provide a basis for understanding the structural and functional evolution of miRNAs in these metazoan parasites.