Ultraviolet disinfection of schistosome cercariae in water

Schistosomiasis is a tropical disease that is contracted by skin contact with water containing cercariae, larvae of the Schistosoma parasite. Providing safe water for contact activities (e.g. laundry, bathing) can help reduce transmission. UV disinfection is a widely used form of water treatment and its application in low-income settings is now becoming a reality through solar-powered units. This thesis examines the effectiveness of UV LED disinfection against schistosome cercariae for use in endemic regions. A systematic review revealed that low UV fluences (5–14mJ/cm2 at 253.7nm) were required to achieve a 1-log10 reduction in worm burden in animal hosts, but the direct effect on cercariae had not been quantified. There were insufficient published data to produce UV disinfection guidelines, therefore experiments were carried out to determine the fluence-response of Schistosoma mansoni cercariae at four peak wavelengths in the germicidal range (253.7nm, 255nm, 265nm, and 285nm). The morphology and motility of cercariae were studied under the microscope to determine if they were alive or dead. At the most effective wavelength (265nm) 247mJ/cm2 was required to achieve a 1-log10 reduction in alive cercariae but this reduced to 127mJ/cm2 and 99mJ/cm2 if samples were stored for 1–3 hours post-exposure, respectively. Fluences were much higher than those required to achieve the same reduction in worm burden in previous studies and further research was needed to investigate the potential disinfection mechanisms. Using an immunological assay to detect dimer formation it was found that DNA was damaged at lower fluences (10–50mJ/cm2, depending on wavelength), but this damage would not be expressed until cercariae penetrate the skin and transform into schistosomula. Further research is required to confirm if cercariae are non-viable at these fluences, until then a conservative approach based on the death of cercariae is appropriate. Due to the high fluences required to kill cercariae, UV disinfection alone is unlikely to be an energy- or cost-efficient water treatment method for combatting schistosomiasis, however improvements in efficiency combined with cheaper production costs may make UV LED technology more competitive in the near future.Open Acces

Ultraviolet sensitivity of WASH (water, sanitation, and hygiene) -related helminths: A systematic review.

BACKGROUND: Helminthiases are a group of disabling neglected tropical diseases that affect billions of people worldwide. Current control methods use preventative chemotherapy but reinfection is common and an inter-sectoral approach is required if elimination is to be achieved. Household and community scale water treatment can be used to provide a safe alternative water supply for contact activities, reducing exposure to WASH (water, sanitation, and hygiene) -related helminths. With the introduction of ultraviolet light emitting diodes (UV-C LEDs), ultraviolet (UV) disinfection could be a realistic option for water treatment in low-income regions in the near future, to provide safe alternative water supplies for drinking and contact activities such as handwashing, bathing, and laundry, but currently there is no guidance for the use of UV or solar disinfection against helminths. METHODOLOGY: A qualitative systematic review of existing literature was carried out to establish which WASH-related helminths are more susceptible to UV disinfection and identify gaps in research to inform future studies. The search included all species that can infect humans and can be transmitted through water or wastewater. Five online databases were searched and results were categorized based on the UV source: sunlight and solar simulators, UV-A and UV-B (long wavelength) sources, and UV-C (germicidal) sources. CONCLUSIONS: There has been very little research into the UV sensitivity of helminths; only 47 studies were included in this review and the majority were carried out before the standard protocol for UV disinfection experiments was published. Only 18 species were studied; however all species could be inactivated by UV light. Fluences required to achieve a 1-log inactivation ranged from 5 mJ/cm2 to over 800 mJ/cm2. Larval forms were generally more sensitive to UV light than species which remain as an egg in the environment. This review confirms that further research is required to produce detailed recommendations for household or community scale UV-C LED or solar disinfection (SODIS) of water for preventing helminthiases

The efficacy of soap against schistosome cercariae: A systematic review.

Background Schistosomiasis is a parasitic disease that is endemic in 78 countries and affects almost 240 million people worldwide. It has been acknowledged that an integrated approach that goes beyond drug treatment is needed to achieve control and eventual elimination of the disease. Improving hygiene has been encouraged by World Health Organisation, and one aspect of good hygiene is using soap during water-contact activities, such as bathing and doing laundry. This hygiene practice might directly reduce the skin exposure to cercariae at transmission sites. A systematic review was carried out to investigate the efficacy of soap against schistosome cercariae and to identify the knowledge gaps surrounding this topic. Methodology Six online databases were searched between 5th and 8th July of 2021. Records returned from these databases were screened to remove duplicates, and the remaining records were classified by reading titles, abstracts, and full texts to identify the included studies. The results were categorised into two groups based on two different protective mechanisms of soap (namely, damage to cercariae and protection of skin). Conclusions Limited research has been conducted on the efficacy of soap against schistosome cercariae and only 11 studies met the criteria to be included in this review. The review demonstrates that soap has the potential of protecting people against schistosome cercariae and there are two protective aspects: (1) soap affects cercariae adversely; (2) soap on the skin prevents cercariae from penetrating the skin, developing into adult worms and producing eggs. Both aspects of protection were influenced by many factors, but the differences in the reported experimental conditions, such as the cercarial endpoint measurement used and the cercaria numbers used per water sample, lead to low comparability between the previous studies. This review indicates that more evidence is needed to inform hygiene advice for people living in schistosomiasis endemic areas

The efficacy of soap against schistosome cercariae: A systematic review

BACKGROUND: Schistosomiasis is a parasitic disease that is endemic in 78 countries and affects almost 240 million people worldwide. It has been acknowledged that an integrated approach that goes beyond drug treatment is needed to achieve control and eventual elimination of the disease. Improving hygiene has been encouraged by World Health Organisation, and one aspect of good hygiene is using soap during water-contact activities, such as bathing and doing laundry. This hygiene practice might directly reduce the skin exposure to cercariae at transmission sites. A systematic review was carried out to investigate the efficacy of soap against schistosome cercariae and to identify the knowledge gaps surrounding this topic. METHODOLOGY: Six online databases were searched between 5th and 8th July of 2021. Records returned from these databases were screened to remove duplicates, and the remaining records were classified by reading titles, abstracts, and full texts to identify the included studies. The results were categorised into two groups based on two different protective mechanisms of soap (namely, damage to cercariae and protection of skin). CONCLUSIONS: Limited research has been conducted on the efficacy of soap against schistosome cercariae and only 11 studies met the criteria to be included in this review. The review demonstrates that soap has the potential of protecting people against schistosome cercariae and there are two protective aspects: (1) soap affects cercariae adversely; (2) soap on the skin prevents cercariae from penetrating the skin, developing into adult worms and producing eggs. Both aspects of protection were influenced by many factors, but the differences in the reported experimental conditions, such as the cercarial endpoint measurement used and the cercaria numbers used per water sample, lead to low comparability between the previous studies. This review indicates that more evidence is needed to inform hygiene advice for people living in schistosomiasis endemic areas

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

The efficacy of soap against schistosome cercariae: A systematic review. Search results

Classification process and codes, a list of excluded and included studies, experimental setups and extracted data for "The efficacy of soap against schistosome cercariae: A systematic review"

The reduction in worm burden (A) and egg load (B) under different soap treatment conditions [32,37].

The reduction in worm burden was calculated by comparing the average of worms recovered in the soap-treated group with that in the untreated group. The species in these two studies was S. mansoni.</p

Soap concentrations and exposure times required to achieve 100% cercaria mortality [34,37,38,42,44].

Data are generated from soaps which were tested in six studies. S. haematobium cercariae were used in the study by Lemma [42], while S. mansoni were used in the other five studies. Several assumptions were made as follows: (1) the study by Mimpfoundi & Dupouny stated that the cercariae survived more than 12 hours in some experimental conditions, and therefore it was assumed that cercariae only survived 12 hours in order to include this research [38]; (2) LC90 was used as the dose for 100% mortality in the study by Monkiedje, Anderson & Englande [34]; (3) only one individual compound existed in both soaps tested in the study by Pacheco & Jansen [44]; (4) in the studies by Mimpfoundi & Dupouny and Okwuosa & Osuala, the exposure time of “immediate cercaricidal effect/death” was assumed to be three seconds based on our estimation that at least three seconds are required to determine cercariae death [37,38]; (5) The concentrations in mg/L and mol/L were converted to ppm, assuming that the liquid density is 1 g/mL.</p

Summary of the soaps considered in the included papers.

Summary of the soaps considered in the included papers.</p

Sex differences in oncogenic mutational processes

Funder: Canadian Network for Research and Innovation in Machining Technology, Natural Sciences and Engineering Research Council of Canada (NSERC Canadian Network for Research and Innovation in Machining Technology); doi: https://doi.org/10.13039/501100002790Funder: Genome Canada (Génome Canada); doi: https://doi.org/10.13039/100008762Funder: Canada Foundation for Innovation (Fondation canadienne pour l'innovation); doi: https://doi.org/10.13039/501100000196Funder: Terry Fox Research Institute (Institut de Recherche Terry Fox); doi: https://doi.org/10.13039/501100004376Abstract: Sex differences have been observed in multiple facets of cancer epidemiology, treatment and biology, and in most cancers outside the sex organs. Efforts to link these clinical differences to specific molecular features have focused on somatic mutations within the coding regions of the genome. Here we report a pan-cancer analysis of sex differences in whole genomes of 1983 tumours of 28 subtypes as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium. We both confirm the results of exome studies, and also uncover previously undescribed sex differences. These include sex-biases in coding and non-coding cancer drivers, mutation prevalence and strikingly, in mutational signatures related to underlying mutational processes. These results underline the pervasiveness of molecular sex differences and strengthen the call for increased consideration of sex in molecular cancer research