Point-of-Use Removal of Cryptosporidium parvum from Water: Independent Effects of Disinfection by Silver Nanoparticles and Silver Ions and by Physical Filtration in Ceramic Porous Media

Exploring the effects of cellulose sources on silver reduction and the bacterial removal of nanocellulose-based hydrogel beads

With water access challenged, there is a need to develop efficient and sustainable alternatives for water purification. Here, cellulose nanofibrils (CNFs) isolated from three source materials (softwood, soybean hulls and oat straw) were compared for the generation of hydrogels beads, and compared as support and reducing agent for silver nanoparticles formation. The silver-functionalized hydrogel beads (Ag-CNFs) were characterized, and the surface energy and specific surface area were evaluated. Antimicrobial testing was conducted to assess the efficacy of the Ag-CNFs against E. coli. The results showed that the Ag-CNFs had a higher specific surface area and lower surface energy compared with unmodified CNFs. Softwood-based Ag-CNFs exhibited the highest silver content and specific surface area, while the soybean hull based showed the highest hydrophobic character. The silver-functionalized soybean hull beads (Ag-sbCNF) showed the highest efficacy in reducing the growth of bacteria. Overall, this study highlights the potential of silver-functionalized CNFs hydrogel beads as a promising environmentally friendly and sustainable material for water filtration and disinfection. The findings also suggest that lower surface energy of the Ag-CNFs play an important role in their antimicrobial effect on tested water by enabling shorter retention, providing useful insights into the design of future water filtration materials.

Nanoparticle Lysis of Cryptosporidium Oocysts

The extraction of DNA from Cryptosporidium oocysts is challenging due to the robust oocyst wall. Nanoparticles have been applied to disinfect Cryptosporidium oocysts; here, we demonstrate the utilisation of nanoparticles to disrupt the oocyst wall to enable sporozoite lysis and detection via PCR. Both silver and zinc oxide nanoparticles are investigated under different conditions and compared to existing techniques. Zinc oxide nanoparticles are shown to be as effective as freeze-thaw methods, suggesting that a nanoparticle lysis approach offers a viable alternative to existing methods.

Impact of pathogenic bacterial communities present in wastewater on aquatic organisms: Application of nanomaterials for the removal of these pathogens

Contaminated wastewater (WW) can cause severe hazards to numerous delicate ecosystems and associated life forms. In addition, human health is negatively impacted by the presence of microorganisms in water. Multiple pathogenic microorganisms in contaminated water, including bacteria, fungi, yeast, and viruses, are vectors for several contagious diseases. To avoid the negative impact of these pathogens, WW must be free from pathogens before being released into stream water or used for other reasons. In this review article, we have focused on pathogenic bacteria in WW and summarized the impact of the different types of pathogenic bacteria on marine organisms. Moreover, we presented a variety of physical and chemical techniques that have been developed to provide a pathogen-free aquatic environment. Among the techniques, membrane-based techniques for trapping hazardous biological contaminants are gaining popularity around the world. Besides, novel and recent advancements in nanotechnological science and engineering suggest that many waterborne pathogens could be inactivated using nano catalysts, bioactive nanoparticles, nanostructured catalytic membranes, nanosized photocatalytic structures, and electrospun nanofibers and processes have been thoroughly examined.

Immunotoxicity of metal and metal oxide nanoparticles: from toxic mechanisms to metabolism and outcomes

The influence of metal and metal oxide nanomaterials on various fields since their discovery has been remarkable. They have unique properties, and therefore, have been employed in specific applications, including biomedicine. However, their potential health risks cannot be ignored. Several studies have shown that exposure to metal and metal oxide nanoparticles can lead to immunotoxicity. Different types of metals and metal oxide nanoparticles may have a negative impact on the immune system through various mechanisms, such as inflammation, oxidative stress, autophagy, and apoptosis. As an essential factor in determining the function and fate of immune cells, immunometabolism may also be an essential target for these nanoparticles to exert immunotoxic effects in vivo. In addition, the biodegradation and metabolic outcomes of metal and metal oxide nanoparticles are also important considerations in assessing their immunotoxic effects. Herein, we focus on the cellular mechanism of the immunotoxic effects and toxic effects of different types of metal and metal oxide nanoparticles, as well as the metabolism and outcomes of these nanoparticles in vivo. Also, we discuss the relationship between the possible regulatory effect of nanoparticles on immunometabolism and their immunotoxic effects. Finally, we present perspectives on the future research and development direction of metal and metal oxide nanomaterials to promote scientific research on the health risks of nanomaterials and reduce their adverse effects on human health.

Nanoscale zero-valent iron/silver@activated carbon-reduced graphene oxide: Efficient removal of trihalomethanes from drinking water

AC-supported nanoscale zero-valent iron composites (nZVI/AC) exhibit significant environmental implications for trihalomethanes (THMs)-contaminated water remediation. To improve the adsorption and degradation capability of AC, herein, a composite (nZVI/Ag@AC-RGO) consisting of AC, reduced graphene oxide (RGO), nanoscale zero-valent iron (nZVI), and silver (Ag) was synthesized and characterized using several techniques, such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, N₂ adsorption-desorption isotherms, and X-ray photoelectron spectroscopy (XPS). The analysis of textural and morphological structures showed that a tightly-attached RGO film, amorphous iron, and weak crystal silver nanoparticles with a size of 20-30 nm were evenly immobilized on the support. Specific surface area increased by 19.12% after supporting RGO, while it decreased after supporting nZVI and Ag due to the partial blockage of micropores. The Fe surface was concurrently coated by iron oxides (Fe₂O₃, FeOOH) and Ag. THMs were eliminated through multilayer reaction processes. The values of the adsorption constant (K_F) of chloroform (CHCl₃), dichlorobromoethane (CHBrCl₂), dibromochloroethane (CHBr₂Cl), and tribromomethane (CHBr₃) adsorbed by nZVI/Ag@AC-RGO increased by 34.4, 33.7, 81.6, and 67.3%, respectively, compared to pristine AC. THMs with more Br atoms exhibited better removal efficiency and adsorption capacity, along with a higher oxidation degree of the Fe surface. CHBrCl₂ and CHBr₂Cl mainly decomposed into chloromethane (CH₃Cl) and dichloromethane (CH₂Cl₂), and CHBr₃ and CHCl₃ primarily degraded into dibromomethane (CH₂Br₂) and CH₂Cl₂, respectively, along with generating Cl^- and Br^-. Conclusively, THMs-contaminated water could be remediated by coupling AC pre-enrichment and the reactivity of nZVI/Ag.

Photocatalytic disinfection for point-of-use water treatment using Ti3+ self-doping TiO2 nanoparticle decorated ceramic disk filter

The challenge from pathogenic infections still threatens the health and life of people in developing areas. An efficient, low-cost, and abundant-resource disinfection method is desired for supplying safe drinking water. This study aims to develop a novel Ti³⁺ doping TiO₂ nanoparticle decorated ceramic disk filter (Ti³⁺/TiO₂@CDF) for point-of-use (POU) disinfection of drinking water. The production of Ti³⁺/TiO₂@CDF was optimized to maximize disinfection efficiency and flow rate. Under optimal conditions, the log reduction value (LRV) could reach up to 7.18 and the flaw rate was 108 mL/h. The influences of environmental factors were also investigated. Natural or slightly alkaline conditions, low turbidity, and low concentration of humic acid were favorable for the disinfection of Ti³⁺/TiO₂@CDF, while co-existing HCO₃^- ions and diatomic cations (Ca²⁺ and Mg²⁺) exhibited the opposite effect. Furthermore, the practicability and stability of Ti³⁺/TiO₂@CDF was demonstrated. Ti³⁺/TiO₂@CDF showed high disinfection efficiency for E. coli and S. aureus under a range of concentrations. Long-term experiment indicated that Ti³⁺/TiO₂@CDF was stable. The underlying disinfection mechanisms were investigated and concluded as the combination of retention, adsorption, and photocatalytic disinfection. The developed Ti³⁺/TiO₂@CDF can provide an effective and reliable disinfection tool for POU water treatment in remote area.

Field and Laboratory Assessment of a New Electrolytic Point-of-Use Water Treatment Technology

This research creates and implements a new electrolytic point-of-use water treatment (POUWT) device. Device development began by applying two voltages common to commercially available batteries to an apparatus with either two silver or copper wires submerged into synthetic groundwater. The effects of wire diameter, ionic strength of groundwater, and other POUWT parameters on metallic ion release were analyzed. We determined that the silver wire apparatus need only to be run for 2 min at 9 V to yield the target 50 µg/L concentration for water treatment. The 50 µg/L silver yielded up to a 5-log reduction in E. coli bacteria. The copper wire apparatus was excluded in prototype fabrication because it required 62 min to release the target 500 µg/L for disinfection when nine volts were applied to the system and was less effective in disinfection than silver wires. The electrolytic prototype was evaluated in 20 households in Limpopo, South Africa, over a four-week period. The device achieved a 2-log reduction in total coliform bacteria in household drinking water, which is comparable to the field performance of other POUWT devices in low-resource settings. The device also consistently released enough silver sufficient for disinfection while remaining below the WHO drinking water guideline.

Chitosan Coagulation Pretreatment to Enhance Ceramic Water Filtration for Household Water Treatment

Viruses are major contributors to the annual 1.3 million deaths associated with the global burden of diarrheal disease morbidity and mortality. While household-level water treatment technologies reduce diarrheal illness, the majority of filtration technologies are ineffective in removing viruses due to their small size relative to filter pore size. In order to meet the WHO health-based tolerable risk target of 10⁻⁶ Disability Adjusted Life Years per person per year, a drinking water filter must achieve a 5 Log₁₀ virus reduction. Ceramic pot water filters manufactured in developing countries typically achieve less than 1 Log₁₀ virus reductions. In order to overcome the shortfall in virus removal efficiency in household water treatment filtration, we (1) evaluated the capacity of chitosan acetate and chitosan lactate, as a cationic coagulant pretreatment combined with ceramic water filtration to remove lab cultured and sewage derived viruses and bacteria in drinking waters, (2) optimized treatment conditions in waters of varying quality and (3) evaluated long-term continuous treatment over a 10-week experiment in surface waters. For each test condition, bacteria and virus concentrations were enumerated by culture methods for influent, controls, and treated effluent after chitosan pretreatment and ceramic water filtration. A > 5 Log₁₀ reduction was achieved in treated effluent for E.coli, C. perfringens, sewage derived E. coli and total coliforms, MS2 coliphage, Qβ coliphage, ΦX174 coliphage, and sewage derived F+ and somatic coliphages.

Modeling of Hydraulic Performance in Disks and Full-Scale Ceramic Water Filters

Ceramic filters for household water treatment can improve water quality and reduce diarrheal disease. Hydraulic performance is critical for quality control and user acceptability, and hydraulic models have previously been developed and tested with experimental full-scale filters. As filters are cumbersome, there is interest in using disks instead of filters in laboratory efficacy studies. To assess the validity of disk use, we collected experimental volume from three sets of full-scale frustum-shaped filters and matching disks with different burn-out material sieve sizes and firing temperatures. We compared the experimental and fitted data by calibrating hydraulic conductivities from filters and disks. Hydraulic conductivities increased with larger burn-out material and higher firing temperatures but were comparable between filters and disks (2.00-6.15 × 10^-7m·s^-1 and 2.69-6.32 × 10^-7m·s^-1, respectively). We found that previously described hydraulic models successfully predicted cumulative volumes for filters and disks with rRMSE ranging from 2.1 to 9.6% (filters) and 3.4 to 4.7% (disks). The error increased slightly (rRMSE: 5.0-15%) when predicting hydraulic parameters for filters from the hydraulic conductivity of disks. Our results validate a method to predict full-scale filter hydraulic performance from hydraulic conductivity of disks and can be used to simplify and increase testing capacity, resulting in higher quality, more acceptable filters that improve household drinking water quality.

Silver Nanoparticle-Based Nanocomposites for Combating Infectious Pathogens: Recent Advances and Future Prospects

Silver nanoparticles (Ag NPs) and their nanocomposites with polymers are potent agents for antibacterial and disinfectant applications. The structural parameters of Ag-NPs, such as size, shape, and surface area, are very critical for developing appropriate formulations for the targeted applications. The impact of these factors on the performance of Ag NPs is analyzed. Ag NPs with a broad spectrum of antibacterial activities have already found applications in wound and burn dressing, food preservation, agricultural ponds, treatment for infected areas, coatings, water treatment, and other biomedical applications. Ag NPs are quite useful against antibiotic-resistant bacteria, but their level of toxicity needs careful investigation as their toxicity could be very harmful to human health and the environment. This review discusses the challenges and prospects of various Ag NPs and their composites. The review will enrich the knowledge about the efficiency and mechanism of various Ag nanoparticle-based antibacterial agents.

Development of Ceramic Water Filter Clay Selection Criteria

Ceramic water filters (CWFs) are point-of-use drinking water treatment systems that are manufactured and used in under-served communities around the world. The clayey material (CM) used to manufacture CWFs is a locally sourced mixture of clay, sand, slit and amorphous material (usually dug near the CWF factory). CM varies in composition and purity depending on the geographical location and geological setting. In this study, a set of 13 CM samples collected from around the world were analyzed using grain size analysis, as well as liquid and plastic limit tests. Mineralogical composition was determined using X-ray diffraction. A selection of three CM samples (Guatemala, Canada, and Guinea Bissau) with a range of compositions were used to study biofilm growth on CM before and after firing. Biofilm coverage was studied on CM (before firing) and CWF material (after firing) using Pseudomonas fluorescens Migula. The average biofilm coverages for Guatemala, Canada, and Guinea Bissau CM were 20.03 ± 2.80%, 19.28 ± 0.91%, and 9.88 ± 4.02%, respectively. The average biofilm formation coverages for Guatemala, Canada, and Guinea Bissau CWF were 13.08 ± 1.74%, 10.36 ± 3.41%, and 8.66 ± 0.13%, respectively. The results presented here suggest that CM can be manipulated to manufacture better performing CWFs by engineering the soil characteristics, such as grain size, liquid and plastic limits, and mineralogy. This could improve the durability and biofilm resistance of CWFs.

Adaptive changes induced by noble-metal nanostructures in vitro and in vivo

The unique features of noble-metal nanostructures (NMNs) are leading to unprecedented expansion of research and exploration of their application in therapeutics, diagnostics and bioimaging fields. With the ever-growing applications of NMNs, both therapeutic and environmental NMNs are likely to be exposed to tissues and organs, requiring careful studies towards their biological effects in vitro and in vivo. Upon NMNs exposure, tissues and cells may undergo a series of adaptive changes both in morphology and function. At the cellular level, the accumulation of NMNs in various subcellular organelles including lysosomes, endoplasmic reticulum, Golgi apparatus, mitochondria, and nucleus may interfere with their functions, causing changes in a variety of cellular functions, such as digestion, protein synthesis and secretion, energy metabolism, mitochondrial respiration, and proliferation. In animals, retention of NMNs in metabolic-, respiratory-, immune-related, and other organs can trigger significant physiological and pathological changes to these organs and influence their functions. Exploring how NMNs interact with tissues and cells and the underlying mechanisms are of vital importance for their future applications. Here, we illustrate the characteristics of NMNs-induced adaptive changes both in vitro and in vivo. Potential strategies in the design of NMNs are also discussed to take advantage of beneficial adaptive changes and avoid unfavorable changes for the proper implementation of these nanoplatforms.

Current Trends in the Application of Nanomaterials for the Removal of Emerging Micropollutants and Pathogens from Water

Water resources contamination has a worldwide impact and is a cause of global concern. The need for provision of clean water is becoming more and more demanding. Nanotechnology may support effective strategies for the treatment, use and reuse of water and the development of next-generation water supply systems. The excellent properties and effectiveness of nanomaterials make them particularly suitable for water/wastewater treatment. This review provides a comprehensive overview of the main categories of nanomaterials used in catalytic processes (carbon nanotubes/graphitic carbon nitride (CNT/g-C₃N₄) composites/graphene-based composites, metal oxides and composites, metal–organic framework and commercially available nanomaterials). These materials have found application in the removal of different categories of pollutants, including pharmaceutically active compounds, personal care products, organic micropollutants, as well as for the disinfection of bacterial, viral and protozoa microbial targets, in water and wastewater matrices. Apart from reviewing the characteristics and efficacy of the aforementioned nanoengineered materials for the removal of different pollutants, we have also recorded performance limitations issues (e.g., toxicity, operating conditions and reuse) for their practical application in water and wastewater treatment on large scale. Research efforts and continuous production are expected to support the development of eco-friendly, economic and efficient nanomaterials for real life applications in the near future.

Nanomaterials for removal of waterborne pathogens

As the nanotechnological applications have taken over in different fields, their applications for water and wastewater treatment is also surfacing as a fast-developing and very promising area. Recent advancements in nanotechnological science and engineering advise that many of the waterborne pathogens could be culminated or debilitated using nanobiosorbents, nanocatalysts, bioactive nanoparticles, nanostructured catalytic membranes, nanobioreactors, nanoparticle-enhanced filtration among other products, and processes resulting from the development of nanotechnology. A detailed insight has been provided for advanced techniques such as photochemical (photocatalytic and advanced oxidation processes) applications of metal oxide nanoparticles, nanomembrane technology, bioinspired nanomaterials, and nanotechnological innovations (nano-Ag, fullerenes, nanotubes, and molecularly imprinted polymers, etc.), which prove to be highly potential as well as promising and cost-effective. However, there are still some shortcomings and challenges that must be overcome which will be looked upon in this chapter.

Silver nanoparticles as a therapeutic agent in experimental cyclosporiasis

Cyclosporiasis is an emerging worldwide infection caused by an obligate intracellular protozoan parasite, Cyclospora cayetanensis. In immunocompetent patients, it is mainly manifested by self-limited diarrhea, which is persistent and may be fatal in immunocompromised patients. The standard treatment for cyclosporiasis is a combination of two antibiotics, trimethoprim and sulfamethoxazole. Gastrointestinal, haematologic and renal side effects were reported with this combination. Moreover, sulfa allergy, foetal anomalies and recurrence were recorded with no alternative drug treatment option. In this study, silver nanoparticles were chemically synthesized to be evaluated for the first time for their anti-cyclospora effects in both immunocompetent and immunosuppressed experimental mice in comparison to the standard treatment. The effect of silver nanoparticles was assessed through studying stool oocyst load, oocyst viability, ultrastructural changes in oocysts, and estimation of serum gamma interferon. Toxic effect of the therapeutic agents was evaluated by measuring liver enzymes, urea and creatinine in mouse sera. Results showed that silver nanoparticles had promising anti-cyclospora potentials. The animals that received these nanoparticles showed a statistically significant decrease in the oocyst burden and number of viable oocysts in stool and a statistically significant increase in serum gamma interferon in comparison to the corresponding group receiving the standard treatment and to the infected non-treated control group. Scanning electron microscopic examination revealed mutilated oocysts with irregularities, poring and perforations. Biochemical results showed no evidence of toxicity of silver nanoparticles, as the sera of the mice showed a statistically non-significant decrease in liver enzymes in immunocompetent subgroups, and a statistically significant decrease in immunosuppressed subgroups. Furthermore, a statistically non-significant decrease in urea and creatinine was recorded in all subgroups. Thus, silver nanoparticles proved their effectiveness against Cyclospora infection, and this will draw the attention to its use as an alternative to the standard therapy.

Inhibitory activity of chitosan nanoparticles against Cryptosporidium parvum oocysts

Cryptosporidium is a ubiquitous harsh protozoan parasite that resists many disinfectants. It remains viable and infective for a long time in water and food causing global outbreaks. Chitosan (the deacetylated chitin molecule) was used in its nanosuspension form to evaluate its effect against Cryptosporidium parvum. The experiments were performed in vitro in serial concentrations and confirmed in mice in vivo infectivity assay. Chitosan nanoparticles (Cs NPs) were toxic to Cryptosporidium oocysts. The effect appeared to decrease the number of Cryptosporidium oocysts and altered their content. The destruction rate of oocysts was dependent on the dose of chitosan and the time of exposure (P < 0.05). Higher doses of Cs NPs over a prolonged period exhibited a significantly higher destruction rate. Using staining and light microscopy, remarkable destructive changes were observed in the oocysts' morphology. The minimal lethal dose for > 90% of oocysts was 3000 μg/ml, no mice infections in vivo were observed. The results in this study elucidate Cs NPs as an effective anti-cryptosporidial agent.

Silver nanoparticles as an effective disinfectant: A review

The paradigm modifications in the metallic crystals from bulky to micro-size to nano-scale have resulted in excellent and amazing properties; which have been the remarkable interests in a wider range of applications. Particularly, Ag NPs have much attention owing to their distinctive optical, chemical, electrical and catalytic properties that can be tuned with surface nature, size, shapes, etc. and hence these crystals have been used in various fields such as catalysis, sensor, electronic components, antimicrobial agents in the health industry etc. Among them, Ag NPs based disinfectants have paid attention due to the practical applications in our daily life. Therefore the Ag NPs have been used in different sectors such as silver-based air/water filters, textile, animal husbandry, biomedical and food packaging etc. In this review, the Ag NPs as a disinfectant in different sectors have been included in detail.

Advancing performance evaluation standards for household water treatment technologies

Diarrheal illnesses and fatalities continue to be major issues in many regions throughout the world. Household water treatment (HWT) technologies (including both point-of-use (POU) and point-of-entry (POE) treatment solutions) have been shown as able to deliver safe water in many low-income communities. However, as shown herein, there are important inconsistencies in protocols employed for validating performance of HWTs. The WHO does not stipulate influent concentration as a parameter that could influence removal efficacy, nor does it indicate an influent concentration range that should be used during technology evaluations. A correlation between influent concentration and removal is evidenced herein (R² = 0.88) with higher influent concentrations resulting in higher log-removal values (LRVs). The absence of a recommended standard influent concentration of bacteria (as well as for viruses and protozoa) could have negative consequences in intervention efforts. Recommendations are provided that regulatory bodies should specify an influent concentration range for testing and verification of HWT technologies.

Prussian blue-encapsulated Fe3O4 nanoparticles for reusable photothermal sterilization of water

Waterborne health issues continue to grow despite the large number of available solutions. Current sterilization techniques to fight with waterborne diseases struggle to meet the demands on cost, efficiency and reach. Effective alternatives are pressingly required. Here we introduce Prussian blue coated ferroferric oxide (Fe₃O₄@PB) composites for water sterilization. The composites exhibit superior photothermal inactivation of bacteria under solar-light irradiation, with nearly complete inactivation of bacterial cells in only 15 min. Even for the mixed bacteria in authentic water matrices, the composites show excellent bacterial inactivation performance. Moreover, the highly magnetized iron core of the Fe₃O₄@PB enables magnetic separation and recycling. Multiple cycle runs reveal that Fe₃O₄@PB composites have exceptional stability and reusability. This work demonstrates a scalable, low-cost, high-efficiency and reusable sterilization method to improve water quality and safety.

A repertoire of biomedical applications of noble metal nanoparticles

The emerging properties of noble metal nanoparticles are attracting huge interest from the translational scientific community. In this feature article, we highlight recent advances in the adaptation of noble metal nanomaterials and their biomedical applications in therapeutics, diagnostics and sensing.

A Randomized Controlled Trial to Assess the Impact of Ceramic Water Filters on Prevention of Diarrhea and Cryptosporidiosis in Infants and Young Children-Western Kenya, 2013

Cryptosporidium is a leading cause of diarrhea among Kenyan infants. Ceramic water filters (CWFs) are used for household water treatment. We assessed the impact of CWFs on diarrhea, cryptosporidiosis prevention, and water quality in rural western Kenya. A randomized, controlled intervention trial was conducted in 240 households with infants 4-10 months old. Twenty-six weekly household surveys assessed infant diarrhea and health facility visits. Stool specimens from infants with diarrhea were examined for Cryptosporidium. Source water, filtered water, and filter retentate were tested for Cryptosporidium and/or microbial indicators. To estimate the effect of CWFs on health outcomes, logistic regression models using generalized estimating equations were performed; odds ratios (ORs) and 95% confidence intervals (CIs) are reported. Households reported using surface water (36%), public taps (29%), or rainwater (17%) as their primary drinking water sources, with no differences in treatment groups. Intervention households reported less diarrhea (7.6% versus 8.9%; OR: 0.86 [0.64-1.16]) and significantly fewer health facility visits for diarrhea (1.0% versus 1.9%; OR: 0.50 [0.30-0.83]). In total, 15% of intervention and 12% of control stools yielded Cryptosporidium (P = 0.26). Escherichia coli was detected in 93% of source water samples; 71% of filtered water samples met World Health Organization recommendations of < 1 E. coli/100 mL. Cryptosporidium was not detected in source water and was detected in just 2% of filter rinses following passage of large volumes of source water. Water quality was improved among CWF users; however, the short study duration and small sample size limited our ability to observe reductions in cryptosporidiosis.

Pathogens transmitted in animal feces in low- and middle-income countries

Animals found in close proximity to humans in low-and middle-income countries (LMICs) harbor many pathogens capable of infecting humans, transmissible via their feces. Contact with animal feces poses a currently unquantified-though likely substantial-risk to human health. In LMIC settings, human exposure to animal feces may explain some of the limited success of recent water, sanitation, and hygiene interventions that have focused on limiting exposure to human excreta, with less attention to containing animal feces. We conducted a review to identify pathogens that may substantially contribute to the global burden of disease in humans through their spread in animal feces in the domestic environment in LMICs. Of the 65 potentially pathogenic organisms considered, 15 were deemed relevant, based on burden of disease and potential for zoonotic transmission. Of these, five were considered of highest concern based on a substantial burden of disease for which transmission in animal feces is potentially important: Campylobacter, non-typhoidal Salmonella (NTS), Lassa virus, Cryptosporidium, and Toxoplasma gondii. Most of these have a wide range of animal hosts, except Lassa virus, which is spread through the feces of rats indigenous to sub-Saharan Africa. Combined, these five pathogens cause close to one million deaths annually. More than half of these deaths are attributed to invasive NTS. We do not estimate an overall burden of disease from improperly managed animal feces in LMICs, because it is unknown what proportion of illnesses caused by these pathogens can be attributed to contact with animal feces. Typical water quantity, water quality, and handwashing interventions promoted in public health and development address transmission routes for both human and animal feces; however, sanitation interventions typically focus on containing human waste, often neglecting the residual burden of disease from pathogens transmitted via animal feces. This review compiles evidence on which pathogens may contribute to the burden of disease through transmission in animal feces; these data will help prioritize intervention types and regions that could most benefit from interventions aimed at reducing human contact with animal feces.

A novel gravity-driven nanofibrous membrane for point-of-use water disinfection: polydopamine-induced in situ silver incorporation

We report a facile method for preparing silver-loaded membranes for point-of-use disinfection and disaster relief applications. A bio-inspired material, polydopamine, was coated onto a highly porous nanofibrous polyacrylonitrile substrate. We then take advantage of the redox properties of polydopamine to form silver nanoparticles in situ. These nanoparticles were uniformly distributed on the surface of nanofibers with no apparent agglomeration at a silver loading up to 4.36 wt.% (cPAN-Ag1.5). The silver-incorporated membrane cPAN-Ag1.5 achieved a high pure water flux of 130 Lm⁻² h⁻¹ at 10-cm water head, demonstrating the feasibility of energy-efficient gravity-driven filtration and eliminating the need for electrical power. The strong anti-bacterial activity and high physical rejection of the membrane led to an excellent disinfection power, with no viable bacterial cells detected in its permeate water. The membrane exhibited >7 log reduction for E. coli and >6 log reduction for B. subtilis. The strategy reported here provides an efficient and green route to synthesize point-of-use membranes. Combining their excellent permeability and disinfection effectiveness, these membranes offer an ideal solution to water supply in disaster-affected areas.