Yellowtail kingfish (Seriola lalandi) is a fast-growing fish species. One of the challenges of farming yellowtail kingfish in recirculating aquaculture systems is their poor faeces integrity, also ...referred to as ‘diarrhoea-like’ faeces. Whether diarrhoea-like faeces occur under conditions when feeding on its natural feed items or are diet induced, is unclear. This study assessed the effect of feed type (pelleted vs. natural feed) on the faecal characteristics and faecal waste production of yellowtail kingfish. Three dietary treatments were studied over a 35-d experimental period: a pelleted diet based on marine ingredients (Marine; open formula); an experimental pelleted feed based on the ingredient composition of a commercial kingfish feed (Commercial Dummy, CD; closed formula); and a diet composed of four, individually fed raw (unprocessed) natural ingredients and commercial dummy pellets at a ratio of 1:1 on dry matter basis (Natural and Commercial Dummy, NCD). The NCD treatment was intended to clarify whether diarrhoea-like faeces are naturally occurring in yellowtail kingfish. Each dietary treatment was tested in four tanks, which were stocked with 27 yellowtail kingfish (mean initial weight 39 g). Fish were fed to apparent satiation twice daily for 1 h. For each tank nutrient digestibility and faecal characteristics were measured. The inclusion of natural ingredients reduced the faecal waste production (p < 0.001). Furthermore, the faeces integrity of yellowtail kingfish fed with natural ingredients was not poor (not diarrhoea-like). At the natural treatment, fish excreted faecal pellets and short strings, which were not observed at the other treatments. Faecal waste collected from fish receiving only pelleted feed was classified as diarrhoea-like. The highest faeces removal efficiency by settling was observed at the NCD treatment compared to the other treatments (p < 0.001). Consequently, the lowest amount of non-removed faeces per feed intake (p < 0.001) was observed at the NCD treatment (62.9 g OM/kg OM FI), followed by the Marine (101.1 g OM/kg OM FI) and Commercial Dummy treatment (111.7 g OM/kg OM FI). In conclusion, this study shows the potential of dietary interventions to alter the amount and integrity of faecal waste. This offers possibilities to reduce the total suspended solid load for yellowtail kingfish farming in recirculating aquaculture systems.
•Poor faeces integrity is not naturally occurring in yellowtail kingfish.•Pelleted diets introduce a poor faeces integrity in yellowtail kingfish.•Natural feed ingredient inclusion improved nutrient digestibility.•Dietary intervention can alter the integrity of faecal waste in yellowtail kingfish.
SARS-CoV-2, the virus that causes COVID-19, has been found in the faeces of infected patients in numerous studies. Stool may remain positive for SARS-CoV-2, even when the respiratory tract becomes ...negative, and the interaction with the gastrointestinal tract poses a series of questions about wastewater and its treatments. This review aims to understand the viral load of SARS-CoV-2 in faeces and sewage and its fate in wastewater treatment plants (WWTPs).
The viral load in the faeces of persons testing positive for SARS-CoV-2 was estimated at between 5·103 to 107.6 copies/mL, depending on the infection course. In the sewerage, faeces undergo dilution and viral load decreases considerably in the wastewater entering a WWTP with a range from 2 copies/100 mL to 3·103 copies/mL, depending on the level of the epidemic. Monitoring of SARS-CoV-2 in sewage, although no evidence of COVID-19 transmission has been found via this route, could be advantageously exploited as an early warning of outbreaks. Preliminary studies on WBE seem promising; but high uncertainty of viral loads in wastewater and faeces remains, and further research is needed.
The detection of SARS-CoV-2 in sewage, based on RNA sequences and RT-PCR, requires a shared approach on sample pre-treatment and on-site collection to ensure comparable results. The finding of viral RNA in stools does not imply that the virus is viable and infectious. Viability of CoVs such as SARS-CoV-2 decreases in wastewater - due to temperature, pH, solids, micropollutants - but high inactivation in WWTPs can be obtained only by using disinfection (free chlorine, UVC light). A reduction in the quantity of disinfectants can be obtained by implementing Membrane-Bioreactors with ultrafiltration to separate SARS-CoV-2 virions with a size of 60–140 nm. In sludge treatment, thermophilic digestion is effective, based on the general consensus that CoVs are highly sensitive to increased temperatures.
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•The route of SARS-CoV-2 from faeces to wastewater treatment plants is analysed.•Viral load in the faeces of positive people for SARS-CoV-2 is 5·103–107.6 copies/mL.•Viral load decreases from 2 copies/100 mL to 3·103 copies/mL when entering a WWTP.•For WBE high uncertainty of viral loads remains, and further research is needed.•CoVs inactivation in WWTPs is enhanced by tertiary treatments and disinfection.
Adherence to the guidelines of The International Organization for Standardization (ISO) for the isolation of Salmonella from faeces is important to laboratory personnel, researchers and ...epidemiologists to ensure effective diagnosis, maximal recovery and high sensitivity/specificity of laboratory tests. The aim of this study is to review the ISO guidelines for the detection of Salmonella from faeces using standards published by ISO and other internationally recognized bodies. The ISO 6579 of 2002 described the process for the detection of Salmonella in faeces. About 25g of faecal samples is collected, mixed together and specimen taken from different parts to ensure maximum recovery of the organism. Processes for the identification of the organism were prescribed by the standard. In the amendment made to ISO 6579 (Annex D) it was recommended that Modified Semisolid Rappaport Vasiliadis (MSRV) be used as selective enrichment medium. Further amendment made to this standard was in 2007 where clause 4 described non-selective pre-enrichment, selective enrichment, use of 2 selective solid media and biochemical tests as the 4 stages of the isolation of Salmonella in faeces. The amendment of ISO 6579 in 2017 combined the guidelines for the isolation of Salmonella species, S. Typhi/Paratyphi from milk/milk-products and faeces. It proposed the use of selenite cysteine broth in addition to Rappaport Vasiliadis (RVS) and Muller-Kauffmann Tetrathionate-Novobiocin (MkTTn) and BSA in addition to Xylose Lysine Deoxycholate (XLD) Agar for the isolation of S. typhi and paratyphi. It recommended the performance of methyl-red, Simmon-citrate, H2S, motility and urease biochemical tests, deleted Vogues Proskaer test while indole and β-Galactosidase (ONPG) tests were made optional. This standard has evolved over the years to ensure efficient recovery of Salmonella from faeces based on real-time result and feedback received by the organization from laboratories all over the world.
This study aimed to assess the molecular prevalence of mite-borne zoonotic pathogen O. tsutsugamushi in household rats of South India through nested polymerase chain reaction amplification of O. ...tsutsugamushi 47-kDa htrA gene and to determine the most suitable sample type for screening of O. tsutsugamushi in rats. Out of 85 rats trapped in Tamil Nadu, Karnataka, and Puducherry regions, 47 rats were found positive for the O. tsutsugamushi genome with prevalence of 55.29 %. Among different sample types screened, faecal samples exhibited the highest positivity rate, followed by liver, spleen, kidney, and blood samples. Agreement between faecal and spleen samples of rats for the presence of O. tsutsugamushi was the highest. Principal component analysis revealed a positive correlation between the spleen, liver, and faeces and a negative correlation between blood and faeces for the presence of O. tsutsugamushi genome. These findings underscore the varied distribution of O. tsutsugamushi among different samples and indicate that the faecal and liver samples of rats are an ideal choice of samples for epidemiological studies. This is the first study to report a high level of presence of O. tsutsugamushi in faecal samples of rats.
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•Molecular prevalence of Orientia tsutsugamushi in household rat population of South India was 55.29 %.•This is the first report identified the presence of O. tsutsugamushi genome in rat faecal samples with 54.55 % positivity.•Positive correlation in the distribution of O. tsutsugamushi was found between rat spleen, liver, and faecal samples.
Wastewater-based epidemiology (WBE) is one of the most promising approaches to effectively monitor the spread of COVID-19. The virus concentration in faeces and its temporal variations are essential ...information for WBE. While some clinical studies have reported SARS-CoV-2 concentrations in faeces, the value varies amongst patients and changes over time. The present study aimed to examine how the temporal variations in the concentration of virus in faeces affect the monitoring of disease incidence. We reanalysed the experimental findings of clinical studies to estimate the duration of virus shedding and the faecal virus concentration. Available experimental data as of 23 October 2020 were collected. The viral shedding kinetics was modelled, and the dynamic model was fitted to the collected data by a Bayesian framework. Using posterior distributions, the duration of viral shedding and the concentration of virus copies in faeces over time were computed. We estimated the median concentration of SARS-CoV-2 in faeces as 3.4 (95% CrI: 0.24–6.5) log copies per gram-faeces over the shedding period, and our model implied that the duration of viral shedding was 26.0 days (95% CrI: 21.7–34.9), given the current standard quantification limit (Ct = 40). With simulated incidences, our results also indicated that a one-week delay between symptom onset and wastewater sampling increased the estimation of incidence by a factor of 17.2 (i.e., 101.24 times higher). Our results demonstrated that the temporal variation in virus concentration in faeces affects microbial monitoring systems such as WBE. The present study also implied the need for adjusting the estimates of virus concentration in faeces by incorporating the kinetics of unobserved concentrations. The method used in this study is easily implemented in further simulations; therefore, the results of this study might contribute to enhancing disease surveillance and risk assessments that require quantities of virus to be excreted into the environment.
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•SARS-CoV-2 is excreted in faeces, but its time course has been understudied.•SARS-CoV-2 concentration in faeces re-analysed using a kinetic viral shedding model•The duration of viral shedding was estimated to be 20–32 days.•Median concentration was 2.6 log copies/g of faeces over the shedding period.•WBE needs to consider temporal variations in viral concentrations in faeces.
The sustainability of commercial aquaculture production depends critically on prioritizing fish welfare management. Besides monitoring welfare parameters such as fish behaviour and water quality, ...fish stress level can also provide a reliable measure of the welfare status of farmed fish. Cortisol and 5 of its metabolites (5β-THF, cortisone, 5β-DHE, 5β-THE, β-cortolone) were previously identified by the authors as suitable stress biomarkers of farmed Atlantic salmon. Based on this knowledge, the present study aimed to investigate the time-related dynamics of these metabolites in plasma, skin mucus, bile and faeces over a 72 h- period. The objective was to determine the optimal sampling time for each matrix and to understand the clearance pathway of these metabolites following stress. An experiment was carried out using a total of 90 Atlantic salmon with an average weight of 438 (±132) g. The average sea temperature was 6.9 °C during the experimental period. A control group of 10 fish was first collected before the remaining 80 fish were submitted to a stress of netting and subsequent relocation into two separate cages. From each of these two stress groups, 10 fish were sampled at 1 h, 2 h, 4 h, 6 h and 12 h, 24 h, 48 h, 72 h after the stress event respectively. The concentrations of cortisol and its metabolites were measured at each of the sampling timepoint. The results demonstrated that plasma cortisol metabolites reached the highest concentration 4 h after stress and remained elevated despite the slight decrease for the remaining timepoints. The peak level was observed at 12 h post-stress in skin mucus and 24 h in bile and faeces. The findings suggest that these timepoints are the optimal for sampling Atlantic salmon post-smolt following stressful events in acute stress studies. Furthermore, the results reveal that analysing cortisol and its metabolites, both in free and conjugated forms, rather than free cortisol provides greater flexibility as their concentrations are less affected by sampling procedure. This study confirms the appropriateness of skin mucus and faeces as less-invasive sample matrices for fish stress evaluation and provides a basis for further developing low invasive tools for monitoring the welfare of farmed salmonid.
•Measuring cortisol metabolite level is a reliable method for assessing fish stress.•Sampling time post-stress is dependent on the matrix used for analysis.•Skin mucus and faeces are low-invasive matrices for analysing fish stress response.
•UF is used as a pre-treatment to reduce membrane distillation fouling.•UF removes particles and colloids from blackwater but low MW fraction increases.•Whilst UF treated blackwater high in organics, ...flux and water quality is stable.•Without UF pre-treatment, severe fouling reduces flux, which reduces quickly.•With UF pre-treatment, permeate quality consistently meets treatment quality.
In this study, the pretreatment of concentrated blackwater using ultrafiltration (UF) was shown to improve the permeability, selectivity and robustness of membrane distillation (MD) for application to wastewater treatment. Concentrated blackwater comprises urine and faeces, with minimal flushwater added. The faecal contribution increased the soluble organic fraction and introduced coarse and colloidal particles into the urine, which increased resistance to filtration during dead-end UF. Ultrafiltration removed the particulate and colloidal fractions (MW > 500 kDa) from the blackwater, which permitted similar permeability and robustness for MD to that observed with urine (29.9 vs 25.9 kg m−2h−1), which comprises a lower colloidal organic concentration. Without UF pretreatment, a higher density organic layer formed on the MD surface (197 vs 70 gCODm−2) which reduced mass transfer, and transformed the contact angle from hydrophobic to hydrophilic (144.9°to49.8°), leading to pore wetting and a dissipation in product water quality due to breakthrough. In comparison, with UF pretreatment, MD delivered permeate water quality to standards satisfactory for discharge or reuse. This is particularly timely as the ISO standard for non-sewered sanitation has been adopted by several countries at a national level, and to date there are relatively few technologies to achieve the treatment standard. Membrane distillation provides a robust means for concentrated blackwater treatment, and since the energy required for separation is primarily heat, this advanced treatment can be delivered into areas with more fragile power networks.
•Membrane distillation configuration studied for water recovery from blackwater.•Selectivity altered by differences in vapour pressure and water flux.•Wetting by organics limited by smaller pore size ...but decreases mass transfer.•Organics fouling more severe for vacuum configuration.•Air gap provides more robust separation over temperature range studied.
Water recovery from concentrated blackwater has been studied using air gap (AGMD), direct contact (DCMD) and vacuum membrane distillation (VMD) to deliver decentralised sanitation. Whilst good water quality was achieved with each configuration, differences in the rejection of volatile compounds was observed. VMD exhibited the highest rejection of volatiles, specifically ammoniacal nitrogen, of all the configurations but fouling inhibited total flux. DCMD exhibited a temperature dependent volatile rejection which resulted in poor rejection at lower feed temperatures (≤40 °C). AGMD was identified as the most promising configuration for application within decentralised sanitation, since the rejection of volatiles was consistent over a range of operating temperatures with ammonia rejection directly related to solution pH. An increase in organic colloids and particles due to faecal contamination reduced COD removal due to the induction of wetting, but was shown to be offset by adoption of a smaller pore size (0.1 μm), and when complemented with upstream solid-liquid separation within a fully integrated system, will provide a robust sanitation solution. Importantly, this work has shown that AGMD can recover water from concentrated blackwater close to international discharge and reuse regulations in a single stage process; this is significant as blackwater consists of only urine and faeces, and is thus 40 times more concentrated than municipal sewage. It is proposed that the water quality produced reflects a step change to delivering safe sanitation, and is complemented by a simple method for heat recovery integration this is similarly advantageous for resource constrained environments common to decentralised sanitation solutions.
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