Inactivation of Ascaris suum in a biodrying compost system

Inactivation of Ascaris Eggs in Human Fecal Material Through In Situ Production of Carboxylic Acids

Discovering new ways to inactivate pathogens in human waste is critical for the improvement of worldwide access to sanitation and for the reduction of the environmental impact of conventional waste treatment processes. Here, we utilized the carboxylate platform and chain elongation to produce n-butyric acid and n-caproic acid via the anaerobic fermentation of human fecal material. Then, we inactivated Ascaris eggs through exposure to these carboxylic acids. Using batch experiments with human fecal material as substrate, we accumulated n-butyric acid and n-caproic acid at total concentrations (uncharged acid plus conjugate base) of 257 and 27.1 mM, respectively. We then showed that carboxylic acids at these concentrations inactivated Ascaris eggs when the pH was below the pK_a for the acids, causing them to exist primarily in the uncharged forms. We observed that uncharged carboxylic acids affected viability rather than the pH itself or conjugate bases. In addition, we modeled the viability of Ascaris eggs as a function of uncharged carboxylic acid concentration for n-butyric acid and n-caproic acid at exposure times of 2, 6, 12, and 20 days. The results presented here indicate that in situ biological production of carboxylic acids in HFM provides a promising method of pathogen inactivation and may lead to new developments in sanitation technology and treatment of fecal sludge.

Decomposition odour profiling in the air and soil surrounding vertebrate carrion

Chemical profiling of decomposition odour is conducted in the environmental sciences to detect malodourous target sources in air, water or soil. More recently decomposition odour profiling has been employed in the forensic sciences to generate a profile of the volatile organic compounds (VOCs) produced by decomposed remains. The chemical profile of decomposition odour is still being debated with variations in the VOC profile attributed to the sample collection technique, method of chemical analysis, and environment in which decomposition occurred. To date, little consideration has been given to the partitioning of odour between different matrices and the impact this has on developing an accurate VOC profile. The purpose of this research was to investigate the decomposition odour profile surrounding vertebrate carrion to determine how VOCs partition between soil and air. Four pig carcasses (Sus scrofa domesticus L.) were placed on a soil surface to decompose naturally and their odour profile monitored over a period of two months. Corresponding control sites were also monitored to determine the VOC profile of the surrounding environment. Samples were collected from the soil below and the air (headspace) above the decomposed remains using sorbent tubes and analysed using gas chromatography-mass spectrometry. A total of 249 compounds were identified but only 58 compounds were common to both air and soil samples. This study has demonstrated that soil and air samples produce distinct subsets of VOCs that contribute to the overall decomposition odour. Sample collection from only one matrix will reduce the likelihood of detecting the complete spectrum of VOCs, which further confounds the issue of determining a complete and accurate decomposition odour profile. Confirmation of this profile will enhance the performance of cadaver-detection dogs that are tasked with detecting decomposition odour in both soil and air to locate victim remains.

Effect of airflow on biodrying of gardening wastes in reactors

Biodrying consists of reducing moisture by using the heat from aerobic bio-degradation. The parameters that control the process are: aeration, temperature during the process, initial moisture of biowaste, and temperature and relative humidity of the input air. Lawn mowing and garden waste from the gardens of the University Jaume I, Castellón (Spain) were used as a substrate. Biodrying was performed in 10 reactors with known air volumes from 0.88 to 6.42 L/(min x kg dry weight). To promote aeration, 5 of the reactors had 15% of a bulking agent added. The experiment lasted 20 days. After the experiments it was found that the bulking agent led to greater weight loss. However, the increased airflow rate was not linearly proportional to the weight loss.

The effects of windrow composting on the viability of Parascaris equorum eggs

Parascaris equorum generally infects horses less than 18 months old and its pathological effects can be severe. Infection occurs when larvated eggs, present in pastures, paddocks, stalls, and on feeding and watering equipment are ingested. The purpose of this study was to examine the effects of windrow composting on the viability of P. equorum eggs at a cooperating central Kentucky horse farm. Three grams of feces containing 2216 P. equorum eggs per gram were sealed in filter bag sentinel chambers. Chambers were exposed to 1 of 3 treatments: constant exposure or intermittent exposure to the interior of the windrow; controls were stored at 4°C. At day 0, all chambers in the experimental treatments were placed in the center of 10 locations of the windrow. On subsequent days when the windrow was turned, chambers in the constant exposure treatment were returned to the interior of the windrow and chambers in the intermittent exposure treatment were alternated between resting on top of, or inside, the windrow. Chambers from each treatment and control chambers were removed at days 2, 4, 6, 8, 10, 12, 14, and 18; and incubated for 21 days at room temperature (24°C). After incubation, eggs were recovered from the chambers using double centrifugation flotation. Eggs were evaluated microscopically, staged according to development and classified as viable or nonviable based on whether embryonation to the larval stage had occurred. Results were reported as the mean percent viable eggs for each treatment and time point. A mixed linear model with repeated measures was used to evaluate the influence of experimental day and treatment on the percent viability of P. equorum eggs. Chambers treated with constant exposure contained 10.73% (SD=0.29) viable eggs on day 2 and declined to an average of 0.00% by day 8. Chambers exposed to the intermittent treatment contained 16.08% (SD=0.26) viable eggs on day 2 and decreased to 0.00% by day 6. Control chambers for days 2, 4, 6, 8, 10, 12, 14, and 18 all had viabilities above 79.00%. A significant fixed effect of experimental day (p<0.0001) and compost treatment (p<0.0001) was observed. There was no significant interaction between experimental day and compost treatment (p>0.7459). The results of this study demonstrate that windrow composting was effective at rendering P. equorum eggs nonviable when it was tested under the conditions at a working horse farm.

Quantitative evaluation of viability- and apoptosis-related genes in Ascaris suum eggs under different culture-temperature conditions

Ascaris suum eggs are inactivated by composting conditions; however, it is difficult to find functional changes in heat-treated A. suum eggs. Here, unembryonated A. suum eggs were incubated at 20℃, 50℃, and 70℃ in vitro, and the gene expression levels related to viability, such as eukaryotic translation initiation factor 4E (IF4E), phosphofructokinase 1 (PFK1), and thioredoxin 1 (TRX1), and to apoptosis, such as apoptosis-inducing factor 1 (AIF1) and cell death protein 6 (CDP6), were evaluated by real-time quantitative RT-PCR. No prominent morphological alterations were noted in the eggs at 20℃ until day 10. In contrast, the eggs developed rapidly, and embryonated eggs and hatched larvae began to die, starting on day 2 at 50℃ and day 1 at 70℃. At 20℃, IF4E, PFK1, and TRX1 mRNA expression was significantly increased from days 2-4; however, AIF1 and CDP6 mRNA expression was not changed significantly. IF4E, PFK1, and TRX1 mRNA expression was markedly decreased from day 2 at 50℃ and 70℃, whereas AIF1 and CDP6 mRNA expression was significantly increased. The expressions of HSP70 and HSP90 were detected for 9-10 days at 20℃, for 3-5 days at 50℃, and for 2 days at 70℃. Taken together, incremental heat increases were associated with the rapid development of A. suum eggs, decreased expression of genes related to viability, and earlier expression of apoptosis-related genes, and finally these changes of viability- and apoptosis-related genes of A. suum eggs were associated with survival of the eggs under temperature stress.

Inactivation of Ascaris suum by short-chain fatty acids

Ascaris suum eggs were inactivated in distilled water and digested sludge by butanoic, pentanoic, and hexanoic acids. The fatty acids (short-chain fatty acids [SCFA]) were effective only when protonated and at sufficient concentrations. The conjugate bases were not effective at the concentrations evaluated. Predictions from an inhibition model (50% inhibitory concentration [IC(50)]) based on quantitative structure-activity relationships were congruent with inactivation data.