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Articles by Weiping Xu in JoVE

 JoVE Immunology and Infection

Biocontained Carcass Composting for Control of Infectious Disease Outbreak in Livestock

1Agriculture and Agri-Food Canada, Lethbridge Research Centre, 2Department of Bioscience and Biotechnology, Dalian University of Technology, 3Agriculture Centre, Alberta Agriculture and Rural Development


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Using readily available materials, this biocontained composting system enables effective on-site disposal of large animal carcasses arising in the event of infectious disease outbreak. This procedure kills most infectious agents in carcasses and contaminated manure. Once infectious agent is confirmed non-viable, mature compost can be spread as fertilizer.

Other articles by Weiping Xu on PubMed

A Biosecure Composting System for Disposal of Cattle Carcasses and Manure Following Infectious Disease Outbreak

During outbreaks of infectious animal diseases, composting may be an effective method of disposing of mortalities and potentially contaminated manure. Duplicate biosecure structures containing 16 cattle (Bos taurus) mortalities (343 kg average weight) were constructed with carcasses placed on a 40-cm straw layer and overlaid with 160 cm of feedlot manure. At a depth of 80 cm (P80), compost heated rapidly, exceeding 55 degrees C after 8 d and maintained temperatures of 55 to 65 degrees C for > 35 d. Temperatures at 160 cm (P160) failed to exceed 55 degrees C, but remained above 40 degrees C for >4 mo. To investigate rates of microbial inactivation, Escherichia coli O157:H7, Campylobacter jejuni, and Newcastle disease virus (NDV) were inoculated in manure (E. coli O157:H7 and C. jejuni approximately 10(8) CFU g(-1); NDV, approximately 10(6) EID(50) g(-1)), embedded at P80 and P160 and retrieved at intervals during composting. Escherichia coli O157:H7 and NDV were undetectable after 7 d at both depths. The C. jejuni DNA was detected up to 84 d at P80 and >147 d at P160. To estimate degradation of recalcitrant substrates, bovine brain, hoof, and rib bones were also embedded at P80 and P160 and retrieved at intervals. Residues of soft tissues remained in carcasses after opening at 147 d and bovine tissue decomposition ranked as brain > hoof > bone. More than 90% dry matter (DM) of brain disappeared after 7 d and 80% DM of hoof decomposed after 56 d. High degradation of cattle carcasses, rapid suppression of E. coli O157:H7 and NDV and reduction in viable cell densities of >6 logs for C. jejuni demonstrates that the biosecure composting system can dispose of cattle carcasses and manure in an infectious disease outbreak.

Purification of Polymerase Chain Reaction (PCR)-amplifiable DNA from Compost Piles Containing Bovine Mortalities

Livestock production systems utilize composting as a method of disposal of livestock mortalities, but there is limited information on the rate and extent of carcass decomposition. Detection of specific DNA fragments by PCR offers a method for investigating the degradation of carcasses and other biological materials during composting. However, the purity of extracted DNA is critical for successful PCR analysis. We applied a method to purify DNA from compost samples and have tested the method by analyzing bovine and plant DNA targets after 0, 4, and 12 month of composting. The concentration of organic matter from composted material posed a particular challenge in obtaining pure DNA for molecular analysis. Initially extracted DNA from composted piles at day 147 was discoloured, and PCR inhibitors prevented amplification of target plant or bovine gene fragments. Bovine serum albumin improved detection by PCR (25-50 microl final volume) through the removal of inhibitors, but only when concentrations of humic acids in extracted DNA were 1.0 ng microl(-1) or less. Optimal purification of DNA from compost was achieved by chromatography using Sepharose 4B columns. The described DNA purification protocol enabled molecular monitoring of otherwise cryptic bovine and plant target genes throughout the composting process. The assay could likely be used to obtain PCR-amplifiable DNA that could be used for the detection of microbial pathogens in compost.

Use of Quantitative and Conventional PCR to Assess Biodegradation of Bovine and Plant DNA During Cattle Mortality Composting

Understanding mortality composting requires assessing the biodegradation efficacy of carcasses and other materials of animal and plant origin. Biosecure (plastic-wrapped) compost structures were built containing 16 cattle carcasses placed on 40 cm straw and covered with 160-cm of feedlot manure. Compost was collected from depths of 80 and 160 cm (P80, P160) and DNA degradation assessed over 147 days of static composting, and during 180 days of active composting. Residual soft tissues from carcasses were collected on day 147. At P80, copies of a 171-bp bovine mitochondrial DNA (Mt171) and 138-bp plant Rubisco gene fragment (Rub138) were reduced compared to initial copy numbers (CN) by 79% and 99% after 147 days, respectively. At P160, Mt171, and Rub138 decreased compared to initial CN by 20% and 99% by day 147, respectively. After 327 days, degradation of Mt171 increased to 91% compared to initial CN. Compared to fresh tissues, residual tissues at day 147 had a 99% reduction in genomic DNA yield. Yield of DNA was related to copies of a 760-bp bovine mitochondrial fragment (Mt760) which were > 93% reduced at both P80 and P160 after 147 day. Secondary composting improved decomposition of bovine tissues and Mt760 was not detectable after 207 days. A 99% reduction in genomic DNA of composted tissue and > 93% reduction of Mt760 suggests almost complete decomposition of carcass soft tissue after 147 days.

Melatonin and Tryptophan Circadian Profiles in Patients with Advanced Non-small Cell Lung Cancer

Accumulating studies indicate that melatonin is a natural oncostatic agent capable of mediating the influence of the psychoneuroendocrine system on cancer growth. Although there is increasing evidence to show that the pineal gland may play a role in human non-small cell lung cancer (NSCLC), there is uncertainty about circadian profiles of melatonin, its precursor tryptophan, and its major metabolite, 6-sulfatoxymelatonin (6-OH-MLT) in NSCLC patients before and after treatment with standard chemotherapy (cisplatin plus vinorelbine). The aim of this study was to investigate the concentration changes of melatonin, tryptophan, and 6-OH-MLT in NSCLC patients treated with standard chemotherapy.

Anaerobic Digestion of Specified Risk Materials with Cattle Manure for Biogas Production

Biogas production from anaerobic digestion (AD) of specified risk materials (SRM) co-digested with cattle manure was assessed in a 3 x 2 factorial design. SRM replaced manure at 0 (control), 10% or 25% (w/w) as the substrate fed to six 2-L biodigesters maintained at 37 degrees C or 55 degrees C. Digesters were fed substrate (30 g L(-1) total volatile solids) at 6-d intervals for 90 d, with a retention time of 30 d. Keratin (<20mg) was added to each digester to model the degradation of beta-sheet rich proteins. Methane production was measured daily, and effluent was collected at feeding to monitor SRM degradation using real-time PCR analysis of bovine-specific DNA fragments. Compared with control, methane production increased by 83% or 161% (P<0.05) with 10% or 25% SRM at 37 degrees C, and by 45% and 87%, respectively, at 55 degrees C (P<0.05). Bovine DNA degradation over 6d was higher (P<0.05) at 37 degrees C as compared to 55 degrees C. Dry matter degradation of keratin at 37 degrees C decreased with increasing SRM concentration (P<0.05), whereas at 55 degrees C no difference between treatments was observed (P>0.05). Inclusion of SRM increases the production of methane during the anaerobic digestion of manure and may offer a means of deriving economic value from the disposal of SRM.

Biodegradation of Genetically Modified Seeds and Plant Tissues During Composting

The increasing global market of genetically modified (GM) crops amplifies the potential for unintentional contamination of food and feed with GM plants. Methods proposed for disposal of crop residues should be assessed to prevent unintended distribution of GM materials. Composting of organic material is inexpensive and location-independent. The objective of this study was to determine the effectiveness of composting for disposal of GM plants in terms of reducing seed viability and promoting the degradation of endogenous as well as transgenic DNA.

A Highly Selective Colorimetric and "off-on-off" Fluorescent Probe for Fluoride Ions

In this paper, a highly selective and sensitive probe for fluoride ions (F(-)), containing a phenylpyridylvinylene derivative reporter and a Si-O bond receptor, was designed and characterized. The reaction mechanism is based on the intramolecular charge transfer (ICT) mechanism. Upon addition of F(-), probe 1 showed a remarkable red-shift (183 nm) in the absorption spectra accompanying with the color changes from colorless to purple, so probe 1 could serve as a "naked-eye" probe for F(-). The absorbance of probe 1 at 545 nm increased linearly with the concentration of F(-) from 20 to 150 µM. The detection limit was calculated to be 0.1 µM. Besides, "off-on-off" fluorescence intensity changes were also observed in the fluorescence spectra. The present results may provide a useful approach for the development of highly selective dual-channel probes for F(-).

Field Scale Evaluation of Bovine-specific DNA As an Indicator of Tissue Degradation During Cattle Mortality Composting

Currently, mortality compost is managed by temperature as extent of tissue degradation is difficult to assess. In the present study, field-scale mortality compost was constructed with composted brain tissue (Brain) and compost adjacent to brain tissue (CAB) sampled over 230 d. Following genomic DNA extraction, bovine-specific mitochondrial DNA (Mt-DNA) and bacterial 16S rDNA fragments were quantified using real-time PCR. Genomic DNA yield of Brain and CAB decreased rapidly (89-98%) and stabilized after 7 d. Compared to d 0, Brain Mt-DNA rapidly decreased (84-91% reduction on d 7). In CAB, Mt-DNA dramatically increased until d 28 (up to 34,500 times) thereafter decreasing by 77-93% on d 112. Quantification of bovine Mt-DNA indicates tissue degradation was initially characterized by rapid decomposition and release of cell contents into surrounding compost matrix followed by further degradation of Mt-DNA by flourishing microorganisms. Consequently, bovine Mt-DNA copies in compost matrix were reliable indicators of tissue degradation.

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