Parameter optimization and uncertainty assessment for rainfall frequency modeling using an adaptive Metropolis-Hastings algorithm.

A new parameter optimization and uncertainty assessment procedure using the Bayesian inference with an adaptive Metropolis-Hastings (AM-H) algorithm is presented for extreme rainfall frequency modeling. An efficient Markov chain Monte Carlo sampler is adopted to explore the posterior distribution of parameters and calculate their uncertainty intervals associated with the magnitude of estimated rainfall depth quantiles. Also, the efficiency of AM-H and conventional maximum likelihood estimation (MLE) in parameter estimation and uncertainty quantification are compared. And the procedure was implemented and discussed for the case of Chaohu city, China. Results of our work reveal that: (i) the adaptive Bayesian method, especially for return level associated to large return period, shows better estimated effect when compared with MLE; it should be noted that the implementation of MLE often produces overy optimistic results in the case of Chaohu city; (ii) AM-H algorithm is more reliable than MLE in terms of uncertainty quantification, and yields relatively narrow credible intervals for the quantile estimates to be instrumental in risk assessment of urban storm drainage planning.

Pathogenicity comparison of duck Tembusu virus in different aged Cherry Valley breeding ducks.

BACKGROUND: Although several studies have revealed that the sensitivity of ducklings to duck Tembusu virus (DTMUV) was related to age, however, DTMUV was originally isolated from egg-laying ducks, and the ovary was the target organ of this virus. Cherry Valley breeding ducks aged 15- and 55-week-old (they are reserve breeding ducks and the normal egg-laying breeding ducks, respectively) were infected with DTMUV, using intramuscular injection, to study the effect of age-related difference on the pathogenicity of DTMUV in breeding ducks. RESULTS: Examinations of clinical symptoms, gross and microscopic lesions, viral loads, cytokines and serum neutralizing antibodies were performed. Results showed that obvious clinical symptoms, such as depression, ruffled feathers, ataxia and egg-laying drop were observed in the 55-week-old laying ducks, with five ducks dying at 5-7 days post infection (dpi). The 15-week-old ducks showed slight symptoms during infection. Gross lesions were severe and characterized by the congestion, hemorrhage and swelling of some organs in the 55-week-old ducks, including the hemorrhage of endocardium, hepatomegaly, splenomegaly, oviduct hemorrhage, hyperemia and deformation of the ovary. Mild endocardial hemorrhage and hepatosplenomegaly were observed in the 15-week-old ducks. Similarly, there was a significant difference in microscopic lesions between the two groups. The older ducks displayed severe microscopic lesions, specifically in the hemorrhage, interstitial inflammatory cell infiltration of the endocardium, typical viral encephalitis and hemorrhage in the ovary. But on the whole, the 15-week-old ducks showed milder lesions. Viral loads in tissues of the older group were significantly higher than those of the younger group. The levels of interferon (IFN)-γ, interleukin (IL)-2 and neutralizing antibody in the 15-week-old ducks were higher than in the 55-week-old ducks at the early stage of the DTMUV infection, suggesting the immune response in the younger ducks to DTMUV was stronger than in the older ducks. CONCLUSIONS: These results demonstrated that age-related differences in susceptibility to DTMUV in breeding ducks was significant, with 55-week-old egg-laying ducks being more susceptible to DTMUV than 15-week-old reserve breeding ducks.

Pollution characteristics, distribution and risk level of heavy metals in sediments of the Yangtze River estuary.

Pollution characteristics, distribution, risk and sources of 7 heavy metals in sediments of Yangtze River Estuary were investigated. Total concentration ranges of As, Cr, Cu, Cd, Pb, Zn and Ni were [0, 16.5], [1.48, 51.3], [2.66, 318], [0, 0.99], [35.6, 992], [8, 91.3] and [1.88, 108] mg/kg, respectively. Based on the potential ecological risk index and Geoaccumulation index, it was determined that Pb is the most polluted heavy metal. According to class I standard of "Marine sediment quality" of China, mean baseline levels multiples were Pb (8.34) > Cu (0.57) > Cr (0.37) > Zn (0.355) > Ni (0.352) > As (0.28) > Cd (0.00). The study also found the heavy metal content of Pb is the most serious, but most of the Pb content comes from the residual state, which has minimal impact on the environment. The East Nanhui Shoal was identified as the most polluted sub-area in terms of Pb pollution, followed by other specific locations. Considering the pollution level and transport costs, the study concluded that dredge soils of the Yangtze River Estuary Deepwater Channel are not suitable for the restoration of East Hengsha Shoal.

Generation and characterization of chimeric Tembusu viruses containing pre-membrane and envelope genes of Japanese encephalitis virus.

Since its outbreak in 2010, Tembusu virus (TMUV) has spread widely throughout China and Southeast Asia, causing significant economic losses to the poultry industry. In 2018, an attenuated vaccine called FX2010-180P (180P) was licensed for use in China. The 180P vaccine has demonstrated its immunogenicity and safety in mice and ducks. The potential use of 180P as a backbone for flavivirus vaccine development was explored by replacing the pre-membrane (prM) and envelope (E) genes of the 180P vaccine strain with those of Japanese encephalitis virus (JEV). Two chimeric viruses, 180P/JEV-prM-E and 180P/JEV-prM-ES156P with an additional E protein S156P mutation were successfully rescued and characterized. Growth kinetics studies showed that the two chimeric viruses replicated to similar titers as the parental 180P virus in cells. Animal studies also revealed that the virulence and neuroinvasiveness of the 180P/JEV-prM-E chimeric virus was decreased in mice inoculated intracerebrally (i.c.) and intranasally (i.n.), respectively, compared to the wild-type JEV strain. However, the chimeric 180P/JEV-prM-E virus was still more virulent than the parent 180P vaccine in mice. Additionally, the introduction of a single ES156P mutation in the chimeric virus 180P/JEV-prM-ES156P further attenuated the virus, which provided complete protection against challenge with a virulent JEV strain in the mouse model. These results indicated that the FX2010-180P could be used as a promising backbone for flavivirus vaccine development.

326K at E Protein Is Critical for Mammalian Adaption of TMUV.

Outbreaks of Tembusu virus (TMUV) infection have caused huge economic losses to the poultry industry in China since 2010. However, the potential threat of TMUV to mammals has not been well studied. In this study, a TMUV HB strain isolated from diseased ducks showed high virulence in BALB/c mice inoculated intranasally compared with the reference duck TMUV strain. Further studies revealed that the olfactory epithelium is one pathway for the TMUV HB strain to invade the central nervous system of mice. Genetic analysis revealed that the TMUV HB virus contains two unique residues in E and NS3 proteins (326K and 519T) compared with duck TMUV reference strains. K326E substitution weakens the neuroinvasiveness and neurovirulence of TMUV HB in mice. Remarkably, the TMUV HB strain induced significantly higher levels of IL-1ß, IL-6, IL-8, and interferon (IFN)-α/ß than mutant virus with K326E substitution in the brain tissue of the infected mice, which suggested that TMUV HB caused more severe inflammation in the mouse brains. Moreover, application of IFN-ß to infected mouse brain exacerbated the disease, indicating that overstimulated IFN response in the brain is harmful to mice upon TMUV infection. Further studies showed that TMUV HB upregulated RIG-I and IRF7 more significantly than mutant virus containing the K326E mutation in mouse brain, which suggested that HB stimulated the IFN response through the RIG-I-IRF7 pathway. Our findings provide insights into the pathogenesis and potential risk of TMUV to mammals.

The emergence of a disease caused by a mosquito origin Cluster 3.2 Tembusu virus in chickens in China.

In 2021, a chicken Tembusu virus (TMUV) caused outbreaks of a disease characterized by retarded growth and egg production decline in chickens in China. Two TMUV strains SD2021 and GX2021 were isolated from the diseased chickens and phylogenetic analysis of the E gene nucleotide sequence revealed that the chicken TMUV SD2021 and GX2021 were most close to mosquito origin TMUV in Cluster 3.2, which was distinct from the prevalent duck TMUVs in Cluster 2. The TMUV SD2021 caused growth retardation and neurological symptoms in chickens through both intranasal and intramuscular infection routes, but has no direct-contact transmissibility among chickens. The findings of this study highlight the pathogenicity of a chicken adapted mosquito-origin TMUV in chickens in China.

A Single Mutation at Position 120 in the Envelope Protein Attenuates Tembusu Virus in Ducks.

A live attenuated duck Tembusu virus (TMUV) vaccine FX2010-180P (180P) was successfully utilized to prevent TMUV infections in ducks in China. Compared with wild-type TMUV, 180P was highly attenuated and lost transmissibility in ducks. However, the mechanism of the attenuation of 180P remains poorly understood. To explore the key molecular basis of attenuation, chimeric and site mutant viruses in the background of the wild-type TMUV-FX2010 (FX) strain were rescued, and the replication, tissue tropism, and transmissibility were characterized in ducks. The results show that the envelope (E) protein was responsible for attenuation and loss of transmission in ducks. Further studies showed that a D120N amino acid mutation located in domain II of the E protein was responsible for the attenuation and transmissibility loss of 180P in ducks. The D120N substitution resulted in an extra high-mannose type N-linked glycosylation (NLG) in the E protein of 180P compared with the wild-type TMUV, which might restrict the tissue tropism and transmissibility of TMUV in ducks. Our findings elucidate that N120 in the E protein is a key molecular basis of TMUV attenuation in ducks and provide new insight into the role of NLG in TMUV tissue tropism and transmissibility.

Sedimentary polycyclic aromatic hydrocarbons (PAHs) along the mouth bar of the Yangtze River Estuary: Source, distribution, and potential toxicity.

The source, distribution, and potential toxicity of sedimentary polycyclic aromatic hydrocarbons (PAHs) along the mouth bar of the Yangtze River Estuary were investigated. Total concentrations of 17 PAHs in the study area ranged from 34.94 to 580.26 ng/g (mean value 146.31 ng/g). Results of PMF model revealed that mixed vehicle emissions (38.43%), natural gas combustion (24.98%), biomass combustion (20.76%) and coal combustion (15.83%) were sources of these sedimentary PAHs. The ERL/ERM, TEL/PEL and TEC/PEC values showed that the potential toxicity of PAHs was at low to medium level, but the presence of benzo[a]pyrene (BaP) and benzo[e]pyrene (BeP) requires more attention and research. Sedimentary PAHs pollution level in the three shoals (East Nanhui Shoal, Jiuduansha Shoal and Hengsha Shoal) was higher than that of the two passages (South Passage and North Passage), which demonstrates the possibility of restoration of the adjacent shoals by dredged soils in terms of PAHs pollution.

Characteristics, distribution, source and ecological risk of polycyclic aromatic hydrocarbons (PAHs) in sediments along the Yangtze River Estuary Deepwater Channel.

Characteristics, distribution, source, and ecological risk level of polycyclic aromatic hydrocarbons (PAHs) in sediments along Yangtze River Estuary Deepwater Channel were investigated. Total concentration of fifteen PAHs of study area ranged between 89.52 and 208.02 ng/g (mean value 140.48 ng/g). PAHs ratios and the statistical analysis showed that local fossil fuels high-temperature combustion (vehicular exhaust, anthropogenic combustion and pyrogenic sources) was the main PAHs origin. According to sediment quality guidelines (SQGs) and other criteria, the potential ecological risks of PAHs in sediments along Yangtze River Estuary Deepwater Channel are at low to medium levels, but the presence of dibenzo[a,h]anthracene (DBahAnt) requires more study and evaluation of potential toxicological effects.

Quantitative Proteomic Analysis of Duck Embryo Fibroblasts Infected With Novel Duck Reovirus.

The novel duck reovirus (NDRV) can cause hemorrhage and necrosis on the spleen of Pekin ducks; this disease has resulted in great economic losses to the duck industry. However, the molecular pathogenesis of NDRV remains poorly understood. In the current study, the quantitative proteomic analysis of NDRV-infected duck embryo fibroblasts was performed to explore the cellular protein changes in response to viral infection through iTRAQ coupled with the liquid chromatography (LC)-tandem mass spectrometry (MS/MS) method. A total of 6,137 proteins were obtained in cell samples at 24 h post-infection. Of these, 179 differentially expressed proteins (DEPs) were identified (cutoff set to 1.5-fold change), including 89 upregulated and 90 downregulated proteins. Bioinformatics analysis showed that DEPs can be divided into the cellular component, molecular function, and biological process; they were mainly involved in signal transduction, infectious diseases, cell growth and death, and the immune system. The subcellular localization of most proteins was in the cytoplasm. Importantly, the expressions of signal transducer and activator of transcription 1 (STAT1) and various interferon-stimulated genes (ISGs) were upregulated after NDRV infection. The mRNA transcripts of some ISGs were consistent with proteomic data, showing an increased trend. Results of our study suggested that NDRV infection can elicit strong expression changes of cellular proteins and activate the expression of ISGs from the point of quantitative proteomic analysis. The study provides a new insight into the understanding of NDRV pathogenesis.

Mechanism of fowl adenovirus serotype 4-induced heart damage and formation of pericardial effusion.

Fowl adenovirus serotype 4 (FAdV-4) is the causative agent of hydropericardium syndrome (HPS), which is characterized by the accumulation of a clear, straw-colored fluid in the pericardial sac, and high mortality rates. In order to explore the mechanism of FAdV-4-induced cardiac damage, dynamic pathology, apoptosis, and inflammatory reactions were analyzed in vivo. Moreover, we detected viral proliferation, and ultrastructure, inflammation and apoptosis of cardiomyocytes (CM) after FAdV-4 infection in vitro. The results showed that FAdV-4 impaired cardiac integrity and function by causing apoptosis and inflammation in vivo. Flow cytometry showed that CM infected with FAdV-4 did not show apoptosis in vitro. In addition, the mRNA expression of four inflammatory cytokines (interleukin (il)1B, il6, il8, and tumor necrosis factor), and activity of three myocardial enzymes were significantly different between FAdV-4 and control groups. However, in vitro, these indexes showed no significant difference between the groups. These observations collectively indicated that the heart was not the target organ of FAdV-4, and the virus may not directly lead to the occurrence of CM apoptosis and inflammation. To explore the source of pericardial effusion, we measured total protein, albumin, aspartate aminotransferase, creatine kinase isoenzyme, lactate dehydrogenase, potassium, sodium, and chloride ions in serum and pericardial effusion. Pericardial effusion was derived from vascular exudation rather than CM degeneration. Further studies are needed to investigate the exudation mechanism of vascular endothelial cells in FAdV-4 infection then weakened or eliminated pericardial effusion to minimize heart injury and/or restore damaged CM.

Difference in pathogenicity of 2 strains of avian leukosis virus subgroup J in broiler chicken.

Avian leukosis virus subgroup J has been found to infect many types of chickens with various genetic backgrounds. The ALV-J strain NX0101, which was isolated from broiler breeders in 2001, mainly induces the formation of myeloid cell tumors. However, strain HN10PY01, which was recently isolated from laying hens, mainly induces the formation of myeloid cell tumors and hemangioma. In order to determine the difference in pathogenicity of the 2 strains in broiler chickens, 2 groups of chicken embryos were infected with NA0101 and HN10PY01 separately. A comparison was made of the mortality, oncogenicity, body weights, indexes for immune organs, levels of ALV group-specific antigen p27, and mRNA expression levels of the tumor-related gene, p53, in ALV-J-infected birds and immune organs of theses chickens in response to Newcastle Disease Virus (NDV) and avian influenza virus subtype H9 (AIV-H9) vaccination. The results indicated that strain NX0101 was highly pathogenic in broiler chickens and led to a 30% mortality rate and 45% oncogenicity, compared with the HN10PY01-infected birds. Weight of chickens was also significantly lower after 15 wk (P < 0.05). In addition, the mRNA expression levels of tumor-related p53 in medulla, liver, and lung in broilers infected with strain NX0101 were significantly higher than those infected with strain HN10PY01 (P < 0.05). These results indicated that strain NX0101 had a higher replication ability in broiler chickens. The findings of this study will contribute to further elucidating the mechanisms underlying host susceptibility and tumor classification in ALV-J-infected chickens.

Fowl adenovirus serotype 4-induced apoptosis, autophagy, and a severe inflammatory response in liver.

Fowl adenovirus serotype 4 (FAdV-4) is a hepatotrophic virus that causes severe liver diseases. Upon histological examination, the most remarkable findings in the liver are small multifocal areas of necrosis and mononuclear cell infiltration, including basophilic intranuclear inclusion bodies in hepatocytes surrounded by a clear halo or which fill the entire nucleus. Here, we examined the mechanism responsible for FAdV-4-mediated hepatocyte damage in vivo and in vitro. The results showed that FAdV-4 impaired liver integrity and function, which decreased albumin and blood glucose concentrations and increased the plasma activity of aspartate aminotransferase and lactate dehydrogenase, compared with a non-infected control group (P<0.05). FAdV-4 induced hepatocyte apoptosis in a time-dependent manner in vivo and in vitro. Additionally, we found that FAdV-4 also induced the autophagy of hepatocytes, which promoted the conversion of microtubule-associated protein light chain 3 (LC3-I) to LC3-II, which is a hallmarks of autophagy. Furthermore, the mRNA expressions of interleukin (IL)-1ß, IL-6, IL-8, and tumor necrosis factor (TNF)-α in vivo and in vitro showed a statistically significant increase (P<0.05) compared to that of the control group. However, the molecular mechanisms underlying the FAdV-4-induced apoptotic and autophagic cell death remain unclear. In summation, our observations suggested that FAdV-4 induced liver injury via apoptosis, autophagy, and a severe inflammatory response.

Pathogenicity and immunosuppressive potential of fowl adenovirus in specific pathogen free chickens.

To elucidate the effect of fowl adenovirus (FAdV)-C in specific-pathogen-free (SPF) chickens, we investigated the pathogenicity, body weights, enzymatic systems, and immune organs of chickens in response to Newcastle disease virus (NDV) and avian influenza virus subtype H9 (AIV-H9) vaccination. Chickens were divided randomly into four groups, which included injection groups (FAdV-C, vaccination, and FAdV-C plus vaccination) and a negative control group. The results indicated that FAdV-C was highly pathogenic in SPF chickens and led to a 40% mortality rate and growth retardation, compared with the control birds. Significant changes in clinical chemical markers of all infected birds, together with histopathological lesions, indicated impairment of the liver and heart integrity and function. Furthermore, chickens in the FAdV-C plus vaccination group had significantly lower titers of antibodies against NDV and AIV-H9 than the uninfected and vaccinated chickens. The results of this study provide new insights into the pathogenesis of hydropericardium syndrome, a disease that progresses to a metabolic disorder and causes serious growth retardation and immunosuppression.

Intensified nitrogen removal of constructed wetland by novel integration of high rate algal pond biotechnology.

High rate algal pond (HRAP) was combined with constructed wetland (CW) to intensify nitrogen removal through optimizing nitrification and denitrification. Nitrification and denitrification process mainly depends on the oxygen content and carbon source level in CWs. Algal biomass was enriched in HRAP, and dissolved oxygen (DO) concentration was increased via photosynthesis. Algal debris increased COD as degradable bioresource. The results showed that HRAP-CW hybrid systems effectively promoted the nitrogen removal performance due to rich DO and COD. The extension of hydraulic retention time in HRAP significantly improved NH4-N and TN removals by 10.9% and 11.1% in hybrid systems, respectively. The highest NH4-N and TN removals in hybrid systems respectively reached 67.2% and 63.5%, which were significantly higher than those in single CW. The study suggested that the hybrid system had the application potentials in nitrogen removal from wastewater.