Xiao-Feng Shan

Isolation of active compounds from methanol extracts of Toddalia asiatica against Ichthyophthirius multifiliis in goldfish (Carassius auratus)

The parasitic ciliate Ichthyophthirius multifiliis infests all species of freshwater fish and can cause severe economic losses in fish breeding. The present study aims to evaluate the antiparasitic activity of the active components from Toddalia asiatica against I. multifiliis. Bioassay-guided fractionation and isolation of compounds with antiparasitic activity were performed on the methanol extract of T. asiatica yielding two bioactive compounds: chelerythrine and chloroxylonine identified by comparing spectral data (NMR and ESI-MS) with literature values. Results from in vitro antiparasitic assays revealed that chelerythrine and chloroxylonine could be 100% effective against I. multifiliis at the concentration of 1.2 mg L(-1) and 3.5 mg L(-1), with the median effective concentration (EC50) values of 0.55 mg L(-1) and 1.90 mg L(-1) respectively. In vivo experiments demonstrated that fish treated with chelerythrine and chloroxylonine at the concentrations of 1.8 and 8.0 mg L(-1) carried significantly fewer parasites than the control (P<0.05). The acute toxicity (LC50) of chelerythrine for goldfish was 3.3 mg L(-1).

Mycobacterium avium Subspecies paratuberculosis and Bovine Leukemia Virus Seroprevalence and Associated Risk Factors in Commercial Dairy and Beef Cattle in Northern and Northeastern China

Mycobacterium avium subspecies paratuberculosis (MAP) and bovine leukemia virus (BLV) are important pathogens, commonly responsible for economical loss to cattle farms all over the world, yet their epidemiology in commercial dairy and beef cattle in China is still unknown. Thus, from September 2013 to December 2014, a large-scale seroprevalence study was conducted to determine the seroprevalence and identify herd-level risk factors associated with MAP and BLV infection. The source sample was 3674 cattle from 113 herds in northern and northeastern China. Antibodies against MAP and BLV were detected using ELISA tests. At animal-level, the seroprevalence of antibodies against MAP and BLV was 11.79% (433/3674) and 18.29% (672/3674), respectively. At herd-level, the seroprevalence of antibodies against MAP and BLV was 20.35% and 21.24% (24/113), respectively. Herd size was identified to be associated with MAP infection while herd size and presence of cattle introduced from other farms were significantly associated with BLV infection. Further research is needed to confirm these findings and improve the knowledge of the epidemiology of these two pathogens in these regions and elsewhere in China.

Hepatitis E virus seroprevalence among farmers, veterinarians and control subjects in Jilin province, Shandong province and Inner Mongolia Autonomous Region, China

China is commonly considered to be a HEV‐endemic region but limited epidemiological data for HEV among farmers and veterinarians are available. Thus, a case‐control study was carried out to detect the seroprevalence and assess potential risk factors associated with the acquisition of HEV infection by farmers and veterinarians in China from July 2013 to May 2015. Three hundred veterinarians and 600 farmers recruited from Jilin province, Shandong province, and Inner Mongolia Autonomous Region and 600 control subjects matched by gender, age, and residence were detected for the presence of anti‐HEV IgG and IgM antibodies using enzyme immunoassays. The seroprevalences of HEV infection in farmers, veterinarians, and control subjects were 34.8%, 26.7%, and 20.2%, respectively. Farmers (P < 0.001) and veterinarians (P = 0.027) have significantly higher seroprevalence than control subjects. The highest seroprevalence of HEV infection was detected in swine farmers (49.1%) and the lowest seroprevalence was found in cattle farmers (26.5%). In veterinarians, farm animal veterinarians have a higher seroprevalence than pet veterinarians, but the difference was not significant (P > 0.05). Residence area, contact with swine and exposure with soil were significantly associated with HEV infection in the study farmers; contact with swine and source of drinking water were significantly associated with HEV infection in the study veterinarians. These results implied the high prevalence of HEV and the considerable potential for the dissemination of HEV infection in farmers and veterinarians in China. J. Med. Virol. 89:872–877, 2017.

Complete genome sequence of the fish pathogen Aeromonas veronii TH0426 with potential application in biosynthesis of pullulanase and chitinase.

Aeromonas veronii TH0426 is a pathogen of the farmed yellow catfish Pelteobagrus fulvidraco but shows high-level expression of pullulanase and chitinase. Here, we present its genome sequence, which is the first reported complete genome of fish pathogen in A. veronii to date. Strain TH0426 harbors a single circular 4,923,009bp chromosome with a GC content of 58.25%. There are 4525 genes identified on its genome, including 4244 protein-coding genes, 32 rRNA genes, 120 tRNA genes, a noncoding RNA and 128 pseudo genes. We believe that the genomic information of A. veronii TH0426 would facilitate to reveal its pathogenic mechanism associated with yellow catfish, develop vaccine to decrease economic losses for fish farming, meanwhile explore the potential application in producing pullulanase and chitinase.

Seroprevalence and Risk Factors Associated with Hepatitis E Virus Infection in Three Species of Pet Birds in Northwest China

Hepatitis E virus (HEV), the causative agent of hepatitis E, has been reported in a wide variety of animals, including birds, but little is known of HEV infection in pet birds in northwest China. The objective of the present investigation was to examine HEV seroprevalence in three species of pet birds, namely, Eurasian siskin, Oriental skylark, and black-tailed grosbeak from Gansu. Serum samples collected from 685 pet birds from August 2011 to September 2012 were examined independently for the presence of antibodies against HEV. A total of 59 (8.31%) pet birds were tested positive for HEV antibodies by the commercially available enzyme immunoassay kits. Of these, the seroprevalence was diverse in different species pet birds; the most frequent level was 10.83% (39/360) in Eurasian siskin, followed by 6.57% (19/289) in Oriental skylark, and 2.29% (1/36) in black-tailed grosbeak. Age and collecting region of pet birds were the main risk factors associated with HEV infection. The present study firstly revealed the seroprevalence of HEV infection in three species of pet birds in northwest China, which provided the baseline data for taking comprehensive countermeasures and measures for effectively preventing and controlling HEV infection in birds.

Coxiella burnetii (Q fever) Infection in Farmed Ruminants in Three Northeastern Provinces and Inner Mongolia Autonomous Region, China.

Coxiella burnetii is the pathogenic agent of Q fever, a zoonosis that occurs worldwide. In China, the organism infects people and a wide range of wild and farmed animals. However, little is known about C. burnetii infection in farmed ruminants in northeastern China, and there appears to have been no previous study on sika deer. The present study was conducted to determine the seroprevalence of C. burnetii in farmed ruminants in this region of China. A total of 3147 domestic ruminants (784 sheep, 1016 cattle, and 1347 sika deer) were randomly collected for this study. An indirect enzyme-linked immunosorbent assay kit was used to detect the antibodies to C. burnetii. The results showed an overall seroprevalence of 16.7% in domestic ruminants (24.9%, 13.5%, and 12.3% in cattle, sheep, and sika deer, respectively). This is the first report of C. burnetii seroprevalence in sika deer in China. Protective and hygiene measures should be applied in farm management to reduce the risk of exposure of C. burnetii to humans.

Oral immunization with recombinant Lactobacillus casei expressing OmpAI confers protection against Aeromonas veronii challenge in common carp, Cyprinus carpio

ABSTRACT Aeromonas veronii is a gram‐negative pathogen capable of infecting both fish and mammals, including humans, and natural infection in fish results in irreparable damage to the aquaculture industry. Lactic acid bacteria (LAB) have a number of properties that make them attractive candidates as delivery vehicles for presentation to the mucosa sites of compounds with pharmaceutical interest, in particular vaccines. In this study, we generated two recombinant Lactobacillus casei (surface‐displayed or secretory) expressing the OmpAI of A.veronii and evaluated the effect on immune responses in fish model. A 1022 bp gene fragment of the 42 kDa OmpAI antigen of A.veronii was cloned into pPG‐1 (surface‐displayed) and pPG‐2 (secretory) and electrotransformed into Lactobacillus casei CC16. The recombinant plasmid in L.casei could be stably inherited over 50 generations, and production of OmpAI protein had slight limited effects on cells growth. Treatment of common carp with the recombinant vaccine candidate stimulated high serum or skin mucus specific antibody titers and induced a higher lysozyme, ACP, SOD activity, while fish fed with Lc‐pPG or PBS had no detectable immobilizing immune responses. Expression of IL‐10, IL‐&bgr;, IFN‐&ggr;, TNF‐&agr; genes in the group immunized with recombinant L.casei were significantly (P < 0.05) up regulated as compared with control groups, indicating that inflammatory response and cell immune response were triggered. Further, viable recombinant L.casei strains were directly delivered and survive throughout the intestinal tract, the recombinant OmpAI was also detected in intestine mucosal. The results showed that common carp received Lc‐pPG1‐OmpAI (66.7%) and Lc‐pPG2‐OmpAI (50.0%) had higher survival rates compared with the controls after challenge with A.veronii, indicating that Lc‐pPG1‐OmpAI and Lc‐pPG2‐OmpAI had beneficial effects on immune response and enhanced disease resistance of common carp against A.veronii infection. Our study here demonstrates, for the first time, the ability of recombinant L.casei as oral vaccine against A.veronii infection in carps. The combination of OmpAI delivery and LAB approach may be a promising mucosal therapeutic agent for treating and controlling A.veronii. Graphical abstract Aeromonas veronii TH0426 strain challenge experiment was performed to evaluated the protective immunity of the recombinant L.casei. A.veronii TH0426 isolated from the farmed Pelteobagrus fulvidraco (yellow catfish). Figure. No caption available. HighlightsThe recombinant L. casei producing OmpAI of A. veronii was engineered in two cellular locations.Common carp (Cyprinus carpio) immunized with recombinant L. casei stimulated specific immune response.Increased expression of IL‐10, IL‐&bgr;, IFN‐&ggr; and TNF‐&agr; genes also observed in recombinant L. casei immunized fish.Viable engineered L. casei was directly delivered and survived throughout the intestine of fish.Protection against A. veronii challenge observed in recombinant L. casei immunized fish.

Comparative genome analysis of Bacillus velezensis reveals a potential for degrading lignocellulosic biomass

Genomes of 24 sequenced Bacillus velezensis strains were characterized to identity shared and unique genes of lignocellulolytic enzymes and predict potential to degrade lignocellulose. All 24 strains had genes that encoded lignocellulolytic enzymes, with potential to degrade cellulose and hemicelluloses. Several lignocellulosic genes related to cellulose degradation were universally present, including one GH5 (endo-1,4-β-glucanase), one GH30 (glucan endo-1,6-β-glucosidase), two GH4 (6-phospho-β-glucosidase, 6-phospho-α-glucosidase), one GH1 (6-phospho-β-galactosidase), one GH16 (β-glucanase) and three GH32 (two sucrose-6-phosphate hydrolase and levanase). However, in the absence of gene(s) for cellobiohydrolase, it was predicted that none of the 24 strains would be able to directly hydrolyse cellulose. Regarding genes for hemicellulose degradation, four GH43 (1,4-β-xylosidase; except strain 9912D), one GH11 (endo-1,4-β-xylanase), three GH43 (two arabinan endo-1,5-α-L-arabinosidase and one arabinoxylan arabinofuranohydrolase), two GH51 (α-N-arabinofuranosidase), one GH30 (glucuronoxylanase), one GH26 (β-mannosidase) and one GH53 (arabinogalactan endo-1,4-β-galactosidase) were present. In addition, two PL1 (pectate lyase) and one PL9 (pectate lyase) with potential for pectin degradation were conserved among all 24 strains. In addition, all 24 Bacillus velezensis had limited representation of the auxiliary activities super-family, consistent with a limited ability to degrade lignin. Therefore, it was predicted that for these bacteria to degrade lignin, pretreatment of lignocellulosic substrates may be required. Finally, based on in silico studies, we inferred that Bacillus velezensis strains may degrade a range of polysaccharides in lignocellulosic biomasses.

Coxiella burnetii Seroprevalence and Risk Factors in Cattle Farmers and Farm Residents in Three Northeastern Provinces and Inner Mongolia Autonomous Region, China.

Little is known about Coxiella burnetii infection among cattle farmers and farm residents in China. Thus, the present study was conducted to detect the seroprevalence of C. burnetii infection and estimate associated risk factors among cattle farmers and farm residents in China. A cross-sectional study was designed, and sera of 362 people living or working on 106 cattle farms were tested for C. burnetii IgG and IgM antibodies by immunofluorescence assay. Overall C. burnetii seroprevalence was 35.6% (129/362, 95% CI: 30.70–40.57), and 112 participants had experienced a past infection and seventeen (4.7%) had experienced a relatively recent infection. In the final combined multilevel model, the following activities were significantly associated with presence of antibodies against C. burnetii: milking cattle, providing general healthcare to cattle, providing birth assistance, contact dead-born animals, urbanization, and presence of mice and/or rats in the stable. Moreover, presence of disinfection equipment was a significant protective factor. This is the first study addressing the seroprevalence and risk factors of C. burnetii infection in cattle farmers and farm residents in three northeastern provinces and Inner Mongolia Autonomous Region, China.

Immunogenicity of extracellular products from an inactivated vaccine against Aeromonas veronii TH0426 in koi, Cyprinus carpio

&NA; Aeromonas veronii is a type of human‐livestock‐aquatic animal pathogen; it is widely found in nature and causes many deaths among aquatic animals. Extracellular products (ECPs) are secreted by the pathogen during growth and reproduction. These products are considered effective protective antigens that can induce the host to produce an immune response. In this study, the ECPs of A.veronii TH0426 were prepared by ultrafiltration, and then the pathogenicity and enzymatic activity of the ECPs were determined. All the groups were injected intraperitoneally, as follows: group one: ECP protein with an equal volume of Freunds adjuvant; group two: ECPs and formalin‐killed cells (FKC) of A.veronii combined with an equal volume of Freunds adjuvant (FKC + ECPs); group three: formalin‐killed cells (FKC) of A.veronii combined with an equal volume of Freunds adjuvant (FKC); and, group four: sterile PBS as the control group. The expression levels of IgM, IL‐1&bgr;, and TNF‐&agr; and the lysozyme activity in blood were examined at 7, 14, and 21 days after the immunizations. The results show that the ECPs can produce protease, lipase, amylase and hemolyase, and there was no lecithinase, urease, or gelatinase activity. The results indicate that the ECPs were clearly pathogenic to koi fish, and the LD50 dose was 391.6 &mgr;g/fish. Throughout this study, the RPS of the three experimental groups were 75%, 50%, and 70%. This study indicates that the ECPs of A.veronii can effectively enhance the ability of kio fish to resist bacterial invasion. HighlightsThe extracellular products (ECPs) of Aeromonas veronii improved immune responses against infection.The expression level of IgM, IL‐1&bgr;, TNF‐&agr; and lysozyme activity observed in immunized fish.The extracellular products (ECPs) of Aeromonas veronii enhanced disease resistance of kio.