S. suis is an important zoonotic pathogen from sick and recessive carrier pigs that poses a serious threat to animal husbandry production and public health. It usually causes horizontal transmission among pigs. The morbidity and mortality of this disease are very high. Human infection is caused through direct or indirect contact with sick pigs. The two large-scale outbreaks in China were due to the outbreak of S. suis on pig farms, which spread to human infection; thus, detecting S. suis in pig herds is crucial. At present, the commercial S. suis ELISA type 2 kits on the market can only detect single serotypes, high probabilities of interaction reactions, and biosafety risks when using inactivated S. suis as an antigen. Phosphate-3-glyceraldehyde dehydrogenase (GAPDH), muramidase-released protein (MRP), and dihydrolipoamide dehydrogenase (DLDH) are important S. suis type 2, S. suis type 7, and S. suis type 9 protective antigens. This study purified the GMD protein (B-cell-dominant epitopes of GAPDH, MRP, and DLDH antigens) and used a diverse combination of dominant epitopes of the multiple different antigens as coated antigens, improving the sensitivity and safety of the indirect ELISA experiments. An indirect ELISA method (GMD-ELISA) was developed for detecting S. suis antibodies. The antigen—antibody response was optimized using checkerboard titration. The results of testing using ELISA for Salmonella enterica (S. enterica), Escherichia coli (E. coli), Staphylococcus aureus (SA), and Streptococcus pyogenes (S. pyogenes) were all negative, indicating that this method had strong specificity. The results were still positive when the dilution ratio of S. suis-positive serum reached 1:6, 400, thus indicating that the method had high sensitivity. The results of the reproducibility assay for indirect ELISA showed that the intra-assay coefficient of variation and the inter-assay coefficient of variation were less than 10%, indicating that the method had good repeatability. We investigated the seroprevalence of S. suis in 167 serum samples collected in East China, and 33.5% of the samples were positive for antibodies against S. suis, indicating that the prevalence of S. suis is high in pig farms in Eastern China. The novel GMD-ELISA is a convenient, sensitive, and specific diagnostic method that provides technical support for rapid diagnosis and epidemiological investigation.

Hebei Province is an important area for breeding broiler chickens in China, but the antimicrobial resistance and prevalence of Escherichia coli (E. coli) are still unclear. A total of 180 cloacal samples from broiler farms in Hebei Province were collected and used for the isolation and identification of E. coli. The isolates were subjected to resistance phenotyping, resistance profiling, and genotyping, and some multiresistant strains were subjected to multilocus sequence typing (MLST). The results showed that 175 strains were isolated. Among both types of broiler farms, the ampicillin resistance rate was the highest, and the meropenem resistance rate was the lowest. Serious multiresistance was present in both types of broiler farms. Thirty strains of multidrug-resistant E. coli were typed by MLST to obtain a total of 18 ST types, with ST10 being the most prevalent. This study was to simply analyze the antimicrobial resistance and prevalence of E. coli in broiler chickens in Hebei Province after the implementation of the pilot work program of action to reduce the use of veterinary antimicrobials in standard farms (SFs) and nonstandard farms (NSFs). This study will provide a research basis and data support for the prevention and control of E. coli in Hebei.

Streptococcus suis (S. suis) is a bacterial pathogen of pigs that has a major animal health and economic impact on the pig industry. Bovine herpesvirus-4 (BoHV-4) is a new virus-based vaccine vector that has been used for the immunogenic delivery of antigens from a variety of pathogens. In the present study, two recombinant BoHV-4-based vectors were evaluated for their ability to induce immunity and protection against S. suis in a rabbit model. The GMD protein is a fusion protein consisting of multiple dominant B-cell epitopes ((B-cell dominant epitopes of GAPDH, MRP, and DLDH antigens) (BoHV-4/GMD)) and the second suilysin (SLY) (BoHV-4/SLY) from S. suis serotype 2 (SS2). Both GMD and SLY delivered by the BoHV-4 vectors were recognized by sera from SS2-infected rabbits. The vaccination of rabbits with the BoHV-4 vectors induced antibodies against SS2, as well as against additional S. suis serotypes, SS7 and SS9. However, sera from BoHV-4/GMD-vaccinated animals promoted a significant level of phagocytic activity by pulmonary alveolar macrophages (PAMs) against SS2, SS7, and SS9. In contrast, sera from rabbits immunized with BoHV-4/SLY induced PAM phagocytic activity against only SS2. In addition, BoHV-4 vaccines differed in the associated level of protection against lethal SS2 challenge, which ranged from high (71.4%) to low (12.5%) for BoHV-4/GMD and BoHV-4/SLY, respectively. These data suggest BoHV-4/GMD as a promising vaccine candidate against S. suis disease.

The abuse of AGPs in animal husbandry has led to severe problems such as drug resistance and ecological, and environmental destruction, which seriously threaten human health and public health security. In recent years, extracts of oregano oil and macleaya cordata have become a hot spot in the research and application of AGP substitutes for their safety and high efficiency. This study is the first to report the effect of oregano oil combined with macleaya cordata oral solution on broiler growth performance. A total of 960 one-day-old broiler chickens were randomly divided into four treatment groups (240 chickens per group). Each treatment group was divided into six replicate groups (40 birds per replicate group). There were four groups in this study: the solvent control group, the oregano essential oil combined with macleaya cordata extract oral solution group (OS group), the oregano essential oil oral solution group (OEO group), and the macleaya cordata extract oral solution group (MCE group). Two chickens from each replicate group were collected and mixed into a composite sample. Six composite samples were obtained for each treatment group. The results showed that the oregano oil combined with macleaya cordata oral solution significantly improved the growth performance of broiler chickens. At the same time, serum biochemical indices, serum antioxidant indices, serum immune indices, serum cytokines, and intestinal morphology were significantly improved by the OS group. This study shows that oregano oil combined with macleaya cordata oral solution has substantial potential to be an alternative to AGPs for broilers.

Canine diarrhea is a common intestinal illness that is usually caused by viruses, bacteria, and parasites, and canine diarrhea may induce morbidity and mortality of domestic dogs if treated improperly. Recently, viral metagenomics was applied to investigate the signatures of the enteric virome in mammals. In this research, the characteristics of the gut virome in healthy dogs and dogs with diarrhea were analyzed and compared using viral metagenomics. The alpha diversity analysis indicated that the richness and diversity of the gut virome in the dogs with diarrhea were much higher than the healthy dogs, while the beta diversity analysis revealed that the gut virome of the two groups was quite different. At the family level, the predominant viruses in the canine gut virome were certified to be Microviridae, Parvoviridae, Siphoviridae, Inoviridae, Podoviridae, Myoviridae, and others. At the genus level, the predominant viruses in the canine gut virome were certified to be Protoparvovirus, Inovirus, Chlamydiamicrovirus, Lambdavirus, Dependoparvovirus, Lightbulbvirus, Kostyavirus, Punavirus, Lederbergvirus, Fibrovirus, Peduovirus, and others. However, the viral communities between the two groups differed significantly. The unique viral taxa identified in the healthy dogs group were Chlamydiamicrovirus and Lightbulbvirus, while the unique viral taxa identified in the dogs with diarrhea group were Inovirus, Protoparvovirus, Lambdavirus, Dependoparvovirus, Kostyavirus, Punavirus, and other viruses. Phylogenetic analysis based on the near-complete genome sequences showed that the CPV strains collected in this study together with other CPV Chinese isolates clustered into a separate branch, while the identified CAV-2 strain D5-8081 and AAV-5 strain AAV-D5 were both the first near-complete genome sequences in China. Moreover, the predicted bacterial hosts of phages were certified to be Campylobacter, Escherichia, Salmonella, Pseudomonas, Acinetobacter, Moraxella, Mediterraneibacter, and other commensal microbiota. In conclusion, the enteric virome of the healthy dogs group and the dogs with diarrhea group was investigated and compared using viral metagenomics, and the viral communities might influence canine health and disease by interacting with the commensal gut microbiome.

Japanese encephalitis (JE), found in pigs, is a serious mosquito-borne zoonotic infectious disease caused by the Japanese encephalitis virus (JEV). JEV is maintained in an enzootic cycle between mosquitoes and amplifying vertebrate hosts, mainly pigs and wading birds. It is transmitted to humans through the bite of an infected mosquito, allowing the pathogen to spread and cause disease epidemics. However, there is little research on JEV genotype variation in mosquitoes and pigs in Fujian province. Previous studies have shown that the main epidemic strain of JEV in Fujian Province is genotype III. In this study, a survey of mosquito species diversity in pig farms and molecular evolutionary analyses of JEV were conducted in Fujian, China, in the summer of 2019. A total of 19,177 mosquitoes were collected at four sites by UV trap. Four genera were identified, of which the Culex tritaeniorhynchus was the most common mosquito species, accounting for 76.4% of the total (14,651/19,177). Anopheles sinensi (19.25%, 3691/19,177) was the second largest species. High mosquito infection rateswere an important factor in the outbreak. The captured mosquito samples were milled and screened with JEV-specific primers. Five viruses were isolated, FJ1901, FJ1902, FJ1903, FJ1904, and FJ1905. Genetic affinity was determined by analyzing the envelope (E) gene variants. The results showed that they are JEV gene type I and most closely related to the strains SH-53 and SD0810. In this study, it was found through genetic evolution analysis that the main epidemic strain of JE in pig farms changed from gene type III to gene type I. Compared with the SH-53 and SD0810 strains, we found no change in key sites related to antigenic activity and neurovirulence of JEV in Fujian JEV and pig mosquito strains, respectively. The results of the study provide basic data for analyzing the genotypic shift of JEV in Fujian Province and support the prevention and control of JEV.