Transboundary and Emerging Diseases

Salmonella Dublin is a bovine-adapted bacterial pathogen that primarily affects dairy cattle. The incidence of S. Dublin has been increasing across North America, including strains that are multidrug resistant. In British Columbia, the Ministry of Agriculture’s Animal Health Center (AHC) reported an increase in cases since 2015, warranting an investigation into how S. Dublin is spreading within the province. The objectives of this study were to make use of historical data collected from dairy farms across the province to (1) describe S. Dublin cases diagnosed at the AHC between 2007 and 2021, (2) identify risk factors for S. Dublin transmission across British Columbia dairy farms, and (3) identify any potential biases associated with passive laboratory-based data that may apply to our results. We found that S. Dublin cases diagnosed at the AHC have been increasing over time. Over half of the cases had respiratory symptoms; however, clinical signs tended to be highly variable. The prevalence of respiratory symptoms was mirrored by florfenicol treatment and was suggested to be due to using a first-line antibiotic for more common causes of pneumonia when presented with an S. Dublin case. Calves were 38 times more likely to have S. Dublin when compared to adults (odds ratio = 38.43, confidence interval = 7.26–203.64), and given the sample population (postmortem cases), it is reasonable to conclude clinical disease is most severe in this age group. Farm premise accounted for a large amount of variability within our model (92% of unexplained variance), suggesting that farm-level management practices may be the most important risk factor for S. Dublin infection. In total, only 54% of BC dairy farms submitted to the laboratory between 2007 and 2021; however, proximity to the laboratory did not appear to influence submissions as proportionally; farms within the Fraser Valley submitted as frequently as farms from other regions. We strongly suggest that future work explore factors associated with farm management practices, given our findings regarding the clustering by premises.

Background. Since 2020, global attention has heightened towards epidemics caused by avian influenza A H5N1 virus of clade 2.3.4.4b in birds and mammals. This study presents the epidemiological history, clinical manifestations, and prognosis of a unique case infected with avian influenza A H5N1 clade 2.3.4.4b, along with the continuation of SARS-CoV-2 viral RNAs, in Eastern China. Methods. We collected and analysed the patient’s clinical, epidemiological, and virological data. Both sputum and bronchoalveolar lavage fluid (BALF) samples were subjected to real-time RT-PCR to test for respiratory pathogens of interests, including SARS-CoV-2 and influenza virus. Influenza virus isolation and propagation were performed on embryonated eggs. Serological tests were used to determine the presence of SARS-CoV-2 antibodies. Phylogenetic analysis was constructed to explore viral evolution and origin of A/H5N1 virus. Results. A 53-year-old female farmer with chronic bronchiectasis was hospitalized with severe pneumonia. Real-time RT-PCR revealed the presence of avian influenza A H5N1 and SARS-CoV-2 in BALF and sputum samples. Sequence analyses classified the human isolate as clade 2.3.4.4b of avian influenza A H5N1. The amino acid motif GlnSerGly at residues 226–228 of the haemagglutinin protein indicated avian-like receptor binding preference. Epidemiological investigation established that the patient had exposure to sick or dead poultry 3 days before illness onset, while no cases of human-to-human H5N1 virus transmission were identified in 31 close contacts. Conclusion. We presented that the clade 2.3.4.4b H5N1 avian influenza virus has the potential to cross-infect humans with serious symptoms, especially in individuals already affected by COVID-19. It is indeed crucial to closely monitor the virus’s evolution in both avian populations and humans. Continued research and surveillance efforts are vital to monitor any potential changes in the virus, as well as to inform public health policies and interventions.

Background. In late 2019, several medical institutions in Wuhan, Hubei Province, China, reported cases of unexplained pneumonia. A novel coronavirus was isolated from human airway epithelial cells causing coronavirus disease-2019 (COVID-19). In recent years, many nonpharmaceutical interventions (NPIs) have been implemented to stop COVID-19 epidemic. This study aimed to explore the effect of NPIs on the circulation of avian influenza virus (AIV) in Wuhan. Materials and Methods. External environmental samples were collected and subjected to viral RNA extraction. Real-time quantitative polymerase chain reaction was used to detect the H5, H7, and H9 subtypes of AIV. Statistical analyses were performed using the chi-square test and binary logistic regression in SPSS 20.0 software. Results. A total of 2,451 external environmental samples were collected from seven districts from 2018 to 2022 in Wuhan, comprising 1,041 samples collected before COVID-19 and 1,410 samples after COVID-19. After COVID-19, the positive rate of AIV decreased significantly with the implementation of NPIs. The dominant subtype was the H9 subtype, followed by the H5 subtype. The positive rates of AIV in live poultry markets and poultry free-range sites were reduced significantly through the implementation of NPIs. Among the different sample types, higher positive rates of AIV were found in chopping boards, sewage, and cages. The positive rate of AIV was higher in trafficked source samples than that in autotrophic source samples. Conclusions. This study identified the characteristics of AIV in terms of different districts, surveillance sites, sample types, and bird sources in Wuhan. This study conducted a multifactorial analysis of the factors affecting AIV infection and provided a theoretical basis and guidance for the future prevention and control of AIV in Wuhan.

The application of tick control strategies on tropical dairy cattle strongly relies on farmers’ uptake, knowledge, and perceptions of the efficacy of control measures. This study aims to identify common and uncommon tick control practices employed by dairy farmers in subtropical areas of Ecuador and associate them with the presence of infestation and acaricide resistance. Data were collected through a cross-sectional survey and participatory meetings. Multiple correspondence analysis was used to explore the association between management variables and the level of tick infestation and resistance. It was determined that the main method of acaricide control is still chemical, mainly using spray baths. Generally, when this form of application is used, acaricides are overdosed, in contrast to the pour-on method with underdosage. Among the measures farmers adopt when chemical treatment has failed is to use overdoses of products, mix different acaricides, and use focused treatments (wipe cloth) with irritant substances. The absence of a high level of infestation was related to acaricide dips every 3–4 weeks and the use of intensive grazing. On the other hand, the high infestation was related to the use of organophosphates, wipe cloth application, and the report of tick-borne diseases (TBDs). A small group of farmers have good knowledge and seek alternatives to chemical control, experimenting with biological controls, herbal extracts, manual tick removal, and paddock control. Additionally, farmers reported the presence of TBDs (47%) and the presence of animals poisoned by acaricides (6%), which died in 75% of those cases. Farmers frequently mentioned that tick infestation induces milk drop production and weight loss and is associated with the presence of TBDs. This information is crucial to improve tick control management in Ecuador, particularly through implementing practices that mitigate resistance to acaricides and ensure long-term solutions that help maintain the efficacy of tick control treatments.

As the H9N2 subtype avian influenza virus (H9N2 AIV) evolves naturally, mutations in the hemagglutinin (HA) protein still occur, which involves some sites with glycosylations. It is widely established that glycosylation of the H9N2 AIV HA protein has a major impact on the antigenicity and pathogenicity of the virus. However, the biological implications of a particular glycosylation modification site (GMS) have not been well investigated. In this study, we generated viruses with different GMSs based on wild-type (WT) viruses. Antigenicity studies revealed that the presence of viruses with a 200G⁺/295G⁻ mutation (with glycosylation at position 200 and deletion of glycosylation at position 295 in the HA protein) combined with a single GMS, such as 87G⁺, 127G⁺, 148G⁺, 178G⁺, or 265G⁺, could significantly affect the antigenicity of the virus. Pathogenicity assays revealed that the addition of GMS, such as 127G⁺, 188G⁺, 148G⁺, 178G⁺, or 54G⁺, decreased the virulence of the virus in mice, except for 87G⁺. The removal of GMS, such as 280G⁻ or 295G⁻, increased the pathogenicity of the virus in mice. Further studies on pathogenicity revealed that 87G⁺/295G⁻ could also enhance the pathogenicity of the virus. Finally, we selected the WT, WT-87G⁺, WT-295G⁻, and WT-87G⁺/295G⁻ strains as our further research targets to investigate the detailed biological properties of the viruses. GMS, which can enhance viral pathogenicity, did not significantly affect replication or viral stability in vitro but significantly promoted the expression of proinflammatory factors to enhance inflammatory responses in mouse lungs. These findings further deepen our understanding of the influence of the glycosylation of the HA protein of H9N2 AIV on the pathogenicity and antigenicity of the virus in mice.

In 2021, a highly virulent strain of duck enteritis virus (DEV), designated as DEV XJ, was isolated from Zhejiang, China, and its complete genome, spanning 162,234 bp with 78 predicted open reading frames (ORFs), was sequenced. While showing relative homology to the DEV CV strain, DEV XJ exhibited distinctions in 38 ORFs, including various immunogenic and virulence-related genes. Amino acid variation analysis, focusing on UL6 and LORF3, indicated a high degree of homology between DEV XJ and the 2085 strain from Europe, as well as the DEV DP-AS-Km-19 strain from India. Subsequently, a full-length infectious bacterial artificial chromosome clone (BAC) of DEV XJ was successfully constructed to delve into the pathogenic mechanisms of this virulent strain. XJ BAC demonstrated substantial similarity to the parental DEV XJ in both in vitro growth properties and the induction of typical pathogenic symptoms in sheldrakes. Furthermore, the US3, LORF3, UL21, and UL36 genes were individually deleted using a two-step RED recombination approach based on the infectious BAC clone. Our findings revealed that the UL21 and UL36 genes play crucial roles in viral proliferation. Although the US3 and LORF3 genes were dispensable for viral replication and cell-to-cell transmission in vitro, they attenuated the replication and transmission efficiency of DEV compared to the WT. In summary, this study accomplished the whole-genome sequencing of a clinically virulent DEV strain and the successful construction of an infectious DEV XJ clone. Moreover, the functional roles of the above-mentioned mutant genes were preliminarily explored through the analysis of their in vitro biological characteristics.