Transboundary and Emerging Diseases最新文献

Newcastle disease (ND) virus (NDV) infection ranks among the most important poultry diseases globally. In Nigeria, ND remains a persistent menace to poultry production, marked by recurrent outbreaks. However, there is limited understanding of the evolutionary changes and transmission dynamics of the virus in the region. A molecular epidemiological study was conducted to elucidate the evolutionary and transmission patterns of NDV in Nigeria. Phylogenetic analysis of seven NDV isolates from cases recorded between 2023 and 2024 in four Northeastern states exhibited genetic diversity and formed distinct clusters that correspond to the prevailing subgenotype XIV.2. The maximum clade credibility (MCC) tree suggests sustained local circulation of the dominant NDV lineage, likely preceded by an international introduction from Southeast Asia. The fusion genes of the Nigerian genotype XIV and another important genotype XVII are mainly under negative selection, but codons 516 (XIV) and 114 (XVII) consistently show positive selection. The Nextstrain analysis reveals ongoing local evolution and genetic diversity of NDV in West Africa, and Central Nigeria acting as a key transmission hub, with evidence of reintroductions from neighboring countries. These findings have implications for NDV control and prevention strategies in Nigeria, highlighting the need for enhanced NDV surveillance, transboundary transmission control, and development of a vaccine tailored to the circulating NDV genotypes. The study also contributes to the understanding of regional spread pattern of NDV and informs evidence-based policies for mitigating the impact of the disease on poultry production.

Animal-origin influenza A virus (IAV) is a perennial candidate for causing the next pandemic. With high risk for interspecies IAV transmission but limited resources for surveillance, particularly in rural areas of low- and middle-income countries (LMICs) such as Laos, there is a need to develop targeted, risk-based strategies for early detection of novel IAVs that may emerge in pigs. We conducted (1) a cross-sectional survey to characterise pig producer types, management practices and pig movement patterns; (2) sampling among pigs in slaughterhouses to quantify IAV seroprevalence and infection; and (3) within- and between-herd disease modelling exploring the relative importance of farm type for the IAV epidemiology. Overall, 31.3% (100/319) of sera and 1.4% (7/515) of nasal swab samples from pigs tested positive for IAV antibodies (ELISA) and viral RNA (PCR detection of IAV M-gene), respectively. Most pigs sampled were exotic breeds and supplied by commercial farms. Using hierarchical Bayesian logistic regression models, seropositivity was significantly higher among exotic breeds compared with local breeds and higher among pigs originating from provinces outside of our study area. Stochastic, individual-based models of within- and between-herd transmission were developed and calibrated for five pig producer types using the cross-sectional data from 202 study participants. The modelling results suggested sustained IAV transmission between farms was unlikely unless the probability of local transmission, independent of pig movement, was relatively high, and the initial infection was seeded in areas with higher densities of smallholders. Between-herd IAV transmission was only sustained in scenarios where persistently infected commercial farms were present to continuously seed infection among the pig smallholder network. Together, these factors underscore risks associated with livestock intensification in commercial and smallholder productions. A larger study is warranted to fully characterise the interprovincial pig movement and evaluate IAV transmission within Laos to inform the national surveillance strategy.

Infectious bursal disease virus (IBDV) is one of the most impactful pathogens of poultry, with disease manifestations ranging from acute forms to subclinical but immunosuppressive infections. This heterogeneity, accompanied by a significant antigenic variability, is sustained by high mutation rates and frequent reassortments between the two genome segments, along with less frequent recombination events. In recent years, the proposal of several classification systems relying on phylogeny contributed to the characterization of several new IBDV genotypes, shedding light on an increasingly diverse epidemiological scenario. One of the most notable examples is the discovery of novel variant IBDVs (nvIBDVs, genotype A2dB1b), which, after emerging in China around 2015, rapidly spread across East and Southeast Asia. More recently, nvIBDVs were also reported in Egypt and Argentina, prompting concern due to their well-established immunosuppressive potential and divergent antigenic features. The detection of A2dB1b strains in Egypt elicited a molecular survey to track their spread within the Middle East. From November 2023 to November 2024, diagnostic samples were collected from 138 flocks in 7 Near East and Persian Gulf countries. The analyses revealed that 55 of them (39.9%) were positive for field strains belonging to 3 genotypes, suggesting a high infectious pressure. Two genotypes, A3B1c and A6B1a, were already reported in the region, although they were found in additional areas. On the other hand, A2dB1b was identified for the first time in Jordan, Lebanon, and the United Arab Emirates, representing a large share of the field viruses detected in these countries. Phylodynamic analyses revealed that this swift spread may have been caused by separate introduction events from Egypt, East Asia, and even South America, highlighting the complexity of IBDV epidemiology. The obtained results will be crucial to better tackle IBDV in the region, guiding monitoring activities and raising awareness toward its proper control.

Controlling populations of Ixodes ticks has emerged as a core strategy for reducing human exposure to tick-borne infections. Several means of reducing the size of the tick population using chemical and biological acaricides show promise in field trials and are frequently used commercially in North America and Europe. The Tick Project (TTP) assessed whether the use of two commercially available methods of reducing the abundance of host-seeking blacklegged ticks (Ixodes scapularis) reduced encounters with ticks and reported cases of tick-borne disease in humans and their outdoor pets. Residential neighborhoods were the units of replication. Here, we synthesize the results of this large-scale, long-term ecological and epidemiological study and integrate them with comparable literature to assess: (1) the peridomestic risk factors linked to tick encounters and cases of tick-borne disease; (2) the spatial scale of these risk and response factors; (3) discordance between ecological consequences of tick control (strongly reduced tick abundance) and weak or undetectable epidemiological responses; (4) possible causes of the failure of tick control to reduce disease incidence; and (5) future approaches to preventing tick-borne disease with environmentally- and behaviorally-based interventions. We conclude that the low efficacy of tick control in reducing cases of tick-borne disease observed to date could be improved with greater attention to human behaviors that affect exposure risk.

The global spread of multidrug-resistant hypervirulent Klebsiella pneumoniae (MDR-HvKp), among which carbapenem-resistant strains are of major concern, poses a severe threat to public health due to its high mortality rate and extremely limited treatment options. While human-derived HvKp strains are well-studied, animal-origin variants remain poorly characterized. Here, we isolated a HvKp strain KPB from a swine farm in China, exhibiting high mortality and extreme virulence (LD₅₀ = 20 CFU). Phylogenomic analysis of 342 K. pneumoniae genomes revealed that the swine-derived KPB (sequence type 25 [ST25] lineage) clusters closely with clinical isolates, suggesting zoonotic transmission risks. Targeted mutagenesis identified wcaJ/wzc-mediated capsule synthesis as the critical virulence determinant, with capsule-deficient mutants showing 100% reduced lethality in mouse infection models. Building on this, we developed a phage therapy achieving 100% survival in infected mice at 10¹ PFU doses. These findings highlight the evolutionary convergence of animal and human HvKp strains and propose phage-based strategies as a promising countermeasure against infections due to HvKp. Our study underscores the urgency of One Health surveillance to mitigate zoonotic threats.

Mosquitoes play a crucial role as vectors of disease pathogens and are among the most socioeconomically important animals in the world. Medically important arboviruses include the Sindbis virus (SINV), which causes chills, skin rashes, and joint pain. Endemic in northern Europe, SINV has been increasingly detected in central Europe. The main objectives of this study were to monitor and screen mosquitoes for the presence of SINV. We included samples of mosquitoes collected throughout the years at different locations in Slovenia. The mosquitoes were first identified and then pooled according to species, sex, date of sampling, and location. Nucleic acid (NA) was isolated from these pools, and the target segment of the SINV genome was amplified using molecular methods. We performed detailed phylogenetic analyses of the SINV-positive mosquito pools. From 2020 to 2024, we monitored mosquitoes at 226 locations in Slovenia and collected 112,001 samples, which were identified and grouped into 11,595 pools. Using real-time reverse transcription polymerase chain reaction (RT-PCR), we found SINV RNA in five pools of Culex modestus mosquitoes collected in two regions of northeastern Slovenia in August 2022 and in July, August, and September 2024. The SINV discovered in Slovenia (SINV-SLO) was classified as Genotype IV. We designed a primer scheme for the whole-genome amplification of SINV based on the alignment of the available SINV-IV sequences and performed molecular characterization of the sequences. Our findings revealed that SINV-SLO is closely related to the SINV strains identified in Russia, Azerbaijan, and China. In Europe, it is Genotype I that is most frequently detected and causes epidemics, whereas Genotype IV, which was detected in Slovenia, has not yet been associated with disease outbreaks.

Peste des petits ruminants (PPR) is a highly contagious viral disease prevalent in sheep and goats, and causes significant economic losses. The study was conducted in 2024 in Punjab Province, Pakistan, to estimate the seroprevalence of the PPR virus (PPRV) and to analyze animal-level risk factors in unvaccinated small ruminants. Over a 12-month period, multistage random sampling provided 722 serum samples of sheep and goats aged 6 months or older, collected across six districts. The anti-PPRV antibodies were detected using competitive enzyme-linked immunosorbent assay (cELISA), and species, age, sex, breed, parity, lactation status, pregnancy status, body condition score (BCS), and reproductive history were analyzed using univariable and multivariable logistic regression analyses. The overall seroprevalence rate was 79.77%, but significantly higher in goats (90.27%) than in sheep (68.75% and p  < 0.0001). The results demonstrated district wise disparity, with variation in seroprevalence between districts: 52.05% (Okara) and 100% (Nankana). An increased likelihood of seropositivity was found to be associated with male sex, some breeds (Makhi Cheeni and Beetal), certain species-district interactions, and age-sex interactions. These data confirm the high endemicity of PPRV in Punjab and justify the targeted vaccination and surveillance in high-risk areas and among susceptible animal populations.

Over the past decade, porcine circoviruses (PCVs) have continued to pose a significant threat to global swine health, and pivotal discoveries have significantly reshaped our understanding of their biology and control. Extensive genomic surveillance has expanded porcine circovirus 2 (PCV2) genotyping from four to at least eight lineages, with PCV2d now globally dominant under vaccine-driven selection pressure. Since 2016, three novel species, PCV3, PCV4, and PCV5, have been identified, linked to reproductive failure, myocarditis, multisystemic inflammation, and potential neuroinvasion; however, their pathogenic potential remains under active investigation. Recent studies have revealed that PCVs evade host defenses by targeting the cyclic GMP-AMP synthase (cGAS)–stimulator of interferon genes (STING)–type I interferon (IFN-I) pathway and modulating regulated cell death pathways, thereby fostering viral persistence and immune dysregulation. PCV–induced immunosuppression not only exacerbates bacterial and viral coinfections but also impairs vaccine efficacy, leading to complex clinical outcomes. Advances in structural virology have clarified the roles of the Cap protein, identifying key antigenic loops and posttranslational modifications that influence immunogenicity and vaccine escape. This knowledge has accelerated the development of novel diagnostic assays and next-generation vaccines. Furthermore, vaccine innovation has progressed beyond traditional inactivated formulations to recombinant subunit, virus-like particle, and DNA platforms, some of which incorporate modular or multivalent designs to address genotype diversity and coinfection scenarios. Despite these advances, challenges persist, including the continuous emergence of immune-escape variants, inconsistent vaccine performance under field conditions, and an incomplete understanding of the pathogenicity of PCV3 to PCV5. Therefore, multidisciplinary strategies integrating molecular epidemiology, structural vaccinology, and advanced biotechnologies will be critical to closing current knowledge gaps and ensuring sustainable PCV control.

Novel duck orthoreovirus (NDRV) infection induces severe splenic necrosis in ducks, resulting in a cascade of detrimental consequences, including immunosuppression, secondary infections, and diminished vaccine efficacy. Avian orthoreovirus (ARV) exhibits high tropism for macrophages, with splenic macrophages being identified as the primary target cells of NDRV. Although ferroptosis has been implicated in this pathological process, the molecular mechanism underlying NDRV-induced cellular damage remains poorly elucidated. In this study, an in vitro model of NDRV infection was established using HD11 cells to systematically investigate its effect on ferroptosis and the associated mechanisms. Our results indicate that NDRV infection triggers ferroptosis and markedly elevates intracellular Fe²⁺ levels. Mechanistically, NDRV upregulates transferrin receptor 1 (TfR1), thereby enhancing iron uptake, promoting iron accumulation, and ultimately inducing ferroptosis. This study is the first to reveal that NDRV induces macrophage ferroptosis by hijacking cellular iron metabolism, providing a theoretical foundation for understanding the mechanism through which NDRV infection mediates splenic necrosis and immune cell injury.

Leptospira is a genetically diverse genus of spirochetes comprising over 68 species, including several pathogenic taxa such as L. interrogans, L. santarosai, L. noguchii, and L. weilii. These bacteria infect a wide range of vertebrates, especially mammals, with infected animals serving as renal carriers that excrete the pathogen through urine. While rodents are the primary reservoirs for some species, multiple vertebrate orders participate in Leptospira transmission cycles in the Americas. This study aimed to assess and compare the genetic diversity of Leptospira populations across mammalian hosts throughout their distribution ranges in the Americas, exploring the influence of host interactions on bacterial diversity. Data for this study were obtained from two sources: (1) original screening of bats and rodents for pathogenic Leptospira and (2) partial gene sequences (16S, LipL32, and SecY) retrieved from GenBank, including sequences from human leptospirosis cases. A total of 321 animals were sampled (104 rodents and 217 bats), with an overall infection frequency of 12.1%. Positive samples were identified via BLAST as L. interrogans, L. noguchii, L. santarosai, L. alexanderi, and L. weilii. Genetic diversity metrics were calculated, and haplotype networks were constructed. Overall analyses revealed greater genetic diversity in bat Leptospira sequences, particularly in the SecY gene. In contrast, artiodactyls exhibited high intraspecific variation, suggesting a potential role in generating new Leptospira variants. Marsupials, rodents, and carnivores showed limited Leptospira diversity. These findings offer new insights into the evolutionary dynamics of Leptospira in the Americas and highlight the role of host ecology in shaping pathogen genetic diversity.