Objective Prepubertal mice are administered subcutaneously with letrozole sustained-release pellets behind the neck and treated with a high-fat diet to establish a mouse model of polycystic ovary syndrome (PCOS). The liver transcriptomes of the model mice are compared with those of the placebo control mice to investigate the underlying mechanisms of liver involvement in the pathogenesis of PCOS. Methods A customized 2 mg dose of letrozole sustained-release pellets with a 40-day release period was used. The control placebo and letrozole pellets were implanted subcutaneously in the dorsal cervical region of 3-4-week-old C57BL/6J mice (8 mice per group) to establish the control group and letrozole-induced PCOS model group. Both groups were treated with a high-fat diet starting the day after administration. The modeling period lasted for 5 weeks, during which body weight and 24-hour food intake were monitored in each group every week. When samples were collected, liver weight was recorded. Pathological changes in ovarian and hepatic tissues were examined by hematoxylin-eosin (HE) staining, while hepatic lipid deposition was observed by Oil Red O staining. The extent of macrophage infiltration in the liver was evaluated via F4/80 immunohistochemical staining, and hepatic fibrosis levels were observed by Masson's trichrome staining. Transcriptomic sequencing was performed to analyze differentially expressed genes (DEGs) in liver tissues between the control and model groups, followed by enrichment analysis of significant DEGs. Quantitative real-time fluorescent quantitative PCR (qPCR) was subsequently used to validate the expression of significant DEGs in liver tissues of both groups. Results Compared with the control group, the model group which received subcutaneous letrozole sustained-release pellets combined with a high-fat diet exhibited significantly increased body weight (P<0.001), prominent polycystic ovarian morphology, and significantly decreased liver-to-body weight ratio (P<0.05). However, no significant changes were observed in absolute liver weight (P>0.05), hepatic histomorphology, or lipid deposition. Transcriptome sequencing identified 119 upregulated and 217 downregulated DEGs in the liver tissues of letrozole-treated mice, which were predominantly enriched in pathways related to cholesterol and steroid biosynthesis, steroid hormone metabolism, and inflammatory responses. qPCR validation demonstrated that mRNA expression of HSD3B2 and HMGCR was significantly upregulated in liver (P<0.01), while mRNA expression of IL4, CCL2 and COL1A1 was downregulated (P<0.05) in the model group compared with the control group. However, Masson's trichrome staining and F4/80 immunohistochemical analysis showed no significant changes in hepatic fibrosis or macrophage infiltration. Conclusion Subcutaneous administration of letrozole sustained-release pellets combined with a high-fat diet successfully establishes a mouse model of PCOS. The model mice exhibited significant changes in hepatic gene expression. Liver may contribute to PCOS pathogenesis through regulating cholesterol and steroid metabolism.

Objective By simulating the etiology of abnormal uterine bleeding-ovulatory dysfunction (AUB-O) and establishing a rat model of abnormal uterine bleeding (AUB), this study aims to provide an experimental platform for investigating pathological mechanisms and developing therapeutic drugs for AUB. Methods After acclimation, 24 adult (10-week-old) female SD rats were randomly divided into a normal control group (6 rats) and a model group (18 rats). The normal control group was housed in a barrier environment, while the model group underwent bilateral ovariectomy via dorsal approach in the same environment and rested for one week before starting to receive modeling drugs. In the model group, from Days 1 to 3 of modeling, each rat received a daily subcutaneous injection of 0.5 mg estradiol into the dorsal region. From Days 4 to 7, a daily subcutaneous injection of 5.0 mg progesterone was administered. On Day 6, rats received bilateral injections of 0.5 mL soybean oil per uterine cavity (total 1.0 mL) via the same dorsal surgical incision. On Day 8, mifepristone (10 mg/kg) was administered via oral gavage. The estrous cycle stage and its dynamic changes were continuously monitored during modeling. Uterine bleeding was recorded during the 48-hour observation period post-modeling. Serum and uterine tissue samples were collected from the model group at 0, 12, 24, 36, and 48 h after mifepristone administration, while the normal control group was sampled at 36 h. The samples were subjected to HE staining, serum sex hormone ELISA, immunohistochemistry, TUNEL apoptosis staining, Western blotting, transcriptome sequencing, and bioinformatics analysis for comprehensive evaluation of the AUB rat model. Results The AUB rats exhibited uterine bleeding, endometrial detachment and injury, incomplete uterine restoration, inflammatory cell infiltration in the endometrium, enhanced tissue apoptosis, and structural damage of the stroma, glands, and vasculature. Compared with the normal control group, the levels of serum follicle-stimulating hormone (FSH), estradiol, and luteinizing hormone (LH) were significantly increased in the AUB rats (P<0.05). The vascular density of the endometrium was significantly reduced (P<0.05). The expression of vascular endothelial growth factor (VEGF) was qualitatively observed to be markedly enhanced at the site of endometrial detachment but significantly decreased around the stromal blood vessels (P<0.01). Matrix metalloproteinase-9 (MMP-9) expression was qualitatively observed to be strongly upregulated at the site of endometrial injury but significantly reduced in the non-detached stroma and glands (P<0.01). Endometrial stromal cell apoptosis was significantly enhanced (P<0.01). The expression levels of fibroblast growth factor 2 (FGF2) and endothelin-1 (ET-1) in uterine tissues were significantly decreased (P<0.05). After comparing the transcriptome sequencing results of uterine tissues between AUB and normal rats, a total of 4 723 differentially expressed genes were identified, including 2 191 up-regulated genes and 2 532 down-regulated genes. KEGG enrichment analysis revealed that these differentially expressed genes were significantly enriched in pathways related to inflammation, immune apoptosis, cell signal transduction, proliferation and differentiation, and muscle contraction, among others. Conclusion An AUB rat model can be successfully established using a sequential administration protocol of estrogen, progesterone, and mifepristone to simulate the etiology of AUB-O. In this model, endometrial injury is associated with inflammation and apoptosis, with pathological manifestations influenced by abnormal vasoconstriction and impaired endometrial regeneration. This rat model closely recapitulates pathological characteristics of non-structural AUB observed in clinical practice, making it a validated experimental platform for exploring the pathological mechanisms and therapeutic interventions of non-structural AUB.

Objective To investigate the changes in oral microbiota of db/db mice and provide an experimental basis for exploring the relationship between type 2 diabetes mellitus and oral microecology. Methods Eight 10-week-old male db/db mice were designated as the diabetes experimental group (db/db group), while eight 10-week-old male db/m mice were assigned as the normal control group (db/m group). After a 5-day adaptive feeding period, tail venous blood samples were collected on the 6th and 37th days, and fasting blood glucose (FBG) levels and oral glucose tolerance test (OGTT) were performed for both groups to verify the reliability of the diabetes model. On the 15th day of feeding with the same diet, oral microbiota samples were collected from the buccal mucosa, dorsal and ventral tongue surfaces, oral floor mucosa, hard palate mucosa, and the gingival areas of both the upper and lower jaws of the two groups. Genomic DNA from the oral microbiota was extracted, and the V3-V4 regions of the 16S ribosomal RNA (16S rRNA) gene were amplified using a GeneAmp 9700 thermocycler. The composition of the oral microbiota was evaluated through double-labelled amplification and sequencing on the Illumina MiSeq platform, followed by bioinformatics analysis using QIIME software(version 1.6.0). Results The FBG levels and OGTT results on the 6th and 37th days after the start of the experiment indicated that db/db mice exhibited more pronounced symptoms of type 2 diabetes compared to db/m mice. Alpha diversity (α diversity) analysis showed no significant difference in the diversity of oral microbiota between the two groups (P>0.05); however, there was a significant difference in richness (P<0.05). Principal coordinate analysis(PCoA) revealed differences in the oral microbiota composition between the db/db group and db/m group (P<0.05). Species composition analysis and LEfSe analysis demonstrated that the relative abundance of oral microbiota in db/db group mice, predominantly composed of p_Proteobacteria, increased significantly at the phylum level (P<0.05). At the genus level, the relative abundances of g_Proteus and g_Enterococcus showed a significant increase (P<0.001). Conclusion The composition and diversity of oral microbiota in db/db mice with type 2 diabetes mellitus significantly differed from those without the disease.

Drug addiction, also referred to as drug dependence or substance use disorder, is a chronic and recurrent brain disease. Its main characteristics are compulsive drug-seeking behavior, continued use of drugs, and a loss of control over intake. Prolonged use of addictive substances can result in both physiological and psychological dependence. When usage is ceased, individuals may experience intense discomfort, including anxiety, insomnia, nausea, vomiting, and a strong craving for the substances. Drug dependence is classified into two types: physical dependence and psychological dependence. Physical dependence describes a pathological state of adaptation that results from the repeated use of addictive substances, leading to severe withdrawal syndrome upon cessation. Psychological dependence involves a mental craving for addictive substances, which is needed to experience the specific euphoria that follows consumption. Regular or continuous use is required to sustain these euphoric effects. The mechanisms of addiction are complex and influenced by genetic, environmental, and various other factors. They involve higher-level neurological activities, such as memory, reward, and decision-making. Currently, effective treatment methods for drug addiction are insufficient. Due to the complexity of drug addiction, laboratory animal research is essential. Using animal behavioral models to simulate human drug addiction can enhance our understanding of the mechanisms of addiction. This research offers a comprehensive overview of various animal experimental models that explore both physical and psychological dependence. It includes detailed descriptions of the methods and procedures used to assess physical dependence, behavioral sensitization, conditioned place preference, drug discrimination, and self-administration experiments. Additionally, the characteristics of each experimental model are compared, and the relevance of these models is discussed, aiming to provide support for the research on addiction mechanisms and the development of therapeutic methods.

Bronchial asthma (hereinafter referred to as asthma) is a common chronic respiratory disease characterized by airway inflammation, airway hyperresponsiveness, and airway remodeling. Its pathogenesis is highly complex and heterogeneous, involving multiple factors such as genetics, immunity, and environmental exposure. Currently, therapeutic options for asthma remain relatively limited, making it an urgent priority to explore its underlying mechanisms, identify effective treatment strategies, and develop new drugs. In this context, the establishment of animal models for asthma plays an irreplaceable and crucial role. However, to date, no single ideal animal model has been able to fully and accurately replicate all the features of the onset and progression of human asthma. This study systematically reviews the research progress over the past five years in the establishment methods of asthma animal models. It provides a detailed overview of commonly used experimental animals (such as mice, rats, and guinea pigs), frequently used sensitizing agents (including ovalbumin, house dust mite, lipopolysaccharide, and toluene diisocyanate), and the methods for establishing asthma models using these animals and sensitizers. This study also presents an objective evaluation of the advantages, limitations, and applicability of each model. Evaluation criteria for asthma models are summarized across multiple dimensions, including behavioral assessments, pulmonary function, histopathology, immunological indicators, and pharmacodynamics. Although methods for establishing refractory asthma models remain underdeveloped, several strategies for modeling refractory asthma have been summarized through a review of relevant literature, aiming to provide useful references for related research. Based on current scientific and technological advancements, it is anticipated that future research on asthma animal models will focus more on clinical relevance, technological innovation, and multidisciplinary integration. Specifically, future models are expected to adopt multi-sensitizer induction protocols, apply cutting-edge tools such as gene editing, enhance clinical relevance and promote diversification and personalization of models. Furthermore, advanced technologies such as bioimaging and biosensing are anticipated to enable dynamic monitoring of airway inflammation and remodeling. Organ-on-a-chip platforms may also be explored as potential alternatives to traditional animal models. The ultimate goal is to develop multifactorial, composite models that better simulate the complexity and heterogeneity of human asthma.

Myasthenia gravis (MG) is an autoimmune disease characterized primarily by skeletal muscle weakness and, in severe cases, respiratory involvement. Western medical treatment predominantly relies on immunosuppressants, but long-term administration often leads to notable side effects. In contrast, traditional Chinese medicine (TCM) offers the advantage of multi-target interventions. However, the pathogenesis of MG has not been fully elucidated, and the establishment of animal models that accurately reflect the clinical characteristics of both Chinese and Western medicine is essential for mechanism research and new drug development. This paper systematically reviews the etiology and pathogenesis, diagnostic criteria, and progress of animal model research for MG from both Chinese and Western medicine perspectives. In Western medicine, the pathogenesis of MG is closely related to genetic susceptibility, environmental factors, and autoantibody-mediated postsynaptic membrane damage. In TCM, MG is classified under the category of "flaccidity syndrome", attributed to congenital deficiencies and acquired malnourishment. Western diagnostic criteria involve a combination of clinical symptoms, fatigue testing, serum antibody assays, and electrophysiological evaluation. In contrast, TCM diagnosis emphasizes the integration of primary and secondary symptoms with tongue and pulse pattern differentiation. Currently available animal models mainly include experimental autoimmune myasthenia gravis (EAMG) and passive transfer myasthenia gravis (PTMG). The Toredo acetylcholine receptor (AChR) induced EAMG model aligns well with Western diagnostic criteria, but poorly matches secondary symptoms in TCM. The synthetic AChR peptide model is widely used, but shows low conformity with TCM syndromes. Models induced by muscle-specific tyrosine kinase (MuSK), low-density lipoprotein receptor-related protein 4 (LRP4), and transgenic models demonstrate high innovation but exhibit low clinical conformity. Evaluation of these models requires integration of behavioral, electrophysiological, and immunological indicators. However, a systematic framework for modelling TCM syndromes is still lacking. Future research should integrate TCM-based etiological modelling methods with the Western pathological mechanisms to construct disease-syndrome combination models. Additionally, it is crucial to establish a TCM syndrome evaluation system based on "validation by prescription", as well as to improve the scientific rigor and practicality of animal models by the incorporation of emerging technologies. This review provides a theoretical foundation for optimizing MG animal model design, advancing the research on the combination of Chinese and Western medicine, and supporting efficacy assessment and mechanism exploration of Chinese herbal prescriptions.

As one of the modern enterprise management systems, the Occupational Health and Safety Management System (OHSMS) has garnered increasing attention. The OHSMS has undergone continuous refinement and expansion across various fields, emerging as a pivotal indicator of enterprise competitiveness. Currently, both the Association for Assessment and Accreditation of Laboratory Animal Care (AAALAC) International and the China National Accreditation Service for Conformity Assessment (CNAS) require for establishing occupational health management related to laboratory animal work. However, within the domestic laboratory animal industry, development of OHSMS is relatively lagging behind due to unfamiliarity with laws and regulations and a lack of experienced management personnel. Consequently, the OHSMS in laboratory animal institutions is still in its early stage. Drawing on the authors' practical experience in establishing OHSMS in laboratory animal institutions, this article first outlines domestic and international occupational health laws, regulations, and safety management systems for laboratory animals, as well as common occupational diseases and their associated risk factors in China. Subsequently, this article highlights key elements for the construction of OHSMS in laboratory animal institutions in areas such as establishing occupational health and safety regulations, conducting training, performing occupational health examinations for staff, monitoring on-site occupational hazard factors, implementing the "three simultaneous" system for occupational disease prevention facilities in construction projects, creating and maintaining occupational health records, developing a notification management system for occupational hazards, and formulating emergency response plans for occupational disease hazard accidents. These points are intended as a reference for professionals in the industry.

Owing to their high genetic and physiological similarities to humans, non-human primates (NHPs) have become pivotal animal models in life sciences research and biomedical development. NHP laboratory animals are not only an ideal platform for exploring the mechanisms of neurological diseases and infectious diseases, but they are also widely used in preclinical safety evaluations of macromolecular drugs, which are considered the "gold standard". Nevertheless, this biological similarity increases the risk of zoonotic disease transmission to personnel working with NHP laboratory animals, their tissues, and body fluids. In light of recent domestic and international outbreaks of zoonotic diseases as well as the implementation of the Biosafety Law, this study examines the occupational risk factors encountered by personnel working with NHPs. This includes biological, chemical, and physical factors. This paper also covers common zoonoses, classification of the corresponding pathogens, transmission routes, risk severity levels, and protocols for post-exposure management. A multidimensional prevention and control framework is proposed, which includes the following components. (1) Risk Assessment and Emergency Response: Regularly identify hazards through an Occupational Health and Safety Committee (OHSC) and develop post-exposure emergency protocols. (2) Optimization of Management Systems: Improve facility design, optimize the allocation of personal protective equipment, and enhance health surveillance and vaccination programs. (3) Technical Training and Standardized Operations: Provide specialized training in NHP laboratory animal ethology and biosafety practices. Additionally, implement intelligent monitoring technologies to reduce the occurrence of aggressive incidents. This paper outlines measures designed to enhance health and safety awareness among personnel working with NHP laboratory animals. It emphasizes the need for strengthened guidance on the use of personal protective equipment (PPE) and the standardization of professional operational practices. The goal is to safeguard personnel health and safety, reduce occupational exposure rates, and effectively prevent occupational diseases related to laboratory animals.

With the rapid development of the laboratory animal industry in China, animal experimentation has become a crucial tool for both scientific research output and classroom teaching in universities. Correspondingly, the workforce engaged in laboratory animal work has expanded significantly. In recent years, while the Chinese government has begun to emphasize the occupational health of laboratory animal practitioners by introducing relevant laws and policies, current prevention and control efforts within universities remain insufficient. This study conducted an in-depth investigation into the occupational health management and protection of laboratory animal practitioners in nine general universities in China, focusing on the management standards within university laboratory animal research centers. The research was carried out through field visits, interviews, and academic exchanges, focusing on standardized management practices within university laboratory animal research centers. The findings highlight five major occupational health risks faced by these practitioners: laboratory animal allergy, zoonotic infectious diseases, mechanical injuries, chemical exposures, and psychological factors. Key challenges identified include underdeveloped management systems, a lack of risk assessment mechanisms, and inadequate protective facilities. To address these issues, the study proposes a three-tiered prevention and control framework. At the university level, institutions should establish comprehensive regulatory systems and increase funding investment. At the laboratory animal center level, biosafety laboratories should be developed, risk source management strengthened, and emergency preparedness and health monitoring enhanced. At the level of individual practitioners, appropriate use of personal protective equipment should be enforced, occupational health training should be provided, standard operating procedures should be strictly followed, and occupational exposure incidents should be reported promptly. Through multi-party collaboration, this study explores feasible paths for constructing a scientific and efficient occupational health protection system in domestic universities, aiming to provide theoretical support and practical references for the sustainable development of the laboratory animal industry in China.

Establishing occupational health related files is a key component of building an occupational health and safety management system in laboratory animal institutions. These files not only serve as a critical means of protecting the legitimate rights and interests of laboratory animal personnel but also provide institutional safeguards. According to relevant laws and regulations, laboratory animal institutions are responsible for establishing and properly maintaining occupational health surveillance files (also known as occupational hygiene files) for both the institution and its personnel. In accordance with the Occupational Health Archives Management Standards, laboratory animal institutions are required to maintain at least seven categories of occupational health management archive folders: the "three simultaneous" occupational health archives for construction projects; occupational health management folders; occupational health publicity and training folders; folders for monitoring and evaluating occupational disease hazard factors; employer occupational health surveillance folders; individual occupational health surveillance folders for employees; and other relevant folders. Building upon this foundation, the Regulations on the Supervision and Administration of Occupational Health in the Workplaces further specify detailed requirements for occupational health files. These include: documents outlining the responsibility system for occupational disease prevention and control; occupational hygiene management systems and standard operating procedures, lists of types of occupational disease hazard factors in workplaces, their distribution by job distribution, and records of work exposure, basic information on occupational disease prevention and emergency rescue facilities, along with records of their allocation, usage, maintenance, inspection and replacement; records concerning the provision, distribution, maintenance and replacement of personal protective equipment (PPE); and reports on occupational disease hazard incidents; and corresponding emergency response records—amounting to twelve specific requirements in total. In short, occupational health management files are a comprehensive collection of data and documentation related to workers' occupational health. Based on the author's practical experience, this paper outlines the main types of occupational health management files, their basic contents, and key points in their development. It also offers a detailed analysis of how to establish such files, aiming to support laboratory animal institutions in successfully developing occupational health management archives and improving their occupational health and safety management systems.

Occupational health is a discipline dedicated to the identification, assessment, prediction, and control of occupational hazards in the workplace and their potential impacts on health. Its core objective is to ensure the safety of workers through targeted preventive strategies and protective mechanisms, thereby minimizing health risks caused by occupational hazards and promoting physical health, mental well-being, and overall social welfare in the workplace. The "three simultaneities" of occupational health protection facilities in construction projects (hereinafter referred to as "three simultaneities") refers to the principle that occupational disease prevention facilities must be designed, constructed, and put into operation simultaneously with the main project. The implementation of "three simultaneities" involves several stages: a preliminary assessment of occupational disease risks, the design of occupational disease protection facilities in accordance with relevant standards, and ensuring these facilities are constructed in parallel with the primary engineering project to maintain integrity and effectiveness. During the construction phase, occupational disease prevention facilities must be constructed simultaneously with the main project to ensure their integrity and effectiveness. Upon project completion, the construction unit is responsible for evaluating the control effects of occupational disease hazards and conducting the acceptance of occupational disease prevention facilities to ensure the occupational health of employees. The implementation of the "three simultaneities" for occupational disease protection facilities in construction projects is a mandatory national regulation, and non-compliance may result in legal penalties such as fines and forced suspension of work. However, for some laboratory animal institutions, the implementation of the "three simultaneities" remains a challenge. This paper aims to provide practical guidance and feasible implementation strategies for such institutions by introducing the development history of the "three simultaneities" in occupational health, explaining its relevance and necessity in the context of laboratory animal facilities, and outlining step-by-step procedures for compliance and implementation.

Objective To investigate the susceptibility and infection characteristics of dengue virus (DENV) in cells derived from diverse tissues of tree shrews and to provide a basis for expanding the repertoire of DENV-permissive cell models in this species. Methods DENV was inoculated at a multiplicity of infection (MOI) of 0.02 into tree shrew skin fibroblasts (TSFs), primary tree shrew renal epithelial cells (pTRECs), tree shrew aortic endothelial cells (TAECs), tree shrew aortic smooth muscle cells (TASMCs), tree shrew hepatocytes (THs), tree shrew corneal stromal cells (TCSCs), tree shrew brain microvascular endothelial cells (TBMECs), and tree shrew retinal microvascular endothelial cells (TRMECs). C6/36, Vero, A549, and BHK-21 cells (commonly used for DENV propagation) were used as positive controls. Over 6 days post-infection, cellular cytopathic effects were monitored at 12-hour intervals using an inverted microscope, viral RNA loads in cell lysates were quantified by real-time fluorescent quantitative PCR to generate proliferation curves, and viral titers were determined by plaque assay. Results Seven types of tree shrew cells, except TRMECs, were susceptible to DENV. Prolonged infection induced pronounced cytopathic effects, including cell rounding, detachment, necrosis, and lysis, across all susceptible cells. The viral RNA loads detected in lysates of pTRECs, TBMECs, TASMCs, TAECs and THs, approached those of positive controls (≥4×10? copies/μL). Infectious progeny viruses were produced by these five cell types, with three (TAECs, 3.13×10⁵ PFU/mL; THs, 2.03×10⁵ PFU/mL; pTRECs, 1.58×10⁵ PFU/mL) exhibiting titers comparable to C6/36 (3.85×10? PFU/mL) and earlier viral harvests. Conclusion DENV exhibits broad susceptibility to tree shrew cells of multiple tissue origins, with proliferation rates surpassing those of conventional cell lines sourced from other species. TAECs, THs, and pTRECs are particularly suitable for large-scale DENV proliferation, suggesting their potential involvement in in vivo infection.

Infectious disease animal models serve as indispensable tools for understanding the transmission patterns, pathogenesis, and anti-infective medicine. During the preparation and application of infectious animal disease models, situations inevitably arise that violate animal welfare and ethics, such as animal pain, suffering, and distress. Considering the biosafety factors, animal mortality is still used as the experimental endpoint in most experiments on infectious animals, which poses extremely high requirements for animal welfare and ethics. It is imperative to establish guiding principles or norms for the welfare and ethics of infectious animal experiments. Based on the fundamental principles of the welfare and ethics of experimental animals, this paper explores the special welfare and ethical requirements in infectious animal experiments. It emphasizes that infectious animal experiments should fully consider the balance among the scientific objectives of the research plan, animal welfare and ethics, and occupational health and safety of personnel. Based on literature research and comparative analysis of the welfare and ethical requirements of conventional animal experiments, special welfare and ethics requirements for infectious animal experiments are proposed, including personnel requirements, experimental animal selection standards, living environment management and equipment, special care and veterinary care, and humane endpoints. Personnel are required to undergo effective biosafety training, and sufficient authority should be granted to the Institutional Animal Care and Use Committee (IACUC), veterinarians, and veterinary technicians to ensure the implementation of animal welfare and ethics practices. The selection of laboratory animals should fully consider the requirements of research objectives, welfare, ethics, and biosafety, with the susceptibility and body size of laboratory animals being the key concerns in high-level biosafety laboratories. It is also clarified that the humane endpoint is an indispensable element of welfare and ethics in infectious animal experiments. Environmental enrichment and special care are necessary guarantees for achieving animal welfare and ethics. Therefore, this study can serve as a reference for relevant work.