1.Construction of a technical indicator framework for the prevention of re-establishment of imported malaria in China during the malaria post-elimination stage
LIU Bowen ; ZHANG Tao ; LIU Jingshu
China Tropical Medicine 2025;25(1):1-
Objective The objective of this research is to construct a technical indicator framework for preventing the of re-establishment of imported malaria at the county level in China, excluding border areas, with the aim of guiding specialist agencies to prevent the re-establishment of imported malaria in a scientific, feasible and comprehensive way. Methods The preliminary framework was built based on literature review and on-site research. Two rounds of Delphi consultation were carried out. The positive coefficient, degree of concentration, degree of coordination, and authority of the experts were calculated. The weights and the combined weights for the indicators were determined using the analytic hierarchy process and probability method, respectively. Results Twenty experts were invited in the 1st round of consultation, and twenty-six in the 2nd round. The authority coefficients of the experts for two rounds were 0.955 and 0.968, respectively. The P value of the degree of coordination of two rounds were less than 0.05. The final framework included 5 primary indicators, 19 secondary indicators and 42 tertiary indicators. Primary indicators included government-led, joint control and prevention, surveillance and response, capacity building and organization guarantee, whose weights were 20.2%, 2.4%, 20.1%, 44.7% and 12.5%, respectively. Among the secondary indicators, the highest combined weight was medical institutions (25.0%) of capacity building, and the lowest was cross-sectoral cooperation (0.3%) of joint control and prevention. The three tertiary indicators with higher combined weights were: "1.2.1 There is a comprehensive plan for preventing the re-establishment of imported malaria, and the responsibilities of relevant departments are clearly defined" accounting for 14.9%; "4.1.4 Laboratory personnel in medical institutions possess the ability to conduct microscopic examinations for malaria detection" accounting for 10.6%; and "4.2.1 Specialized malaria surveillance laboratories have been established and are fully equipped with the necessary capabilities to conduct effective surveillance" accounting for 7.6%. Conclusions A framework has been created for the prevention of re⁃establishment of imported malaria at the county level in China, excluding border areas. The framework provides an operational, scientific and comprehensive technical guidance for county-level areas from the perspective of the effectiveness of government-led, joint prevention and control, surveillance and response, capacity building and organizational support. The importance of maintaining the capacity to prevent re-establishment of imported malaria and whole-process case management under medical and preventive cooperation in the post-elimination stage was highlighted.
2.Spatial epidemiological characteristics and hotspots distribution changing of imported malaria in Jiangsu, 2016-2022
LIU Kaixuan ; CAO Yuanyuan ; CHONG Zeyin
China Tropical Medicine 2025;25(1):9-
Objective To identify the temporal-spatial distribution patterns and changing of hotspot areas of malaria importations, and high-risk importation areas for imported malaria in Jiangsu Province, in order to provide the scientific evidence for prevention of malaria reintroduction in China. Methods Cases with imported malaria in Jiangsu Province from 2016 to 2022 were accessed from the National Notifiable Disease Report System and the Information Management System for Parasitic Disease Control in China. The county-level vector map of Jiangsu Province was obtained from the National Fundamental Geographic Information System, China. ArcGIS 10.7 software was utilized to create a thematic map depicting the distribution of imported malaria cases in Jiangsu Province at the county level. Global and local autocorrelation analysis was then conducted to investigate the spatiotemporal changes in malaria import hotspot counties. Results There were a total of 1 189 cases with imported malaria reported in 77 counties (81.05%, 77/95) of Jiangsu Province from 2016 to 2022. The global spatial autocorrelation analysis showed that a global spatial cluster of imported malaria in Jiangsu was only identified in 2020 ( Moran's I =0.46, Z=4.37, P<0.01), but local spatial autocorrelation analysis found that a total 60 hotspot counties existed from 2016 to 2022. There are 23 counties in central Jiangsu (38.33%), and 20 counties in southern Jiangsu (33.33%), 17 counties in northern Jiangsu (28.33%). The distribution of hotspot counties exhibits continuity. For instance, Chongchuan District, which falls under the jurisdiction of Nantong City, has consistently emerged as a hotspot county for 2016-2021. Since 2020, two recurring hotspot counties emerged in northern Jiangsu and southern Jiangsu. These counties are Ganyu District, under the jurisdiction of Lianyungang City, and Lishui District, under the jurisdiction of Nanjing City. Conclusions The spatial-temporal cluster of cases with imported malaria was identified at the county level in Jiangsu, that hotspot counties were consistently detected. It is essential to maintain the sustainability of malaria surveillance and response in hotspot counties which were new detected, and strengthen the capacity of surveillance and response in hotspot counties which were continually detected based on the spatial-temporal distribution characteristics and changing rules of imported malaria.
3.Impact of capsaicin on the gut microbiota and antimicrobial peptides expression of Anopheles stephensi
ZHENG Dan ; LIU Zhilong ; WANG Jing
China Tropical Medicine 2025;25(1):15-
Objective To investigate the effects of capsaicin on gut microbiota and antimicrobial peptide expression of Anopheles stephensi, providing experimental references for the application of capsaicin in mosquito-borne disease prevention and control. Methods Anopheles stephensi were continuously fed with sugary water containing capsaicin or DMSO for the capsaicin-treated group and the control, respectively. The DNA of the female mosquito's midguts and gut bacteria was extracted. Bacterial 16S rDNA high-throughput sequencing and real-time fluorescence quantitative PCR were used to analyze and compare the bacteria diversity, gut flora composition, relative abundance, and total bacterial load in female mosquitoes’ midgut between the control and capsaicin treatment groups. Total RNA was extracted from the midguts of the two groups of Anopheles mosquitoes, and the transcriptional levels of important antimicrobial peptides were detected and compared by reverse transcription and real-time fluorescence quantitative PCR. Results A total of 10 phyla, 11 classes, 28 orders, 43 families, and 62 genera were identified in the two groups. The capsaicin-treated group had fewer taxa, with significantly reduced bacterial diversity, and different community composition and relative abundance of the flora compared to the control group. At the phylum level, Bacteroidota, Proteobacteria, and Firmicutes predominated in both two groups. At the order level, Flavobacteriales, Acetobacterales, Pseudomonadales, and Lactobacillales were the dominant bacteria, with reduced relative abundance of Pseudomonadales and Acetobacterales and increased relative abundance of Flavobacteriales and Lactobacillales in the capsaicin-treated group. At the genus level, Elizabethkingia was predominantly abundant in both samples, with higher relative abundance of Elizabethkingia, Leuconostoc, and Gluconobacter in the capsaicin-treated group, while Asaia and Acinetobacter had significantly lower relative abundance compared to the control group. In addition to these changes, the total bacterial load was increased and the transcriptional levels of attacin C, cecropin A, and defensin were significantly decreased by capsaicin treatment. Conclusions Capsaicin treatment significantly affects the composition of the gut flora in Anopheles stephensi and increases the total bacterial load while inhibiting the expression of antimicrobial peptides. Based on the analysis, it indicates that capsaicin might affect the fecundity and vector competence of Anopheles by changing the energy metabolism and immune-related bacteria.
4.Isolation and coding region sequence of Japanese encephalitis virus from Culex tritaeniorhynchus in Shuangjiang County, Yunnan Province
GU Yangyang ; HE Yuwen ; RUAN Fangchao
China Tropical Medicine 2025;25(1):22-
BHK-21 cells, cytopathic effects (CPE) were detected, and flavivirus primers were amplified as positive. After the complete sequence of the virus was determined and spliced, a 10 840 nucleotide long sequence was obtained, encoding 3 432 amino acids. Phylogenetic analysis based on the whole gene sequence and E gene sequence showed that: The newly isolated SJM23-22 was most closely related to the GⅠa strain (C081) in Cambodia, with 98.5% nucleotide homology and 99.8% amino acid homology, while the homology with other genotypes was below 90% for nucleotides and below 98% for amino acids. The results of site analysis revealed 22 amino acid difference sites on the E gene compared to the live attenuated vaccine strain SA14-14-2, with 7 differences at 8 neurovirulence-related key amino acid sites. The results of important epitopes analysis indicated an exact match in three important epitopes in domain Ⅲ between the Shuangjiang isolates and the live attenuated vaccine strains. The results of secondary structure and tertiary structure prediction showed that the strain was characterized by random curling. Conclusions One strain of GⅠa-type JEV was isolated from Culex tritaeniorhynchus in Shuangjiang County, with no significant changes in the key amino acid sites related to antigenic epitopes. This study enriches the virus-carrying situation of Culex tritaeniorhynchus in Shuangjiang County, Yunnan Province, providing a reference for the prevention and control of the insect-borne epidemic in the province.Objective To investigate the status and molecular characteristics of Japanese encephalitis virus (JEV) carried by mosquitoes in Shuangjiang County, Lincang City, Yunnan Province. Methods Mosquito specimens were collected from cattle pens using mosquito traps in Shuangjiang County, Lincang City in August 2023. After mosquito species identification, BHK-21 cells and C6/36 cells were used in one group of 25 mosquitoes each. Positive isolates were identified by flavivirus primers. Subsequently, the full-length GⅠ-type JEV was amplified using 15 pairs of primers with RT-PCR, sequenced, and spliced, and sequence analysis was performed using bioinformatics software such as MEGA X, DNAstar, GeneDoc, SOPMA, and SWISS-MODEL. Results A total of 1 300 Culex tritaeniorhynchus were collected and divided into 52 groups for virus isolation, leading to the identification of one positive isolate (SJM23-22). After inoculation with C6/36 and
5.Impact of GM-CSF deficiency on the disease course and immune response in mice infected with Exophiala oligosperma
DONG Qi ; LU Jiejie ; WU Weiwei
China Tropical Medicine 2025;25(1):28-
Objective To investigate the role of granulocyte-macrophage colony-stimulating factor (GM-CSF) deficiency in the pathogenesis of Exophiala oligosperma (E. oligosperma) infection, a dematiaceous fungus, aiming to provide new insights and evidence for the treatment of dematiaceous fungal infections. Methods C57BL/6 wild-type (WT) mice and Csf2 gene knockout (KO) mice (C57BL/6 background) were selected. Using E. oligosperma isolated from patients with caspase recruitment domain-containing protein 9 (CARD9) gene deficiency, a murine subcutaneous infection model was established to simulate the human infection route. The natural progression of infection in the mice was observed for six weeks, with skin lesion tissues collected at appropriate time points for pathological analysis and monitoring immune responses. Results Both WT and Csf2 KO mice exhibited spontaneous pathogen clearance and gradual recovery of foot tissue appearance during the progression of infection, with a 100% survival rate at the end of observation. Compared to WT mice, Csf2 KO mice showed reduced footpad swelling at 1 and 2 weeks post-infection (t=4.674, t=5.961, P<0.01). Fungal clearance in Csf2 KO mice was delayed, with fungal colonies still detectable in lesion tissues at week 4, and Periodic Acid-Schiff (PAS)-positive fungal spores observed in histopathological sections. There was no significant difference found in macrophage infiltration between WT and Csf2 KO mice during the early stages of infection (1-2 weeks) (P>0.05), while neutrophil infiltration was significantly reduced in Csf2 KO mice at week 2 (t=3.287, P<0.01). In addition, Csf2 KO mice exhibited lower levels of IL-6 and IL-1β in foot lesion homogenates at week 1 (t=4.686, t=4.102, P<0.05). Conclusions This study demonstrated that GM-CSF deficiency delays pathogenic fungi clearance, prolongs the disease course and affects early inflammatory cytokine production as well as neutrophil infiltration during the early stages of fungal infections.
6.lague epidemiology in plague focus of wild rodents in Yunnan Province, 2017-2023
SHI Qingxi ; PU Ennian ; SU Liqiong
China Tropical Medicine 2025;25(1):36-
Objective To analyze the epidemic characteristics of plague epidemics, host and vector community structure, and abundance in plague focus of wild rodents in Yunnan Province, 2017-2023, providing a scientific basis for formulating plague prevention strategies and forecasting warning for this epidemic foci. Methods Following the requirements of the "National Plague Surveillance Plan" and the "Yunnan Provincial Plague Surveillance Plan", host-vector surveillance, etiology, and serological testing were carried out, and plague epidemic data and host-vector surveillance data in plague focus of wild rodents in Yunnan Province, 2017-2023 were collected and sorted using Excel 2019 software to create a database for descriptive analysis. Results From 2017 to 2023, 11 animal plague epidemics were discovered in the wild plague foci of Yunnan Province, with 18 epidemic spots. From the altitude distribution point of view, 7 epidemic spots were distributed at an altitude of 2 800-3 000 meters, another seven at 3 000 and 3 200 meters, and four spots were located in areas with an altitude of ≥3 200 meters; a total of 36 samples of host and vector animals were detected positive, including 28 positive samples of host animals and 8 positive samples of vector animals, and 29 strains of Yersinia pestis were isolated; in terms of species composition, Eothenomys miletus accounted for the largest proportion of 41.67%, followed by Apodemus chevrieri at 22.22%; Ctenophthalmus quadratus at 11.11%; Rattus tanezumi and Neopsylla specialis each at 8.33%, and Dremomys pernyi, rat carcass, and Frontopsyllas padix each accounted for 2.78%; the epidemic peaked in April, and no human cases were found. A total of 453 220 rat cages (traps) were placed, capturing 27 677 rodents, with an average capture rate of 6.11%. A total of 25 075 main hosts, Apodemus chevrieri and Eothenomys miletus, were captured, accounting for 90.60% of the total capture rate. A total of 14 700 fleas were seized on the surface of small animals, with a total flea infection rate of 23.13% and a flea index of 0.59. The main vectors were Ctenophthalmus quadratus and Neopsylla specialis, with constituting ratios of 45.71% and 22.69%, respectively. Conclusions From 2017 to 2023, the population density of main host animals in Yunnan's wild rodent plague foci was relatively high and showed an upward trend, possibly related to the local planting structures. Plague plays a regulatory role in host population structures. Epidemics among animals showed obvious seasonality, with a trend of expanding epidemic areas. No human cases were found, but Yersinia pestis was detected in Rattus tanezumi in human settlements, raising the possibility that animal plague could spread to humans. It suggests strengthening the monitoring of areas adjacent to the epidemic source, eradicating rats and fleas in spring, improving the accuracy of plague prediction and early warning, providing strong technical support for the early detection of plague among animals, and preventing the spread of the epidemic to humans.
7.Analysis of soil-transmitted helminthiasis surveillance in China from 2017 to 2022
ZHAO Jin ; ZHOU Yinzhu ; CHEN Shuilian
China Tropical Medicine 2025;25(1):41-
Objective To analyze the current epidemic status of soil-transmitted helminthiasis (STHs) in China, providing reference data for the prevention and control of soil-transmitted helminthiasis. Methods Surveillance data on soil-transmitted helminthiasis in China from 2017 to 2022 were collected and statistically analyzed to investigate the infection status, infection trends, and spatial autocorrelation. Results From 2017 to 2022, the average annual infection rate (AAIR) of soil-transmitted helminthiasis was 1.12% (25 123/2 251 632), with hookworm, roundworm, and whipworm having AAIRs of 0.70%, 0.26%, and 0.20% (15 827 cases, 5 836 cases and 4 586 cases), respectively. The infection rate of soil-transmitted helminths decreased annually by an average of 17.16% (AAPC =-17.16, P=0.007), with annual decreases in the infection rates of hookworm, roundworm, and whipworm being 14.70%, 22.13%, and 20.56%, respectively (AAPC=-14.70, P=0.025; AAPC=-22.13, P=0.015; AAPC =-20.56, P=0.029). The spatial distribution of hookworm, roundworm, and whipworm exhibited spatial positive correlation (Moran's I=0.09, P=0.121; Moran's I=0.46, P=0.001; Moran's I=0.23, P=0.013), with roundworm showing the highest spatial aggregation. The AAIRs of males and females were 1.03% (11 308/1 100 016) and 1.20% (13 851/1 149 286), respectively, with statistical significance (χ2=154.19, P<0.001). The highest AAIR was 1.85% (10 949/590 621) in individuals over 60 years old, with statistical significance across different age groups (χ2=4426.44, P<0.001). Hookworm, roundworm, and whipworm were mainly mild infections. The average annual positive rates of soil ascaris eggs and hookworms were 4.06% (649/15 984) and 2.45%(391/15 984), respectively, with statistical significance (χ2=66.16,P<0.001). Conclusions The infection rate of soil-transmitted helminthiasis in China is relatively low and shows a downward trend. Yet, there are local high-prevalence areas, with the elderly and females being the risk-prone populations. Comprehensive measures including expanding the monitoring scope, innovating monitoring technology, and promoting the rural toilet revolution are necessary to block the spread of soil-transmitted helminthiasis further.
8.Current infection status and genotype of isolated strains of Echinococcus multilocularis in small rodents of Southern Xinjiang
ZHAO Jiangshan ; WANG Shuo ; ZHANG Yue
China Tropical Medicine 2025;25(1):46-
Objective To understand the current infection status and genotype of Echinococcus multilocularis in small rodents in southern Xinjiang, and to provide a theoretical basis for the formulation of local prevention and control measures. Methods In 2023, small rodents were captured and necropsied in Wuqia County, Atushi City, and Hejing County, Xinjiang. DNA was extracted from diseased organs, Cox1 and Nad2 genes were amplified by PCR and sequenced, and MEGA software constructed the phylogenetic tree. Dnasp analyzed the genotype genetic polymorphism of the isolates, and NetWork10 was used to draw the gene haplotype network. Results A total of 1 541 small rodents were captured in three counties (cities), with common voles (Microtus arvalis)(53.01%) and Apodemus sylvaticus (28.1%) being predominant. After necropsy and PCR identification, 13 small rodents were found to be infected with Echinococcus multilocularis, with an overall infection rate of 0.84% (13/1 541). Among them, 11 were common voles, with an infection rate of 1.35% (11/817), and 2 were Apodemus sylvaticus, with an infection rate of 0.46% (2/433). There was no significant difference in the infection rate of echinococcosis between voles and Apodemus sylvaticus (χ2=2.15, P>0.05). The infection rates of Echinococcus multilocularis in small rodents in Hejing County, Atushi City, and Wuqia County were 1.40% (7/500), 1.15% (6/527), and 0, respectively (χ2=6.77, P<0.05). The results of the phylogenetic tree showed that 13 isolates belonged to the Asian type. The results of DNA polymorphism analysis showed that the haplotype diversity of Cox1 gene sequence was Hd=0.834±0.054, with a low nucleotide diversity of Pi=0.004 60±0.000 87; for Nad2 gene, haplotype diversity was Hd=0.758±0.076, and nucleotide diversity was Pi=0.005 99±0.001 59, indicating high haplotype diversity and low nucleotide diversity for both Cox1 and Nad2 genes. The haplotype network diagram showed that the 13 Cox1 gene sequences were dominated by H1 haplotype, with H2, H3, Sichuan (AB477012), Xinjiang (MH259773), and Kazakhstan (AB461415) distributed in a scattered manner and connected to it. The 13 Nad2 gene sequences were classified as H1 haplotype along with those from Xinjiang (OP628494), Japan (OP628493), and Kazakhstan (AB461406). Conclusions Echinococcus multilocularis infections exist in small rodents in Hejing County and Atushi City in southern Xinjiang. The common vole and Apodemus sylvaticus can be used as the dominant intermediate hosts of local Echinococcus multilocularis in the region. There are genetic variations in the Cox1 and Nad2 genes, with the genotypes of all 13 isolates being Asian genotype, and haplotype predominantly H1.
9.Surveillance analysis of SARS-CoV-2 variants in Hainan Province from January 2023 to March 2024
China Tropical Medicine 2025;25(1):52-
Objective To analyze the monitoring data of SARS-CoV-2 variants from local cases in Hainan Province between January 2023 and March 2024, and to understand the predominant variants epidemic situation and population characteristics of SARS-CoV-2 in Hainan Province, providing scientific guidance for the prevention and control strategies formulation, early warning of the risk of SARS-CoV-2 infection. Methods The variation surveillance data submitted by five sentinel monitoring hospitals in Hainan Province from January 2023 to March 2024 were collected, and general descriptive analysis was conducted on the dynamic epidemic trend of the dominant clade, population characteristics, and disease severity. Results From January 2023 to March 2024, a total of 2 600 local cases clade information in Hainan Province were collected, all of which were Omicron variant strains involving 115 evolutionary branches. The three phases identified include: the co-dominance of BA.5.2.48 and BF.7 from the first week of 2023 to the 13th week of 2024; the prevalence of XBB and its subclades from the 16th to the 52nd week of 2023; and the predominance of BA.2.86 and its subclades from the first to the 13th week of 2024, with Omicron BA.2.75 causing small-scale sporadic outbreaks. Among all the age groups of branch infection cases, individuals aged >18~60 years constituted the largest group, while those under 4 years were the smallest, with no significant gender differences. The severity of the clinical disease was mainly asymptomatic and mild. Conclusions Different dominant evolutionary clades of SARS-CoV-2 showed sequential replacement characteristics, and the clinical severity of illnesses has gradually decreased. In the future, the focus should be on individuals aged >60 years and above and those aged >18~60 years with underlying conditions, along with continuous enhancement of variant monitoring and analysis. This will ensure a timely understanding of the dynamic epidemic trend of dominant evolutionary clades in time, and focus on the immunogenicity of the new variant branch and changes in immunogenicity and vaccine protection of new variant clades, providing scientific guidance for the vaccine research, clinical treatment, and immunization strategy formulation.
10.Multicenter epidemiological features of parainfluenza virus respiratory tract infections among children in Hainan Province, 2012-2022
CHEN Qiuxia ; LU Chun ; ZHANG Xuemei
China Tropical Medicine 2025;25(1):57-
Objective To explore the parainfluenza virus (PIV) infection in children hospitalized in Hainan between March 2012 and December 2022, and to analyze its epidemiological characteristics. Methods The samples were obtained from 62 553 kids with respiratory infections who were hospitalized in the Department of Pediatrics of multiple hospitals in various regions of Hainan from March 2012 to December 2022. Indirect immunofluorescence was employed to detect IgM antibodies in serum for nine respiratory pathogens, including PIV, adenovirus, influenza A virus, Legionella pneumophila, respiratory syncytial virus, Mycoplasma pneumoniae, influenza B virus, Coxiella burnetii, and Chlamydia pneumoniae. Epidemiological and clinical data (time, gender, age, season, etc.) of PIV-IgM antibody-positive cases were analyzed in a descriptive study. Results The total PIV-IgM antibody positive rate of 62 553 respiratory tract infected children was 3.29% (2 015/62 553), with the highest positive rate of 11.01% (385/3 496) in 2017, and the second highest positive rate of 8.37% (351/4 196) in 2016, which were significantly higher than the positive rate of the rest of the years (P<0.001). The PIV positive rate was 3.18% (1 248/39 225) in males and 3.29% (767/23 328) in females, with no statistically significant difference (P>0.05). PIV infection occurred in all age groups, with the highest positive rate in the 6 to <12 years group at 4.50% (357/7 941), followed by the 3 to <6 years group at 4.47% (656/14 689), significantly higher than other age groups (P<0.001). The highest positive rate for PIV was in summer at 4.30% (693/16 093), followed by 3.78% (598/15 804) in spring, and the lowest rate of 2.27% (342/15 065) in winter, with statistically significant differences (P<0.001). Single PIV infection accounted for 63.08% (1 271/2 015), while mixed infections accounted for 36.92% (744/2 015), and the most common co-infection being with Mycoplasma pneumoniae infection at 23.13% (466/2 015). Conclusions PIV is an important pathogen for children's acute respiratory infections in Hainan Province, exhibiting year-round sporadic occurrence with alternating high and low periods characteristics. PIV infection is to the gender of the child, predominantly affects preschool and school-age children, peaks in spring and summer, and commonly co-infects with Mycoplasma pneumoniae infection.
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