Spatiotemporal heterogeneity and long-term impact of meteorological, environmental, and socio-economic factors on scrub typhus in China from 2006 to 2018.

BACKGROUND: Large-scale outbreaks of scrub typhus combined with its emergence in new areas as a vector-borne rickettsiosis highlight the ongoing neglect of this disease. This study aims to explore the long-term changes and regional leading factors of scrub typhus in China, with the goal of providing valuable insights for disease prevention and control. METHODS: This study utilized a Bayesian space-time hierarchical model (BSTHM) to examine the spatiotemporal heterogeneity of scrub typhus and analyze the relationship between environmental factors and scrub typhus in southern and northern China from 2006 to 2018. Additionally, a GeoDetector model was employed to assess the predominant influences of geographical and socioeconomic factors in both regions. RESULTS: Scrub typhus exhibits a seasonal pattern, typically occurring during the summer and autumn months (June to November), with a peak in October. Geographically, the high-risk regions, or hot spots, are concentrated in the south, while the low-risk regions, or cold spots, are located in the north. Moreover, the distribution of scrub typhus is influenced by environment and socio-economic factors. In the north and south, the dominant factors are the monthly normalized vegetation index (NDVI) and temperature. An increase in NDVI per interquartile range (IQR) leads to a 7.580% decrease in scrub typhus risk in northern China, and a 19.180% increase in the southern. Similarly, of 1 IQR increase in temperature reduces the risk of scrub typhus by 10.720% in the north but increases it by 15.800% in the south. In terms of geographical and socio-economic factors, illiteracy rate and altitude are the key determinants in the respective areas, with q-values of 0.844 and 0.882. CONCLUSIONS: These results indicated that appropriate climate, environment, and social conditions would increase the risk of scrub typhus. This study provided helpful suggestions and a basis for reasonably allocating resources and controlling the occurrence of scrub typhus.

Fine-scale genetic structure and wolbachia infection of aedes albopictus (Diptera: Culicidae) in Nanjing city, China.

Background: Aedes albopictus is an indigenous primary vector of dengue and Zika viruses in China. Wolbachia is a gram-negative and common intracellular bacteria, which is maternally inherited endosymbionts and could expand their propagation in host populations by means of various manipulations. Compared with research on the dispersion of Ae. albopictus at the macrospatial level (mainly at the country or continent level), little is known about its variation and Wolbachia infection at the microspatial level, which is essential for its management. Meanwhile, no local cases of dengue fever have been recorded in the history of Nanjing, which implies that few adulticides have been applied in the city. Thus, the present study examines how the Ae. albopictus population varies and the Wolbachia infection status of each population among microspatial regions of Nanjing City. Methods: The genetic structure of 17 Aedes albopictus populations collected from urban, urban fringe, and rural regions of Nanjing City was investigated based on 9 microsatellite loci and the mitochondrial coxI gene. The Wolbachia infection status of each population was also assessed with Wolbachia A- and Wolbachia B-specific primers. Results: Nine out of 58 tested pairs of microsatellite markers were highly polymorphic, with a mean PIC value of 0.560, and these markers were therefore chosen for microsatellite genotyping analysis. The Na value of each Ae. albopictus population was very high, and the urban area populations (7.353 ± 4.975) showed a lower mean value than the urban fringe region populations (7.866 ± 5.010). A total of 19 coxI haplotypes were observed among 329 Ae. albopictus individuals via haplotype genotyping, with the highest diversity observed among the urban fringe Ae. albopictus populations (Hd = 0.456) and the lowest among the urban populations (Hd = 0.277). Each Ae. albopictus population showed significant departure from HWE, and significant population expansion was observed in only three populations from the urban (ZSL), urban fringe (HAJY), and rural areas (HSZY) (p < 0.05). Combined with DAPC analysis, all the Ae. albopictus populations were adequately allocated to two clades with significant genetic differences according to population structure analysis, and the best K value was equal to two. AMOVA results showed that most (96.18%) of the genetic variation detected in Ae. albopictus occurred within individuals (FIT = 0.22238, p < 0.0001), while no significant positive correlation was observed via isolation by distance (IBD) analysis (R 2 = 0.03262, p = 0.584). The TCS network of all haplotypes showed that haplotype 1 (H1) and haplotype 4 (H4) were the most frequent haplotypes among all populations, and the haplotype frequency significantly increased from urban regions (36.84%) to rural regions (68.42%). Frequent migration was observed among Ae. albopictus populations from rural to urban regions via the urban fringe region, with four direct migration routes between rural and urban regions. Furthermore, Wolbachia genotyping results showed that most of the individuals of each population were coinfected with Wolbachia A and Wolbachia B. The independent infection rate of Wolbachia A was slightly higher than that of Wolbachia B, and no significant differences were observed among different regions. Conclusion: In the microspatial environment of Nanjing City, the urban fringe region is an important region for the dispersion of Ae. albopictus populations between rural and urban areas, and Wolbachia A and Wolbachia B coinfection is the most common Wolbachia infection status in all Ae. albopictus populations among different regions.

The potential ecological risk assessment of soil heavy metals using self-organizing map.

Heavy metal pollution control zoning aiming at the health maintenance of watershed soil ecosystem has become an important means of soil environmental protection and governance. Based on the self-organizing map (SOM), this study classifies the data sets of eight heavy metals such as Co, Cd, Zn, Cr, Cu, Pb, Ni, and Tl in 354 samples, calculates the potential ecological risk value of soil heavy metals in combination with the potential Hakansom Risk index (HRI), and uses the geographic information system (GIS) for visualization. In the research results, SOM has divided five soil ecological risk categories. The highest average ecological risk value of 85.95 is found in cluster IV, which is clustered and distributed in urban development areas in the upper reaches of the river. The average ecological risk values of cluster I and cluster V are relatively close at 79.64 and 79.19, respectively. Cluster I and cluster V are distributed in the north of the river in a linear and cluster manner, respectively, and are located on a concave bank with a relatively gentle slope. The average ecological risk of soil pollution in cluster II is 77.59, which is linearly distributed on both banks of the river. The ecological risk of soil pollution in cluster III is the lowest (74.39), mainly scattered in the south of rivers with less human activities. The study further identified the environmental factors that affect the soil ecological risk value in different cluster units and put forward the classified and differentiated management and control strategies for different cluster units. The research shows that SOM can cluster the data sets of heavy metals with high sensitivity and low threshold through competitive learning to effectively provide the distribution information of abnormal soil ecological risk areas. This information is helpful for urban environmental management departments and planning departments to take targeted management and recovery measures to avoid the health risks related to soil heavy metal pollution.

Rapid Spread of Severe Fever with Thrombocytopenia Syndrome Virus by Parthenogenetic Asian Longhorned Ticks.

Severe fever with thrombocytopenia syndrome virus (SFTSV) is spreading rapidly in Asia. This virus is transmitted by the Asian longhorned tick (Haemaphysalis longicornis), which has parthenogenetically and sexually reproducing populations. Parthenogenetic populations were found in ≥15 provinces in China and strongly correlated with the distribution of severe fever with thrombocytopenia syndrome cases. However, distribution of these cases was poorly correlated with the distribution of populations of bisexual ticks. Phylogeographic analysis suggested that the parthenogenetic population spread much faster than bisexual population because colonization is independent of sexual reproduction. A higher proportion of parthenogenetic ticks was collected from migratory birds captured at an SFTSV-endemic area, implicating the contribution to the long-range movement of these ticks in China. The SFTSV susceptibility of parthenogenetic females was similar to that of bisexual females under laboratory conditions. These results suggest that parthenogenetic Asian longhorned ticks, probably transported by migratory birds, play a major role in the rapid spread of SFTSV.

Correction to: The polymorphism and geographical distribution of knockdown resistance of adult Anopheles sinensis populations in eastern China.

Please be advised that since publication of the original article [1] the authors have flagged that they omitted to provide the up-to-date version of Fig. 1 and, as such, the wrong version of Fig. 1 is present in the article.

The polymorphism and geographical distribution of knockdown resistance of adult Anopheles sinensis populations in eastern China.

BACKGROUND: Anopheles sinensis is one of the major malaria vectors in China and other southeast Asian countries, including Vietnam, Cambodia, Thailand. Vector control is considered to be the critical measure for malaria control, while the increasing prevalence of insecticide resistance caused by long-term use of insecticides, especially pyrethroids, is threatening the successful control of An. sinensis. In order to understand the underlying resistance mechanisms involved and molecular basis, the principal malaria vector, An. sinensis from Jiangsu and Anhui provinces, Southeast China, was investigated. METHODS: The adult Anopheles mosquitoes were sampled from multiple sites across Jiangsu and Anhui provinces, and sufficient mosquitoes collected from eleven sites for insecticide susceptibility bioassays. The DIIS4-DIIS6 region of the para-type sodium channel gene was amplified and sequenced, then multiple PCR and Taqman assays were used to assess the frequencies of kdr mutations at the target gene. RESULTS: In the present study, most of the adult An. sinensis populations were pyrethroids resistant, which indicated the presence of kdr resistance mutations in the para-type sodium channel gene. Sequence analyses demonstrated the kdr mutation existed at codon 1014 in Jiangsu and Anhui provinces. In adult An. sinensis, three mutant types (TTT L1014F, TTC L1014F, and TGT L1014C) of kdr alleles were detected, while no wild type (TTG L1014) was observed. The TTC L1014F mutation was first reported in Anhui province. CONCLUSIONS: The highly polymorphic kdr alleles were observed in all the adult An. sinensis populations, which suggested that in-depth studies are required for carrying on insecticide resistance monitoring and specific resistance mechanisms studying into establish effective long-term malaria vector control program in eastern China.

Comparison study on the performance of two different gas-permeable membranes used in a membrane-aerated biofilm reactor.

This study compared the performance of two different gas-permeable membranes, PVDF and PP membrane, in a membrane-aerated biofilm reactor (MABR). The surface characteristics and membrane pore blocking of these two membrane materials were studied utilizing AFM, SEM and CLSM. The PVDF membrane surface was more rough and hydrophilic, and possessed a better microbial affinity compared to PP. Furthermore, the MABR equipped with a PVDF membrane removed more COD (97.06 ±â€¯0.97%) and TN (85.66 ±â€¯0.87%) compared to the MABR with PP membrane (87.13 ±â€¯0.87% and 71.13 ±â€¯0.71%, respectively). As well, the PP membrane exhibited severe membrane pore blocking and had a lower oxygen transfer rate than the PVDF membrane. It is concluded that the PVDF membrane has potential as an aeration membrane material for MABRs.

The phylogenetic relationships of known mosquito (Diptera: Culicidae) mitogenomes.

The known mosquito mitogenomes, containing a total of 34 species, which belong to five genera, were collected from GenBank, and the practicality and effectiveness of the variation in the complete mitochondrial DNA genome and portions of mitochondrial COI gene were assessed to reconstruct the phylogeny of mosquitoes. Phylogenetic trees were reconstructed on the basis of parsimony, maximum likelihood, and Bayesian (BI) methods. It is concluded that: (1) Both mitogenomes and COI gene support the monophly of following taxa: Subgenus Nyssorhynchus, Subgenus Cellia, Anopheles albitarsis complex, Anopheles gambiae complex, and Anopheles punctulatus group; (2) Genus Aedes is not monophyletic relative to Ochlerotatus vigilax; (3) The mitogenome results indicate a close relationship between Anopheles epiroticus and Anopheles gambiae complex, Anopheles dirus complex and Anopheles punctulatus group, respectively; (4) The Bayesian posterior probability (BPP) within phylogenetic tree reconstructed by mitogenomes is higher than COI tree. The results show that phylogenetic relationships reconstructed using the mitogenomes were more similar to those based on morphological data.

Experimental infections of mosquitoes with severe fever with thrombocytopenia syndrome virus.

BACKGROUND: Severe fever with thrombocytopenia syndrome (SFTS) is a newly identified emerging infectious disease, which is caused by a novel bunyavirus (termed SFTSV) in Asia. Although mosquitoes have not been identified as the primary vectors, as revealed by epidemiological surveys, their role in transmitting this SFTSV as a suspicious vector has not been validated. FINDINGS: In this study, we conducted experimental infections of mosquitoes with SFTSV to examine the role of mosquitoes in the transmission of the virus. We did not detect viral replication in Culex pipiens pallens, Aedes aegyptis and Anopheles sinensis as revealed by qRT-PCR assay. In addition, we failed to isolate SFTSV from the Vero cells cultured with suspensions of SFTSV-infected mosquitoes. CONCLUSION: The results of the present study demonstrate little possibility that mosquitoes act as vectors for the emerging pathogen SFTSV.

Japanese Encephalitis Virus Infection Rate and Detection of Genotype I From Culex tritaeniorhynchus Collected From Jiangsu, China.

Information regarding the infection rate and genotype shifts for Japanese encephalitis virus (JEV) are important for JE vaccine application. In Jiangsu province, China, which is one of the provinces with a high prevalence of JE, JEV infection in swine and mosquitoes in certain cities has only been investigated in 2008-2009. Lianyungang City has one of the highest numbers of JE cases in Jiangsu province, and it has a high risk of JEV invasion via migrant birds. JEV infection in vectors in Lianyungang City, which has urban and rural parts, has not been investigated. In 2015-2016, we collected mosquitoes in cowsheds with ultraviolet light traps and detected JEV by reverse transcription-polymerase chain reaction (RT-PCR) method in Culex tritaeniorhynchus in Xintan village, Xuzhuang village, and Xiaogaozhuang village in Lianyungang City, China. The proportion of positive pools, which is calculated by the number of infected pools to the total number of pools tested in these villages, were 16.67%, 20.00%, and 4.17%, respectively, and the minimum infection rates, which is calculated as the ratio of the number of positive pools to the total number of mosquitoes tested, were 3.33‰, 4.00‰, and 0.83‰, respectively. Four JEV strains from positive samples were coded as LYG-1, LYG-2, LYG-3, and LYG-4, and the complete E genes were sequenced. Furthermore, the complete genome of LYG-3 was sequenced. The phylogenetic analysis indicated that all the four JEV strains belonged to genotype I-b. This is the first report of genotype I JEV strain in Jiangsu province. The high JEV infection rate in Culex tritaeniorhynchus indicated a high risk of JE reemergence in Lianyungang. The detected JEV strains may have similar antigenicity to that of SA14-14-2 according to molecular characters. These findings suggest that the vaccine can still be effective in Lianyungang.

Comparative Study of L-Asparaginase-Based LOP Regimen Over CHOP Regimen Before Radiotherapy for Stage IIE Extranodal Nasal Type NK/T Cell Lymphoma: A Study of 2 Centers.

BACKGROUND: In this study we evaluated the efficacy of an L-asparaginase-based LOP (L-asparaginase, vincristine, and dexamethasone) regimen in extranodal Natural Killer (NK)/T-cell lymphoma (ENKTL) patients in the Guizhou province of China. PATIENTS AND METHODS: Forty-eight patients were treated with the LOP (L-asparaginase, vincristine and dexamethasone) regimen chemotherapy (CT) and 32 patients with the CHOP (cyclophosphamide, tetrahydropyanyl adriamycin, vincristine, and prednisone) regimen. These patients then received involved-field radiotherapy (RT) with the doses of DT = 49-59 Gy. RESULTS: A significant improvement of clinical end points with the LOP regimen was noticed compared with the CHOP regimen: 33 (68.8%) versus 16 (50.0%) for complete responses; 10 (20.8%) versus 5 (15.6%) for partial responses. There were statistical differences in objective response rates (43 [89.6%] for LOP vs. 21 [65.6%] for CHOP; P = .009), 3 years of overall survival (42 [87.5%] for LOP vs. 20 [62.5%] for CHOP; P = .006) and progression-free survival (32 [79.2%] for LOP vs. 16 [50.0%] for CHOP; P = .007). CONCLUSION: The results showed that the LOP regimen is safe and much more efficient than the CHOP regimen for stage IIE ENKTL patients. They indicate that the LOP regimen is a satisfying alternative protocol among the other L-asparaginase-based regimens reported so far, such as SMILE (dexamethasone, methotrexate, ifosfamide, L-asparaginase, and etoposide), GELOX (gemcitabine, oxaliplatin, and L-asparaginase), CHOP-L, and sandwich (CT, then RT, then CT).

Multiple-Insecticide Resistance and Classic Gene Mutations to Japanese Encephalitis Vector Culex tritaeniorhynchus from China.

Widespread resistance of insect pests to insecticides has been widely reported in China and there is consequently an urgent need to adjust pest management strategies appropriately. This requires detailed information on the extent and causes of resistance. The aim of the present study was to investigate levels of resistance to 5 insecticides among 12 strains of Culex tritaeniorhynchus, a major vector of Japanese encephalitis in China. Resistance to deltamethrin, beta-cypermethrin, permethrin, dichlorvos, and propoxur were measured using larval bioassays. The allelic frequency of knockdown resistance (kdr) and acetylcholinesterase (AChE) mutations were determined in all strains. Larval bioassay results indicated that the field strains collected from different sites were resistant to deltamethrin, beta-cypermethrin, permethrin, dichlorvos, and propoxur, with resistance ratio values ranging from 1.70- to 71.98-fold, 7.83- to 43.07-fold, 3.54- to 40.03-fold, 291.85- to 530.89-fold, and 51.32- to 108.83-fold, respectively. A polymerase chain reaction amplification of specific alleles method for individual was developed to detect genotypes of the AChE gene mutation F455W in Cx. tritaeniorhynchus. The frequency of the AChE gene mutation F455W was 100.00% in all strains, making this mutation of no value as a marker of resistance to organophosphorous and carbamate pesticides in Cx. tritaeniorhynchus in China. The kdr allele was present in all strains at frequencies of 10.00-29.55%. Regression analysis indicated a significant correlation between kdr allele frequencies and levels of resistance to deltamethrin, beta-cypermethrin, and permethrin. These results highlight the need to monitor and map insecticide resistance in Cx. tritaeniorhynchus and to adjust pesticide use to minimize the development of resistance in these mosquitoes.

An Unmanned Aerial Vehicle-Mounted Cold Mist Spray of Permethrin and Tetramethylfluthrin Targeting Aedes albopictus in China.

Aedes albopictus is the primary vector of dengue fever and dengue hemorrhagic fever in China. Although there are previous studies on the application of adulticides to control this species, the application methods have either been back-pack or vehicle-mounted systems. However, many sites are too large to be effectively treated with back-pack sprayers, and the lack of roads restricts the use of vehicle-mounted sprayers. This paper provides the first study of using unmanned aerial vehicles to conduct cold mist sprays on Ae. albopictus habitats. A spray containing 4% permethrin and 1% tetramethylfluthrin was applied at an effective application rate of 9.0 mg/m(2). This method reduced Ae. albopictus populations by more than 90%. The results indicate this novel spray system is a powerful method to achieve a rapid decline of mosquito population in Ae. albopictus habitats in China.

Sequencing and analysis of the complete mitochondrial genome of Culex tritaeniorhynchus (Dipera: Culicidae) in China.

The complete sequence of the mitochondrial genome of the Culex tritaeniorhynchus (Diptera: Culicidae) is presented using traditional Sanger sequencing. Its mitogenome are 15,123 bp in length, consisting of 13 protein-coding genes, 2 ribosomal RNA genes (rRNA) and 22 transfer RNA (tRNA) genes. The percent of A + T of the mitogenome is 77.73%. Most mitochondrial genes are encoded on the heavy strand, except for NAD5, NaD4, NAD4L, NAD1, two rRNA and nine tRNA genes, which are encoded on the light strand. The results of phylogenetic analyzes showed that the Cx. tritaeniorhynchus has close relationship with the species of genus Culex.

First report on co-occurrence knockdown resistance mutations and susceptibility to beta-cypermethrin in Anopheles sinensis from Jiangsu Province, China.

The increasing prevalence of insecticide resistance in Anopheles sinensis, a major vector of malaria in Jiangsu province in eastern China, threatens to compromise the successful use of insecticides in malaria control strategies. It is therefore vital to understand the insecticide resistance status of An. sinensis in the region. This study examined the nucleotide diversity of the para-sodium channel and knockdown resistance (kdr) in five field populations of adult An. sinensis mosquitoes collected in Jiangsu province, identifying the L1014F and L1014C substitutions for the first time. Competitive polymerase chain reaction (PCR) amplification of specific allele (cPASA) and polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) for resistance diagnosis were developed and validated. Comparing the results with direct sequencing revealed that the PCR-RFLP method was more sensitive and specific whereas the cPASA method was more convenient and suitable. The significant positive correlation between kdr allele frequency and bioassay-based resistance phenotype demonstrates that the frequency of L1014F and L1014C substitutions in the kdr gene provides a useful molecular marker for monitoring beta-cypermethrin resistance in natural populations of An. sinensis. Our results point to the L1014F substitution as the key mutation associated with beta-cypermethrin resistance. The high resistance and mutation frequency detected in the five populations also suggest cross-resistance with other pyrethroids may occur in An. sinensis, highlighting the need for further surveys to map insecticide resistance in China and the adoption of a rational management of insecticide application for resistance management and mosquito vector control.