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    30 April 2020, Volume 32 Issue 2
    Management of coronavirus disease 2019 (COVID?19): experiences from imported malaria control in China
    LIU Yao-Bao, CAO Jun
    2020, 32(2):  113. 
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    Currently, the local transmission of coronavirus disease 2019 (COVID?19) has been effectively contained in China; however, the epidemic situation of this highly infectious disease is more and more serious outside of China. Importation of COVID?19 cases from other countries and territories is therefore becoming a new challenge for the control of COVID?19 in China. Malaria was once widely epidemic in China. Nevertheless, the local transmission of this parasitic disease has been interrupted in China since the launch of the national malaria elimination programme in 2010, and great successes have been achieved in the management of appropriately 3 thousand malaria cases imported from other countries and territories annually. Hereby, the epidemiological characteristics and current epidemic situation of COVID?19 in China were analyzed and compared with malaria. Based on the successful experiences from the management of overseas imported malaria in China, the strategy and countermeasures for COVID?19 control were proposed, so as to provide insights into the response to the importation of COVID?19 from other countries and territories and the consolidation of the control achievements in China.
    Pharmacological characteristics of chloroquine and suggestions for its use in treatment of coronavirus disease 2019 (COVID-19)
    GAO Qi
    2020, 32(2):  119. 
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    A novel coronavirus disease (COVID-19) was identified in Wuhan City, Hubei Province of China by the end of 2019, and then, the disease spread across China and became a global pandemic. Nevertheless, there are no effective treatments or vaccines for COVID-19 until now. In addition to the treatment of patients with COVID-19, the China Medical Treatment Expert Group for COVID-19 is active to study and screen effective antiviral drugs, and has found that chloroquine, an old antimalarial, shows activity against SARS-CoV-2. Then, chloroquine was included in the Guidelines for the Diagnosis and Treatment of COVID-19 in China (version 6) issued by National Health Commission of the People’s Republic of China. Currently, chloroquine phosphate and hydroxychloroquine sulfate, two chloroquine derivatives, are under clinical use. Although these two agents exhibit similar mechanisms of drug actions, there is a difference between these two chemicals in terms of target populations, therapeutic efficacy and adverse reactions. This paper summarizes the currently available data and experiences from clinical treatment for malaria with chloroquine drugs, so as to provide insights into the more rational use of chloroquine agents for the treatment of COVID-19.
    Identification and functional study of the Schistosoma japonicum epidermal growth factor receptor gene
    XIANG Man-Yu,LI Jian,LUO Fang,SUN Cheng-Song,ZHU Bing-Kuan,WANG Ji-Peng,Mo Xiao-Jin,ZHANG Ting,XU Bin,FENG Zheng,HU Wei
    2020, 32(2):  123. 
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    Objective To characterize the epidermal growth factor receptor (EGFR) gene in Schistosoma japonicum (SjEGFR gene) and investigate the role of the EGFR gene in regulating the growth, reproductive system, maturation and fecundity of S. japonicum. Methods Rapid amplification of cDNA ends (RACE) was performed to obtain the full length of the SjEGFR gene, and the SjEGFR gene expression was quantified in different developmental stages of S. japonicum using a quantitative real-time PCR (qPCR) assay. The tissue localization of the SjEGFR gene was detected in 22-day parasite using whole-mount in situ hybridization (WISH). Following RNA interference (RNAi)-induced knockdown of the SjEGFR gene, the worm length, pairing rate and worm burden of S. japonicum were measured, and the worm morphology was observed using optical microscopy and confocal microscopy. Results The SjEGFR gene was identified with a conserved tyrosine-kinase active site, and the SjEGFR gene expression was detected at various developmental stages in male and female parasites. WISH showed that the transcript of the SjEGFR gene was localized on the tegument and in the digestive organs of S. japonicum. RNAi-induced SjEGFR knockdown resulted in marked suppression of the worm growth, smaller size of male testicles that contained more immature spermatocytes, and apparent impairment of ovary and vitelline gland development. In addition, no eggs were found in the uterus of SjEGFR knocked-down female parasites, indicating the interruption of egg production. Conclusions Inhibition of SjEGFR expression may remarkably suppress the growth and maturation of S. japonicum, and interrupt the egg production
    Impact of water body environments on the microbial community of Oncomelania hupensis snails in marshlands around the eastern Dongting Lake
    DONG Shu-Rong, JIANG Jie, WANG Ying-Jian, LI Chun-Lin, SHI Ying, YANG Yu, YANG Ya, LI Lin-Han, CAI Bin, YOU Jia-Bian, JIANG Feng, JIANG Qing-Wu, ZHOU Yi-Biao
    2020, 32(2):  132. 
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    Objective To evaluate the effects of water body environments on the microbial community of Oncomelania hupensis snails in marshlands of the eastern Dongting Lake where natural extinction of O. hupensis snails are found, so as to explore the correlation between the natural extinction of O. hupensis snails and the microbial community in snails. Methods Snails were caged water bodies in the Qianliang Lake marshland (Qianliang Lake regions) where natural extinction of snails was found and in the Junshan Park marshland (Junshan Park regions) in the eastern Dongting Lake for 30 days, and then all snails were collected and identified for survival or death. DNA sequencing of the fungi and bacteria was performed in snails before and after immersion in waters, and the biodiversity and abundance were analyzed. Results The survival rates of O. hupensis snails were 28.0% (70/250) and 64.8% (162/250) in Qianliang Lake regions and Junshan Park regions 30 days after immersion in waters, respectively (χ2 = 81.365, P < 0.01). The number of the fungal community and the biodiversity of the bacterial community were both greater in snails caged in Qianliang Lake regions post?immersion than pre?immersion, and there was a significant difference in the structure of the fungal and bacterial communities. The microbial community with a significant difference included Flavobacteriaceae, which was harmful to O. hupensis snails. Conclusion The water body environment affects the composition of the microbial community in O. hupensis snails in marshlands with natural snail distinction around the eastern Dongting Lake; however, further studies are required to investigate whether the natural distinction of snails is caused by water body environments?induced changes of the microbial spectrum in O. hupensis snails.
    Spatiotemporal distribution of Oncomelania hupensis snail habitats in Anhui Province
    GAO Feng-Hua, ZHANG Shi-Qing, WANG Tian-Ping, HE Jia-Chang, LI Ting-Ting, XU Xiao-Juan, XUE Jing-Bo
    2020, 32(2):  140. 
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    Objective To investigate the spatiotemporal distribution of Oncomelania hupensis snails and infected snails in the endemic areas of schistosomiasis in Anhui Province. Methods Based on the snail survey data in Anhui Province in 2016, the distribution of snails and infected snails were analyzed, and the spatial distribution of snails and spatial cluster patterns of infected snails were investigated in snail habitats in Anhui Province from 1950 to 2016. Results A total of 22 757 snail habitats and 5 004 infected snail habitats were identified in Anhui Province from 1950 to 2016, which appeared single?peak and double?peak patterns, with an inflection point seen in 1970. There were 141 000 hm2 historically accumulative snail habitats, 88.08% of which were firstly identified from 1950 to 1979, and totally 114 500 hm2 snail habitats were eradicated, 77.17% of which were eradicated from 1970 to 1999. There were 4 830 snail habitats identified until 2016, in which 1 051 were once detected with infected snails. In addition, 78.12% of current snail habitats had been present for over 40 years, and infected snails had been eliminated in 65.75% of the infected snail habitats within 10 years. There was a spatial autocorrelation of the living snail density in current snail habitats in Anhui Province (Moran’s I = 0.196, Z = 139.63, P < 0.001), and local hotspot analysis showed spatial clusters of living snails density in snail habitats, with high?value clusters in south of the Yangtze River and low?value clusters in north of the Yangtze River. The 21 high?value clusters of living snail density with statistical significance were distributed along the Yangtze River basin and its branches. Spatiotemporal scan analysis revealed spatiotemporal clusters of infected snails in 4 current snail habitats. Conclusions The current snail habitats have been present for a long period of time, and snails are difficult to be eliminated by chemical treatment alone, which requires the combination of environment improvements. There are spatial clusters of living snail density in current snail habitats in Anhui Province. The epidemic factors and risk of human and animal infections still remain in some clusters of historical infected snail habitats revealed by spatiotemporal scan analysis, which should be considered as the key target areas for snail control in Anhui Province.
    Effect of schistosomiasis japonica on the development of gastric and colorectal cancer
    WANG Zi-Jian, YANG Jiang-Hua
    2020, 32(2):  148. 
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    Objective To examine the effect of schistosomiasis on the development of gastric cancer and colorectal cancer. Methods The clinical data of patients with gastric cancer and colorectal cancer with and without schistosomiasis japonica that were admitted to the Yijishan Hospital Affiliated to Wannan Medical College from January 2014 to December 2018 were collected. All cases were divided into schistosomal gastric cancer group and non?schistosomal gastric cancer group, schistosomal colorectal cancer group and non?schistosomal colorectal cancer group. The risk factors of gastric cancer and colorectal cancer were identified using univariate analysis and multivariate logistic regression analysis, and the effects of schistosomiasis on the development and progression of gastric cancer and colorectal cancer were evaluated. In addition, the survival of 32 patients with schistosomal colorectal cancer and 68 cases with non?schistosomal colorectal were estimated using telephone follow?up, and compared. Results There were 113 patients with schistosomal gastric cancer and 3 741 cases with non?schistosomal gastric cancer enrolled in this study, and there were significant differences between them in terms of sex ratio, age and prevalence of Helicobacter pylori infection (all P values < 0.05). Logistic regression analysis revealed that age, H. pylori infection, and schistosomiasis were independent risk factors for gastric cancer (all P values < 0.05). There were 184 patients with schistosomal colorectal cancer and 2 205 cases with non?schistosomal colorectal cancer recruited in this study, and there were significant differences between them in terms of age, sex ratio, rate of history of alcohol consumption and rate of positive fecal occult blood test (all P values < 0.05). The phenotypes of both schistosomal and non?schistosomal colorectal cancer were predominantly ulcerative; however, the proportion of patients with invasive and protruded colorectal cancer was significantly greater than that of patients with non?schistosomal colorectal cancer (P = 0.003). Logistic regression analysis revealed that age (P = 0.003), gender (P = 0.002), phenotype (P = 0.005) and schistosomiasis (P = 0.029) were independent risk factors for colorectal cancer. The 5?year survival rate was significantly higher in patients with schistosomal colorectal cancer (68.90%) than in those with non?schistosomal colorectal cancer (46.40%), and the dead patients with schistosomal colorectal cancer had a significantly greater mean age than those with non?schistosomal colorectal cancer [(66.33 ± 3.08) years vs. (56.29 ± 1.94), P < 0.05]. Conclusions  Schistosomiasis may alter the pathogenesis of colorectal cancer, resulting in the differences in the epidemiology, clinical characteristics and 5?year survival rate between patients with schistosomal and non?schistosomal colorectal cancer. Periodical gastrointestinal endoscopy and other examinations are recommended to exclude the likelihood of gastrointestinal cancers in men with anemia of unknown causes and at ages of 60 years living in schistosomiasis?endemic areas.
    Clinical characteristics and distribution of peripheral T lymphocyte subsets in patients with schistosomal hepatic diseases in Suzhou City
    YAO Yun-Hai, ZHAO Wei-Feng, GAN Jian-He
    2020, 32(2):  154. 
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    Objective To investigate the clinical characteristics and the distribution of peripheral blood T lymphocyte subsets in patients with schistosomal hepatic cirrhosis in Suzhou City. Methods A total of 32 inpatients with liver diseases due to advanced schistosomiasis at the Department of Infectious Diseases, The First Affiliated Hospital of Soochow University from January 2016 to January 2018 were recruited and assigned into the infection and non?infection groups according to presence of co?infections, and 20 old healthy volunteers served as controls. Venous blood samples were collected on the day of admission, and the proportions of CD4+ T cells, CD8+ T cells, regulatory T (Treg) cells and Th17 cells were detected in peripheral blood using flow cytometry. Results Most patients with liver disorders due to advanced schistosomiasis were admitted to hospital in Suzhou City because of portal hypertension?associated complications, with a high prevalence of co?infections (59.38%, 19/32). The proportions of peripheral CD4+ and CD8+ T cells and Th17 cells were all significantly lower in patients with liver disorders due to advanced schistosomiasis than in controls (t = -5.111, -4.470 and -2.749, all P < 0.05), and a higher proportion of Treg cells was detected in patients than in controls (t = 5.628, P < 0.05). In addition, there were significant differences among the infection group, non?infection group and controls in terms of the percentage of CD4+ T cells, CD8+ T cells, Th17 cells and Treg cells (F = 15.837, 16.594, 9.290 and 27.866, all P < 0.05). Conclusion Portal hypertension?associated complications are predominantly seen in patients with liver diseases due to advanced schistosomiasis at admission in Suzhou City, and co?infections are common. Imbalance of peripheral T cell subsets is detected in patients with liver diseases due to advanced schistosomiasis in Suzhou City.
    Molecular identification of Tricula spp. and the parasitized trematode cercariae in schistosomiasis-endemic areas of Yunnan Province
    DU Chun-Hong, Lü Shan, ZHANG Yun, LI Shi-Zhu, XIONG Meng-Tao, HE Zhi-Hai, LI Zhi-Hua, WU Ming-Shou, SUN Jia-Yu, REN Yin-Ben, CHEN Chun-Qiong, GU Qiong, WANG Yun-Song, DONG Yi
    2020, 32(2):  159. 
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    Objective To characterize a species of the genus Tricula and parasitized trematodes in schistosomiasis?endemic areas of Yunnan Province using a molecular analysis, so as to understand their taxonomic positions. Methods Tricula spp. and Oncomelania snails were collected from Xiangyun County, Yunnan Province, and cercaria parasitizing snails were observed using crushing followed by microscopy. Cercaria parasitizing Tricula snails at various morphologies were sampled using a shedding method. Genomic DNA was extracted from snail soft tissues and cercariae, and the 16S rRNA, COI, 28S rDNA genes in snails and the ND1 and 28S rDNA genes in cercariae were amplified using a PCR assay and sequenced. The species of Tricula snails and their parasitized trematodes was characterized using sequence alignment and phylogenetic analysis. Results Among 382 Tricula snails detected, there were three types of trematode cercariae found, including the non?forked (20.94%, 80/382), double?forked (3.40%, 13/382) and swallow shapes (7.07%, 27/382). Sequence and phylogenetic analyses showed that the 16S rRNA, COI and 28S rDNA gene sequences of this species of Tricula had high homology to those in Delavaya dianchiensis, and were clustered in a branch. Sequencing analysis of the ND1 and 28S rDNA genes revealed that the non?forked cercariae belonged to the family Pleurogenidae, the swallow?shaped cercariae belonged to the family Opecoelidae, and the double?forked cercariae belonged to another species of the genus Schistosoma that was different from S. sinensium and S. ovuncatum. Conclusion The species and taxonomy of Triculla spp. and their parasitized trematodes?are preliminarily determined in schistosomiasis?endemic areas of Yunnan Province; however, further studies are required to investigate the more definite taxonomy and pathogenicity.
    Establishment of a recombinase-aided isothermal amplification assay for nucleic acid detection of Echinococcus multilocularis and its preliminary application
    ZHOU Hong-Rang, CHEN Mu-Xin, YU Qing, AI Lin, WANG Ying, XU Qiu-Li, XIAO Ning
    2020, 32(2):  168. 
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    To establish a rapid nucleic acid detection technique for identification of Echinococcus multilocularis based on the recombinase aided isothermal amplification assay (RAA) and assess its diagnostic efficiency. Methods The mitochondrial gene sequence of E. multilocularis (GenBank accession number: AB018440) was used as a target sequence. The primers were designed according to the RAA reaction principle and synthesized, and RAA was performed using the generated primers. E. multilocularis genomic DNA at various concentrations and the pMD19?T (Simple) vector containing various copies of the target gene fragment were amplified using RAA to evaluate its sensitivity for detection of E. multilocularis, and RAA was employed to detect the genomic DNA of E. granulosus G1 genotype, Taenia saginata, T. asiatica, T. multiceps, Dipylidium caninum, Toxocara canis, Trichuris trichiura, Giardia lamblia, Fasciola hepatica, Paragonimus westermani, Fasciola gigantica and Clonorchis sinensis to evaluate its specificity. In addition, the optimized RAA was employed to detect nine tissue specimens of E. granulosus?infected animals, 3 fecal samples from E. granulosus?infected dogs and 2 fecal samples from field infected dogs to examine its reliability and feasibility. Results The established RAA was able to detect the specific target gene fragment of E. multilocularis within 40 min. The lowest detect limit of RAA was 10 pg if E. multilocularis genomic DNA served as a template. If the recombinant plasmid was used as a template, the minimally detectable copy number of RAA was 104. In addition, RAA was negative for the genomic DNA of E. granulosus G1 genotype, T. saginata, T. asiatica, T. multiceps, D. caninum, T. canis, T. trichiura, G. lamblia, F. hepatica, P. westermani, F. gigantica and C. sinensis. The established RAA was positive for detection of the tissue specimens of infected animals, and simulated and field dog stool samples. Conclusion A rapid, sensitive and specific RAA is established, which shows promising values in identification of E. multilocularis and gene diagnosis of alveolar echinococcosis.
    Analysis of chloroquine-resistant gene polymorphisms in Plasmodium falciparum imported into China in 2012 and 2018
    YAN He, WANG Xiao-Xiao, FENG Jun, ZHANG Li, YIN Jian-Hai, LI Mei, XIA Zhi-Gui, HUANG Fang
    2020, 32(2):  174. 
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    Objective To detect the chloroquine?resistant molecular marker polymorphisms in Plasmodium falciparum imported into China, investigate the mutation types of P. falciparum chloroquine resistant transporter (Pfcrt) gene at positions 72 to 76, and analyze the specificity of the P. falciparum specimens with different origins. Methods A total of 674 filter paper blood samples were collected from the National Malaria Diagnosis Reference Laboratory of China in 2012 and 2018. The amino acid positions 72 to 76 of the Pfcrt gene on chromosome 7 were amplified using nested PCR assay and sequenced, and the sequencing results of the target gene fragment and the geographical region?specific prevalence of the mutations in the Pfcrt gene were analyzed. Results Among the 674 imported P. falciparum malaria cases in China in 2012 and 2018, 99.5% (644/674) were from Africa, which were predominantly from western and central Africa (80.4%, 518/644), and 4.5% (30/674) from Southeast Asia and Oceania (Papua New Guinea). A total of 4 site mutations (C72S, M74I, N75E and K76T) and 5 haplotypes (CVMNK, CVIET and SVMNT and two mixed types) were identified, with haplotypes CVMNK and CVIET present in parasites of both African and Southeast Asian origins, SVMNT detected in Southeast Asia (Myanmar) and Papua New Guinea isolates, the mixed type of haplotypes CVMNK/CVIET detected in P. falciparum of African and Southeast Asian origins, and the mixed type of haplotypes CVMNK/SVMNT detected only in the Myanmar isolate. Most P. falciparum parasites of the African origin carried the wild?type Pfcrt allele (77.7%, 478/615), and 68.0% (17/25) of the P. falciparum parasites of the Southeast Asian and Papua New Guinea origins harbored chloroquine resistant molecular markers ([χ2] = 28.5, P < 0.05). The constituent ratio of the wild? and mutant?type Pfcrt allele varied in different geographical regions of Africa (P < 0.01), and the lowest prevalence of the wild?type Pfcrt allele was seen in western Africa. Conclusion Among the 674 imported malaria cases in China in 2012 and 2018, the P. falciparum imported from Sotheast Asia habors a higher proportion of resistance to chloroquine and a higher molecular polymophism at amino acid positions 72 to 76 of the Pfcrt gene than the parasite of the African origin.
    Polarization of bone marrow-derived macrophages induced by recombinant Trichinella spiralis cysteine protease inhibitors in vitro
    XIE Hong, CHU Liang, WU Ling-Qin, FAN Xing-Yu, WANG Pu, MA Si-Yu, ZHENG Dong-Xue, LI Kun-Long, CHEN Xing-Zhi, YANG Xiao-Di
    2020, 32(2):  181. 
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    Objective To investigate the regulatory role of recombinant Trichinella spiralis cysteine protease inhibitors (rTs?Cys) in induction of polarization of bone marrow?derived macrophages (BMDMs) in vitro. Methods BMDMs were captured and cultured in conditioned medium for 7 days. Then, mature BMDMs were harvested and assigned into four groups. Cells in Group A (negative control) were given 10 ng/mL IFN?γ combined with 100 ng/mL LPS, cells in Group B (positive control) were treated with IL?4 and IL?10 (at 10 ng/mL both), and cells in Group C (recombinant protein alone) were stimulated with 1 μg/mL rTs?Cys, while cells in Group D (protein co?culture) were simultaneously treated with 1 μg/mL rTs?Cys, 10 ng/mL IFN?γ and 100 ng/mL LPS. Cells and culture supernatant were collected 24 hour post?treatment, and the proportions of F4/80+, CD11b+, CD206+ and CD11c+ cells were detected by flow cytometry. The levels of interleukin IL?6 (IL?6), tumor necrosis factor?α (TNF?α), IL?10 and transforming growth factor?β (TGF?β) in the cell culture supernatant were measured by ELISA and the CD86+ and CD206+ phenotypes were identified by immunofluorescent staining. Results Flow cytometry detected no significant difference in the proportion of F4/80+ CD11b+ CD11c+ cells among the four groups (F = 46.184, P < 0.001), and a lower proportion of F4/80+ CD11b+ CD11c+ cells was seen in groups C and D than in group A (all P values < 0.001). There was a significant difference in the proportion of F4/80+ CD11b+ CD206+ cells among the four groups (F = 11.032, P < 0.001), and a greater proportion of F4/80+ CD11b+ CD206+ cells was seen in groups C and D than in group A (all P values < 0.01). Immunofluorescent staining showed higher CD206+ expression and lower CD86+ expression in groups C and D than in Group A. There were significant differences in the IL?6 and (F = 3.950, P < 0.001) and TNF?α (F = 205.827, P < 0.001) levels in the cell culture supernatants among the four groups, and significantly lower IL?6 and TNF?α levels were measured in groups C and D than in Group A (both P < 0.05). There were significant differences in the IL?10 and (F = 8.274, P < 0.001) and TGF?β (F = 13.559, P < 0.01) levels in the cell culture supernatants among the four groups, and greater IL?10 and TGF?β levels were measured in Group C than in Group A (both P values < 0.01). In addition, the TGF?β level was significantly higher in Group D than in Group A (P < 0.05); however, there was no significant difference in the IL?10 level between groups D and A (P > 0.05). Conclusion rTs?Cys may induce the polarization of BMDMs to anti?inflammatory M2 macrophages in vitro and inhibit the activation of M1 macrophages.
    Acute toxicity of four heavy metal ions to Oncomelania hupensis
    ZHANG Qin, GAO Meng-Yang, ZHOU Shu-Lin, ZENG Xiao-Long
    2020, 32(2):  187. 
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    Objective To assess the acute toxicity of Cu2+, Cd2+, Hg2+ and Pb2+ to Oncomelania hupensis. Methods Cu2+, Cd2+, Hg2+ and Pb2+ solutions were prepared at five concentrations, and 10 snails were exposed to each concentration for 24, 48, 72 h and 96 h. Then, the inhibition of snail activity and snail death was observed, and the half maximal effective concentration (EC50) and median lethal concentrations (LC50) were estimated. Results The 24, 48, 72 h and 96 h EC50 values of Cu2+, Cd2+, Hg2+ and Pb2+ were 0.74, 0.56, 0.46, 0.37 mg/L, 4.79, 3.52, 1.70, 1.26 mg/L, 1.90, 1.49, 0.83, 0.76 mg/L and 21.40, 9.98, 7.90, 5.42 mg/L for snails, respectively. The 96 h LC50 values of Cu2+, Cd2+, Hg2+ and Pb2+ were 0.43, 2.96, 1.12 mg/L and 12.22 mg/L for snails, the safe concentrations were 0.004 3, 0.029 6, 0.011 2, 0.122 2 mg/L, respectively. Conclusion Cu2+ shows a high acute toxicity to snails, and Cd2+ and Hg2+ exhibit a moderate acute toxicity to snails, while Pb2+ is lowly toxic to snails.
    Characterization of Echinostoma miyagawai in domestic ducks in Wuhu City
    GU Sheng-Li, LUO Mei-Yuan, GUO Wei, PAN Yang, ZHAN Xiao-Dong
    2020, 32(2):  191. 
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    Objective To investigate the morphological characteristics of Echinostoma miyagawai in domestic ducks in Wuhu area, and to explore the feasibility of the cytochrome oxidase subunit?1 (Cox1) gene as a molecular marker for the identification of E. miyagawai. Methods E. miyagawai was isolated from free?ranged domestic ducks in Wuhu area, and the parasites were stained and identified. In addition, the mitochondrial Cox1 gene of E. miyagawai was amplified using a PCR assay, and the amplification product was sequenced and aligned with the GenBank database to yield the homology for the identification of parasite species in combination with morphological findings. Intra?species comparison was done based on the Cox1 gene sequence. Results The prevalence of E. miyagawai infection was 16.67% in domestic ducks in Wuhu area, and the adult E. miyagawai was 6.6 to 13.2 mm in length. The size of the E. miyagawai Cox1 gene was approximately 660 bp, which had a 99.68% homology to the E. miyagawai accessed in GenBank. The morphological findings were in agreement with molecular identification. Conclusion E. miyagawai infection is common in domestic ducks in Wuhu area, and the mitochondrial Cox1 gene is a feasible marker of intra? and inter?species molecular identification of Echinostoma.
    Transmission electron microscopic observation on gonad of Oncomelania hupensis offspring bred in Weishan Lake areas
    MIAO Feng, WU Zhong-Dao, WU Jin-Lang, SHI Shi-Jun, ZENG Xin, WANG Jing, YAN Hao-Yun, ZHANG Chong-Xing, LIU Xin
    2020, 32(2):  195. 
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    Objective To observe the morphological changes in the testes and ovaries of adult 12th?generation Oncomelania hupensis bred for 12 winters in Weishan Lake areas. Methods The offspring of the adult O. hupensis snails bred in the Weishan Lake that were originated from the Yangzhou section of the Yangtze River was defined as the experiment group, while uninfected, adult O. hupensis snails captured from the marshland of the Yangzhou section of the Yangtze River served as the control group. Snails were dissected and intact testicular and ovarian specimens were sampled, routinely fixed, dehydrated, embedded, polymerized in an oven and sliced on an ultramicrotome. The sections were visualized under a transmission electron microscope, and the ultrastructure of the snail gonad was compared between the experiment and control groups. Results Transmission electron microscopy showed “9 + 2” microtubules on the transverse sections of the tails of sperm cells in the testes of male snails in the control group, with triangular acrosomes and spiral, dense nuclei seen in the tip, while in the experiment group, the “9 + 2” microtubules disappeared on the transverse sections of the tails of sperm cells in the testes of male snails, with low chromatin density found in the tip. Transmission electron microscopy revealed clear nucleolus and nuclear membranes in the ova of female snail ovaries, and displayed yolk body, liposomes and endoplasmic reticulum in the cytoplasm, bilayer twists of nuclear membrane and a uniform nucleolus in the control group, while in the experiment group, smooth nuclear membrane and unclear nucleolus were observed in the ova of female snail ovaries, with few contents seen within cells. Conclusions Following breeding for 12 winters in the Weishan Lake, the 12th?generation O. hupensis snails fail to fully adapt to the natural environment in northern China, and the remarkable changes in the ultrastructure of the snail gonad may be a cause of gradual decline and even extinction of O. hupensis in the Weishan Lake areas.
    Survival analysis of laboratory-bred smooth-shelled Oncomelania snails in Yunnan Province
    HUANG Ning-Bo, FENG Xi-Guang, DONG Yi, ZHANG Yun, WU Ming-Shou
    2020, 32(2):  198. 
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    Objective To investigate the survival period of Yunnan Province?derived smooth?shelled Oncomelania snails bred in laboratory. Methods nails were sampled from Heqing and Yongsheng counties where schistosomiasis is endemic, and uninfected adult snails were collected and bred in laboratory. The survival period of snails sampled from these two counties was compared. Results The 1?, 2?, 3? and 4?year survival rates of laboratory?bred smooth?shelled snails sampled from Yunnan Province were 72.36%, 29.11%, 13.08% and 0.21%, respectively, and were 74.66%, 38.91%, 19.46% and 0.45% for snails derived from Heqing County, and 70.36%, 20.55%, 7.51% and 0 for snails sampled from Yongsheng County, respectively. The mean and median survival period of Yunnan Province?derived adult snails was 20.90 and 20.67 months, and there were significant differences between the snails sampled from Heqing and Yongsheng counties in terms of the mean (22.94 vs. 19.13 months, P < 0.05) and median survival period (21.63 vs. 19.81 months, P < 0.05). Conclusion The mean survival period of Yunnan Province?derived smooth?shelled adult snails is approximately 20 months in laboratory, and the survival varies in geographical areas.
    Value of discriminant analysis for screening of clonorchiasis sinensis
    ZHANG Ya-Ming, ZHANG Wen-Jia, CHEN Hong-Yu, YU Yang, WANG Yue
    2020, 32(2):  200. 
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    Objective To build a discriminant function of clonorchiasis sinensis using stepwise discriminant analysis, so as to investigate the feasibility of discriminant analysis for clonorchiasis sinensis screening. Methods Ten villages in Mulan County of Harbin City were sampled as the study sites using a cluster random sampling method. The fecal samples were collected from the permanent residents in the study sites and detected for Clonorchis sinensis eggs using the modified Kato?Katz smear technique. A questionnaire of clonorchiasis sinensis was designed. All data were entered into Epidata 3.1, and a discriminant analysis was performed using the software SPSS version 15.0. Variable were screened using the stepwise discriminant analysis, and the discriminant function was built using the Fisher’s discriminant analysis method. The effectiveness of the discriminant function for clonorchiasis sinensis screening was evaluated by comparison with the modified Kato?Katz smear method. Results Eight variables with statistical significance were included to build the discriminant function, including chronic cholecystitis, cholangitis, gender, eating raw fish, abdominal distension, ethnicity, abdominal pain and age, and the correction rate of the discriminant function was 88.75% to identify clonorchiasis sinensis. Conclusions The discriminant function of clonorchiasis sinensis can be rapidly and simply built based on the strong data processing and analysis capability of the SPSS software, which is rapid to screen clonorchiasis sinensis in Harbin City. Such a function has a high discriminant analysis capability, and provides insights into the establishment of rapid screening of clonorchiasis sinensis in other endemic areas.
    Relationship between parasitic infections and hygiene hypothesis: a review
    MU Sha-Sha, YANG Jun-Qi
    2020, 32(2):  203. 
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    Recently, the incidence of infectious diseases continues to decline in many developed countries; however, the incidence of autoimmune diseases and allergic asthma appears a tendency towards a rise over years. “Hygiene hypothesis” provides new insights into the treatment of autoimmune disorders and allergic diseases based on parasitic infections. Increasing evidence shows that parasitic infections may effectively inhibit the development of diabetes, multiple sclerosis, inflammatory bowel disease, rheumatoid arthritis and allergic asthma. There are complex mechanisms underlying the relationship between parasitic infections and “hygiene hypothesis”, among which regulatory T (Treg) cells and Th17 cells are becoming a hot topic of research. This paper reviews the progresses in the research on the relationship between parasitic infections and “hygiene hypothesis”, and summarizes the roles of Treg cells and Th17 cells in the interplay between parasitic infections and “hygiene hypothesis”.
    Progresses on research on patterns and monitoring approaches of Oncomelania hupensis spread
    JIANG Tian-Tian, YANG Kun
    2020, 32(2):  208. 
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    Oncomelania snail is the only intermediate host of Schistosoma japonicum, and controlling snail breeding and spread is an important intervention for schistosomiasis control. This review summarizes factors affecting snail spread, characteristics of snail spread in various endemic areas, high?risk environments of snail spread and monitoring methods of snail spread, so as to provide insights into the prevention of snail spread.
    Hepatic cystic and alveolar echinococcosis co-infections: a report of 3 cases
    WANG Xiang-Qian, HAN Xiu-Min, TIAN Qing-Shan, ZHAO Shun-Yun, A Ji-De
    2020, 32(2):  213. 
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    Objective To investigate the diagnosis and surgical treatment of co?infection with hepatic cystic and alveolar echinococcosis, so as to provide insights into the diagnosis and treatment of these patients. Methods The clinical data of patients with co?infections of hepatic cystic and alveolar echinococcosis in Qinghai Provincial People’s Hospital between 2017 and 2018 were retrospectively analyzed. Results Three patients were diagnosed with co?infection of hepatic cystic and alveolar echinococcosis. One patient was diagnosed by preoperative CT scan, and confirmed intraoperatively. The other two cases were diagnosed as cystic echinococcosis by preoperative color ultrasonography and imaging examinations, and were definitively diagnosed as co?infection of hepatic cystic and alveolar echinococcosis by intraoperative examination of the lesion morphology and postoperative pathology. Two patients were given radical surgery, and another case was given removal of the internal capsule and subtotal excision of the outer capsule of Echinococcus granulous in the liver following exploration. Conclusions Co?infection with hepatic cystic and alveolar echinococcosis is easy for missed diagnosis and misdiagnosis prior to operation, and the definitive diagnosis may be made by means of imaging examinations combined with postoperative pathology. The surgery is relatively complicated and difficult for patients with co?infection of hepatic cystic and alveolar echinococcosis, and individualized surgical treatment regimen should be employed for patients with various types of infections.
    Human Gongylonema pulchrum infection in esophagus: a case report
    ZHANG Qing-Qing
    2020, 32(2):  217. 
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    This paper reports a female patient with Gongylonema pulchrum parasitizing in the esophagus, with aims to call for the attention to the role of parasite detection in the diagnosis of human diseases.