Objective To collect data on imported malaria cases in Jiangsu Province from 2019 to 2023 after malaria elimination and to analyze the current epidemic situation and prevention and control measures of imported malaria, discussing future prevention and control strategies. Methods Malaria case information for Jiangsu Province from 2019 to 2023 was extracted and downloaded from the China Information System for Disease Control and Prevention (CISDCP) as well as the Jiangsu Provincial malaria epidemic database. Statistical analysis was conducted using Stata 12.0 and SPSS 16.0 software. Results From 2019 to 2023, a total of 534 cases of malaria were directly reported online in Jiangsu Province, with annual cases numbering 244, 90, 32, 36, and 132 respectively, all being laboratory-confirmed imported malaria cases from abroad. During the COVID-19 pandemic from 2020 to 2022, the number of imported malaria cases significantly decreased, with several months reporting zero cases. Among the 534 malaria cases, the vast majority were individuals who had traveled to countries in sub-Saharan Africa and Southeast Asia for work, business, international studies, or tourism. Over the five years, the median, minimum, and maximum days for patients from onset of illness to health-seeking were 1(0,12), 1(0,8), 0(0,6), 0(0,10), and 1(0,18) days, with a statistically significant difference in health-seeking time among patients (Fisher's exact test, P=0.03). Over the past three years of the COVID-19 pandemic, compared to outside centralized isolation stations, malaria cases within centralized isolation stations were diagnosed in a shorter time (Fisher exact test, P=0.007). A total of 24 severe malaria cases were reported, with no deaths, including 23 cases of P. falciparum and 1 case of P. ovale. Conclusions After the elimination of malaria, imported malaria cases in Jiangsu Province have sharply decreased due to the impact of the COVID-19 pandemic. Malaria cases in centralized isolation stations (CIS) for COVID-19 control of Jiangsu Province are more likely to be promptly diagnosed, and the timeliness from onset to health-seeking among malaria patients returning from high-malaria areas improved. As COVID-19 prevention and control policies adjusted, there has been a sharp increase in imported malaria cases in 2023. It's still necessary to strengthen measures for malaria prevention and control and maintain the capacity to prevent malaria re-transmission in Jiangsu Province.

Objective To create risk predictive models of healthcare-seeking delay among imported malaria patients in Jiangsu Province based on machine learning algorithms, so as to provide insights into early identification of imported malaria cases in Jiangsu Province. Methods Case investigation, first symptoms and time of initial diagnosis of imported malaria patients in Jiangsu Province in 2019 were captured from Infectious Disease Report Information Management System and Parasitic Disease Prevention and Control Information Management System of Chinese Center for Disease Control and Prevention. The risk predictive models of healthcare-seeking delay among imported malaria patients were created with the back propagation (BP) neural network model, logistic regression model, random forest model and Bayesian model using thirteen factors as independent variables, including occupation, species of malaria parasite, main clinical manifestations, presence of complications, severity of disease, age, duration of residing abroad, frequency of malaria parasite infections abroad, incubation period, level of institution at initial diagnosis, country of origin, number of individuals travelling with patients and way to go abroad, and time of healthcare-seeking delay as a dependent variable. Logistic regression model was visualized using a nomogram, and the nomogram was evaluated using calibration curves. In addition, the efficiency of the four models for prediction of risk of healthcare-seeking delay among imported malaria patients was evaluated using the area under curve (AUC) of receiver operating characteristic curve (ROC). The importance of each characteristic was quantified and attributed by using SHAP to examine the positive and negative effects of the value of each characteristic on the predictive efficiency. Results A total of 244 imported malaria patients were enrolled, including 100 cases (40.98%) with the duration from onset of first symptoms to time of initial diagnosis that exceeded 24 hours. Logistic regression analysis identified a history of malaria parasite infection [odds ratio (OR) = 3.075, 95% confidential interval (CI): (1.597, 5.923)], long incubation period [OR = 1.010, 95% CI: (1.001, 1.018)] and seeking healthcare in provincial or municipal medical facilities [OR = 12.550, 95% CI: (1.158, 135.963)] as risk factors for delay in seeking healthcare among imported malaria cases. BP neural network modeling showed that duration of residing abroad, incubation period and age posed great impacts on delay in healthcare-seek among imported malaria patients. Random forest modeling showed that the top five factors with the greatest impact on healthcare-seeking delay included main clinical manifestations, the way to go abroad, incubation period, duration of residing abroad and age among imported malaria patients, and Bayesian modeling revealed that the top five factors affecting healthcare-seeking delay among imported malaria patients included level of institutions at initial diagnosis, age, country of origin, history of malaria parasite infection and individuals travelling with imported malaria patients. ROC curve analysis showed higher overall performance of the BP neural network model and the logistic regression model for prediction of the risk of healthcare-seeking delay among imported malaria patients (Z = 2.700 to 4.641, all P values < 0.01), with no statistically significant difference in the AUC among four models (Z = 1.209, P > 0.05). The sensitivity (71.00%) and Youden index (43.92%) of the logistic regression model was higher than those of the BP neural network (63.00% and 36.61%, respectively), and the specificity of the BP neural network model (73.61%) was higher than that of the logistic regression model (72.92%). Conclusions Imported malaria cases with long duration of residing abroad, a history of malaria parasite infection, long incubation period, advanced age and seeking healthcare in provincial or municipal medical institutions have a high likelihood of delay in healthcare-seeking in Jiangsu Province. The models created based on the logistic regression and BP neural network show a high efficiency for prediction of the risk of healthcare-seeking among imported malaria patients in Jiangsu Province, which may provide insights into health management of imported malaria patients.

Objective To understand the malaria epidemic situation and characteristics in Jiangsu Province in 2015,so as to provide the evidence for malaria elimination. Methods The data of malaria cases in Jiangsu Province in 2015 were collected from China's routine diseases surveillance information system. Results Totally 405 imported cases were reported in Jiangsu Province in 2015,and the cases increased by 14.08％compared with those in 2014. All the malaria cases were imported,and 5 cases(1.23％)were from Southeast Asia and 400(98.77％)were from 25 African countries or regions. The imported malaria cases were reported in 13 cities across Jiangsu Province,where Taizhou,Lianyungang,Nantong,Huaian and Yangzhou cities accounted for 68.64％of all the cases in the province. Jiangsu Institute of Parasitic Diseases(JIPD)reference lab checked all the cases and classified 299 falciparum malaria cases,13 vivax malaria cases,18 quartan malaria cases,71 ovale malaria cas-es,and 4 mixed Plasmodium infection cases. Conclusions In Jiangsu Province,there are no local malaria cases for 4 consecu-tive years,but the imported cases are on the rise. Compared to 2014,the imported vivax cases increased significantly in 2015. It should be the key points to strengthen the surveillance of imported malaria cases,improve malaria diagnosis and treatment abili-ties for all levels of medical institutions,and promote the abilities of Plasmodium check,and focus survey and disposal of all Center for Disease Control(CDC)staffs across Jiangsu Province.

Objective To understand the integrated ability of parasitic disease prevention and control of professional person-nel of Jiangsu Province through the contest. Methods Totally 56 players from the whole province were selected,and all the players participated in the contest. The theory knowledge and skill scores were collected and the statistical analyses were con-ducted. Results The average theoretical score of the participants was 88.86±15.56 and the passing rate was 91.1％. The aver-age skill operating score was 69.16 ± 16.01 and the passing rate was 67.9％. The average Plasmodium microscopy score was 16.54±8.09 and the passing rate was 50％. The average helminth egg microscopy score was 34.27±10.66 and the passing rate was 67.9％. There were statistical differences among the age groups and different levels of schistosomiasis endemic situation (F =5.10,6.39,both P<0.01). The theoretical knowledge including schistosomiasis,malaria,hydatid disease and others and the score rates were 91.07％,90.94％,85.83％and 90.93％,respectively. The hydatid disease score rate was lower(χ2=19.17, P<0.01). The radar chart displayed that the score rates of tabletting and microscopy test in Kato-Katz film production ,malaria blood film production and microscopy test were all low. Conclusion In Jiangsu Province,the participants have higher score in the theory test. However,they have lower skill test score,especially in the parasite species identification. The operational skills still need to be strengthened for center for disease control(CDC)participants.

Objective To understand the epidemic situation and influencing factors of malaria in Jiangsu Province and grasp its epidemic regularity and trend. Methods According to the malaria prevalence in Jiangsu Province,6 counties(city,dis-trict)including Yixing,Suining,Wujin,Hai’an,Ganyu and Xuyi were selected as provincial surveillance sites to survey malar-ia epidemic conditions. The basic information,blood test results of fever patients,case investigation information of malaria pa-tients,monitoring data of investigation and disposition of the malaria focus were collected and analyzed. Results In 2013,the blood tests of 66 723 fever patients were performed,the average blood smear checking rate was 1.10%,and the average positive rate was 0.08%(52 plasmodium positive individuals)in the 6 areas. For these 52 plasmodium positive individuals,the blood re-tests and case investigations were completed within 3 days after these cases were reported by the network system,and the investi-gation confirmed that they were foreign imported malaria cases. The malaria focus investigation and disposition were finished within 1 week and the data were reported by the Parasitic Diseases Information System. Four of 52 cases were recrudescence dur-ing the follow-up. Among the 52 cases,20 people went abroad themselves and 4 were labors of private enterprises,21 people came back without the accompanied. Conclusions With the development of the malaria elimination program in Jiangsu Prov-ince,the eliminating malaria“targeted 1-3-7”working pattern has been comprehensively implemented. The personnel monitor-ing for labors who returned from overseas working will be a key in the future.

Objective To understand the malaria epidemic situation and characteristics in Jiangsu Province in 2013,so as to provide the evidence for formulating and adjusting effective malaria elimination strategies and measures. Methods The re-ported malaria cases from the Internet Reporting System and the epidemiological data of malaria in Jiangsu Province were collect-ed and analyzed. Results A total of 341 malaria cases were reported in Jiangsu Province in 2013 with the incidence of 0.050/10 000,which increased by 72.22% compared with that in 2012(198 cases). All the cases were imported from other countries including one infected by blood transfusion resulted from imported infection. The cases were mainly distributed in Li-anyungang City(15.84%,54 cases),Nantong City(14.08%,48 cases),Yangzhou City(14.08%,48 cases),Huaian City (11.44%,39 cases)and Yancheng City(8.50%,29 cases). All the cases were confirmed in Jiangsu Provincial Reference Labo-ratory and there were 286 cases of Plasmodium falciparum,8 cases of P. vivax,9 cases of P. malariae,30 cases of P. ovale and 8 cases of mixed infections. Conclusions There were no local malaria cases reported from Jiangsu Province in the last two years which reflected effective achievements of malaria elimination. However,the situation of imported malaria is more serious and the species of infected plasmodium are more diverse. Imported malaria from other countries remains the key of malaria con-trol in Jiangsu Province.

Objective To understand the malaria epidemic situation and characteristics in Jiangsu Province in 2012,so as to provide the evidence for formulating and adjusting effective malaria elimination strategies and measures. Methods The reported malaria cases from the Internet Reporting System and the epidemiological data of malaria in Jiangsu Province were collected and analyzed. Results A total of 198 malaria cases were reported in Jiangsu Province in 2012 with the incidence of 0.026/10 000, which decreased by 47.06%compared with that in 2011(374 cases). A total of 198 malaria cases were reported from 13 prefec-tures of Jiangsu and the cases were mainly distributed in Yangzhou(34 cases),Nantong(31 cases),Nanjing(22 cases),Tai-zhou(21 cases),Xuzhou(17 cases)and Huaian(17 cases),which accounted for 71.72%(142/198)among the total cases of the province. There were no local malaria cases reported from Jiangsu in 2012,and the imported malaria cases from other countries de-creased by 45.15%compared with that in 2011. Conclusions For the first time,there are no local malaria cases reported from Ji-angsu in 2012. However,the imported case distribution is further expanded and the infected plasmodium parasites are more di-verse. Imported malaria from other countries remains the key for malaria control in Jiangsu Province.

Objective To observe the residual effect of Demand CS - impregnated bednets to Anopheles sinensis.Methods The numbers of adult mosquitoes which were knocked down at every minute after treatment were observed by using the enforced contact method recommended by WHO,and the mortality of mosquitoes tested after 24 h was calculated.Results The Kt_(50) of Demand CS - impregnated bednets with impregnations concentrations of 10,15,20 mg/m~2 to Anopheles sineasis were 21.40,16.20,15.70 min,respectively,and the 24 h mortality was 100%.The Kt_(50) of Responsar SC (12.5 % Beta - cyfluthrin) impregnated bednets with a impregnation concentration of 15 mg/m~2 to Anopheles sinensis was 16.06 min,and the 24 h mortality was 100%,too.Conclusions Both the Demand CS - impregnated bednets and the Responsar SC impregnated bednets can kill Anopheles sinensis.

Objective To establish a simple,convenient,quick and high sensitive method of loop-mediated isothermal amplification (LAMP) for detection of Plasmodium vivax-carrying mosquitoes.Methods The species conservative regions of P.v CSP gene were selected to design 2 pairs of primers which recognized 6 distinct regions.To evaluate the specificity of detection by LAMP,infected Anopheles,An.sinensis (An.s),Plasmodium falciparum (P.f),and healthy human blood DNA were selected as templates.To assess the sensitivity of detection,1.3×10~6,1.3×10~5,1.3×10~4,1.3×10~3,1.3×10~2,1.3×10~1 and 1.3×10~0 copies of P.v CSP plasmid DNA mixed with 1.0 μl An.s DNA were used as the templates of LAMP.The infected An.s DNAs were diluted with negative An.s DNA by 1:2,1:4,1:8,1:16,1:32,1:64,1:128 and 1:256 and then detected by LAMP to show the sensitivity of batch quantity detection.The applied value of this method was evaluated by detecting the same batch of 67 artificial infected An.s mosquitoes,and compared with the detection of microscopic examination and nested PCR in parallel.Results By using LAMP,the detection of infected An.s was positive,while the control samples were all negative.The limits of detection of different proportion dilutions of the mixture of P.v CSP plasmid DNA with An.s DNA were 1.3×10~2 copies.The limits of detection of different proportion dilutions of the mixture of infected An.s DNA with An.s DNA were 1:128.The positive rate of detecting the same batch of 67 artificial infected mosquitoes was 47.76% by LAMP,25.37% by the microscopic examination (X~2 = 7.24,P<0.01),40.30% by nested PCR (X~2 = 0.73,P>0.05).Compared with the test of the microscopic examination and then with a statistical analysis,the sensitivity of LAMP was 100%,which agreed well with the sensitivity of nested PCR (100%).Conclusion The method of LAMP is simple,convenient and high sensitive,and it is a potential method for detecting Plasmodium vivax-carrying mosquitoes in the field.

Objective To explore the sample reIated factors affecting the short-term culture of erythrocytic Plasmodium dvax in vitro.Methods The vivax malaria blood samples were collected from the patients with malaria in endemic areas,and then incubated with McCoy's 5A medium in an incubator containing 5%CO_2 at 37℃.The factors affecting the short-term culture of Plasmodium vivax were analyzed.Results Plasmodium vivax could finish one asexual cycle in the selected medium.By analyzing the culture results of 74 samples.it was found that the factors affecting the short-term culture included long time delaying al room temperature(>4 h),single stage(only parasites in ring stage were found),patients taking antimalarials,antibiotics or sulfonamides.and low parasitemia.Conclusion The sample related factors are important to the short-term culture of erythrocytic Plasmodium vivax in vitro.