Wei Ruan

Background: Babesia , an intraerythrocytic protozoan, is globally distributed and poses a significant public health burden. In China, human babesiosis is mainly caused by Babesia microti , and the Zhejiang Province is endemic. This study aimed to determine the prevalence of B. microti in the population, reservoir hosts, and vectors; assess population exposure risks; and gain further insight into the genotype structure in Zhejiang. Methods: From May 2020 to October 2023, blood samples from local residents and blood donors, as well as blood or liver tissues from rodents and questing or host-attached ticks, were collected from seven counties in southern Zhejiang Province. DNA was extracted for the detection of B. microti and identification of the rodent and tick species. A retrospective investigation was conducted on individuals who tested positive. Positive samples were sequenced for phylogenetic analyses. Results: In total, 4,728 samples were collected, including 2,475 local residents, 358 blood donors, 1,615 rodents, and 280 questing or host-attached ticks. B. microti was detected in six local residents, 71 rodents, and nine ticks, with infection rates of 0.24, 4.40, and 3.21%, respectively. Human infections and positive ticks were found in specific counties, whereas positive rodents were detected in all counties. All six infected individuals were asymptomatic carriers with a history of outdoor activities in forested areas, and four also reported contact with animals. A total of 17 rodent species were identified, among which Niviventer lotipes exhibited the highest risk. The tick species identified included Haemaphysalis longicornis , Ixodes granulatus , Rhipicephalus haemaphysaloides , and Rhipicephalus microplus . Positive samples were detected for both I. granulatus and R. microplus . Sequencing and phylogenetic analyses of the positive samples revealed that all the sequences belonged to the Kobe type. Conclusion: This study is the first comprehensive report of B. microti infection across its life cycle in Zhejiang Province, revealing a wide prevalence in rodents and ticks. Asymptomatic infections in humans have also been reported. N. lotipes appears to be the predominant rodent reservoir host. In addition, I. granulatus and R. microplus may serve as primary tick vectors. These findings provide valuable information for developing preventive strategies against babesiosis in China.

Human babesiosis, an emerging zoonosis with ongoing geographic expansion, is primarily caused by Babesia microti , a tick‐borne apicomplexan parasite that resides within host erythrocytes. While small mammals serve as its recognized reservoir hosts, the relative contribution of sympatric wild rodents and shrews in subtropical mountain endemic areas of Eastern China remains poorly characterized. In South‐central Zhejiang, an endemic focus of human babesiosis, systematic data on local small‐mammal hosts remain limited. In this study, 630 small mammals, comprising six rodent species and the shrew Suncus murinus , were captured across six counties in Zhejiang Province of China. Host identity was confirmed by morphological examination and mitochondrial cytochrome b ( cytb ) barcoding. Whole‐blood DNA was screened for B . microti by TaqMan real‐time quantitative PCR (qPCR); positive specimens were further analyzed by nested PCR (NPCR) targeting the 18S rRNA gene, followed by sequencing for genotype identification. The overall qPCR‐positive rate was 3.0% (19/630). Geographically, B. microti infections were detected in four out of six surveyed counties, with Jinyun County showing the highest prevalence of 6.9%, followed by Qingyuan (4.0%), Wencheng (3.2%), and Qingtian (3.0%); no positive samples were identified in the Yunhe and Jingning counties. Among the sampled species, Niviventer lotipes showed the highest prevalence (11.7%, 12/103), followed by S. murinus (3.8%, 2/52), Alexandromys fortis (3.7%, 3/81), Apodemus agrarius (1.0%, 1/99), and Rattus norvegicus (0.5%, 1/222). No positive results were detected in R. tanezumi ( n = 62) or Leopoldamys edwardsi ( n = 11). Fifteen of the 19 samples yielded positive amplification by NPCR and were successfully sequenced. All 15 sequenced isolates were assigned to the Kobe genotype and exhibited close genetic relatedness to previously reported local human‐derived and tick‐derived strains. The dominance of a single haplotype ( n = 14) across host species and counties indicates genetically homogeneous circulation of the Kobe genotype within local small‐mammal communities, with host species rather than sampling county as the significant determinant of infection risk. These findings suggest that N. lotipes may be an important reservoir host in this region, and shrews may represent understudied secondary hosts, supporting the inclusion of both rodents and shrews in regional babesiosis surveillance.

Introduction: The provincial malaria diagnosis reference laboratories review and assess malaria cases diagnosed in health facilities for supporting the malaria elimination efforts and preventing re-transmission of imported malaria. The study aimed to evaluate the detection capability of malaria diagnosis in China from 2014 to 2021.Methods: Data on malaria cases reported in the provincial-level administrative divisions (PLADs) of Anhui, Henan, Hubei, Guangxi, and Zhejiang from 2014 to 2021 were collected and analyzed.Results: In total, 5,770 malaria cases were reported from 2014 to 2021, and 99.05% (5,715/5,770) were submitted to the provincial malaria diagnosis reference laboratories. The median time between malaria cases being reported and the samples being received by reference laboratories was 6 days (Interquartile range, IQR:3–12 days) from 2017 to 2021. Diagnosis of 5,680 samples in the laboratory were confirmed by provincial reference laboratories, including 3,970 cases of Plasmodium falciparum, 414 of P. vivax, 1,055 of P. ovale, 158 of P. malariae, 1 of P. knowlesi, and 82 of mixed infections. Plasmodium species of 5,141 confirmed cases were consistent with the initial diagnosis, with a species accuracy rate of 90.53% (5,141/5,679). The accuracy of P. falciparum diagnosis in health facilities was higher than that of non-falciparum species. The inconsistency between microscopy and nested polymerase chain reaction (nPCR) results of confirmatory diagnosis was mainly in malaria-positive versus malaria-negative cases, as well as in mixed versus single infection cases.Conclusion: The provincial malaria diagnosis reference laboratories have played an important role in ensuring the accuracy and reliability of Plasmodium diagnosis in health facilities. However, the results of this study imply that capacity training for the identification of Plasmodium species in health facilities is warranted.

Objectives: The widespread occurrence of anti-malarial drug resistance threatens the current efforts to control malaria in African regions. Molecular marker surveillance helps to track the emergence and spread of drug-resistant malaria cases.Methods: A total of 237 Plasmodium falciparum infections imported from central Africa to Zhejiang Province, China, between 2016 and 2021, were investigated. Genomic DNA was extracted from blood samples of each patient and nested PCRs was used to detect molecular markers in k13, Pfcrt, and Pfmdr1 genes. The spatial and temporal distributions of the molecular markers were analyzed.Results: A limited polymorphism of k13 was observed, including two nonsynonymous (D464E and K503E) and five synonymous mutations. Wild-type CVMNK of Pfcrt predominated (78.5%), whereas 19.5% of the samples harbored the mutant haplotype, CVIET. The point mutation Y184F and the single mutant haplotype NF of Pfmdr1 were the most frequently observed. The geographical distributions of the Pfcrt and Pfmdr1 haplotypes displayed distinct patterns, with the mutant haplotype of Pfcrt more common in Gabon (53.9%) and Congo (50.0%), and wild haplotypes of Pfmdr1 more frequently found in Cameroon, Angola, and Congo. The prevalence of wild-type CVMNK of Pfcrt increased from 68.5–74.6% in 2016–2017 to 81.8–87.5% in 2018–2021. The proportion of wild-type Pfmdr1 also increased from 27.1% in 2016 to 38.5% in 2019.Conclusion: The geographical and temporal distribution of k13, Pfcrt, and Pfmdr1 polymorphisms in P. falciparum parasites imported from central Africa between 2016 and 2021 are demonstrated. Our data provide updated evidence that can be used to adjust anti-malarial drug policies in central Africa and China.

The global battle against malaria is facing formidable challenges, particularly in controlling Plasmodium vivax and Plasmodium ovale, whose cases have not been reduced as effectively as Plasmodium falciparum because of their relapse. This study investigates the current situation and underlying factors contributing to relapse or recrudescence of imported cases of P. vivax and P. ovale, and seeks to provide a reference for reducing relapse or recrudescence in malaria-free areas and offers a scientific basis for designing strategies to prevent imported re-transmission. This study analysed imported P. vivax and P. ovale in Anhui, Zhejiang, Henan, Hubei, and Guangxi provinces during 2014–2021 by retrospective analysis. A case–control study was conducted on patients who experienced relapse or recrudescence. From 2014 to 2021, 306 cases of P.vivax and 896 cases of P.ovale were included in the study, while 75 cases had relapse or recrudescence, including 49 cases of P. ovale (65.33%) and 26 cases of P. vivax (34.67%). Within less than 5 weeks after returning to the country, 122 cases of P. vivax (39.87%, 122/306) and 265 cases of P. ovale (29.58%, 265/896) occurred. Within less than 53 weeks, the ratio of P. vivax was 94.77% (290/306), and that of P. ovale was 89.96% (806/896). Among the cases experiencing relapse or recrudescence, only 1 case of P. vivax (1/26 3.85%) and 3 cases of P. ovale (3/49 6.12%) occurred within less than 5 weeks after the first onset, whereas 21 cases of P. vivax (21/26 80.77%) and 42 cases of P. ovale (42/49 85.71%) occurred within less than 53 weeks after the first onset. The difference in relapse or recrudescence due to different drugs and medication regimens and medical activities at various levels of medical institutions was statistically significant. In areas where malaria has been eliminated, routine health screening in a scientific time frame for people returning from at-risk areas can effectively improve the efficiency of preventing re-transmission, thereby reducing prevention costs and disease burden. Preventing patients from self-treating and strengthening medication regulations in health facilities are key measures to reduce relapse or recrudescence.

Background: This study aimed at exploring the epidemiological pattern of imported malaria in China before malaria elimination in 2021, to provide evidence-based data for preventing malaria re-establishment in China.Methods: Nine-year surveillance data on imported malaria in four provincial-level administrative divisions (PLADs) (Anhui, Chongqing, Guangxi, and Zhejiang) between 2011 and 2019 were thoroughly collected and analyzed.Results: A quite stable trend in imported malaria cases between 2011 and 2019 was observed. In total, 6,064 imported patients were included. Plasmodium falciparum was the most frequently reported species (4,575, 75.6%). Cases of malaria were most frequently imported from Western Africa (54.4%). We identified an increasing trend in P. ovale and a persistence of P. vivax infections among the cases of malaria imported from Western Africa. Most patients (97.5%) were 20–50 years old. Among imported malaria infections, the main purposes for traveling abroad were labor export (4,914/6,064, 81.0%) and business trips (649, 10.7%). Most patients (2,008/6,064, 33.1%) first visited county-level medical institutions when they sought medical help in China. More patients were diagnosed within 3 days after visiting Centers for Disease Control and Prevention (CDCs) or entry–exit quarantine facilities (EQFs) (1,147/1609, 71.3%) than after visiting medical institutions (2,182/3993, 54.6%).Conclusion: Imported malaria still poses a threat to the malaria-free status of China. County-level institutions are the primary targets in China to improve the sensitivity of the surveillance system and prevent the re-establishment of malaria. Health education should focus on exported labors, especially to Western and Central Africa. Increasing trend in P. ovale and persistence of P. vivax infections indicated their underestimations in Western Africa. Efficient diagnostic tools and sensitive monitoring systems are required to identify Plasmodium species in Africa.

Background: In areas where malaria has been eliminated, delayed care-seeking and diagnosis of imported malaria are constant threats. This study aimed to describe the profile and determinants of delayed care-seeking and diagnosis among patients with imported malaria in China. Methods: This retrospective study assessed surveillance data obtained from 2014 to 2021 in the Chinese provincial-level administrative divisions (PLADs) of Anhui, Henan, Hubei, and Zhejiang, and Guangxi. Epidemiological characteristics were analyzed using descriptive statistics. Furthermore, factors associated with delayed care-seeking and diagnosis among imported malaria cases were identified using multivariate logistic regression. Results: Overall, 11.81% and 30.08% of imported malaria cases had delays in seeking care and diagnosis, respectively. During the study period, there was a decreasing trend in the proportion of imported malaria cases with delayed care-seeking (χ² = 36.099, P < 0.001) and diagnosis (χ² = 11.395, P = 0.001). In multivariate analysis, independent risk factors associated with delayed care-seeking include PLADs (Guangxi as reference), consultations in high-level facilities for the first medical visit, infections with non-Plasmodium falciparum species, and older age. However, PLADs (Guangxi as reference), the purpose of traveling (labour as reference), and infections with non-P. falciparum species increased the risk of delayed diagnosis. Delayed care-seeking (adjusted odds ratio: 1.79, P = 0.001) and diagnosis (adjusted odds ratio: 1.62, P = 0.004) were risk factors for severe disease development. Conclusions: Based on this study’s findings, we strongly advocate for improved access to quality healthcare to reduce the rate of misdiagnosis at the first visit. Infections caused by non-P. falciparum species should be highlighted, and more sensitive and specific point-of-care detection methods for non-P. falciparum species should be developed and implemented. In addition, education programs should be enhanced to reach target populations at risk of malaria infection. All these factors may reduce delayed care-seeking and diagnosis of imported malaria. Graphical

Monitoring drug resistance is important for malaria control because its early detection enables timely action to prevent its spread and mitigate its impact. The wide geographic spread and the increasing trend of highly resistant Pfdhfr genes between 2016 and 2021 found in our study are worrisome and emphasize the urgency to monitor their updated status in central Africa.

Monitoring the current resistance to antimalarial drugs is critical to enable timely action to prevent its spread and limit its impact. The high prevalence of wild-type Pfcrt found in our study is an optimistic signal to reevaluate chloroquine (CQ) sensitivity in Nigeria, which is cost-effective and once played a crucial role in the fight against malaria.