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Abstract Grid management is a grassroots governance strategy widely implemented in China since 2004 to improve the government’s efficiency to actively find and solve problems among populated regions. A grid-based strategy surveillancing high-risk groups, including mobile and migrant populations (MMPs), in the China–Myanmar border region has played an indispensable role in promoting and consolidating the malaria elimination efforts by tracking and timely identification of potential importation or re-establishment of malaria among MMPs. A sequential mixed methods was implementated to explore the operational mechanism and best practices of the grid-based strategy including through the focus group discussions (FGDs), comparison of before and after the implementation of a grid-based strategy in the field sites, and data collection from the local health system.This paper distills the implementation mechanism and highlights the role of the grid-based strategy in the elimination and prevention of re-establishment of malaria transmission.

Abstract Background Mosquito-based arbovirus surveillance can serve as an early warning in evaluating the status of mosquito-borne virus prevalence and thus prevent local outbreaks. Although Tengchong County in Yunnan Province—which borders Myanmar—is abundant and diverse in mosquitoes, very few mosquito-based arbovirus investigations have been conducted in the recent decade. Herein, this study aims to evaluate the presence and the diffusion of mosquito-borne pathogens, currently prevalent in this region. Methods We collected 9486 mosquitoes, representing eight species, with Culex tritaeniorhynchus and Anopheles sinensis as the dominant species, during high mosquito activity seasons (July–October) in Tengchong, in 2018. Samples collected from 342 pools were tested using reverse-transcription PCR to determine the species, distribution, and infection rates of virus and parasite, and further analyze their genotypes, phylogenetic relationships, infection rate, and potential pathogenicity. Results Fifteen Japanese encephalitis virus (JEV) strains from Cx. tritaeniorhynchus pools were detected. Seven strains of insect-specific flaviviruses (ISFVs), including two Aedes flavivirus (AeFV) and Yunnan Culex flavivirus strains each, one Culex theileri flavivirus, Yamadai flavivirus (YDFV) and Anopheles-associated flavivirus (AAFV) strains each were detected in Aedes albopictus, Cx. tritaeniorhynchus, Cx. vagans, Cx. pseudovihnui, and An. sinensis pools, respectively. The whole-genome was successfully amplified in one strain of JEV and AeFV each. Phylogenetic analysis using the E gene placed all the newly detected JEV strains into the GI-b genotype. They showed highly nucleotide identities, and were most closely related to the strain detected in Tengchong in 2010. The comparison of the E protein of JEV strains and vaccine-derived strain, showed six amino residue differences. The bias-corrected maximum likelihood estimation values (and 95% confidence interval) for JEV in Cx. tritaeniorhynchus collected in Tengchong in 2018 were 2.4 (1.4–3.9). Conclusions A potential Japanese encephalitis epidemic focus with the abundance of host mosquitoes and high JEV infection rate was observed in Tengchong. In addition, at least five species of ISFVs co-circulate in this area. This study highlights the importance of widespread and sustained mosquito-based arbovirus surveillance in local areas to prevent the transmission of JEV, and other emerging/re-emerging mosquito-borne pathogens. Graphic Abstract

Abstract Background Many tick species have great morphological similarity and are thus grouped into species complexes. Molecular methods are therefore useful in the classification and identification of ticks. However, little is known about the genetic diversity of hard ticks in China, especially at the subspecies level. Tengchong is one of the epidemic foci of tick-borne diseases in China, but the tick species inhabiting the local area are still unknown. Methods Eighteen villages in Tengchong County, China, were selected for sampling carried out from September to October 2014. Infesting hard ticks were removed from the body surface of domestic animals and questing ticks were collected from grazing fields. After morphological identification, molecular characteristics of each tick species were analyzed based on both 16S rRNA and cytochrome c oxidase subunit 1 (cox1) gene fragments. Results Six tick species were identified based on morphology: Rhipicephalus microplus, R. haemaphysaloides, Ixodes ovatus, Haemaphysalis longicornis, H. shimoga and H. kitaokai. Phylogenetic analysis using the cox1 gene revealed that R. microplus ticks from the present study belong to clade C. For tick samples of both R. haemaphysaloides and I. ovatus, three phylogenetic groups were recognized, and the intergroup genetic distances exceeded the usual tick species boundaries. Haemaphysalis longicornis ticks were clustered into two separate clades based on the cox1 gene. For ticks from both H. shimoga and H. kitaokai, two phylogenetic groups were recognized based on the phylogenetic analysis of the 16S rRNA gene, and the intergroup genetic distances also exceeded the known boundaries for closely related tick species. Conclusions According to molecular analyses, new species or subspecies closely related to R. haemaphysaloides, I. ovatus, H. shimoga and H. kitaokai probably exist in the China-Myanmar border Tengchong County, or these ticks form species complexes with highly divergent mitochondrial lineages. Morphological comparisons are warranted to further confirm the taxonomic status of these tick species.

Babesiosis is a tick-borne, zoonotic disease caused by Babesia spp. Two cases of babesiosis were detected by nested polymerase chain reaction (PCR) in Yunnan province, China, and further confirmed by molecular assay. The blood smears showed intraerythrocytic ring form and tetrads typical of small B. microti. In both cases, the rapid diagnostic test (RDT) ruled out the possibility of co-infections with malaria. Neither case was initially diagnosed because of the low Babesia parasitemia. These two cases of babesiosis in areas along the Myanmar–China border pose the question of the emergence of this under recognized infection in countries or areas where malaria is endemic.[Figure: see text]

Objective: To analyze the results of malaria focus investigation and disposal in Tengchong City, Yunnan Province between 2015 and 2016, so as to provide evidences for interrupting potential malaria transmission., Methods: The malaria foci were investigated and disposed according to the malaria cases reported from "China Information System for Disease Control and Prevention" in Tengchong City between 2015 and 2016. The mosquitoes were captured by mosquito-lured lamp overnight to investigate the malaria vector in local. The peripheral blood samples were collected from the local residents with a febrile history in the foci within two weeks and the accompanists of the cases, and then the rapid malaria diagnosis tests were used to screen the malaria carriers., Results: Totally 145 imported malaria cases were reported in Tengchong City between 2015 and 2016, and the focus investigation and disposal rate within 7 d was 100% (145/145). A total of 16 186 mosquitoes of 12 species of Anopheles were captured, among which An. sinensis was the predominant, accounting for 64.31% (10 410/16 186), followed by An. kunmingensis and An. minimus , with the constituent ratios of 14.15% (2 291/16 186) and 11.66% (1 887/16 186), respectively. One person (1.96%, 1/51) in the 51 accompanists of the cases was positive in the malaria rapid diagnosis test., Conclusions: The malaria transmission vectors such as An. sinensis , An. kunmingensis , An. minimus etc. are still distributed in Tengchong City, and An. sinensis is the predominant species. Therefore, the relevant authorities should continue to strengthen the focus investigation and disposal to interrupt the potential introduced malaria transmission by imported cases in the future.

Objective: To analyze the malaria epidemiological characteristics in Tengchong City from 2010 to 2015, so as to provide the evidence for adjusting and formulating measures in the elimination stage., Methods: The malaria data were collected and analyzed by using Microsoft Excel 2010 in Tengchong City from 2010 to 2015., Results: There were 1 408 malaria cases reported in Tengchong City from 2010 to 2015, including 1 091 cases of Plasmodium vivax infection, 256 cases of P. falciparum infection, 5 cases of P. malariae infection, 1 case of Plasmodium ovale infection, 1 case of mixed infections, and 54 unclassified cases. Totally 1 390 imported cases were recorded and 98.06% of them (1 363/1 390) were imported from Myanmar. Most of the patients ( n = 908) were aged from 21 to 40 years, and the male to female ratio was 11.03∶1. The highest-risk populations were farmers and migrant workers. The most cases were observed in April and June, and at that time, most of the floating workers returned., Conclusions: Imported malaria is severe in Tengchong City, and there is a great challenge to malaria elimination.

Objective: To study the prevalence of tick bites and relative factors of outpatients with fever from health care facilities in Tengchong County., Methods: From July to August, 2014, the outpatients with fever in five health care facilities namely Tengchong Center for Disease Control and Prevention, Hehua Health Center, Jietou Health Center, Qushi Health Center and Xinhua Health Center were investigated by questionnaires. The factors related to tick bites were explored with the univariate analysis and multiple regression models., Results: Totally 884 effect questionnaires were acquired. Among the 884 participants, 85 (9.6%) had experienced tick bites. The frequency of tick bites was associated with locations, gender, age group, ownership of cattle, working at foreign country, firewood cutting and lumbering in the forest (all P < 0.05). The multiple regression revealed that the male and people raising cattle, working at foreign country, engaging in firewood cutting and lumbering in the forest had a more risk for tick bites., Conclusions: Tick bites are common in the residents of Tengchong County. The risk of being bitten varies in different populations. The local health departments should promote health education in the high-risk population to reduce the risk of infecting tick-borne diseases.