Malaria from hyperendemicity to elimination along international borders in Yunnan, China during 2003‒2020: a case study

Managing vector-borne diseases in a geoAI-enabled society. Malaria as an example

More than 17 % of all infectious diseases are caused by vector-borne diseases resulting in more than 1 billion cases and over 1 million deaths each year. Of these malaria continues to be a global burden in over eighty countries. As societies become more digitalised, the availability of geospatially enabled health and disease information will become more abundant. With this, the ability to assess health and disease risks in real-time will become a reality. The purpose of this study was to examine how geographic information, geospatial technologies and spatial data science are being used to reduce the burden of vector-borne diseases such as malaria and explore the opportunities that lie ahead with GeoAI and other geospatial technology advancements. Malaria is a dynamic and complex system and as such a range of data and approaches are needed to tackle different parts of the malaria cycle at different local and global scales. Geospatial technologies provide an integrated framework vital for monitoring, analysing and managing vector-borne diseases. GeoAI and technological advancements are useful for enhancing real-time assessments, accelerating the decision making process and spatial targeting of interventions. Training is needed to enhance the use of geospatial information for the management of vector-borne diseases.

Cooperative Sentinel Surveillance of Malaria in Laiza and Nearby Areas of Myanmar and Importation Threat Monitoring - China, 2019-2023

Introduction

Laiza and nearby areas (LNA) in Myanmar are identified as the primary malaria hotspots in the bordering regions of Yunnan Province, China.

Methods

Six sentinel surveillance sites were established at the China-Myanmar border in LNA to monitor malaria. Data from 2019 was used as a baseline to analyze malaria incidence and trends in LNA and Myanmar, as well as the importation of malaria cases into China from 2019 to 2023.

Results

Plasmodium vivax was the predominant species, representing 99.95% (14,060/14,066) of confirmed malaria cases in LNA. A total of 8,356 malaria cases were identified in 2023, with an annual parasite incidence (API) of 19.78 per 100 person-years. Compared to 2019, the incidence rate ratio was 21.47 (95% confidence interval: 18.84, 24.48), indicating that the API in 2023 was 21.47 times higher than that in 2019. In Yunnan, out of 1,016 reported cases, 545 imported cases (53.64%) originated from LNA and spread to 18 (13.95%) out of 129 counties. Ten provinces in China, including Yunnan, reported imported malaria cases from LNA in Myanmar.

Conclusions

The increase in population, particularly among internally displaced persons, along with inadequate healthcare services, has led to a notable resurgence of malaria in LNA. This resurgence poses a risk to preventing the re-emergence of malaria transmission in China. There is an urgent need for novel collaborative policies, as well as financial and technical assistance, to enhance malaria control efforts in LNA, Myanmar.

Artemisinin-naphthoquine plus lower-dose primaquine to treat and prevent recurrence of Plasmodium vivax malaria: an open-label randomized and non-inferiority trial

BACKGROUND

Plasmodium vivax malaria, with the widest geographic distribution, can cause severe disease and death. Primaquine is the main licensed antimalarial drug that can kill hypnozoites. The dose-dependent acute haemolysis in individuals with glucose-6-phospate dehydrogenase (G6PD) deficiency is the main safety concern when using primaquine. The recommended treatment regimen for P. vivax malaria is chloroquine plus primaquine for 14 days (CQPQ14) in Myanmar. The study aimed to evaluate the therapeutic efficacy, safety and adherence for the regimen of artemisinin-naphthoquine plus primaquine for 3 days (ANPQ3) in patients with P. vivax infections compared to those with CQPQ14.

METHODS

The patients in the ANPQ3 group were given fixed-dose artemisinin-naphthoquine (a total 24.5 mg/kg bodyweight) plus a lower total primaquine dose (0.9 mg/kg bodyweight) for 3 days. The patients in the CQPQ14 group were given a total chloroquine dose of 30 mg/kg body weight for 3 days plus a total primaquine dose of 4.2 mg/kg bodyweight for 14 days. All patients were followed up for 365 days.

RESULTS

A total of 288 patients completed follow-up, 172 in the ANPQ3 group and 116 in the CQPQ14 group. The first recurrence patients were detected by day 58 in both groups. By day 182, 16 recurrences had been recorded: 12 (7.0%) patients in the ANPQ3 group and 4 (3.4%) in the CQPQ14 group. The difference in recurrence-free patients was 3.5 (-8.6 to 1.5) percentage points between ANPQ3 and CQPQ14 group (P = 0.2946). By day 365, the percentage of recurrence-free patients was not significant between the two groups (P = 0.2257). Mean fever and parasite clearance time of ANPQ3 group were shorter than those in CQPQ14 group (P ≤ 0.001). No severe adverse effect was observed in ANPQ3 group, but five (3.9%) patients had acute haemolysis in CQPQ14 group (P = 0.013). Medication percentage of ANPQ3 group was significantly higher than that of CQPQ14 group (P < 0.0001).

CONCLUSIONS

Both ANPQ3 and CQPQ14 promised clinical cure efficacy, and the radical cure efficacy was similar between the ANPQ3 and CQPQ14 group. ANPQ3 clears fever and parasites faster than CQPQ14. ANPQ3 is safer and shows better patient adherence to the regimen for treatment of P. vivax malaria along the China-Myanmar border.

TRIAL REGISTRATION

ChiCTR-INR-17012523. Registered 31 August 2017, https://www.chictr.org.cn/showproj.html?proj=21352.

Seasonal prediction of the distribution of three major malaria vectors in China: Based on an ecological niche model

Against the backdrop of a global malaria epidemic that remains severe, China has eradicated indigenous malaria but still has to be alert to the risk of external importation. Understanding the distribution of vectors can provide an adequate and reliable basis for the development and implementation of vector control strategies. However, with the decline of malaria prevalence in recent years, the capacity of vector monitoring and identification has been greatly weakened. Here we have used new sampling records, climatic data, and topographic data to establish ecological niche models of the three main malaria vectors in China. The model results accurately identified the current habitat suitability areas for the three species of Anopheles and revealed that in addition to precipitation and temperature as important variables affecting the distribution of Anopheles mosquitoes, topographic variables also influenced the distribution of Anopheles mosquitoes. Anopheles sinensis is the most widespread malaria vector in China, with a wide region from the northeast (Heilongjiang Province) to the southwest (Yunnan Province) suitable for its survival. Suitable habitat areas for Anopheles lesteri are concentrated in the central, eastern, and southern regions of China. The suitable habitat areas of Anopheles minimus are the smallest and are only distributed in the border provinces of southern China. On this basis, we further assessed the seasonal variation in habitat suitability areas for these three major malaria vectors in China. The results of this study provide new and more detailed evidence for vector monitoring. In this new era of imported malaria prevention in China, regular reassessment of the risk of vector transmission is recommended.

Assessing the risk of malaria local transmission and re-introduction in China from pre-elimination to elimination: A systematic review

Assessing the risk of malaria local transmission and re-introduction is crucial for the preparation and implementation of an effective elimination campaign and the prevention of malaria re-introduction in China. Therefore, this review aims to evaluate the risk factors for malaria local transmission and re-introduction in China over the period of pre-elimination to elimination. Data were obtained from six databases searched for studies that assessed malaria local transmission risk before malaria elimination and re-introduction risk after the achievement of malaria elimination in China since the launch of the NMEP in 2010, employing the keywords "malaria" AND ("transmission" OR "re-introduction") and their synonyms. A total of 8,124 articles were screened and 53 articles describing 55 malaria risk assessment models in China from 2010 to 2023, including 40 models assessing malaria local transmission risk (72.7%) and 15 models assessing malaria re-introduction risk (27.3%). Factors incorporated in the 55 models were extracted and classified into six categories, including environmental and meteorological factors (39/55, 70.9%), historical epidemiology (35/55, 63.6%), vectorial factors (32/55, 58.2%), socio-demographic information (15/26, 53.8%), factors related to surveillance and response capacity (18/55, 32.7%), and population migration aspects (13/55, 23.6%). Environmental and meteorological factors as well as vectorial factors were most commonly incorporated in models assessing malaria local transmission risk (29/40, 72.5% and 21/40, 52.5%) and re-introduction risk (10/15, 66.7% and 11/15, 73.3%). Factors related to surveillance and response capacity and population migration were also important in malaria re-introduction risk models (9/15, 60%, and 6/15, 40.0%). A total of 18 models (18/55, 32.7%) reported the modeling performance. Only six models were validated internally and five models were validated externally. Of 53 incorporated studies, 45 studies had a quality assessment score of seven and above. Environmental and meteorological factors as well as vectorial factors play a significant role in malaria local transmission and re-introduction risk assessment. The factors related to surveillance and response capacity and population migration are more important in assessing malaria re-introduction risk. The internal and external validation of the existing models needs to be strengthened in future studies.

Dihydroartemisinin-piperaquine efficacy in Plasmodium falciparum treatment and prevalence of drug-resistant molecular markers along China-Myanmar border in 2014-2023

OBJECTIVES

The study aims to monitor dihydroartemisinin-piperaquine (DHA-PPQ) efficacy in Plasmodium falciparum and detect molecular markers associated with its resistance.

METHODS

The World Health Organization's standard protocol for therapeutic efficacy studies (TES) was performed from 2014 to 2018; integrated drug efficacy surveillance (iDES) was performed from from 2019 to July 2023. Molecular markers were detected by polymerase chain reaction. The association between gene mutations and delayed parasite clearance was analysed by multivariate logistic regression analysis.

RESULTS

A total of 226 P. falciparum patients were enrolled in the TES from 2014 to 2018, and 26 patients with P. falciparum from Africa were recruited in the iDES from 2019 to July 2023. The PCR-adjusted clinical and parasitological cure rate was 93.7% (95% CI: 92.6-99.5%) in the TES and 96.2% (95% CI: 80.4-99.9%) in the iDEs. Twelve mutants and an overall 55.0% prevalence of pfK13 mutations were detected. Of them, G533S, C447R, C447S, N458Y, C469Y, and A676D were first detected out along the China-Myanmar border. Referred to the wild strain, adjusted odds ratios of treatment failure for G533S, N458Y, and P574L by 42 days were 7.54 (95% CI: 1.605-45.86), 13.68 (95% CI: 1.95-130.72), and 89.00 (95% CI: 1.98-2482.1), respectively.

CONCLUSION

The efficacy of DHA-PPQ from 2014 to 2018 declined in comparison with 2003 to 2013, but it is still effective for treatment of P. falciparum malaria. Results of the iDES indicate a risk of artemisinin resistance in Africa. G533S, N458Y, and P574L are associated with delayed parasite clearance and treatment failure.

Treatment-seeking behaviours of malaria patients versus non-malaria febrile patients along China-Myanmar border

BACKGROUND

Appropriate malaria treatment-seeking behaviour (TSB) is critical for timely detecting malaria, prompt treatment, and prevention of onward transmission of the disease in a community. This study aimed to compare treatment-seeking behaviours between malaria patients and non-malaria febrile patients, and to analyse the factors associated with appropriate TSB along the China-Myanmar border.

METHODS

A cross-sectional study was carried out to investigate the appropriate TSB of microscopy-confirmed malaria patients versus non-malaria febrile (NMF) patients. An unconditional logistic regression analysis (LRA) was used to identify factors associated with appropriate TSB.

RESULTS

Among 223 malaria patients and 446 NMF patients, 129 (57.8%) of the malaria patients versus 163 (36.5%) of the NMF patients firstly sought treatment in health facilities without laboratory testing for malaria (P < 0.0001). A total of 85(38.1%) of the malaria patients versus 278 (62.3%) of the NMF patients had appropriate TSB, namely, seeking treatment in health facilities with laboratory testing for malaria within 48 h (P < 0.0001). Multivariate LRA identified that the malaria patients with Chinese nationality had less appropriate TSB compared to those with other nationalities (adjusted odds ratio [AOR]: 0.21, 95% confidence interval CI 0.07-0.68, P = 0.0097), and malaria patients residing in urban areas had more appropriate TSB compared to those living in rural areas (AOR: 2.16, 95%CI 1.06-4.39, P = 0.0337).

CONCLUSIONS

TSB was not appropriate in malaria patients. Chinese citizenship and rural residence were two independent factors associated with inappropriate malaria TSB. It is urgently necessary to improve appropriate malaria TSB through effective campaigns of information, education, and communication for malaria control in Myanmar and preventing reestablishment of malaria transmission in Yunnan, China.

The public health response to an outbreak of border-spill malaria along China-Myanmar border

INTRODUCTION

Malaria importation can be caused by cross-border movement either of both people and anopheline mosquitoes. However, there still lacks robust evidence of imported malaria caused by Plasmodium spp. infected anopheles along international border areas (border-spill malaria). The objectives of this study were to confirm whether an outbreak of Plasmodium vivax malaria is border-spill malaria and assess the effects of China's public health response along China-Myanmar border.

METHODS

Epidemiological, parasitological and entomological investigations were conducted to investigate the outbreak of border-spill malaria. Meanwhile, comprehensive interventions were carried out to prevent further transmission and reintroduction of malaria.

RESULTS

Rapid diagnostic testing, microscopy and polymerase chain reaction were performed and the infections were confirmed as P. vivax. A total of 22 (9.21%) of 239 workers contracted P. vivax during the outbreak. Multivariate logistic regression analysis identified that the distance of worker shelters in China within 300 meters to the internally displaced person (IDP) camps in Myanmar was a risk factors associated with malaria infection (adjusted odds ratio 7.5920; 95% confidence interval, 2.6079-22.1013; P = 0.0002). After comprehensive interventions, malaria transmission was successfully interpreted and prevented at the project site till the completion of project on 14 January 2020, and recurrence of P. vivax malaria was not detected by the end of 2020.

CONCLUSION

This study provided robust evidence of border-spill malaria along China-Myanmar border. Malaria parasite reservoir and distance travelled by female anopheline mosquitoes are two determinants for border-spill malaria. The public health response to the outbreak indicates that the malaria surveillance and response system works well in preventing reintroduction of malaria. However, prevention of border-spill malaria is still a major challenge in the Yunnan border area, China.

Achievements of the national malaria control and elimination program in the People's Republic of China: the Atlas of Malaria Transmission in China

In 2017, China achieved the target of zero indigenous malaria case for the first time, and has been certified as malaria free by World Health Organization in 2021. To further summarize the historical achievements and technical experiences of the elimination program, a project on the Roadmap Analysis and Verification for Malaria Elimination in China was carried out. Results of the project were compiled and published as the Atlas of Malaria Transmission in China (The Atlas). The Atlas using modern digital information technologies, has been supported by various data from 24 malaria endemic provinces of China since 1950, to assess the changes in malaria epidemic patterns from 1950 to 2019 at national and provincial levels. The Atlas is designed as two volumes, including a total of 1850 thematic maps and more than 130 charts, consisting of introductory maps, thematic maps of malaria epidemic and control at national and provincial levels. It objectively and directly shows the epidemic history, evolution process, and great achievements of the national malaria control and elimination program in China. The Atlas has important reference value for summing up historical experience in the national malaria elimination program of China, and malaria control and elimination in other endemic countries in the world.