Malaria in China: a longitudinal population-based surveillance study

The Immunomodulatory Role of Estrogen in Malaria: A Review of Sex Differences and Therapeutic Implications

BACKGROUND

Malaria remains a significant global health challenge, with substantial mortality rates, particularly in tropical and subtropical regions. A notable sexual dimorphism exists in malaria, with males often experiencing higher infection and mortality rates compared to females.

OBJECTIVE

This review explores the role of estrogen in modulating immune responses to malaria, potentially explaining the observed sex differences. Estrogen, through its receptors, influences immune cell activation and cytokine production, which are critical in the immune response to malaria.

RESULTS

Utilizing data from the Global Burden of Disease (GBD) study, we analyzed sex differences in malaria burden in Central Sub-Saharan Africa from 2000 to 2021, revealing a significantly lower mortality burden for females compared to males. Epidemiological data and animal model results support the notion that estrogen plays a significant role in modulating immune responses to malaria. Estrogen receptors are widely expressed in immune cells, and estrogen can influence the activation, proliferation, and differentiation of these cells, thereby affecting cytokine production and immune response type. Additionally, selective estrogen receptor modulators (SERMs) show potential as therapeutic agents, with some studies demonstrating their efficacy in reducing parasitemia and improving malaria outcomes.

CONCLUSION

Understanding the sex differences in the pathogenesis of malaria is crucial for its prevention, treatment, and vaccine development. Estrogen's role in immune regulation highlights the need for sex-specific approaches in disease management.

Deep learning hybrid model for analyzing and predicting the impact of imported malaria cases from Africa on the rise of Plasmodium falciparum in China before and during the COVID-19 pandemic

BACKGROUND

Plasmodium falciparum cases are rising in China due to the imported malaria cases from African countries. The main goal of this study is to examine the impact of imported malaria cases in African countries on the rise of P. falciparum cases in China before and during the COVID-19 pandemic.

METHODS

A generalized regression model was used to investigate the association of time trends between imported malaria cases from 45 African countries and P. falciparum cases in 31 provinces of China from 2012 to 2018 before the COVID-19 pandemic and during the COVID-19 pandemic from October 2020 to May 2021. Based on the analysis, we proposed a statistical and deep learning hybrid approach to model the resurgence of malaria in China using monthly data of P. falciparum from 2004 to 2016. This study builds a hybrid model known as the ARIMA-GRU approach for modeling the P. falciparum cases in all provinces of China and the number of malaria deaths in China before and during the COVID-19 pandemic.

RESULTS

The analysis showed an emerging link between the rise of imported malaria cases from Africa and P. falciparum cases in many provinces of China. Many imported malaria cases from Africa were P. falciparum cases. The proposed deep learning model achieved a high prediction accuracy score on the testing dataset of 96%.

CONCLUSION

The study provided an analysis of the reduction of P. falciparum cases and deaths caused by imported P. falciparum cases during the COVID-19 pandemic due to the control measures regarding the limitation of international travel in China. The Chinese government has to prepare the imported malaria control measures after the normalization of international travel, to prevent the resurgence of malaria disease in China.

A rapid multiplex assay of human malaria parasites by digital PCR

BACKGROUND

Blood smear examination through traditional optical microscopy is the gold standard for malaria diagnosis. However, it imposes strict requirements for operational staff and its sensitivity cannot perfectly satisfy the needs of clinical requirements. More sensitive and accurate modern technologies should be applied to this field. Digital PCR (dPCR), as an absolute quantification detection method, can serve as an effective tool to facilitate the diagnosis and classification of different malaria species.

OBJECTIVE

We aimed to establish a new multiplex dPCR detection system for four main Plasmodium species: P. vivax, P. falciparum, P. ovale and P. malariae, which can distinguish exact species of malaria by one PCR reaction.

METHODS

A total of 39 patients were identified as malaria-positive by microscopic examination in Huashan Hospital from 2016 to 2021; seventy blood samples from these patients were collected. Additionally, 20 healthy individuals, 20 patients with fever and 6 patients with other types of blood parasites infection were also included in this study. Each blood sample was subjected to examination by both blood smears and dPCR. By optimizing four different fluorescence-labeled probes in one reaction system, dPCR permitted the performance of accurate quantitation and working out the exact number of copies of malaria DNA per microliter in whole blood. Rapid diagnostic tests were also conducted to verify part of the results obtained by dPCR.

RESULTS

The dPCR system was able to make rapid diagnosis and quantification of malaria DNA samples. The analytical sensitivity of multiplex dPCR was as low as 0.557 copies/μL (95% CI 0.521 to 0.607), and it had a sensitivity of 98.0% and a specificity of 100% in clinical samples. Additionally, three multiple malaria co-infection samples have been detected by this dPCR system, including one triple malaria infection case. By testing consecutive daily blood samples of Patient 39, dPCR facilitated monitoring the efficacy of drug treatment. It showed that the DNA concentrations of P. falciparum ranged from 5474 copies/μL to 0 copies/μL, which can reflect the efficacy of antimalarials in real time. This study also found that haemocyte samples (plasma removed) rather than whole blood had higher malaria detection capability and an enhanced positive rate.

CONCLUSION

The multiplex dPCR system newly established here made a substantial contribution in detecting malaria infection at low concentrations. It is suitable for mixed-infection diagnosis and multi-sample continuous monitoring, and presents a promising candidate as an absolute quantitative tool in clinical practice.

Analysis of epidemiological changes and elimination effects for malaria in Handan city, the north China

The elimination of malaria requires high-quality surveillance data to quickly detect and respond to individual cases. This study aims to analyze the epidemiological characteristics of malaria and ascertain the long-term epidemic trends of malaria by 2020 in Handan China. Case-level data for the period 2011 to 2020 were extracted from Chinese Information System for Disease Control and Prevention. The lamp trap method was used to capture mosquitoes so that the characteristics of mosquitoes can be analyzed. The incidence, accuracy, and timeliness of malaria case diagnosis, reporting and investigation were evaluated at the elimination stage (2011-2020) in Handan City, China. Between 2011 and 2020, 94 malaria cases were reported in Handan City, of which 93 malaria cases were male and all of which were imported from abroad. The annual average incidence decreased from 622.33/100,000 to 0.11/100,000 in the elimination stage. Since the initiation of the National Malaria Elimination Program in 2010, malaria cases have been consistent with the increase in overseas export channels and labor personnel service. There is a need to strengthen malaria surveillance of returning workers from Africa and to conduct timely blood tests to diagnose and treat imported infections. Local authorities ensure that imported malaria cases can be timely diagnosed, reported, treated and investigated at local level.

Factors associated with prolonged hospital stay of imported malaria cases in Chengdu, China: a retrospective study

BACKGROUND

Although China has entered the post-malaria-elimination era, imported cases remain a public health concern in China.

METHODS

We retrospectively analyzed data from cases of imported malaria from January 2017 to December 2020 in Chengdu Public Health Clinical Center. We assessed potential clinical, epidemiological, geographical, and seasonal effects on duration of hospital stay. Cox proportional hazards model was used to identify predictive factors for prolonged hospital stay. Multivariate logistic regression was used to assess the potential risk factors associated with severe cases.

RESULTS

The highest number of imported cases of malaria were from the Democratic Republic of the Congo (23%, 34/150) and most patients (74%, 26/34) were infected by Plasmodium falciparum. The Edwards test indicated no significant seasonality in imported cases of malaria (χ² = 2.51, p = 0.28). Bacterial infection (adjusted hazard ratio [aHR] for discharge = 0.58, p = 0.01) and thrombocytopenia (aHR = 0.66, p = 0.02) were risk factors for prolonged hospital stay. The C-reactive protein (OR = 1.02, p = 0.01) and procalcitonin (OR = 1.03, p = 0.01) were risk factors for severe cases.

CONCLUSIONS

Bacterial infection and thrombocytopenia are risk factors for prolonged hospital stay among imported malaria cases. The C-reactive protein and procalcitonin level were risk factors for severe cases.

Outbreak of autochthonous cases of malaria in coastal regions of Northeast Brazil: the diversity and spatial distribution of species of Anopheles

BACKGROUND

Brazil has the fourth highest prevalence of malaria of all countries in the Americas, with an estimated 42 million people at risk of contracting this disease. Although most cases occur in the Amazon region, cases of an autochthonous nature have also been registered in the extra-Amazonian region where Anopheles aquasalis and An. albitarsis are the mosquito species of greatest epidemiological interest. In 2019, the municipality of Conde (state of Paraíba) experienced an epidemic of autochthonous cases of malaria. Here we present preliminary results of an entomological and case epidemiology investigation, in an attempt to correlate the diversity and spatial distribution of species of Anopheles with the autochthonous cases of this outbreak of malaria.

METHODS

Case data were collected using case report forms made available by the Conde Municipal Health Department. The entomological survey was carried out from July to November 2019. The various methods of capture included the use of battery-powered aspirators, mouth aspirators, Shannon traps, BG-Sentinel traps (with and without dry ice) and CDC light traps. Captured mosquitoes were separated, packaged and sent to the laboratory for sexing and molecular identification of the various species of anophelines. The data were tabulated and analyzed using Microsoft Excel. Spatial analysis of the data was performed using ArcGis 10 software.

RESULTS

In 2019, 20 autochthonous cases and one imported case of malaria caused by Plasmodium vivax were diagnosed, with three cases of relapses. A total of 3713 mosquitoes were collected, of which 3390 were culicines and 323 were anophelines. Nine species of genus Anopheles were identified, with the most abundant being An. aquasalis (38.9%), followed by An. minor (18.2%) and An. albitarsis (9.0%). Spatial analysis of the data showed that the area could be considered to be at risk of malaria cases and that there was a high prevalence of Anopheles.

CONCLUSIONS

The results presented indicate that this extra-Amazonian region has an environment conducive to maintenance of the malaria transmission cycle owing to the wide diversity of Anopheles species. This environment in combination with the high influx of people from endemic areas to the study area provides a perfect setting for the occurrence and maintenance of malaria.