Malaria Surveillance — United States, 2018

Time trends in malaria incidence from 1992 to 2021 in high-risk regions: an age‑period‑cohort analysis based on the Global Burden of Disease study 2021

OBJECTIVES

Malaria, caused by plasmodium parasites, remains one of the world's most significant infectious diseases due to its high incidence and mortality. This study aims to analyze malaria incidence globally, identify high-risk regions, and examine long-term trends in incidence to provide important evidence for malaria eradication.

METHODS

We used data from the Global Burden of Disease Study (GBD) 2021, applying the age-period-cohort model to estimate the effects of age, period and cohort on malaria incidence from 1992 to 2021. We calculated the net drift (overall annual percentage change), local drift (annual percentage change for each age group), longitudinal age curves (expected longitudinal age-specific rates), and period(cohort) relative risks.

RESULTS

In 2021, the global age-standardized incidence rate of malaria declined to 3,485.3 per 100,000 (95% uncertainty interval [UI]: 2804.5 to 4435.7), a 5.24% decrease since 1992. Sub-Saharan Africa has the highest age-standardized rate at 20225.9 per 100,000 (95% UI: 16033.5 to 25862.6), accounting for 92% of all new cases globally. From 1992 to 2021, age-standardized malaria incidence rates generally declined across highest-risk regions, although Sub-Saharan Africa saw the smallest decline, with a net drift of -0.74% (95% confidence interval [CI]: -1.32 to 0.17). The 0-4 age group faces the highest risk, which decreases with age.

CONCLUSIONS

Malaria continues to threaten public health in Sub-Saharan Africa, particularly among the 0-4 age group. Efforts should focus on enhancing access to malaria control measures and implementing targeted public health policies for priority groups.

Viability of Plasmodium falciparum parasites in human plasma under different storage conditions

BACKGROUND AND OBJECTIVES

Malaria risk deferral policies are important for mitigating the risk of transfusion-transmitted malaria and apply to all transfusable components, including plasma. While donors of plasma components are deferred for malaria risk in the United States, the viability of intraerythrocytic Plasmodium falciparum parasites present in human plasma components stored under different temperatures and durations has not been previously reported.

MATERIALS AND METHODS

We spiked human plasma with a low level of ring-stage P. falciparum-infected red blood cells and then determined their viability in cultures after storage at room temperature (22°C), refrigeration (4°C) and frozen conditions at -20 and -80°C.

RESULTS

P. falciparum parasites spiked in human plasma remained viable after storage at 22°C for a maximum of 7 days. When stored at 4°C, parasites were viable after 1 and 3 days of storage and only for 1 day after storage at -20°C. Storage at -80°C had a cryopreserving effect and parasites remained viable for up to 176 days, the longest period tested.

CONCLUSION

P. falciparum parasites can survive for short durations in human plasma when stored at room temperature, or in refrigerated or frozen conditions at -20°C. However, when stored at -80°C, viable parasites were detected for up to 176 days, the maximum duration for which viability was assessed. In summary, Plasmodium parasites can survive in human plasma under different storage conditions and pose a risk of transfusion-transmitted infection.

Geo-classification of drug-resistant travel-associated Plasmodium falciparum using Pfs47 and Pfcpmp gene sequences (USA, 2018-2021)

Travel-related malaria is regularly encountered in the United States, and the U.S. Centers for Disease Control and Prevention (CDC) characterizes Plasmodium falciparum drug-resistance genotypes routinely for travel-related cases. An important aspect of antimalarial drug resistance is understanding its geographic distribution. However, specimens submitted to CDC laboratories may have missing, incomplete, or inaccurate travel data. To complement genotyping for drug-resistance markers Pfcrt, Pfmdr1, Pfk13, Pfdhps, Pfdhfr, and PfcytB at CDC, amplicons of Pfs47 and Pfcpmp are also sequenced as markers of geographic origin. Here, a bi-allele likelihood (BALK) classifier was trained using Pfs47 and Pfcpmp sequences from published P. falciparum genomes of known geographic origin to classify clinical genotypes to a continent. Among P. falciparum-positive blood samples received at CDC for drug-resistance genotyping from 2018 to 2021 (n = 380), 240 included a travel history with the submission materials, though 6 were excluded due to low sequence quality. Classifications obtained for the remaining 234 were compared to their travel histories. Classification results were over 96% congruent with reported travel for clinical samples, and with collection sites for field isolates. Among travel-related samples, only two incongruent results occurred; a specimen submitted citing Costa Rican travel classified to Africa, and a specimen with travel referencing Sierra Leone classified to Asia. Subsequently, the classifier was applied to specimens with unreported travel histories (n = 140; 5 were excluded due to low sequence quality). For the remaining 135 samples, geographic classification data were paired with results generated using CDC's Malaria Resistance Surveillance (MaRS) protocol, which detects single-nucleotide polymorphisms in and generates haplotypes for Pfcrt, Pfmdr1, Pfk13, Pfdhps, Pfdhfr, and PfcytB. Given the importance of understanding the geographic distribution of antimalarial drug resistance, this work will complement domestic surveillance efforts by expanding knowledge on the geographic origin of drug-resistant P. falciparum entering the USA.

Laboratory detection of donors implicated in transfusion-transmitted malaria

BACKGROUND

Transfusion-transmitted malaria (TTM) is rare in non-endemic areas (non-EAs) but can potentially be fatal. This review analyzes the laboratory results of donors causing TTM in non-EAs, to assess the detectability of their Plasmodium infection by molecular or antibody tests.

STUDY DESIGN AND METHODS

TTM cases in the United States, Canada, and Europe since 2010 were identified through a literature review. Authors and laboratories were contacted for missing details about sample types and laboratory methods. Results of Plasmodium polymerase chain reaction (PCR) and antibody tests were summarized.

RESULTS

Twelve cases of TTM and one bone marrow transplant transmission were identified. Of the 13 source donors, 12 were tested by PCR, 10 were positive on at least one sample; the 2 negative donors were tested only on retained segments of blood refrigerated for several weeks. All donors were PCR positive on a fresh sample except one who was positive on a retained but not a fresh sample. These PCRs targeted Plasmodium DNA with sensitivities in the range of 1000-10,000 parasites/mL. Antibody EIA was positive in only three of seven donors tested.

DISCUSSION

This review found that antibody EIAs failed to detect four of the seven TTM donors tested. DNA-based PCRs were able to detect Plasmodium infection in all donors tested except for two tested only on samples likely to have deteriorated from prolonged storage. Recently developed ribosomal RNA-based molecular donor screening assays are approximately 1000 fold more sensitive than these DNA-based PCRs, holding promise as a potential method to further reduce TTM.

Plasmodium proteases and their role in development of Malaria vaccines

Malaria remains a major health hazard for humans, despite the availability of efficacious antimalarial drugs and other interventions. Given that the disease is often deadly for children under 5 years and pregnant women living in malaria-endemic areas, an efficacious vaccine to prevent transmission and clinical disease would be ideal. Plasmodium, the causative agent of malaria, uses proteases and protease inhibitors to control and process to invade host, modulate host immunity, and for pathogenesis. Plasmodium parasites rely on these proteases for their development and survival, including feeding their metabolic needs and invasion of both mosquito and human tissues, and have thus been explored as potential targets for prophylaxis. In this chapter, we have discussed the potential of proteases like ROM4, SUB2, SERA4, SERA5, and others as vaccine candidates. We have also discussed the role of some protease inhibitors of plasmodium and mosquito origin. Inhibition of plasmodium proteases can interrupt the parasite development at many different stages therefore understanding their function is key to developing new drugs and malaria vaccines.

Plasmodium vivax Infections among Immigrants from China Traveling to the United States

Beginning in 2023, we observed increased Plasmodium vivax malaria cases at an institution in Los Angeles, California, USA. Most cases were among migrants from China who traveled to the United States through South and Central America. US clinicians should be aware of possible P. vivax malaria among immigrants from China.

Autochthonous Plasmodium vivax Infections, Florida, USA, 2023

During May-July 2023, a cluster of 7 patients at local hospitals in Florida, USA, received a diagnosis of Plasmodium vivax malaria. Whole-genome sequencing of the organism from 4 patients and phylogenetic analysis with worldwide representative P. vivax genomes indicated probable single parasite introduction from Central/South America.

Malaria among members of the U.S. Armed Forces, 2023

MSMR publishes annual updates on the incidence of malaria among U.S. service members. Malaria infection remains a potential health threat to U.S. service members located in or near endemic areas due to duty assignment, participation in contingency operations, or personal travel. In 2023, a total of 39 active and reserve component service members were diagnosed with or reported to have malaria, an 8.3% increase from the 36 cases identified in 2022. Over half of the malaria cases in 2023 were caused by Plasmodium falciparum (53.8%; n=21) followed by unspecified types of malaria (35.9%; n=14) and P vivax and other Plasmodia (5.1%; n=2 each ). Malaria cases were diagnosed or reported from 22 different medical facilities: 18 in the U.S., 2 in Germany, 1 in Africa, 1 in South Korea. Of the 33 cases with known locations of diagnoses, 6 (18.2%) were reported from or diagnosed outside the U.S.

Notes from the Field: Increases in Imported Malaria Cases - Three Southern U.S. Border Jurisdictions, 2023

Malaria is a severe and potentially fatal mosquitoborne disease caused by infection with Plasmodium spp. parasites. Although malaria is no longer endemic in the United States, imported infections are reported annually; the primary risk group has been U.S. residents traveling to areas where malaria is endemic (1). In 2023, sporadic locally acquired mosquito-transmitted malaria cases were reported in several U.S. states (2,3). This report describes increases in imported malaria cases in 2023 compared with 2022 in three public health jurisdictions along the U.S. southern border.

Unsuspected Malaria Diagnosed on a Routine Peripheral Smear Review

Prompt diagnosis of malaria infection is critical for effective management, yet it can be challenging due to varying incubation periods and the need for physician-initiated laboratory workups. We present a case of a 40-year-old male with fever and dark-colored urine, initially evaluated for sepsis. Plasmodium vivax was incidentally identified on a peripheral smear review after obtaining a remote travel history from a malaria-endemic area. Consultation with the Centers for Disease Control confirmed the diagnosis, emphasizing the importance of thorough travel history assessment and timely laboratory investigation in suspected cases of malaria. This case underscores the significance of early diagnosis in managing this potentially life-threatening infection.

Imported malaria into Australia: surveillance insights and opportunities

BACKGROUND

Malaria continues to pose a significant burden in endemic countries, many of which lack access to molecular surveillance. Insights from malaria cases in travellers returning to non-endemic areas can provide valuable data to inform endemic country programmes. To evaluate the potential for novel global insights into malaria, we examined epidemiological and molecular data from imported malaria cases to Australia.

METHODS

We analysed malaria cases reported in Australia from 2012 to 2022 using National Notifiable Disease Surveillance System data. Molecular data on imported malaria cases were obtained from literature searches.

RESULTS

Between 2012 and 2022, 3204 malaria cases were reported in Australia. Most cases (69%) were male and 44% occurred in young adults aged 20-39 years. Incidence rates initially declined between 2012 and 2015, then increased until 2019. During 2012-2019, the incidence in travellers ranged from 1.34 to 7.71 per 100 000 trips. Cases were primarily acquired in Sub-Saharan Africa (n = 1433; 45%), Oceania (n = 569; 18%) and Southern and Central Asia (n = 367; 12%). The most common countries of acquisition were Papua New Guinea (n = 474) and India (n = 277). Plasmodium falciparum accounted for 58% (1871/3204) of cases and was predominantly acquired in Sub-Saharan Africa, and Plasmodium vivax accounted for 32% (1016/3204), predominantly from Oceania and Asia. Molecular studies of imported malaria cases to Australia identified genetic mutations and deletions associated with drug resistance and false-negative rapid diagnostic test results, and led to the establishment of reference genomes for P. vivax and Plasmodium malariae.

CONCLUSIONS

Our analysis highlights the continuing burden of imported malaria into Australia. Molecular studies have offered valuable insights into drug resistance and diagnostic limitations, and established reference genomes. Integrating molecular data into national surveillance systems could provide important infectious disease intelligence to optimize treatment guidelines for returning travellers and support endemic country surveillance programmes.

Establishing and applying an adaptive framework for imported malaria: a field practice in Anhui Province, China from 2012 to 2022

BACKGROUND

Anhui Province is currently facing an increase in imported malaria cases as a result of globalization and international travel. In response, Anhui Province has implemented a comprehensive adaptive framework to effectively address this threat.

METHODS

This study collected surveillance data from 2012 to 2022 in Anhui Province. Descriptive statistics were used to analyze the epidemiological characteristics of imported malaria cases. Additionally, multivariate logistic regression was employed to identify factors associated with severe malaria. Documents were reviewed to document the evolution of the adaptive framework designed to combat imported malaria. The effectiveness of the adaptive framework was evaluated based on the rates of timely medical visits, timely diagnosis, and species identification.

RESULTS

During the study period, a total of 1008 imported malaria cases were reported across 77 out of 105 counties in Anhui Province, representing a coverage of 73.33%. It was found that 10.52% of imported cases went undiagnosed for more than seven days after onset. The multivariate analysis revealed several potential risk factors for severe malaria, including increasing age (OR = 1.049, 95%CI:1.015-1.083), occupation (waitperson vs. worker, OR = 2.698, 95%CI:1.054-6.906), a longer time interval between onset and the initial medical visit (OR = 1.061, 95%CI:1.011-1.114), and misdiagnosis during the first medical visit (OR = 5.167, 95%CI:2.535-10.533). Following the implementation of the adaptive framework, the rates of timely medical visits, timely diagnosis, and species identification reached 100.00%, 78.57%, and 100.00%, respectively.

CONCLUSIONS

Anhui Province has successfully developed and implemented an adaptive framework for addressing imported malaria, focusing on robust surveillance, prompt diagnosis, and standardized treatment. The experiences gained from this initiative can serve as a valuable reference for other non-endemic areas.

Preventing malaria spread in the US

ABSTRACT

Locally acquired malaria is rare in the US; however, in 2023, cases were reported in Florida, Texas, Maryland, and Arkansas. Prompt diagnosis and treatment of malaria are essential to prevent severe malaria disease. This article details malaria and offers treatment guidelines.

Presence and abundance of malaria vector species in Miami-Dade County, Florida

BACKGROUND

Malaria outbreaks have sporadically occurred in the United States, with Anopheles quadrimaculatus serving as the primary vector in the eastern region. Anopheles crucians, while considered a competent vector, has not been directly implicated in human transmission. Considering the locally acquired Plasmodium vivax cases in Sarasota County, Florida (7 confirmed cases), Cameron County, Texas (one confirmed case), and Maryland (one confirmed case) in the summer of 2023. The hypothesis of this study is that major cities in the United States harbour sufficient natural populations of Anopheles species vectors of malaria, that overlap with human populations that could support local transmission to humans. The objective of this study is to profile the most abundant Anopheles vector species in Miami-Dade County, Florida-An. crucians and An. quadrimaculatus.

METHODS

This study was based on high-resolution mosquito surveillance data from 2020 to 2022 in Miami-Dade County, Florida. Variations on the relative abundance of An. crucians and An. quadrimaculatus was assessed by dividing the total number of mosquitoes collected by each individual trap in 2022 by the number of mosquitoes collected by the same trap in 2020. In order to identify influential traps, the linear distance in meters between all traps in the surveillance system from 2020 to 2022 was calculated and used to create a 4 km buffer radius around each trap in the surveillance system.

RESULTS

A total of 36,589 An. crucians and 9943 An. quadrimaculatus were collected during this study by the surveillance system, consisting of 322 CO2-based traps. The findings reveal a highly heterogeneous spatiotemporal distribution of An. crucians and An. quadrimaculatus in Miami-Dade County, highlighting the presence of highly conducive environments in transition zones between natural/rural and urban areas. Anopheles quadrimaculatus, and to a lesser extent An. crucians, pose a considerable risk of malaria transmission during an outbreak, given their high abundance and proximity to humans.

CONCLUSIONS

Understanding the factors driving the proliferation, population dynamics, and spatial distribution of Anopheles vector species is vital for implementing effective mosquito control and reducing the risk of malaria outbreaks in the United States.

Delayed Plasmodium falciparum Malaria in Pregnant Patient with Sickle Cell Trait 11 Years after Exposure, Oregon, USA

Delayed Plasmodium falciparum malaria in immigrants from disease-endemic countries is rare. Such cases pose a challenge for public health because mosquitoborne transmission must be rigorously investigated. We report a case of delayed P. falciparum malaria in a pregnant woman with sickle cell trait 11 years after immigration to the United States.

Assessing trainee critical thinking skills using a novel interactive online learning tool

BACKGROUND

Critical thinking is essential for the accurate diagnosis and management of patients. It is correlated with academic success.

OBJECTIVE

Our objective was to design a novel tool for interactive online learning to improve knowledge and to assess trainees' critical thinking skills using the framework of the American Philosophical Association (APA).

METHODS

Residents, fellows and students participated in an online, self-directed case-based vignette activity to learn malaria diagnosis and management. Pre and post-tests with multiple choice and open-ended case-based questions assessed knowledge and critical thinking. Comparison between pre and post-test scores across subgroups were performed using paired t-tests or one-way ANOVA.

RESULTS

Between 4 April 2017 to 14 July 2019, 62 of 75 (82%) eligible subjects completed both the pre and the post-test. Improved post-test scores occurred in 90% of medical students, p=0.001, 77% of residents, p<0.001, 60% of fellows, p=0.72 and 75% of trainees overall, p=<0.001. Fellows had higher pre-test scores than students or residents but there was no difference by level of training on the post-test.

CONCLUSIONS

This interactive online learning activity effectively imparted medical knowledge and improved trainee responses to questions requiring critical thinking. To our knowledge, this is the first time the APA's critical thinking framework has been incorporated into interactive online learning and assessment of critical thinking skills in medical trainees. We applied this innovation specifically in global health education, but there is obvious potential to expand it to a wide variety of areas of clinical training.

Malaria and Pregnancy

Recent identification of local mosquito-borne transmission of malaria in Florida, Texas, and Maryland and increasing travel to malaria-endemic countries raise the likelihood that U.S. obstetricians might encounter a pregnant patient with malaria. Pregnancy increases the risk of becoming infected with malaria and of developing severe disease. Malaria during pregnancy also increases the risk of adverse pregnancy outcomes, including low birth weight, pregnancy loss, and preterm birth; thus, prevention and prompt diagnosis and treatment are essential. Diagnosis can be challenging during pregnancy among persons with partial immunity because placental sequestration of parasite-infected red blood cells can result in lower parasite levels in peripheral blood. Treatment for uncomplicated malaria depends on the expected resistance pattern, which is determined by the specific Plasmodium species identified and where infection was acquired. For severe disease, parenteral artesunate treatment needs to be initiated immediately. Given the dire consequences of malaria in pregnancy, prevention is crucial. For persons born and raised in endemic areas, interventions include use of insecticide-treated bed nets, intermittent preventive treatment, and prompt diagnosis and treatment of illness. U.S. pregnant persons should avoid travel to endemic countries; for unavoidable travel, pregnant travelers should receive chemoprophylaxis and avoid mosquito bites. Although the risk is low to U.S. pregnant persons who are not traveling internationally, avoiding mosquito bites is important, especially for pregnant persons residing in or visiting areas with recent local mosquito-borne transmission.

Evidence of malarial chemoprophylaxis among travellers who died from malaria: a systematic review and meta-analysis

BACKGROUND

Chemoprophylaxis is a prevention method for malaria during travel in malaria-endemic countries. This study aimed to collate and synthesize the evidence of malarial chemoprophylaxis among malaria death cases.

METHODS

Studies documenting malarial chemoprophylaxis related to malaria deaths were searched in PubMed, Scopus, MEDLINE, Embase, and CENTRAL until 3 July 2022. The pooled proportion of malarial chemoprophylaxis among death cases was synthesized using logit transformation and back transformation to a proportion performed using generalized linear mixed models. The pooled log odds ratio (log-OR) with a 95% confidence interval (CI) of malarial chemoprophylaxis in death cases compared to survivors were synthesized.

RESULTS

Fifty-eight studies were included in the systematic review and the meta-analysis. Of 602 pooled malaria death cases, the number of patients who took chemoprophylaxis was 187 (30%) (95% CI 22-40, P < 0.01, 58 studies), and those who took adequate chemoprophylaxis were 24 (5%) (95% CI 2-13, P < 0.01, 42 studies). A comparable log-OR of underwent chemoprophylaxis was observed between malaria death cases and survivors (P = 0.94, pooled log-OR: - 0.02, 95% CI - 0.46-0.42, I2: 0%, 17 studies). Similarly, a comparable log-OR of adequate chemoprophylaxis was identified between malaria death cases and survivors (P = 0.15, pooled log-OR: 0.83, 95% CI - 0.30-1.97, I2: 47.08%, 11 studies).

CONCLUSIONS

Among the studies where malarial chemoprophylaxis was reported, approximately 30% of malaria death cases had taken such prophylaxis. Notably, only 5% of these cases adhered fully or adequately to the recommended chemoprophylactic regimen. However, the analysis did not reveal a significant difference in the odds of malarial chemoprophylaxis between malaria death cases and survivors.

Determine the enzymatic kinetic characteristics of CYP3A4 variants utilizing artemether-lumefantrine

Artemether-lumefantrine is an artemisinin-based combination therapy for the treatment of malaria, which are primarily metabolized by cytochrome P450 3A4. Therapeutic difference caused by gene polymorphisms of CYP3A4 may lead to uncertain adverse side effects or treatment failure. The aim of this study was to evaluate the effect of CYP3A4 gene polymorphism on artemether-lumefantrine metabolism in vitro. Enzyme kinetics assay was performed using recombinant human CYP3A4 cell microsomes. The analytes, dihydroartimisinin and desbutyl-lumefantrine, were detected by ultra-performance liquid chromatography tandem mass spectrometry. The results demonstrated that compared to CYP3A4.1, the intrinsic clearance of CYP3A4.4, 5, 9, 16, 18, 23, 24, 28, 31-34 significantly reduced for artemether (58.5%-93.3%), and CYP3A4.17 almost loss catalytic activity. Simultaneously, CYP3A4.5, 14, 17, 24 for lumefantrine were decreased by 56.1%-99.6%, and CYP3A4.11, 15, 18, 19, 23, 28, 29, 31-34 for lumefantrine was increased by 51.7%-296%. The variation in clearance rate indicated by molecular docking could be attributed to the disparity in the binding affinity of artemether and lumefantrine with CYP3A4. The data presented here have enriched our understanding of the effect of CYP3A4 gene polymorphism on artemether-lumefantrine metabolizing. These findings serve as a valuable reference and provide insights for guiding the treatment strategy involving artemether-lumefantrine.

Plasmodium knowlesi (Pk) Malaria: A Review & Proposal of Therapeutically Rational Exchange (T-REX) of Pk-Resistant Red Blood Cells

Plasmodium knowlesi (Pk) causes zoonotic malaria and is known as the "fifth human malaria parasite". Pk malaria is an emerging threat because infections are increasing and can be fatal. While most infections are in Southeast Asia (SEA), especially Malaysia, travelers frequently visit this region and can present with Pk malaria around the world. So, clinicians need to know (1) patients who present with fever after recent travel to SEA might be infected with Pk and (2) Pk is often misdiagnosed as P. malariae (which typically causes less severe malaria). Here we review the history, pathophysiology, clinical features, diagnosis, and treatment of Pk malaria. Severe disease is most common in adults. Signs and symptoms can include fever, abdominal pain, jaundice, acute kidney injury, acute respiratory distress syndrome, hyponatremia, hyperparasitemia, and thrombocytopenia. Dengue is one of the diseases to be considered in the differential. Regarding pathophysiologic mechanisms, when Pk parasites invade mature red blood cells (RBCs, i.e., normocytes) and reticulocytes, changes in the red blood cell (RBC) surface can result in life-threatening cytoadherence, sequestration, and reduced RBC deformability. Since molecular mechanisms involving the erythrocytic stage are responsible for onset of severe disease and lethal outcomes, it is biologically plausible that manual exchange transfusion (ET) or automated RBC exchange (RBCX) could be highly beneficial by replacing "sticky" parasitized RBCs with uninfected, deformable, healthy donor RBCs. Here we suggest use of special Pk-resistant donor RBCs to optimize adjunctive manual ET/RBCX for malaria. "Therapeutically-rational exchange transfusion" (T-REX) is proposed in which Pk-resistant RBCs are transfused (instead of disease-promoting RBCs). Because expression of the Duffy antigen on the surface of human RBCs is essential for parasite invasion, T-REX of Duffy-negative RBCs-also known as Fy(a-b-) RBCs-could replace the majority of the patient's circulating normocytes with Pk invasion-resistant RBCs (in a single procedure lasting about 2 h). When sequestered or non-sequestered iRBCs rupture-in a 24 h Pk asexual life cycle-the released merozoites cannot invade Fy(a-b-) RBCs. When Fy(a-b-) RBC units are scarce (e.g., in Malaysia), clinicians can consider the risks and benefits of transfusing plausibly Pk-resistant RBCs, such as glucose-6-phosphate dehydrogenase deficient (G6PDd) RBCs and Southeast Asian ovalocytes (SAO). Patients typically require a very short recovery time (<1 h) after the procedure. Fy(a-b-) RBCs should have a normal lifespan, while SAO and G6PDd RBCs may have mildly reduced half-lives. Because SAO and G6PDd RBCs come from screened blood donors who are healthy and not anemic, these RBCs have a low-risk for hemolysis and do not need to be removed after the patient recovers from malaria. T-REX could be especially useful if (1) antimalarial medications are not readily available, (2) patients are likely to progress to severe disease, or (3) drug-resistant strains emerge. In conclusion, T-REX is a proposed optimization of manual ET/RBCX that has not yet been utilized but can be considered by physicians to treat Pk malaria patients.

Plasmodium knowlesi Infection in Traveler Returning to Canada from the Philippines, 2023

A 55-year-old man sought treatment for an uncomplicated febrile illness after returning to Canada from the Philippines. A suspected diagnosis of Plasmodium knowlesi infection was confirmed by PCR, and treatment with atovaquone/proguanil brought successful recovery. We review the evolving epidemiology of P. knowlesi malaria in the Philippines, specifically within Palawan Island.

Relationship between Duffy Genotype/Phenotype and Prevalence of Plasmodium vivax Infection: A Systematic Review

The Duffy protein, a transmembrane molecule, functions as a receptor for various chemokines and facilitates attachment between the reticulocyte and the Plasmodium Duffy antigen-binding protein. Duffy expression correlates with the Duffy receptor gene for the chemokine, located on chromosome 1, and exhibits geographical variability worldwide. Traditionally, researchers have described the Duffy negative genotype as a protective factor against Plasmodium vivax infection. However, recent studies suggest that this microorganism's evolution could potentially diminish this protective effect. Nevertheless, there is currently insufficient global data to demonstrate this phenomenon. This study aimed to evaluate the relationship between the Duffy genotype/phenotype and the prevalence of P. vivax infection. The protocol for the systematic review was registered in PROSPERO as CRD42022353427 and involved reviewing published studies from 2012 to 2022. The Medline/PubMed, Web of Science, Scopus, and SciELO databases were consulted. Assessments of study quality were conducted using the STROBE and GRADE tools. A total of 34 studies were included, with Africa accounting for the majority of recorded studies. The results varied significantly regarding the relationship between the Duffy genotype/phenotype and P. vivax invasion. Some studies predominantly featured the negative Duffy genotype yet reported no malaria cases. Other studies identified minor percentages of infections. Conversely, certain studies observed a higher prevalence (99%) of Duffy-negative individuals infected with P. vivax. In conclusion, this systematic review found that the homozygous Duffy genotype positive for the A allele (FY*A/*A) is associated with a higher incidence of P. vivax infection. Furthermore, the negative Duffy genotype does not confer protection against vivax malaria.

Epidemiological shifts: the emergence of malaria in America

Plasmodium is a genus of parasites that comprises different species. The species falciparum, vivax, malariae, ovale, and knowlesi are known to cause a vector-borne illness called malaria, and among these, falciparum is known to cause major complications. The vector, the Anopheles mosquito, is commonly found in warmer regions close to the equator, and hence transmission and numbers of cases tend to be higher in Sub-Saharan Africa, South Asia, and Central America. The number of cases of malaria in the United States has remained stable over the years with low transmission rates, and the disease is mostly seen in the population with a recent travel history to endemic regions. The main reason behind this besides the weather conditions is that economically developed countries have eliminated mosquitos. However, there have been reports of locally reported cases with Plasmodium vivax in areas such as Florida and Texas in patients with no known travel history. This paper aims to familiarize US physicians with the pathophysiology, clinical features, and diagnostic modalities of malaria, as well as available treatment options.

Outbreak of Locally Acquired Mosquito-Transmitted (Autochthonous) Malaria - Florida and Texas, May-July 2023

Eight cases of locally acquired, mosquito-transmitted (i.e., autochthonous) Plasmodium vivax malaria, which has not been reported in the United States since 2003, were reported to CDC from state health departments in Florida and Texas during May 18-July 17, 2023. As of August 4, 2023, case surveillance, mosquito surveillance and control activities, and public outreach and education activities continue in both states. U.S. clinicians need to consider a malaria diagnosis in patients with unexplained fever, especially in areas where autochthonous malaria has been recently reported, although the risk for autochthonous malaria in the United States remains very low. Prompt diagnosis and treatment of malaria can prevent severe disease or death and limit ongoing transmission to local Anopheles mosquitoes and other persons. Preventing mosquito bites and controlling mosquitoes at home can prevent mosquitoborne diseases, including malaria. Before traveling internationally to areas with endemic malaria, travelers should consult with a health care provider regarding recommended malaria prevention measures, including potentially taking malaria prophylaxis. Malaria is a nationally notifiable disease; continued reporting of malaria cases to jurisdictional health departments and CDC will also help ensure robust surveillance to detect and prevent autochthonous malaria in the United States.

Travel Medicine

International travel can cause new illness or exacerbate existing conditions. Because primary care providers are frequent sources of health advice to travelers, they should be familiar with destination-specific disease risks, be knowledgeable about travel and routine vaccines, be prepared to prescribe chemoprophylaxis and self-treatment regimens, and be aware of travel medicine resources. Primary care providers should recognize travelers who would benefit from referral to a specialized travel clinic for evaluation. Those requiring yellow fever vaccination, immunocompromised hosts, pregnant persons, persons with multiple comorbid conditions, or travelers with complex itineraries may warrant specialty referral.

Updates on Malaria Epidemiology and Prevention Strategies

Purpose of Review

The objective of this review was to provide an update on recent malaria epidemiology, both globally and in non-endemic areas, to identify the current distribution and repercussions of genetically diverse Plasmodium species and summarize recently implemented intervention and prevention tools.

Recent Findings

Notable changes in malaria epidemiology have occurred in recent years, with an increase in the number of total cases and deaths globally during 2020-2021, in part attributed to the COVID-19 pandemic. The emergence of artemisinin-resistant species in new areas and the expanding distribution of parasites harbouring deletions of the pfhrp2/3 genes have been concerning. New strategies to curb the burden of this infection, such as vaccination, have been implemented in certain endemic areas and their performance is currently being evaluated.

Summary

Inadequate control of malaria in endemic regions may have an effect on imported malaria and measures to prevent re-establishment of transmission in malaria-free areas are essential. Enhanced surveillance and investigation of Plasmodium spp. genetic variations will contribute to the successful diagnosis and treatment of malaria in future. Novel strategies for an integrated One Health approach to malaria control should also be strengthened.

Plasmodium vivax Presenting With Septic Shock and Disseminated Intravascular Coagulation (DIC): A Case Report

Malaria has various causative agents that can have a spectrum of disease manifestations, some potentially fatal. Various species have been established as etiologies of malaria, though our understanding of the severity of various species is changing. We present a unique case of Plasmodium vivax malaria that resulted in severe disease, a magnitude rarely seen in previous literature. Our patient was a 35-year-old healthy woman who presented to the emergency department with abdominal pain, nausea, vomiting, and fever. Further workup revealed severe thrombocytopenia with prolonged prothrombin (PT) and partial thromboplastin time (PTT). An initial thick smear failed to detect any Plasmodium species, but a thin smear revealed P. vivax. The patient's hospital stay was complicated by septic shock requiring intensive care unit (ICU) admission. This unique case represents P. vivax as the causative agent of severe malaria even in healthy, immunocompetent patients.

Evaluation of an Innovative Point-of-Care Rapid Diagnostic Test for the Identification of Imported Malaria Parasites in China

BACKGROUND

China was certified malaria-free by the World Health Organization on 30 June 2021. However, due to imported malaria, maintaining a malaria-free status in China is an ongoing challenge. There are critical gaps in the detection of imported malaria through the currently available tools, especially for non-falciparum malaria. In the study, a novel point-of-care Rapid Diagnostic Test designed for the detection of imported malaria infections was evaluated in the field.

METHODS

Suspected imported malaria cases reported from Guangxi and Anhui Provinces of China during 2018-2019 were enrolled to evaluate the novel RDTs. Diagnostic performance of the novel RDTs was evaluated based on its sensitivity, specificity, positive and negative predictive values, and Cohen's kappa coefficient, using polymerase chain reaction as the gold standard. The Additive and absolute Net Reclassification Index were calculated to compare the diagnostic performance between the novel RDTs and Wondfo RDTs (control group).

RESULTS

A total of 602 samples were tested using the novel RDTs. Compared to the results of PCR, the novel RDTs presented sensitivity, specificity, PPV, NPV, and diagnostic accuracy rates of 78.37%, 95.05%, 94.70%, 79.59%, and 86.21%, respectively. Among the positive samples, the novel RDTs found 87.01%, 71.31%, 81.82%, and 61.54% of P. falciparum, P. ovale, P. vivax, and P. malariae, respectively. The ability to detect non-falciparum malaria did not differ significantly between the novel and Wondfo RDTs (control group). However, Wondfo RDTs can detect more P. falciparum cases than the novel RDTs (96.10% vs. 87.01%, p < 0.001). After the introduction of the novel RDTs, the value of the additive and absolute Net Reclassification Index is 1.83% and 1.33%, respectively.

CONCLUSIONS

The novel RDTs demonstrated the ability to distinguish P. ovale and P. malariae from P. vivax which may help to improve the malaria post-elimination surveillance tools in China.

Costs of malaria treatment in the United States

We estimated inpatient and outpatient payments for malaria treatment in the USA. The mean cost per hospitalized patient was significantly higher than for non-hospitalized patients (e.g. $27 642 vs $1177 among patients with private insurance). Patients with severe malaria payed two to four times more than those hospitalized with uncomplicated malaria.

Recent Advances in Imported Malaria Pathogenesis, Diagnosis, and Management

Purpose of Review

Malaria is an important human parasitic disease affecting the population of tropical, subtropical regions as well as travelers to these areas.The purpose of this article is to provide clinicians practicing in non-endemic areas with a comprehensive overview of the recent data on microbiologic and pathophysiologic features of five Plasmodium parasites, clinical presentation of uncomplicated and severe cases, modern diagnostic methods, and treatment of malaria.

Recent Findings

Employment of robust surveillance programs, rapid diagnostic tests, highly active artemisinin-based therapy, and the first malaria vaccine have led to decline in malaria incidence; however, emerging drug resistance, disruptions due to the COVID-19 pandemic, and other socio-economic factors have stalled the progress.

Summary

Clinicians practicing in non-endemic areas such as the United States should consider a diagnosis of malaria in returning travelers presenting with fever, utilize rapid diagnostic tests if available at their practice locations in addition to microscopy, and timely initiate guideline-directed management as delays in treatment can lead to poor clinical outcomes.