Health problems and exposure to infectious risks in returning humanitarian aid workers.

BACKGROUND: Humanitarian aid workers are exposed to deployment-related health threats. Identifying subgroups at a higher risk of infection in this diverse population could help optimize prevention. METHODS: We carried out a retrospective study based on anonymized data of humanitarian aid workers that visited our clinic for a post-deployment visit between 1 January 2018 and 31 December 2021. We conducted a descriptive analysis of basic demographic data, self-reported risk exposure and health problems encountered during deployment extracted from a standard questionnaire. RESULTS: The questionnaire was administered to 1238 aid workers during 1529 post-deployment medical consultations. The median age was 37.2 years (IQR 31.7-44.3), and 718/1529 (47.0%) were female aid workers. The median duration of deployment was 6 months (IQR 3-12 months). Most deployments (1321/1529 (86.4%)) were for a medical organization and in Sub-Saharan Africa (73.2%). The most common risk exposures were contact with freshwater in schistosomiasis endemic regions (187/1308 (14.3%)), unprotected sexual contact with a person other than a regular partner (138/1529 (9.0%)), suspected rabies exposure (56/1529 (3.7%)) and accidental exposure to blood (44/1529 (2.9%)). Gastrointestinal problems (487/1529 (31.9%)), malaria (237/1529 (15.5%)) and respiratory tract infections (94/1529 (6,2%)) were the most encountered health problems. Fifteen volunteers (1%) were hospitalized during deployment and 19 (1.2%) repatriated due to health problems. Adherence to malaria chemoprophylaxis was poor, only taken according to the prescription in 355 out of 1225 (29.0%) of aid workers for whom prophylaxis was indicated. CONCLUSION: Humanitarian aid workers deployed abroad encounter significant rates of health problems and report a high level of risk exposure during their deployment, with the risks being greatest among younger people, those deployed to rural areas, and those working for non-medical organizations. These findings help guide future pre-deployment consultations, to increase awareness and reduce risk behaviour during deployment, as well as focus on adherence to medical advice such as malaria chemoprophylaxis.

Expanding the role of village malaria workers in Cambodia: Implementation and evaluation of four health education packages.

BACKGROUND: Early access to correct diagnosis and appropriate treatment is essential for malaria elimination, and in Cambodia this relies on village malaria workers (VMWs). Decreasing malaria transmission leave VMWs with diminished roles. Activities related to the control of other health conditions could keep these community health workers relevant. METHODS: During 2022, 120 VMWs attended training at local health centres on four health education packages: 1. hygiene and sanitation; 2. disease surveillance; 3. management of mild illness; 4. vaccination and antenatal care. All training and evaluation sessions were documented through meeting minutes, and 19 focus group discussions (FGDs) were conducted among VMWs and health centre personnel. Audio-records of FGDs were transcribed and translated in English and underwent thematic analysis. RESULTS: VMWs reported strong interest in the training and welcomed the expansion of their roles thus assuring their continued relevance. VMWs prioritized disease surveillance and management of mild illness among the available training packages because these topics were seen as most relevant. While training was considered comprehensible and important, the low literacy among VMWs was an impediment suggesting training materials need to be delivered visually. Since VMWs have limited resources, incentives could ensure that VMWs are motivated to undertake additional roles and responsibilities. CONCLUSIONS: The transformation of VMWs into community health workers with roles beyond malaria is a promising approach for sustaining health care provision in remote areas. Training needs to consider the low scientific literacy, time constraints and limited resources of VMWs.

Practices and challenges related to antibiotic use in paediatric treatment in hospitals and health centres in Niger and Uganda: a mixed methods study.

BACKGROUND: Antibiotic resistance is a significant public health problem and is responsible for high mortality in children and new-borns. Strengthening the rational use of antibiotics and improving the quality and access to existing antibiotics are important factors in the fight against antibiotic resistance. This study aims to provide knowledge on the use of antibiotics in children in resource-limited countries in order to identify problems and possible avenues for improvement of antibiotics use. METHODS: We conducted a retrospective study in July 2020 and collected quantitative clinical and therapeutic data on antibiotic prescriptions between January and December 2019 in 4 hospitals or health centres in both Uganda and Niger, respectively from January to December 2019. Semi-structured interviews and focus groups were conducted among healthcare personnel and carers for children under 17 years of age, respectively. RESULTS: A total of 1,622 children in Uganda and 660 children in Niger (mean age of 3.9 years (SD 4.43)) who received at least one antibiotic were included in the study. In hospital settings, 98.4 to 100% of children prescribed at least one antibiotic received at least one injectable antibiotic. Most hospitalized children received more than one antibiotic in both Uganda (52.1%) and Niger (71.1%). According to the WHO-AWaRe index, the proportion of prescriptions of antibiotics belonging to the Watch category was 21.8% (432/1982) in Uganda and 32.0% (371/1158) in Niger. No antibiotics from the Reserve category were prescribed. Health care provider's prescribing practices are rarely guided by microbiological analyses. Prescribers are faced with numerous constraints, such as lack of standard national guidelines, unavailability of essential antibiotics at the level of hospital pharmacies, the limited financial means of the families, and pressure to prescribe antibiotics from caregivers as well as from drug company representatives. The quality of some antibiotics provided by the National Medical Stores to the public and private hospitals has been questioned by some health professionals. Self-medication is a widespread practice for the antibiotic treatment of children for economic and access reasons. CONCLUSION: The study findings indicate that an intersection of policy, institutional norms and practices including individual caregiver or health provider factors, influence antibiotic prescription, administration and dispensing practices.

Short tandem repeat polymorphism in the promoter region of cyclophilin 19B drives its transcriptional upregulation and contributes to drug resistance in the malaria parasite Plasmodium falciparum.

Resistance of the human malaria parasites, Plasmodium falciparum, to artemisinins is now fully established in Southeast Asia and is gradually emerging in Sub-Saharan Africa. Although nonsynonymous SNPs in the pfk13 Kelch-repeat propeller (KREP) domain are clearly associated with artemisinin resistance, their functional relevance requires cooperation with other genetic factors/alterations of the P. falciparum genome, collectively referred to as genetic background. Here we provide experimental evidence that P. falciparum cyclophilin 19B (PfCYP19B) may represent one putative factor in this genetic background, contributing to artemisinin resistance via its increased expression. We show that overexpression of PfCYP19B in vitro drives limited but significant resistance to not only artemisinin but also piperaquine, an important partner drug in artemisinin-based combination therapies. We showed that PfCYP19B acts as a negative regulator of the integrated stress response (ISR) pathway by modulating levels of phosphorylated eIF2α (eIF2α-P). Curiously, artemisinin and piperaquine affect eIF2α-P in an inverse direction that in both cases can be modulated by PfCYP19B towards resistance. Here we also provide evidence that the upregulation of PfCYP19B in the drug-resistant parasites appears to be maintained by a short tandem repeat (SRT) sequence polymorphism in the gene's promoter region. These results support a model that artemisinin (and other drugs) resistance mechanisms are complex genetic traits being contributed to by altered expression of multiple genes driven by genetic polymorphism at their promoter regions.

Ten-year persistence and evolution of Plasmodium falciparum antifolate and anti-sulfonamide resistance markers pfdhfr and pfdhps in three Asian countries.

BACKGROUND: The amplification of GTP cyclohydrolase 1 (pfgch1) in Plasmodium falciparum has been linked to the upregulation of the pfdhfr and pfdhps genes associated with resistance to the antimalarial drug sulfadoxine-pyrimethamine. During the 1990s and 2000s, sulfadoxine-pyrimethamine was withdrawn from use as first-line treatment in southeast Asia due to clinical drug resistance. This study assessed the temporal and geographic changes in the prevalence of pfdhfr and pfdhps gene mutations and pfgch1 amplification a decade after sulfadoxine-pyrimethamine had no longer been widely used. METHODS: A total of 536 P. falciparum isolates collected from clinical trials in Thailand, Cambodia, and Lao PDR between 2008 and 2018 were assayed. Single nucleotide polymorphisms of the pfdhfr and pfdhps genes were analyzed using nested PCR and Sanger sequencing. Gene copy number variations of pfgch1 were investigated using real-time polymerase chain reaction assay. RESULTS: Sequences of the pfdhfr and pfdhps genes were obtained from 96% (517/536) and 91% (486/536) of the samples, respectively. There were 59 distinct haplotypes, including single to octuple mutations. The two major haplotypes observed included IRNI-AGEAA (25%) and IRNL-SGKGA (19%). The sextuple mutation IRNL-SGKGA increased markedly over time in several study sites, including Pailin, Preah Vihear, Ratanakiri, and Ubon Ratchathani, whereas IRNI-AGEAA decreased over time in Preah Vihear, Champasak, and Ubon Ratchathani. Octuple mutations were first observed in west Cambodia in 2011 and subsequently in northeast Cambodia, as well as in southern Laos by 2018. Amplification of the pfgch1 gene increased over time across the region, particularly in northeast Thailand close to the border with Laos and Cambodia. CONCLUSION: Despite the fact that SP therapy was discontinued in Thailand, Cambodia, and Laos decades ago, parasites retained the pfdhfr and pfdhps mutations. Numerous haplotypes were found to be prevalent among the parasites. Frequent monitoring of pfdhfr and pfdhps in these areas is required due to the relatively rapid evolution of mutation patterns.

Comment on Weitzman et al. Resistance to Antimalarial Monotherapy Is Cyclic. J. Clin. Med. 2022, 11, 781.

Weitzman et al. used PubMed text mining to determine the trends of antimalarial resistance over the last 40 years [...]

Disc-like lesions in the intestinal tract after renal transplantation.

We report a case of intestinal lesions in a patient with a history of lupus nephritis and renal transplantation. Biopsy revealed an EBV-driven post-transplant lymphoproliferative disease (PTLD). An EBV-driven PTLD is a major complication after renal transplantation and is an important differential diagnostic consideration in the follow-up of renal transplant recipients.

Triple therapy with artemether-lumefantrine plus amodiaquine versus artemether-lumefantrine alone for artemisinin-resistant, uncomplicated falciparum malaria: an open-label, randomised, multicentre trial.

BACKGROUND: Late treatment failures after artemisinin-based combination therapies (ACTs) for falciparum malaria have increased in the Greater Mekong subregion in southeast Asia. Addition of amodiaquine to artemether-lumefantrine could provide an efficacious treatment for multidrug-resistant infections. METHODS: We conducted an open-label, randomised trial at five hospitals or health centres in three locations (western Cambodia, eastern Cambodia, and Vietnam). Eligible participants were male and female patients aged 2-65 years with uncomplicated Plasmodium falciparum malaria. Patients were randomly allocated (1:1 in blocks of eight to 12) to either artemether-lumefantrine alone (dosed according to WHO guidelines) or artemether-lumefantrine plus amodiaquine (10 mg base per kg/day), both given orally as six doses over 3 days. All received a single dose of primaquine (0·25 mg/kg) 24 h after the start of study treatment to limit transmission of the parasite. Parasites were genotyped, identifying artemisinin resistance. The primary outcome was Kaplan-Meier 42-day PCR-corrected efficacy against recrudescence of the original parasite, assessed by intent-to-treat. Safety was a secondary outcome. This completed trial is registered at ClinicalTrials.gov (NCT03355664). FINDINGS: Between March 18, 2018, and Jan 30, 2020, 310 patients received randomly allocated treatment; 154 received artemether-lumefantrine alone and 156 received artemether-lumefantrine plus amodiaquine. Parasites from 305 of these patients were genotyped. 42-day PCR-corrected treatment efficacy was noted in 151 (97%, 95% CI 92-99) of 156 patients with artemether-lumefantrine plus amodiaquine versus 146 (95%, 89-97) of 154 patients with artemether-lumefantrine alone; hazard ratio (HR) for recrudescence 0·6 (95% CI 0·2-1·9, p=0·38). Of the 13 recrudescences, 12 were in 174 (57%) of 305 infections with pfkelch13 mutations indicating artemisinin resistance, for which 42-day efficacy was noted in 89 (96%) of 93 infections with artemether-lumefantrine plus amodiaquine versus 73 (90%) of 81 infections with artemether-lumefantrine alone; HR for recrudescence 0·44 (95% CI 0·14-1·40, p=0·17). Artemether-lumefantrine plus amodiaquine was generally well tolerated, but the number of mild (grade 1-2) adverse events, mainly gastrointestinal, was greater in this group compared with artemether-lumefantrine alone (vomiting, 12 [8%] with artemether-lumefantrine plus amodiaquine vs three [2%] with artemether-lumefantrine alone, p=0·03; and nausea, 11 [7%] with artemether-lumefantrine plus amodiaquine vs three [2%] with artemether-lumefantrine alone, p=0·05). Early vomiting within 1 h of treatment, requiring retreatment, occurred in no patients of 154 with artemether-lumefantrine alone versus five (3%) of 156 with artemether-lumefantrine plus amodiaquine, p=0·06. Bradycardia (≤54 beats/min) of any grade was noted in 59 (38%) of 154 patients with artemether-lumefantrine alone and 95 (61%) of 156 with artemether-lumefantrine plus amodiaquine, p=0·0001. INTERPRETATION: Artemether-lumefantrine plus amodiaquine provides an alternative to artemether-lumefantrine alone as first-line treatment for multidrug-resistant P falciparum malaria in the Greater Mekong subregion, and could prolong the therapeutic lifetime of artemether-lumefantrine in malaria-endemic populations. FUNDING: Bill & Melinda Gates Foundation, Wellcome Trust.

Immune reconstitution inflammatory syndrome induced by gluteal silicones in a transgender woman living with HIV.

We report a case of an immune reconstitution inflammatory syndrome induced by gluteal silicones in a transgender woman living with HIV following the start of antiretroviral therapy. This case resembles the autoimmune/inflammatory syndrome induced by adjuvants (ASIA) syndrome that has been described as a complication of insertions of materials such as injected or implanted silicones. The potential of developing an inflammatory response in patient with injected or implanted silicones/foreign substances should be considered in patients who have recently started antiretroviral therapy.

Artemisinin resistance in the malaria parasite, Plasmodium falciparum, originates from its initial transcriptional response.

The emergence and spread of artemisinin-resistant Plasmodium falciparum, first in the Greater Mekong Subregion (GMS), and now in East Africa, is a major threat to global malaria elimination ambitions. To investigate the artemisinin resistance mechanism, transcriptome analysis was conducted of 577 P. falciparum isolates collected in the GMS between 2016-2018. A specific artemisinin resistance-associated transcriptional profile was identified that involves a broad but discrete set of biological functions related to proteotoxic stress, host cytoplasm remodelling, and REDOX metabolism. The artemisinin resistance-associated transcriptional profile evolved from initial transcriptional responses of susceptible parasites to artemisinin. The genetic basis for this adapted response is likely to be complex.

Are national treatment guidelines for falciparum malaria in line with WHO recommendations and is antimalarial resistance taken into consideration? - A review of guidelines in non-endemic countries.

OBJECTIVE: Plasmodium falciparum infections are a relatively rare but potentially deadly disease found in returning travellers. We compare the national treatment guidelines of non-endemic countries with the WHO guidelines for the treatment of Plasmodium falciparum infections. METHODS: Review. We identified non-endemic countries with an incidence rate of imported malaria of at least one per 100,000 population and at least 50 cases annually. Using PubMed and Google Search, we reviewed national guidelines published before 1 March 2021. RESULTS: Thirteen guidelines were identified. For uncomplicated falciparum malaria, 11 of 13 countries (85%) recommend an artemisinin-based combination therapy as first-line regimen in adults, of which artemether-lumefantrine was the most common. For severe malaria, all guidelines recommend the use of intravenous artesunate. Only three countries adjust treatment recommendations based on expected artemisinin resistance. CONCLUSION: Treatment guidelines for uncomplicated falciparum malaria in non-endemic countries generally adhere to WHO recommendations but often fail to mention the risk of drug resistance in returning travellers. Artemisinin-based Combination Therapies (ACTs) should be the first choice for all uncomplicated malaria cases. Furthermore, the choice between ACTs should be based on regional resistance patterns.

Evolution of Multidrug Resistance in Plasmodium falciparum: a Longitudinal Study of Genetic Resistance Markers in the Greater Mekong Subregion.

Increasing resistance in Plasmodium falciparum to artemisinins and their artemisinin combination therapy (ACT) partner drugs jeopardizes effective antimalarial treatment. Resistance is worst in the Greater Mekong subregion. Monitoring genetic markers of resistance can help to guide antimalarial therapy. Markers of resistance to artemisinins (PfKelch mutations), mefloquine (amplification of P. falciparum multidrug resistance-1 [PfMDR1]), and piperaquine (PfPlasmepsin2/3 amplification and specific P. falciparum chloroquine resistance transporter [PfCRT] mutations) were assessed in 6,722 P. falciparum samples from Vietnam, Lao People's Democratic Republic (PDR), Cambodia, Thailand, and Myanmar between 2007 and 2019. Against a high background prevalence of PfKelch mutations, PfMDR1 and PfPlasmepsin2/3 amplification closely followed regional drug pressures over time. PfPlasmepsin2/3 amplification preceded piperaquine resistance-associated PfCRT mutations in Cambodia and reached a peak prevalence of 23/28 (82%) in 2015. This declined to 57/156 (38%) after first-line treatment was changed from dihydroartemisinin-piperaquine to artesunate-mefloquine (ASMQ) between 2014 and 2017. The frequency of PfMDR1 amplification increased from 0/293 (0%) between 2012 and 2017 to 12/156 (8%) in 2019. Amplification of PfMDR1 and PfPlasmepsin2/3 in the same parasites was extremely rare (4/6,722 [0.06%]) and was dispersed over time. The mechanisms conferring mefloquine and piperaquine resistance may be counterbalancing. This supports the development of ASMQ plus piperaquine as a triple artemisinin combination therapy.

Arterolane-piperaquine-mefloquine versus arterolane-piperaquine and artemether-lumefantrine in the treatment of uncomplicated Plasmodium falciparum malaria in Kenyan children: a single-centre, open-label, randomised, non-inferiority trial.

BACKGROUND: Triple antimalarial combination therapies combine potent and rapidly cleared artemisinins or related synthetic ozonides, such as arterolane, with two, more slowly eliminated partner drugs to reduce the risk of resistance. We aimed to assess the safety, tolerability, and efficacy of arterolane-piperaquine-mefloquine versus arterolane-piperaquine and artemether-lumefantrine for the treatment of uncomplicated falciparum malaria in Kenyan children. METHODS: In this single-centre, open-label, randomised, non-inferiority trial done in Kilifi County Hospital, Kilifi, coastal Kenya, children with uncomplicated Plasmodium falciparum malaria were recruited. Eligible patients were aged 2-12 years and had an asexual parasitaemia of 5000-250 000 parasites per µL. The exclusion criteria included the presence of an acute illness other than malaria, the inability to tolerate oral medications, treatment with an artemisinin derivative in the previous 7 days, a known hypersensitivity or contraindication to any of the study drugs, and a QT interval corrected for heart rate (QTc interval) longer than 450 ms. Patients were randomly assigned (1:1:1), by use of blocks of six, nine, and 12, and opaque, sealed, and sequentially numbered envelopes, to receive either arterolane-piperaquine, arterolane-piperaquine-mefloquine, or artemether-lumefantrine. Laboratory staff, but not the patients, the patients' parents or caregivers, clinical or medical officers, nurses, or trial statistician, were masked to the intervention groups. For 3 days, oral artemether-lumefantrine was administered twice daily (target dose 5-24 mg/kg of bodyweight of artemether and 29-144 mg/kg of bodyweight of lumefantrine), and oral arterolane-piperaquine (arterolane dose 4 mg/kg of bodyweight; piperaquine dose 20 mg/kg of bodyweight) and oral arterolane-piperaquine-mefloquine (mefloquine dose 8 mg/kg of bodyweight) were administered once daily. All patients received 0·25 mg/kg of bodyweight of oral primaquine at hour 24. All patients were admitted to Kilifi County Hospital for at least 3 consecutive days and followed up at day 7 and, thereafter, weekly for up to 42 days. The primary endpoint was 42-day PCR-corrected efficacy, defined as the absence of treatment failure in the first 42 days post-treatment, of arterolane-piperaquine-mefloquine versus artemether-lumefantrine, and, along with safety, was analysed in the intention-to-treat population, which comprised all patients who received at least one dose of a study drug. The 42-day PCR-corrected efficacy of arterolane-piperaquine-mefloquine versus arterolane-piperaquine was an important secondary endpoint and was also analysed in the intention-to-treat population. The non-inferiority margin for the risk difference between treatments was -7%. The study is registered in ClinicalTrials.gov, NCT03452475, and is completed. FINDINGS: Between March 7, 2018, and May 2, 2019, 533 children with P falciparum were screened, of whom 217 were randomly assigned to receive either arterolane-piperaquine (n=73), arterolane-piperaquine-mefloquine (n=72), or artemether-lumefantrine (n=72) and comprised the intention-to-treat population. The 42-day PCR-corrected efficacy after treatment with arterolane-piperaquine-mefloquine (100%, 95% CI 95-100; 72/72) was non-inferior to that after treatment with artemether-lumefantrine (96%, 95% CI 88-99; 69/72; risk difference 4%, 95% CI 0-9; p=0·25). The 42-day PCR-corrected efficacy of arterolane-piperaquine-mefloquine was non-inferior to that of arterolane-piperaquine (100%, 95% CI 95-100; 73/73; risk difference 0%). Vomiting rates in the first hour post-drug administration were significantly higher in patients treated with arterolane-piperaquine (5%, 95% CI 2-9; ten of 203 drug administrations; p=0·0013) or arterolane-piperaquine-mefloquine (5%, 3-9; 11 of 209 drug administrations; p=0·0006) than in patients treated with artemether-lumefantrine (1%, 0-2; three of 415 drug administrations). Upper respiratory tract complaints (n=26 for artemether-lumefantrine; n=19 for arterolane-piperaquine-mefloquine; n=23 for arterolane-piperaquine), headache (n=13; n=4; n=5), and abdominal pain (n=7; n=5; n=5) were the most frequently reported adverse events. There were no deaths. INTERPRETATION: This study shows that arterolane-piperaquine-mefloquine is an efficacious and safe treatment for uncomplicated falciparum malaria in children and could potentially be used to prevent or delay the emergence of antimalarial resistance. FUNDING: UK Department for International Development, The Wellcome Trust, The Bill & Melinda Gates Foundation, Sun Pharmaceutical Industries.

Deploying triple artemisinin-based combination therapy (TACT) for malaria treatment in Africa: ethical and practical considerations.

Malaria remains a major cause of morbidity and mortality in Africa, particularly in children under five years of age. Availability of effective anti-malarial drug treatment is a cornerstone for malaria control and eventual malaria elimination. Artemisinin-based combination therapy (ACT) is worldwide the first-line treatment for uncomplicated falciparum malaria, but the ACT drugs are starting to fail in Southeast Asia because of drug resistance. Resistance to artemisinins and their partner drugs could spread from Southeast Asia to Africa or emerge locally, jeopardizing the progress made in malaria control with the increasing deployment of ACT in Africa. The development of triple artemisinin-based combination therapy (TACT) could contribute to mitigating the risks of artemisinin and partner drug resistance on the African continent. However, there are pertinent ethical and practical issues that ought to be taken into consideration. In this paper, the most important ethical tensions, some implementation practicalities and preliminary thoughts on addressing them are discussed. The discussion draws upon data from randomized clinical studies using TACT combined with ethical principles, published literature and lessons learned from the introduction of artemisinin-based combinations in African markets.

Triple Artemisinin-Based Combination Therapies for Malaria - A New Paradigm?

Recent gains in the fight against malaria are threatened by the emergence and spread of artemisinin and partner drug resistance in Plasmodium falciparum in the Greater Mekong Subregion (GMS). When artemisinins are combined with a single partner drug, all recommended artemisinin-based combination therapies have shown reduced efficacy in some countries in the GMS at some point. Novel drugs are not available for the near future. Triple artemisinin-based combination therapies, combining artemisinins with two currently available partner drugs, will provide one of the last remaining safe and effective treatments for falciparum malaria that can be deployed rapidly in the GMS, whereas their deployment beyond the GMS could delay or prevent the global emergence and spread of resistance to currently available drugs.

Modulation of Triple Artemisinin-Based Combination Therapy Pharmacodynamics by Plasmodium falciparum Genotype.

The first-line treatments for uncomplicated Plasmodium falciparum malaria are artemisinin-based combination therapies (ACTs), consisting of an artemisinin derivative combined with a longer acting partner drug. However, the spread of P. falciparum with decreased susceptibility to artemisinin and partner drugs presents a significant challenge to malaria control efforts. To stem the spread of drug resistant parasites, novel chemotherapeutic strategies are being evaluated, including the implementation of triple artemisinin-based combination therapies (TACTs). Currently, there is limited knowledge on the pharmacodynamic and pharmacogenetic interactions of proposed TACT drug combinations. To evaluate these interactions, we established an in vitro high-throughput process for measuring the drug concentration-response to three distinct antimalarial drugs present in a TACT. Sixteen different TACT combinations were screened against 15 parasite lines from Cambodia, with a focus on parasites with differential susceptibilities to piperaquine and artemisinins. Analysis revealed drug-drug interactions unique to specific genetic backgrounds, including antagonism between piperaquine and pyronaridine associated with gene amplification of plasmepsin II/III, two aspartic proteases that localize to the parasite digestive vacuole. From this initial study, we identified parasite genotypes with decreased susceptibility to specific TACTs, as well as potential TACTs that display antagonism in a genotype-dependent manner. Our assay and analysis platform can be further leveraged to inform drug implementation decisions and evaluate next-generation TACTs.