Gametocyte Carriage, Antimalarial Use, and Drug Resistance in Cambodia, 2008-2014

Gametocytes are the malaria parasite stages responsible for transmission from humans to mosquitoes. Gametocytemia often follows drug treatment, especially as therapies start to fail. We examined Plasmodium falciparum gametocyte carriage and drug resistance profiles among 824 persons with uncomplicated malaria in Cambodia to determine whether prevalent drug resistance and antimalarial use has led to a concentration of drug-resistant parasites among gametocyte carriers. Although report of prior antimalarial use increased from 2008 to 2014, the prevalence of study participants presenting with microscopic gametocyte carriage declined. Gametocytemia was more common in those reporting antimalarial use within the past year, and prior antimalarial use was correlated with higher IC50s to piperaquine and mefloquine, as well as to increased pfmdr1 copy number. However, there was no association between microscopic gametocyte carriage and parasite drug resistance. Thus, we found no evidence that the infectious reservoir, marked by those carrying gametocytes, is enriched with drug-resistant parasites

Evaluation of the CareStart™ glucose-6-phosphate dehydrogenase (G6PD) rapid diagnostic test in the field settings and assessment of perceived risk from primaquine at the community level in Cambodia.

BACKGROUND:Primaquine is an approved radical cure treatment for Plasmodium vivax malaria but treatment can result in life-threatening hemolysis if given to a glucose-6-phosphate dehydrogenase deficient (G6PDd) patient. There is a need for reliable point-of-care G6PD diagnostic tests. OBJECTIVES:To evaluate the performance of the CareStart™ rapid diagnostic test (RDT) in the hands of healthcare workers (HCWs) and village malaria workers (VMWs) in field settings, and to better understand user perceptions about the risks and benefits of PQ treatment guided by RDT results. METHODS:This study enrolled 105 HCWs and VMWs, herein referred to as trainees, who tested 1,543 healthy adult male volunteers from 84 villages in Cambodia. The trainees were instructed on G6PD screening, primaquine case management, and completed pre and post-training questionnaires. Each trainee tested up to 16 volunteers in the field under observation by the study staff. RESULTS:Out of 1,542 evaluable G6PD volunteers, 251 (16.28%) had quantitative enzymatic activity less than 30% of an adjusted male median (8.30 U/g Hb). There was no significant difference in test sensitivity in detecting G6PDd between trainees (97.21%), expert study staff in the field (98.01%), and in a laboratory setting (95.62%) (p = 0.229); however, test specificity was different for trainees (96.62%), expert study staff in the field (98.14%), and experts in the laboratory (98.99%) (p < 0.001). Negative predictive values were not statistically different for trainees, expert staff, and laboratory testing: 99.44%, 99.61%, and 99.15%, respectively. Knowledge scores increased significantly post-training, with 98.7% willing to prescribe primaquine for P.vivax malaria, an improvement from 40.6% pre-training (p < 0.001). CONCLUSION:This study demonstrated ability of medical staff with different background to accurately use CareStart™ RDT to identify G6PDd in male patients, which may enable safer prescribing of primaquine; however, pharmacovigilance is required to address possible G6PDd misclassifications

Efficacy of Two versus Three-Day Regimens of Dihydroartemisinin-Piperaquine for Uncomplicated Malaria in Military Personnel in Northern Cambodia: An Open-Label Randomized Trial

<div><p>Introduction</p><p>Emerging antimalarial drug resistance in mobile populations remains a significant public health concern. We compared two regimens of dihydroartemisinin-piperaquine in military and civilians on the Thai-Cambodian border to evaluate national treatment policy.</p><p>Methods</p><p>Efficacy and safety of two and three-day regimens of dihydroartemisinin-piperaquine were compared as a nested open-label evaluation within a malaria cohort study in 222 otherwise healthy volunteers (18% malaria-infected at baseline). The first 80 volunteers with slide-confirmed <i>Plasmodium falciparum</i> or <i>vivax</i> malaria were randomized 1:1 to receive either regimen (total dose 360mg dihydroartemisinin and 2880mg piperaquine) and followed weekly for up to 6 months. The primary endpoint was malaria recurrence by day 42. Volunteers with <i>vivax</i> infection received primaquine at study discharge with six months follow-up.</p><p>Results</p><p>Eighty patients (60 <i>vivax</i>, 15 <i>falciparum</i>, and 5 mixed) were randomized to dihydroartemisinin-piperaquine. Intention-to-treat all-species efficacy at Day 42 was 85% for the two-day regimen (95% CI 69–94) and 90% for the three-day regimen (95% CI 75–97). PCR-adjusted <i>falciparum</i> efficacy was 75% in both groups with nearly half (45%) still parasitemic at Day 3. Plasma piperaquine levels were comparable to prior published reports, but on the day of recrudescence were below measurable <i>in vitro</i> piperaquine IC₅₀ levels in all <i>falciparum</i> treatment failures.</p><p>Conclusions</p><p>In the brief period since introduction of dihydroartemisinin-piperaquine, there is early evidence suggesting declining efficacy relative to previous reports. Parasite IC₅₀ levels in excess of plasma piperaquine levels seen only in treatment failures raises concern for clinically significant piperaquine resistance in Cambodia. These findings warrant improved monitoring of clinical outcomes and follow-up, given few available alternative drugs.</p><p>Trial Registration</p><p>ClinicalTrials.gov <a href="http://clinicaltrials.gov/ct2/show/NCT01280162" target="_blank">NCT01280162</a></p></div

Human Sentinel Surveillance of Influenza and Other Respiratory Viral Pathogens in Border Areas of Western Cambodia

<div><p>Little is known about circulation of influenza and other respiratory viruses in remote populations along the Thai-Cambodia border in western Cambodia. We screened 586 outpatients (median age 5, range 1–77) presenting with influenza-like-illness (ILI) at 4 sentinel sites in western Cambodia between May 2010 and December 2012. Real-time reverse transcriptase (rRT) PCR for influenza was performed on combined nasal and throat specimens followed by viral culture, antigenic analysis, antiviral susceptibility testing and full genome sequencing for phylogenetic analysis. ILI-specimens negative for influenza were cultured, followed by rRT-PCR for enterovirus and rhinovirus (EV/RV) and EV71. Influenza was found in 168 cases (29%) and occurred almost exclusively in the rainy season from June to November. Isolated influenza strains had close antigenic and phylogenetic relationships, matching vaccine and circulating strains found elsewhere in Cambodia. Influenza vaccination coverage was low (<20%). Western Cambodian H1N1(2009) isolate genomes were more closely related to 10 earlier Cambodia isolates (94.4% genome conservation) than to 13 Thai isolates (75.9% genome conservation), despite sharing the majority of the amino acid changes with the Thai references. Most genes showed signatures of purifying selection. Viral culture detected only adenovirus (5.7%) and parainfluenza virus (3.8%), while non-polio enteroviruses (10.3%) were detected among 164 culture-negative samples including coxsackievirus A4, A6, A8, A9, A12, B3, B4 and echovirus E6 and E9 using nested RT-PCR methods. A single specimen of EV71 was found. Despite proximity to Thailand, influenza epidemiology of these western Cambodian isolates followed patterns observed elsewhere in Cambodia, continuing to support current vaccine and treatment recommendations from the Cambodian National Influenza Center. Amino acid mutations at non-epitope sites, particularly hemagglutinin genes, require further investigation in light of an increasingly important role of permissive mutations in influenza virus evolution. Further research about the burden of adenovirus and non-polio enteroviruses as etiologic agents in acute respiratory infections in Cambodia is also needed.</p></div

Pharmacokinetic parameters calculated from a 2-compartment model comparing two versus three-day courses of DHA-piperaquine.

<p>*Mann-Whitney U test comparing 2 and 3 day treatment groups. **PK analysis could not be performed in 10 and 7 subjects from Group 1 and 2, respectively due to insufficient time points. PK Parameters are expressed as medians and <i>(25–75% percentiles)</i>, with significantly different values in <b>bold</b>.</p

Mean trough QTcF intervals for patients treated daily with DHA-piperaquine (360/2880 mg cumulative) divided over 2 or 3 days (n = 40 in each group).

<p>Error bars indicate +1 standard deviation.</p

Study Schematic Inset and Trial Profile.

<p>*Randomization goal met, 2 withdrew. **Prolonged QTc. ^¥PCR-corrected speciation. ^aNot included are 2^nd recurrences (1 Pf, 1 Pv, 1 mixed). ^bNot included are 2nd recurrences (2 Pf, 5 Pv) and a 3^rd recurrence (1 Pv). ^#Study discharge varied, median 115 days follow-up.</p