Publications

A latex agglutination test for the detection of Pseudomonas pseudomallei antigen in urine was evaluated for the rapid diagnosis of melioidosis. With unconcentrated urine, antigen was detected in only 18% of patients with melioidosis overall. However, when urine was concentrated 100-fold, antigen was detected in 47% overall and in 67% of patients with septicaemia or disseminated infection, in whom a rapid diagnosis is most important. The specificity of the test was 100%. These results compared favourably with an enzyme immunoassay. This latex agglutination test is a simple, rapid and highly specific method of diagnosing melioidosis, and will be particularly useful in areas with limited laboratory facilities.

Summary Multiple alleles at the kelch13 locus conferring artemisinin resistance (ART-R) are currently spreading through malaria parasite populations in Southeast Asia, providing a unique opportunity to directly observe an ongoing soft selective sweep, to investigate why resistance alleles have evolved multiple times and to determine fundamental population genetic parameters for Plasmodium. We sequenced the kelch13 gene (n=1,876), genotyped 75 flanking SNPs, and measured clearance rate (n=3,552) in parasite infections from Western Thailand (2001-2014). We describe 32 independent coding mutations: these included common mutations outside the kelch13 propeller region associated with significant reductions in clearance rate. Mutations were first observed in 2003 and rose to 90% by 2014, consistent with a selection coefficient of ~0.079. There was no change in diversity in flanking markers, but resistance allele diversity rose until 2012 and then dropped as one allele (C580Y) spread to high frequency. The rapid spread of C580Y suggests that the genomic signature may be considerably harder in the near future, and that retrospective studies may underestimate the complexity of selective sweeps. The frequency with which adaptive alleles arise is determined by the rate of mutation to generate beneficial alleles and the population size. Two factors drive this soft sweep: (1) multiple amino-acid mutations in kelch13 can confer resistance providing a large mutational target – we estimate the target size is between 87 and 163bp. (2) The population mutation parameter ( Θ =2 N e μ ) can be estimated from the frequency distribution of resistant alleles and is ~ 5.69, suggesting that short term effective population size is between 88 thousand and 1.2 million. This is 52 to 705-fold greater than N e estimates based on fluctuation in allele frequencies, suggesting that we have previously underestimated the capacity for adaptive evolution in Plasmodium. Our central conclusions are that retrospective studies may underestimate the complexity of selective events, ART-R evolution is not limited by availability of mutations, and the N e relevant for adaptation for malaria is considerably higher than previously estimated. Significance Statement Previous work has identified surprisingly few origins of resistance to antimalarial drugs such as chloroquine and pyrimethamine. This has lead to optimism about prospects for minimizing resistance evolution through combination therapy. We studied a longitudinal collection of malaria parasites from the Thai-Myanmar border (2001–14) to examine an ongoing selective event in which ≥32 independent alleles associated with ART-R evolved. Three factors appear to explain the large number of origins observed: the large number of amino acid changes that result in resistance (i.e. large mutational “target size”), the large estimated effective population size ( N e ), and the fact that we were able to document this selective event in real time, rather than retrospectively.

The spread of artemisinin-resistant Plasmodium falciparum compromises the therapeutic efficacy of artemisinin combination therapies (ACTs) and is considered the greatest threat to current global initiatives to control and eliminate malaria. This is particularly relevant in Vietnam, where dihydroartemisinin-piperaquine (DP) is the recommended ACT for P. falciparum infection. The propeller domain gene of K13, a molecular marker of artemisinin resistance, was successfully sequenced in 1,060 P. falciparum isolates collected at 3 malaria hot spots in Vietnam between 2009 and 2016. Eight K13 propeller mutations (Thr474Ile, Tyr493His, Arg539Thr, Ile543Thr, Pro553Leu, Val568Gly, Pro574Leu, and Cys580Tyr), including several that have been validated to be artemisinin resistance markers, were found. The prevalences of K13 mutations were 29% (222/767), 6% (11/188), and 43% (45/105) in the Binh Phuoc, Ninh Thuan, and Gia Lai Provinces of Vietnam, respectively. Cys580Tyr became the dominant genotype in recent years, with 79.1% (34/43) of isolates in Binh Phuoc Province and 63% (17/27) of isolates in Gia Lai Province carrying this mutation. K13 mutations were associated with reduced ring-stage susceptibility to dihydroartemisinin (DHA) in vitro and prolonged parasite clearance in vivo An analysis of haplotypes flanking K13 suggested the presence of multiple strains with the Cys580Tyr mutation rather than a single strain expanding across the three sites.

Abstract Background Seasonal malaria chemoprevention (SMC) using monthly sulfadoxine-pyrimethamine-amodiaquine (SPAQ) is being deployed in East Africa, where antimalarial drug-resistance levels are high. Dihydroartemisinin-piperaquine (DP) is a potential alternative. Methods A prospective 28-day pharmacometric assessment of SMC was conducted in Karamoja, northern Uganda. In 2 villages children received SPAQ and in a third were randomized to DP versus no SMC. The primary outcome was malaria infection defined by capillary blood sample quantitative PCR (qPCR) positivity on day 28, or presentation with fever and slide or rapid test positivity after day 2. Results Baseline qPCR malaria parasitemia prevalence among 1250 enrolled children was 46% (575/1250); Plasmodium falciparum 85%, other malarias (mainly Plasmodium ovale) 25%. Breakthrough parasitemias occurred in 7% (33/496) of DP, 31% (158/504) of SPAQ, and 39% (98/250) of no drug recipients. Clinical malaria (all P falciparum) developed in 17% of no drug (42/250; 1 severe), 8% of SPAQ (38/504; 2 severe), and 2% of DP (13/496) recipients. Adjusted protective efficacies against all malaria parasitemia, P falciparum parasitemia, and clinical malaria for SPAQ were 56% (95% CI, 35%–70%), 46% (11%–68%), and 60% (27%–78%) and for DP were 84% (77%–89%), 86% (75%–92%), and 86% (74%–92%), respectively. Some asymptomatic P falciparum infections were not cleared by SPAQ. All 260 P falciparum isolates genotyped were PfCRT K76 (haplotype CVMNK, marker of 4-aminoquinoline susceptibility); most were quintuple Pfdhfr/dhps mutants (ie, relatively sulfadoxine-pyrimethamine resistant). The chemoprevention drug exposure–response relationship was strong for desethylamodiaquine, but weak for sulfadoxine. Conclusions SPAQ SMC had low clinical and parasitological chemopreventive efficacy in northern Uganda, whereas DP was effective. Clinical Trials Registration NCT05323721.

Mass anti-malarial administration has been proposed as a key component of the malaria elimination strategy in South East Asia. The success of this approach depends on the local malaria epidemiology, nature of the anti-malarial regimen and population coverage. Community engagement is used to promote population coverage but little research has systematically analysed its impact. This systematic review examines population coverage and community engagement in programmes of mass anti-malarial drug administration. This review builds on a previous review that identified 3049 articles describing mass anti-malarial administrations published between 1913 and 2011. Further search and application of a set of criteria conducted in the current review resulted in 51 articles that were retained for analysis. These 51 papers described the population coverage and/or community engagement in mass anti-malarial administrations. Population coverage was quantitatively assessed and a thematic analysis was conducted on the community engagement activities. The studies were conducted in 26 countries: in diverse healthcare and social contexts where various anti-malarial regimens under varied study designs were administered. Twenty-eight articles reported only population coverage; 12 described only community engagement activities; and 11 community engagement and population coverage. Average population coverage was 83% but methods of calculating coverage were frequently unclear or inconsistent. Community engagement activities included providing health education and incentives, using community structures (e.g. existing hierarchies or health infrastructure), mobilizing human resources, and collaborating with government at some level (e.g. ministries of health). Community engagement was often a process involving various activities throughout the duration of the intervention. The mean population coverage was over 80% but incomplete reporting of calculation methods limits conclusions and comparisons between studies. Various community engagement activities and approaches were described, but many articles contained limited or no details. Other factors relevant to population coverage, such as the social, cultural and study context were scarcely reported. Further research is needed to understand the factors that influence population coverage and adherence in mass anti-malarial administrations and the role community engagement activities and approaches play in satisfactory participation.

No abstract is provided for this article.

No abstract is provided for this article.

Summary Severe tetanus is characterised by muscle spasms and autonomic dysfunction. We recently reported the results of a randomised placebo controlled trial of magnesium sulphate infusions for the treatment of severe tetanus which showed magnesium was associated with improved muscle spasm and cardiovascular control. We hypothesised that magnesium controlled autonomic dysfunction by reducing catecholamine release and thus urinary excretion. Urinary adrenaline and noradrenaline concentrations were measured during the first 24 h of therapy in 180 adults with severe tetanus randomised to treatment with magnesium ( n = 92) or placebo ( n = 88). Magnesium therapy was associated with lower urinary adrenaline excretion and higher urinary noradrenaline excretion. High urinary adrenaline concentrations were associated with documented autonomic dysfunction. Patients given magnesium had significantly less autonomic dysfunction, required less cardiovascular stabilising drugs, and had lower urinary concentrations of adrenaline. These findings suggest adrenaline is important in the pathophysiology of severe tetanus and magnesium controls autonomic dysfunction by reducing adrenaline release.

Genetic analysis of the number of Plasmodium falciparum genotypes per infected person in regions of holoendemic and hyperendemic malaria suggest that in areas of lower transmission intensity, significantly fewer parasite genotypes per infected person should be found. A predominance of single clone infections in the human population could generate the controversial clonal population structure proposed for P. falciparum by Tibayrenc and others. Characterization of P. falciparum from individuals on the Thai-Burmese border, an area of hypoendemic transmission, revealed a higher number of genotypes per infected person than that predicted. Possible reasons for this observation are discussed, with particular attention paid to human migration and multidrug resistance.

In an open-label, randomized trial, 44 Vietnamese children with diphtheria were given penicillin therapy (intramuscular benzylpenicillin, 50,000 U/[kg·d] for 5 days and then oral penicillin, 50 mg/ [kg·d] for 5 days), and 42 were given erythromycin therapy (50 mg/[kg·d] orally for 10 days). There were no differences in times to membrane clearance or bacteriologic clearance, but median times to fever clearance were 27 hours (95% confidence interval [CI], 19–30; range, 0–124 hours) for penicillin recipients and 46 hours (95% CI, 34–54; range, 0–148 hours) for erythromycin recipients (P = .0004). In the penicillin group, acute treatment failed for one patient, and one patient relapsed. Three patients in the penicillin group developed diphtheritic myocarditis as evidenced by abnormal electrocardiograms. Erythromycin did not cause prolongation of the QT interval corrected for heart rate. Cultures of specimens from 15 patients (17.4%) were positive for toxigenic Corynebacterium diphtheriae. All isolates were susceptible to penicillin, but four isolates (27%), all of which were from patients who received penicillin treatment, were resistant to erythromycin (minimum inhibitory concentrations, >64 mg/L). Penicillin is recommended as first-line treatment for diphtheria in Vietnam.

Summary Objective Thiamin deficiency complicates severe Plasmodium falciparum malaria in Thailand and may contribute to acidosis. We therefore estimated the frequency of biochemical thiamin deficiency in patients presenting with uncomplicated falciparum malaria in southern Laos. Methods Red cell transketolase activation coefficients ( α ) were measured in 310 patients presenting with uncomplicated falciparum malaria and 42 days after starting treatment. Results Twelve per cent of patients had biochemical evidence of severe deficiency ( α values >1.31) at presentation, declining to 3% 42 days later. Conclusion Thiamin deficiency was common in Lao patients admitted with uncomplicated P. falciparum infection and was reduced following treatment of malaria and multivitamin supplementation. The role of this preventable and treatable disorder in malaria and other acute infections, and the incidence of beriberi in rural Laos, needs further investigation.

Abstract Background The study of olfaction as a sensory modality has been relatively neglected in comparison to other sensory cues, particularly in wildlife research. Furthermore, the genetic basis of olfaction remains poorly understood in non-model species. Recently, receptors belonging to trace amine-associated receptor (TAAR) family have been identified, and they exhibit considerable natural diversity and copy number variations across a range of species. As such, they represent a promising avenue for exploring olfactory processes, particularly in conjunction with more established olfactory receptors. In meerkats ( Suricata suricatta ), olfaction plays a significant role in foraging, social communication and predator defence. However, no prior research has investigated the genetics of meerkat olfaction. In this study, we leveraged the extensive longitudinal dataset from the Kalahari Meerkat Project, using samples from 398 individuals alive between 1996 and 2023, to develop a high-throughput sequencing approach for assessing TAAR diversity in wild meerkats. Results A total of nine TAAR-loci were identified in meerkats, with both copy number variations and allelic polymorphisms observed for TAAR6 and TAAR8. Two distinct paralogues of TAAR6 and eleven distinct amino acid alleles across these paralogues were identified. Additionally, three paralogues of TAAR8, containing 14 distinct amino acid alleles, were discovered. Within each paralogue of both TAAR loci, a single allele is present in almost all individuals, while additional alleles show a markedly higher degree of variability in frequency. A similar pattern emerges in the relative abundance of TAAR alleles throughout the course of the study, which spanned more than 20 years. In line with the high prevalence of specific alleles and the considerable number of synonymous nucleotide exchanges, we found evidence for multiple sites under purifying selection in TAAR6 and TAAR8. Conclusion This is the first study to examine TAAR diversity in a cooperative breeder. Investigating the genetic basis of olfaction and inter-individual natural variation in TAAR diversity has the potential to expand the toolbox for integrative zoological research. Such insights could help elucidate the genetic underpinnings of behaviour, such as social communication, mate choice, and life-history strategies all in relation to TAAR diversity.