Ex vivo Sensitivity Profile of Plasmodium falciparum Clinical Isolates to a Panel of Antimalarial Drugs in Ghana 13 Years After National Policy Change.

PURPOSE: Malaria continues to be a major health issue globally with almost 85% of the global burden and deaths borne by sub-Saharan Africa and India. Although the current artemisinin derived combination therapies in Ghana are still efficacious against the Plasmodium falciparum (Pf) parasite, compounding evidence of artemisinin and amodiaquine resistance establish the need for a full, up-to-date understanding and monitoring of antimalarial resistance to provide evidence for planning control strategies. MATERIALS AND METHODS: The study was cross-sectional and was conducted during the peak malaria transmission seasons of 2015, 2016, and 2017 in two ecological zones of Ghana. Study participants included children aged 6 months to 14 years. Using ex vivo 4,6-diamidino-2-phenylindole (DAPI) drug sensitivity assay, 330 Pf isolates were used to investigate susceptibility to five antimalarial drugs: chloroquine (CQ), amodiaquine (AMD) dihydroartemisinin (DHA), artesunate (ART) and mefloquine (MFQ). RESULTS: The pooled geometric mean IC50S (GMIC50) of the five drugs against the parasites from Cape Coast and Begoro were 15.5, 42.4, 18.9, 4.6 and 27.3nM for CQ, AMD, DHA, ART, and MFQ, respectively. The GMIC50 values for CQ (p<0.001), ART (p<0.011) and DHA (p<0.018) were significantly higher for Cape Coast isolates as compared to Begoro isolates. However, GMIC50 estimates for MFQ (p<0.022) were significantly higher for Begoro isolates. Positive correlations were found between each pair of drugs with the weakest found between MFQ and DHA (r = 0.34;p<0.001), and the strongest between ART and DHA (r =0.66; p<0.001). CONCLUSION: The parasites showed reduced sensitivities to three (AMD, DHA and MFQ) out of the five drugs assessed. The study also demonstrated the continual return of chloroquine-sensitive parasites after 13 years of its withdrawal as the first-line drug for the treatment of uncomplicated malaria in Ghana. The ex vivo DAPI assay is a reliable method for assessing antimalarial drug sensitivities of Pf field isolates under field settings.

The transcriptome of circulating sexually committed Plasmodium falciparum ring stage parasites forecasts malaria transmission potential.

Malaria is spread by the transmission of sexual stage parasites, called gametocytes. However, with Plasmodium falciparum, gametocytes can only be detected in peripheral blood when they are mature and transmissible to a mosquito, which complicates control efforts. Here, we identify the set of genes overexpressed in patient blood samples with high levels of gametocyte-committed ring stage parasites. Expression of all 18 genes is regulated by transcription factor AP2-G, which is required for gametocytogenesis. We select three genes, not expressed in mature gametocytes, to develop as biomarkers. All three biomarkers we validate in vitro using 6 different parasite lines and develop an algorithm that predicts gametocyte production in ex vivo samples and volunteer infection studies. The biomarkers are also sensitive enough to monitor gametocyte production in asymptomatic P. falciparum carriers allowing early detection and treatment of infectious reservoirs, as well as the in vivo analysis of factors that modulate sexual conversion.

Publisher Correction: Plasmodium falciparum sexual differentiation in malaria patients is associated with host factors and GDV1-dependent genes.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Plasmodium falciparum sexual differentiation in malaria patients is associated with host factors and GDV1-dependent genes.

Plasmodium sexual differentiation is required for malaria transmission, yet much remains unknown about its regulation. Here, we quantify early gametocyte-committed ring (gc-ring) stage, P. falciparum parasites in 260 uncomplicated malaria patient blood samples 10 days before maturation to transmissible stage V gametocytes using a gametocyte conversion assay (GCA). Seventy six percent of the samples have gc-rings, but the ratio of gametocyte to asexual-committed rings (GCR) varies widely (0-78%). GCR correlates positively with parasitemia and is negatively influenced by fever, not hematocrit, age or leukocyte counts. Higher expression levels of GDV1-dependent genes, ap2-g, msrp1 and gexp5, as well as a gdv1 allele encoding H217 are associated with high GCR, while high plasma lysophosphatidylcholine levels are associated with low GCR in the second study year. The results provide a view of sexual differentiation in the field and suggest key regulatory roles for clinical factors and gdv1 in gametocytogenesis in vivo.

Efficacy of Artesunate/Amodiaquine in the Treatment of Uncomplicated Malaria among Children in Ghana.

The declining efficacy of chloroquine in the early 2000s in Ghana led to its replacement with artesunate/amodiaquine (AS/AQ) combination as first-line drug for treating uncomplicated malaria in 2005. Since then efficacy studies have been ongoing in the country to provide continuous data on the efficacy of AS/AQ and other alternative antimalarials (artemether/lumefantrine and dihyroartemisinin/piperaquine combinations) introduced in 2008. In vivo AS/AQ efficacy studies were conducted between June and October 2014 among children aged 6 months to 14 years, in two sentinel sites representing the forest and coastal zones of the country. The 2009 World Health Organization protocol for monitoring antimalarial drug efficacy was used in these studies. The studies showed an overall cumulative polymerase chain reaction-corrected day 28 cure rate of 97.2% (95% confidence interval [CI]: 93.6-99.1): 97.7% (95% CI: 92.0-99.7) within the forest zone and 96.7% (95% CI: 90.7-99.3) within the coastal zone (P = 0.686). Prevalence of fever declined from 100% to < 4% after first day of treatment in both ecological zones. All children in the coastal zone had cleared parasites by day 2. Three children (3.2%) in the forest zone were parasitemic on day 2, whereas one child was parasitemic on day 3. Gametocytemia was absent in both zones after day 14, and mean hemoglobin concentration significantly increased from 10.3 g/dL (95% CI: 10.1-10.5) on day 0 to 11.8 g/dL (95% CI: 11.6-12.0) on day 28. We conclude that AS/AQ combination remains efficacious in the treatment of uncomplicated malaria in Ghana.

Surveillance of molecular markers of Plasmodium falciparum resistance to sulphadoxine-pyrimethamine 5 years after the change of malaria treatment policy in Ghana.

In 2005, sulphadoxine-pyrimethamine (SP) became the drug of choice for intermittent preventive treatment of Plasmodium falciparum malaria in pregnancy (IPTp) in Ghana. Reports suggest the use of SP by others to treat uncomplicated malaria. Because of the increased use of SP, the prevalence of mutations in the genes, dihydrofolate reductase (dhfr), and dihydropteroate synthetase (dhps), linked to SP resistance in P. falciparum were determined. Blood samples from 945 children with uncomplicated malaria collected at nine sites from 2003 to 2010 were analyzed using polymerase chain reaction and restriction fragment length polymorphism. Prevalence of the dhfr triple and dhfr plus dhps quadruple mutations showed significant increase in trend from 2003 to 2010 (χ(2) = 18.78, P < 0.001, χ(2) = 15.11, P < 0.001, respectively). For dhps double mutant G437 + E540 the prevalence was low (1.12%) caused by the very low prevalence of E540. Our findings show the wide use of SP in Ghana and therefore its use for IPTp needs to be closely monitored.

A comparative analysis of tuberculosis treatment success between Hunan Province of China and Eastern Ghana.

OBJECTIVE: To assess the differences in tuberculosis (TB) treatment success between Hunan and Eastern Ghana. SUBJECTS AND METHODS: The study was a retrospective comparative study using 2005-2006 surveillance data from the Hunan province of China and the Eastern region of Ghana. Data analyzed were from the provincial/regional capital and a randomly selected city of lower economic status. χ(2) test and Fisher's exact test were used to do general and stratified comparison of treatment success rates within/between the two areas. Multivariate logistic regression was used to analyze the independent effect of explanatory variables on treatment success. RESULTS: Generally, the treatment success rate was significantly higher in Hunan (93.1 vs. 60.7%, p = 0.000). Stratified analyses showed a similar pattern for almost all the group-specific rates. Key predictors of TB treatment success in Hunan were gender, age group, and type of city of residence whilst in Eastern Ghana treatment success was associated with only age group. Odds ratios for treatment success in Hunan were significantly lower for males (OR = 0.78; 95% CI = 0.63, 0.97), and higher for patients resident in the provincial capital (OR = 1.35; 95% CI = 1.12, 1.62). In both countries treatment success rates decreased with increasing age. CONCLUSION: TB treatment success in Hunan was comparatively better than that in Eastern Ghana. Gender, age group, and type of city of residence were the key predictors of treatment success in Hunan whilst in Eastern Ghana age group was the key predictor.

Antimalarial drug use among caregivers in Ghana.

BACKGROUND: Chloroquine remains the first line antimalarial drug in Ghana. However, the emergence of Plasmodium falciparum resistance to chloroquine is a major obstacle to the national control strategy of case management. This study provides information on some of the reasons underlying chloroquine treatment failure in the country. METHODOLOGY: Household surveys, using multi-stage sampling, were conducted in 2 sentinel districts, Wassa West and Kassena Nankana, established to monitor chloroquine resistance in the country. Five hundred caregivers were interviewed in each district to determine patterns of antimalarial drug use among caregivers of children under 10 years. Inventory on home-kept drugs was conducted. RESULTS: Two hundred and four households in the Wassa West district kept a cumulative total of 248 drugs, whereas 228 households in the Kassena Nankana district kept a cumulative total of 410 drugs. One hundred and ninety-nine (80.2%) of the drugs kept in the Wassa West district and 181 (44.2%) of drugs kept in the Kassena Nankana district were antimalarials. The most commonly kept antimalarial drug in homes was chloroquine (88% and 96% in the Wassa West and Kassena Nankana districts respectively). Reasons given for keeping antimalarials were mainly "leftover after previous treatment". Caregivers' descriptions of the amount of chloroquine given to family members suspected to have malaria within the 2-week period preceding the survey were mostly inappropriate in the 2 districts. However, the proportion of appropriateness of doses was significantly lower in the Wassa West district (11.1% vs 36.4%; p < 0.0001). CONCLUSIONS: The significantly higher proportion of inappropriateness of chloroquine use in the Wassa West district could be a factor influencing the lower sensitivity of Plasmodium falciparum to chloroquine in the district compared to the Kassena Nankana district.