Different patterns of pfcrt and pfmdr1 polymorphisms in P. falciparum isolates from Nigeria and Brazil: the potential role of antimalarial drug selection pressure

Sub-microscopic Plasmodium falciparum infections and multiple drug resistant single nucleotide polymorphic alleles in pregnant women from southwestern Nigeria

OBJECTIVES

The study evaluated sub-microscopic malaria infections in pregnancy using two malaria Rapid Diagnostic Tests (mRDTs), microscopy and RT-PCR and characterized Plasmodium falciparum dihydrofolate reductase (Pfdhfr) and Plasmodium falciparum dihydropteroate synthase (Pfdhps) drug resistant markers in positive samples.

METHODS

This was a cross sectional survey of 121 pregnant women. Participants were finger pricked, blood drops were collected for rapid diagnosis with P. falciparum histidine-rich protein 11 rapid diagnostic test kit and the ultra-sensitive Alere Pf malaria RDT, Blood smears for microscopy and dried blood spots on Whatman filter paper for molecular analysis were made. Real time PCR targeting the var acidic terminal sequence (varATS) gene of P. falciparum was carried out on a CFX 96 real time system thermocycler (BioRad) in discriminating malaria infections. For each run, laboratory strain of P. falciparum 3D7 and nuclease free water were used as positive and negative controls respectively. Additionally, High resolution melt analyses was employed for genotyping of the different drug resistance markers.

RESULTS

Out of one hundred and twenty-one pregnant women sampled, the SD Bioline™ Malaria Ag P.f HRP2-based malaria rapid diagnostic test (mRDT) detected eight (0.06%) cases, the ultra-sensitive Alere™ malaria Ag P.f rapid diagnostic test mRDT had similar outcome in the same samples as detected by the HRP2-based mRDT. Microscopy and RT-PCR confirmed four out of the eight infections detected by both rapid diagnostic tests as true positive and RT-PCR further detected three false negative samples by the two mRDTs providing a sub-microscopic malaria prevalence of 3.3%. Single nucleotide polymorphism in Pfdhps gene associated with sulphadoxine resistance revealed the presence of S613 mutant genotypes in three of the seven positive isolates and isolates with mixed wild/mutant genotype at codon A613S. Furthermore, four mixed genotypes at the A581G codon were also recorded while the other Pfdhps codons (A436G, A437G and K540E) showed the presence of wild type alleles. In the Pfdhfr gene, there were mutations in 28.6%, 28.6%, and 85.7% at the I51, R59 and N108 codons respectively. Mixed wild and mutant type genotypes were also observed in 28.6% each of the N51I, and C59R codons. For the Pfcrt, two haplotypes CVMNK and CVIET were observed. The SVMNT was altogether absent. Triple mutant CVIET 1(14.3%) and triple mutant + wild genotype CVIET + CVMNK 1(14.3%) were observed. The Pfmdr1 haplotypes were single mutants YYND 1(14.3%); NFND 1(14.3%) and double mutants YFND 4(57.1%); YYDD 1(14.3%).

Prevalence of Plasmodium falciparum Pfcrt and Pfmdr1 alleles in settings with different levels of Plasmodium vivax co-endemicity in Ethiopia

Plasmodium falciparum and P. vivax co-exist at different endemicity levels across Ethiopia. For over two decades Artemether-Lumefantrine (AL) is the first line treatment for uncomplicated P. falciparum, while chloroquine (CQ) is still used to treat P. vivax. It is currently unclear whether a shift from CQ to AL for P. falciparum treatment has implications for AL efficacy and results in a reversal of mutations in genes associated to CQ resistance, given the high co-endemicity of the two species and the continued availability of CQ for the treatment of P. vivax. This study thus assessed the prevalence of Pfcrt-K76T and Pfmdr1-N86Y point mutations in P. falciparum. 18S RNA gene based nested PCR confirmed P. falciparum samples (N = 183) collected through community and health facility targeted cross-sectional surveys from settings with varying P. vivax and P. falciparum endemicity were used. The proportion of Plasmodium infections that were P. vivax was 62.2% in Adama, 41.4% in Babile, 30.0% in Benishangul-Gumuz to 6.9% in Gambella. The Pfcrt-76T mutant haplotype was observed more from samples with higher endemicity of P. vivax as being 98.4% (61/62), 100% (31/31), 65.2% (15/23) and 41.5% (22/53) in samples from Adama, Babile, Benishangul-Gumuz and Gambella, respectively. However, a relatively higher proportion of Pfmdr1-N86 allele (77.3–100%) were maintained in all sites. The observed high level of the mutant Pfcrt-76T allele in P. vivax co-endemic sites might require that utilization of CQ needs to be re-evaluated in settings co-endemic for the two species. A country-wide assessment is recommended to clarify the implication of the observed level of variation in drug resistance markers on the efficacy of AL-based treatment against uncomplicated P. falciparum malaria.

Surveillance of Antimalarial Resistance Pfcrt, Pfmdr1, and Pfkelch13 Polymorphisms in African Plasmodium falciparum imported to Shandong Province, China

Antimalarial drug resistance is a major public health problem in China. From 2012 to 2015, more than 75% of malaria cases in Shandong Province were P. falciparum returned from Africa. However, molecular marker polymorphisms of drug resistance in imported P. falciparum cases have not been evaluated. In this study, we analyzed polymorphisms of the Pfcrt, Pfmdr1, and Pfkelch13 genes in 282 P. falciparum cases returned from Africa to Shandong between 2012 and 2015. Among the isolates, polymorphisms were detected in codons 74–76 of Pfcrt and 86, 184, 1246 of Pfmdr1, among which K76T (36.6%) and Y184F (60.7%) were the most prevalent, respectively. Six Pfcrt haplotypes and 11 Pfmdr1 haplotypes were identified and a comparison was made on the prevalence of haplotypes among East Africa, West Africa, Central Africa and South Africa. One synonymous and 9 nonsynonymous mutations in Pfkelch13 were detected in the isolates (4.6%), among which a candidate artemisinin (ART) resistance mutation P553L was observed. The study establishes fundamental data for detection of chloroquine resistance (CQR) and ART resistance with molecular markers of the imported P. falciparum in China, and it also enriches the genetic data of antimalarial resistance for the malaria endemic countries in Africa.

Efficacy of Artemether-Lumefantrine for Uncomplicated Plasmodium falciparum Malaria in Cruzeiro do Sul, Brazil, 2016

We evaluated the therapeutic efficacy of artemether-lumefantrine (AL) fixed-dose combination to treat uncomplicated Plasmodium falciparum malaria in Cruzeiro do Sul, Acre State, in the Amazon region of Brazil. Between December 2015 and May 2016, we enrolled 79 patients, 5-79 years old with fever or history of fever in the previous 48 hours and P. falciparum monoinfection confirmed by microscopy. Attempts were made to provide direct observation or phone reminders for all six doses of AL, and patients were followed-up for 28 days. AL was well tolerated, with no adverse events causing treatment interruption. All but one of the 74 patients who completed the 28-day follow-up had an adequate clinical and parasitologic response = 98.6% (95% CI: 93.2-100%). We could not amplify the one isolate of the case with recurrent infection to differentiate between recrudescence and reinfection. Five (6.3%) patients demonstrated persistent asexual parasitemia on Day 3, but none met definition for early treatment failure. We found no mutations in selected kelch13 gene domains, known to be associated with artemisinin resistance in P. falciparum isolates from Day 0. These results strongly support the continued use of AL as a first-line therapy for uncomplicated P. falciparum malaria in Acre. Routine monitoring of in vivo drug efficacy coupled with molecular surveillance of drug resistance markers remains critical.

Assessment of copy number variation in genes related to drug resistance in Plasmodium vivax and Plasmodium falciparum isolates from the Brazilian Amazon and a systematic review of the literature

Background

Parasite resistance to anti-malarials represents a great obstacle for malaria elimination. The majority of studies have investigated the association between single-nucleotide polymorphisms (SNPs) and drug resistance; however, it is becoming clear that the copy number variation (CNV) is also associated with this parasite phenotype. To provide a baseline for molecular surveillance of anti-malarial drug resistance in the Brazilian Amazon, the present study characterized the genetic profile of both markers in the most common genes associated with drug resistance in Plasmodium falciparum and Plasmodium vivax isolates. Additionally, these data were compared to data published elsewhere applying a systematic review of the literature published over a 20-year time period.

Methods

The genomic DNA of 67 patients infected by P. falciparum and P. vivax from three Brazilian States was obtained between 2002 and 2012. CNV in P. falciparum multidrug resistance gene-1 (pfmdr1), GTP cyclohydrolase 1 (pfgch1) and P. vivax multidrug resistance gene-1 (pvmdr1) were assessed by real-time PCR assays. SNPs in the pfmdr1 and pfcrt genes were assessed by PCR–RFLP. A literature search for studies that analysed CNP in the same genes of P. falciparum and P. vivax was conducted between May 2014 and March 2017 across four databases.

Results

All analysed samples of P. falciparum carried only one copy of pfmdr1 or pfgch1. Although the pfcrt K76T polymorphism, a determinant of CQ resistance, was present in all samples genotyped, the pfmdr1 N86Y was absent. For P. vivax isolates, an amplification rate of 20% was found for the pvmdr1 gene. The results of the study are in agreement with the low amplification rates for pfmdr1 gene evidenced in the Americas and Africa, while higher rates have been described in Southeast Asia. For P. vivax, very low rates of amplification for pvmdr1 have been described worldwide, with exceptions in French Guiana, Cambodia, Thailand and Brazil.

Conclusions

The present study was the first to evaluate gch1 CNV in P. falciparum isolates from Brazil, showing an absence of amplification of this gene more than 20 years after the withdrawal of the Brazilian antifolates therapeutic scheme. Furthermore, the rate of pvmdr1 amplification was significantly higher than that previously reported for isolates circulating in Northern Brazil.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-017-1806-z) contains supplementary material, which is available to authorized users.

Molecular mutation profile of pfcrt in Plasmodium falciparum isolates imported from Africa in Henan province

Background

Anti-malarial drug resistance is a primary public health problem. Haplotypes of pfcrt gene have been implicated to be molecular markers of chloroquine (CQ) resistance. This study aims to explore the prevalence of polymorphisms in pfcrt in Plasmodium falciparum-infected patients imported from Africa in Henan province.

Methods

Blood samples were collected from 502 patients who were infected with P. falciparum returning from Africa in Henan province during 2012–2015. The single nucleotide polymorphisms in pfcrt (codons 72–76) were assessed by nested PCR with DNA sequencing and restriction digestion, the haplotype prevalences were also determined.

Results

Four haplotypes coding 72–76 of pfcrt were found including CVMNK (wild type), CVIET (mutation type), CVIEK (mutation type), and CV M/I N/E/D/K K/T (mixed type), with 61.95 % (311/502), 33.07 % (166/502), 0.20 % (1/502), and 4.78 % (24/502) prevalence, respectively. Except mixed type, CVIET and CVIEK were the largest proportion of the mutant type in West Africa, accounting for 44.83 % (91/203), followed by East Africa (8/21, 38.10 %), North Africa (4/11, 36.36 %), Central Africa (36/135, 26.67 %), and South Africa (28/132, 21.21 %). There was significant difference among the groups (χ² = 23.78, P < 0.05). Mixed type was the largest proportion in North Africa (9.09 %), followed by Central Africa (6.67 %), East Africa (4.76 %), South Africa (4.55 %), and West Africa (3.45 %). There was no significant difference among the groups (χ² = 2.31, P > 0.05). The position 72 and 73 of pfcrt showed predominance for the wild type with rates of 100 % (502/502).

Conclusions

This study identified four haplotypes of pfcrt in P. falciparum-infected patients imported from Africa in Henan province. The prevalence of mutations in the pfcrt was dropped comparing with other people’s researches. It establishes fundamental data for detection of P. falciparum CQR with molecular markers for the imported P. falciparum in China, and it also provides complementary information of CQR for the malaria endemic countries and assesses the evolution of anti-malarial drug resistance.

Healthcare-Associated Transmission of Plasmodium falciparum in New York City

A patient with no risk factors for malaria was hospitalized in New York City with Plasmodium falciparum infection. After investigating all potential sources of infection, we concluded the patient had been exposed to malaria while hospitalized less than 3 weeks earlier. Molecular genotyping implicated patient-to-patient transmission in a hospital setting. Infect. Control Hosp. Epidemiol. 2015;37(1):113-115.

Significant geographical differences in prevalence of mutations associated with Plasmodium falciparum and Plasmodium vivax drug resistance in two regions from Papua New Guinea

Background

Drug resistance remains a major obstacle to malaria treatment and control. It can arise and spread rapidly, and vary substantially even at sub-national level. National malaria programmes require cost-effective and timely ways of characterizing drug-resistance at multiple sites within their countries.

Methods

An improved multiplexed post-PCR ligase detection reaction—fluorescent microsphere assay (LDR-FMA) was used to simultaneously determine the presence of mutations in chloroquine resistance transporter (crt), multidrug resistance 1 (mdr1), dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) genes in Plasmodium falciparum (n = 727) and Plasmodium vivax (n = 574) isolates collected in 2006 from cross-sectional community population surveys in two geographically distinct regions (Madang and East Sepik) of Papua New Guinea (PNG) where strong regional differences in in vivo aminoquinoline and antifolate therapeutic efficacy had previously been observed. Data were compared to those of a follow-up survey conducted in 2010.

Results

Despite some very low parasite densities, the assay successfully amplified all P. falciparum and P. vivax loci in 77 and 69 % of samples, respectively. In 2006, prevalences of pfdhfr (59R-108 N) double mutation/wild type pfdhps haplotype, pfcrt SVMNT haplotype (72S-76T double mutation), and 86Y pfmdr1 mutation all exceeded 90 %. For P. vivax, 65 % carried at least two pvdhfr mutations, 97 % the 647P pvdhps mutation and 54 % the 976F pvmdr1 mutation. Prevalence of mutant haplotypes was higher in Madang than East Sepik for pfcrt SVMNT (97.4 vs 83.3 %, p = 0.001), pfdhfr (59R-108 N) (100 vs 90.6 %, p = 0.001), pvdhfr haplotypes (75.8 vs 47.6 %, p = 0.001) and pvmdr1 976F (71.2 vs 26.2 %, p < 0.001). Data from a subsequent Madang survey in 2010 showed that the prevalence of pfdhps mutations increased significantly from <5 % to >30 % (p < 0.001) as did the prevalence of pvdhfr mutant haplotypes (from 75.8 to 97.4 %, p = 0.012).

Conclusions

This LDR-FMA multiplex platform shows feasibility for low-cost, high-throughput, rapid characterization of a broad range of drug-resistance markers in low parasitaemia infections. Significant geographical differences in mutation prevalence correlate with previous genotyping surveys and in vivo trials and may reflect variable drug pressure and differences in health-care access in these two PNG populations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-015-0879-9) contains supplementary material, which is available to authorized users.

Molecular mutation profile of Pfcrt and Pfmdr1 in Plasmodium falciparum isolates from Bioko Island, Equatorial Guinea

BACKGROUND

Antimalarial drug resistance is a primary public health problem. Haplotypes of pfcrt and pfmdr1 gene have been implicated to be molecular markers of chloroquine (CQ) resistance. This study aims to explore mutation distribution of Pfcrt and Pfmdr1 in Bioko Island, Equatorial Guinea (EG).

METHODS

Blood samples were collected from different districts of Bioko. The single nucleotide polymorphisms in Pfcrt (codons 72 to 76) and Pfmdr1 (codons 86, 130, 184, 1034, 1042, 1109 and 1246) were assessed by nested PCR with DNA sequencing and haplotype prevalences were also determined.

RESULTS

Analysis of Pfcrt and Pfmdr1 mutations was successful in 151 and 157 samples respectively out of the 172 samples taken for this study. The mutations of Pfcrt and Pfmdr1 were found in 98.67% and 89.81% isolates, respectively. The Pfcrt 74-76, Pfmdr1 86, and Pfmdr1 184 were 92.05%, 50.32%, and 87.26% found mostly of mutation type, respectively. Three haplotypes coding 72-76 of Pfcrt were found including CVMNK, CVIET, and CVM/I N/E K/T, which accounted for 1.33%, 92.05%, and 6.62%, respectively. No mutation in Pfmdr1-N1 codon at 130 and Pfmdr1-N2 (S1034C, N1042D, V1109I, and D1246Y) was detected. The types coding 86 and 184 in Pfmdr1 were found including NY, YY, NF, YF, NY/F and YY/F, which accounted for 10.19%, 2.55%, 33.76%, 45.22%, 5.73% and 2.55%, respectively.

CONCLUSION

High prevalence of Pfcrt CVIET and Pfmdr1 86Y, 184F double mutations confirm high-level CQ resistance (CQR) and might suggest reduced susceptibility of Plasmodium falciparum isolates to AQ in Bioko, EG. It establishes fundamental data for detection of P. falciparum CQR with molecular markers and will promotes the surveillance level of drug resistance in Bioko, EG.

Prevalence of Plasmodium falciparum anti-malarial resistance-associated polymorphisms in pfcrt, pfmdr1 and pfnhe1 in Muheza, Tanzania, prior to introduction of artemisinin combination therapy

BACKGROUND

A report of the chloroquine and amodiaquine resistance pfcrt-SVMNT haplotype in Tanzania raises concern about high-level resistance to the artesunate-amodiaquine combination treatment widely employed in Africa. Mutations in the pfmdr1 multi-drug resistance gene may also be associated with resistance, and a highly polymorphic microsatellite (ms-4760) of the pfnhe1 gene involved in quinine susceptibility has not been surveyed in Tanzania.

METHODS

A total of 234 samples collected between 2003 - 2006 from an observational birth cohort of young children in Muheza, Tanzania were analysed. In these children, 141 cases of P. falciparum infections were treated with AQ and 93 episodes were treated with QN. Haplotypes of pfcrt and pfmdr1 were determined by a Taqman assay, and ms-4760 repeats in pfnhe1 were assessed by nested PCR amplification and direct sequencing. Parasite population diversity was evaluated using microsatellite markers on five different chromosomes.

RESULTS

The pfcrt-CVIET haplotype was present alone in 93.6% (219/234) of the samples over the study period; the wild-type chloroquine- and amodiaquine-sensitive haplotype pfcrt-CVMNK was present in 4.3% (10/234) of the samples; and both haplotypes were present in 2.1% (5/234) of the samples. No significant change in wild-type pfcrt-CVMNK prevalence was evident over the 4-year period of the study. The pfcrt-SVMNT haplotype associated with high-level amodiaquine resistance was not detected in this study. The pfmdr1 locus was genotyped in 178 of these samples. The pfmdr1-YYNY haplotype predominated in 67.4% (120/178) of infections and was significantly associated with the pfcrt-CVIET haplotype. All samples carried the wild-type pfmdr1-N1042 codon. The ms-4760 repeat on pfnhe1 locus displayed 12 distinct haplotypes with ms-4760-1 predominating in the population. Analysis of these haplotypes showed no association of a particular haplotype with quinine treatment outcome.

CONCLUSION

The pfcrt-CVIET chloroquine resistance haplotype dominated in the collection of P. falciparum samples from Muheza. The pfcrt-SVMNT haplotype, which threatens the efficacy of amodiaquine and was reported in the same time period from Korogwe, Tanzania, 40 Km from Muheza, was not detected. Relative low prevalence of pfcrt-SVMNT in Africa may result from genetic or other factors rendering P. falciparum less supportive of this haplotype than in South America or other regions.

TRIAL REGISTRATION

Trial Protocol Number: 08-I-N064.

Efficacy and safety of a combination of azithromycin and chloroquine for the treatment of uncomplicated Plasmodium falciparum malaria in two multi-country randomised clinical trials in African adults

BACKGROUND

Given increasing rates of resistance to existing therapy, new options for treatment and prophylaxis of malaria are needed.

METHODS

Two randomised, comparative, non-inferiority studies were conducted in Africa, one double-blinded and one open-label. Adults with fever, a positive peripheral blood smear, and a positive rapid diagnostic test for Plasmodium falciparum were randomised in both studies to either azithromycin (AZ) 1,000 mg plus chloroquine (CQ) 600-mg base (AZCQ 1,000 mg) once daily for three days or mefloquine hydrochloride (MQ) 1,250 mg (split dose). In the first study, an additional regimen of AZ 500 mg plus CQ 600-mg base (AZCQ 500 mg) once daily for three days was included. All study participants were hospitalised until three consecutive daily blood smears were negative for asexual P. falciparum parasitaemia. Study participants were evaluated weekly for 42 days, with Day 28 polymerase chain reaction (PCR)-corrected parasitological clearance rate as primary endpoint.

RESULTS

A total of 467 subjects were randomised in the two studies. At 28 days' follow-up, PCR-corrected parasitological clearance rates in the per protocol population in the first study were 101/103 (98%) with AZCQ 1,000 mg compared with 102/103 (99%) with MQ (95% confidence interval [CI]: -5.2, 3.3). The AZCQ 500-mg regimen was stopped during an interim study review (six [86%] clearance of seven evaluable; two lost to follow-up). In the second study, clearance rates were similar: AZCQ 1,000 mg 107/107 (100%) vs MQ 111/112 (99%; 95% CI: -1.8, 3.6). Among the participating countries, in vitro CQ resistance based on pfcrt mutation frequency in the baseline isolates across both studies ranged from 20.8% (Zambia) to 96.1% (Uganda). Serious adverse events (AEs; all causality) were observed more frequently with MQ compared with AZCQ (four vs one, respectively), though discontinuations for AEs were similar (four vs three, respectively). Common AEs in the AZ-containing arms included pruritus, vomiting, dizziness, and headache.

CONCLUSIONS

Among adults with symptomatic uncomplicated falciparum malaria in Africa, the combination of AZ 1,000 mg and CQ 600-mg base once daily for three days resulted in Day 28 PCR-corrected parasitological clearance rates of ≥98% and was non-inferior to treatment with MQ. AZCQ was well tolerated.

TRIAL REGISTRATION

ClinicalTrials.gov identifiers NCT00082576 and NCT00367653.

Efficacy of artemisinin-based combination treatments of uncomplicated falciparum malaria in under-five-year-old Nigerian children

The efficacy of 3-day regimens of artemether-lumefantrine and artesunate-amodiaquine were evaluated in 747 children < 5 years of age with uncomplicated malaria from six geographical areas of Nigeria. Fever clearance was significantly faster (P = 0.006) and the proportion of children with parasitemia 1 day after treatment began was significantly lower (P = 0.016) in artesunate-amodiaquine-compared with artemether-lumefantrine-treated children. Parasite clearance times were similar with both treatments. Overall efficacy was 96.3% (95% confidence interval [CI] 94.5-97.6%), and was similar for both regimens. Polymerase chain reaction-corrected parasitologic cure rates on Day 28 were 96.9% (95% CI 93.9-98.2%) and 98.3% (95% CI 96.1-99.3%) for artemether-lumefantrine and artesunate-amodiaquine, respectively. Gametocyte carriage post treatment was significantly lower than pretreatment (P < 0.0001). In anemic children, mean time to recovery from anemia was 10 days (95% CI 9.04-10.9) and was similar for both regimens. Both treatments were well tolerated and are safe and efficacious treatments of uncomplicated falciparum malaria in young Nigerian children.

Genetic polymorphisms of candidate markers and in vitro susceptibility of Plasmodium falciparum isolates from Thai-Myanmar border in relation to clinical response to artesunate-mefloquine combination

The genetic polymorphisms of the candidate markers of antimalarial drug resistance pfcrt, pfmdr1, pfatp6, and pfmrp1 were investigated in relationship with in vitro susceptibility of Plasmodium falciparum isolates and clinical response following artesunate (AS)-mefloquine (MQ) combination in 21 and 27 samples obtained from patients with recrudescence and adequate clinical response, respectively. MQ (21.0 vs. 49.9nM) and AS (1.6 vs. 2.8nM) IC50 values (concentrations that inhibit parasite growth by 50%) were significantly higher in isolates collected from patients with recrudescence. Furthermore, a significantly higher MQ IC50 was found in isolates from patients with recrudescence that carried pfmrp1 mutations at amino acid residues 191Y, 437A, and 876V. For AS sensitivity, a significant association was also detected in isolates from patients with recrudescence that carried gene mutations at amino acid residues 437A and 876V. MQ IC50 of the isolates with recrudescence which carried ≥4 pfmdr1 gene copies was significantly higher than that carrying only one gene copy. In addition, a significantly higher proportion of isolates carrying one gene copy was detected in the group with adequate clinical response compared with recrudescence. Results from this limited sample size suggested the potential link between pfmdr1 gene copy number and pfmrp1 gene mutation, in vitro parasite susceptibility, and AS-MQ treatment response.

Malaria prevalence in north-eastern Nigeria: a cross-sectional study

OBJECTIVE

To assess the prevalence of malaria parasitemia in north-east Nigeria and to evaluate the measures for the prevention of malaria.

METHODS

A village in north-eastern Nigeria was selected for the cross sectional study at the height of the rainy season in October 2011. A total of 550 inhabitants of a hamlet were recruited for this study. After obtaining the consent individuals received a structured interview and were tested for malaria parasites in their blood films. Recruits testing positive for malaria were given a course of artemesinin-based combination therapy (ACT).

RESULTS

A total of 497 inhabitants representing approximately 90 percent of the population participated: a quarter of the study group carried malaria parasitesexclusively Plasmodium falciparum(P. falciparum)-representing a P. falciparum parasite rate (PfPR) of 24.5%. Besides, 53/138 in the age group of 2 to < 10 years old children tested positive for P. falciparum representing a PfPR2-10 value of 38.4%. Malaria control measures were used in just under a third (157/497) of this cohort. Despite these measures 28/157 (17.8%) still tested positive for P. falciparum.

CONCLUSIONS

The malaria burden is overestimated for this region in north-east Nigeria. The findings support an intermediate pattern of malaria endemicity. The 30% bed nets coverage for malaria control is well below the WHO estimates for 2011.

Return of chloroquine-sensitive Plasmodium falciparum parasites and emergence of chloroquine-resistant Plasmodium vivax in Ethiopia

BACKGROUND

Increased resistance by Plasmodium falciparum parasites led to the withdrawal of the antimalarial drugs chloroquine and sulphadoxine-pyrimethamine in Ethiopia. Since 2004 artemether-lumefantrine has served to treat uncomplicated P. falciparum malaria. However, increasing reports on delayed parasite clearance to artemisinin opens up a new challenge in anti-malarial therapy. With the complete withdrawal of CQ for the treatment of Plasmodium falciparum malaria, this study assessed the evolution of CQ resistance by investigating the prevalence of mutant alleles in the pfmdr1 and pfcrt genes in P. falciparum and pvmdr1 gene in Plasmodium vivax in Southern and Eastern Ethiopia.

METHODS

Of the 1,416 febrile patients attending primary health facilities in Southern Ethiopia, 329 febrile patients positive for P. falciparum or P. vivax were recruited. Similarly of the 1,304 febrile patients from Eastern Ethiopia, 81 febrile patients positive for P. falciparum or P. vivax were included in the study. Of the 410 finger prick blood samples collected from malaria patients, we used direct sequencing to investigate the prevalence of mutations in pfcrt and pfmdr1. This included determining the gene copy number in pfmdr1 in 195 P. falciparum clinical isolates, and mutations in the pvmdr1 locus in 215 P. vivax clinical isolates.

RESULTS

The pfcrt K76 CQ-sensitive allele was observed in 84.1% of the investigated P.falciparum clinical isolates. The pfcrt double mutations (K76T and C72S) were observed less than 3%. The pfcrt SVMNT haplotype was also found to be present in clinical isolates from Ethiopia. The pfcrt CVMNK-sensitive haplotypes were frequently observed (95.9%). The pfmdr1 mutation N86Y was observed only in 14.9% compared to 85.1% of the clinical isolates that carried sensitive alleles. Also, the sensitive pfmdr1 Y184 allele was more common, in 94.9% of clinical isolates. None of the investigated P. falciparum clinical isolates carried S1034C, N1042D and D1246Y pfmdr1 polymorphisms. All investigated P. falciparum clinical isolates from Southern and Eastern Ethiopia carried only a single copy of the mutant pfmdr1 gene.

CONCLUSION

The study reports for the first time the return of chloroquine sensitive P. falciparum in Ethiopia. These findings support the rationale for the use of CQ-based combination drugs as a possible future alternative.

High prevalence of pfcrt-CVIET haplotype in isolates from asymptomatic and symptomatic patients in south-central Oromia, Ethiopia

Background

As a result of extensive chloroquine resistance (CQR) in Plasmodium falciparum in late 1990s, Ethiopia replaced CQ with sulphadoxine-pyrimethamine (SP) as first-line drug, which in turn was replaced by artemisinin combination therapy in 2004. Plasmodium falciparum resistance to CQ is determined by the mutation at K76T of the P. falciparum chloroquine resistance transporter (pfcrt) gene. Understanding diversity in the P. falciparum genome is crucial since it has the potential to influence important phenotypes of the parasite such as drug resistance. Limited data is available regarding the type of pfcrt mutant allelic type, the effect of CQ withdrawal and diversity of the parasite population in south-central Oromia, Ethiopia.

Methods

Finger-pricked blood spotted on Whatman 3MM filter papers were collected from falciparum malaria patients. Parasite DNA was extracted from individual blood spots on the filter papers. The presence of K76T mutations was determined using nested PCR for all isolates. Complete sequencing of mutations in pfcrt 72-76 was done for a set of randomly selected resistant isolates. Four microsatellite (MS) markers were analysed to determine the heterozygosity.

Results

Although CQ was withdrawn for more than a decade, 100% of the parasites still carried the pfcrt K76T mutation. All isolates were mutant at the K76T polymorphism. Based on combinations of MS markers, seven different Ethiopian CQR variants (E1-E7) were identified. Heterozygosity (H_e) for MS flanking the pfcrt chloroquine resistance allele ranged from 0.00 (mscrt -29, -29.268 kb) to 0.21 (mscrt -2, -2.814 kb). H_e ranged from 0.00 (msint 3, 0 kb) to 0.19 (msint 2, 0 kb) for MS within the pfcrt gene. Both intronic and MS flanking the pfcrt gene showed low levels of diversity.

Conclusion

pfcrt CQR allele seems to be fixed in the study area. Of the different haplotypes associated with CQR, only the CVIET genotype was identified. No reversal to the wild-type has occurred in Ethiopia unlike in many Africa countries where CQR parasites declined after cessation of CQ use. Decreased diversity in CQR isolates surrounding pfcrt suggests CQ selection and homogenization among CQR parasite population. While mutation in msint 3 and mscrt -29 of the mutant pfcrt allele is being fixed, it seems that mutations in msint 2 and mscrt -2 are still evolving and may indicate the start of re-diversification of the population from a fixed 76 T population.

PfCRT and its role in antimalarial drug resistance

Plasmodium falciparum resistance to chloroquine, the former gold standard antimalarial drug, is mediated primarily by mutant forms of the chloroquine resistance transporter (PfCRT). These mutations impart upon PfCRT the ability to efflux chloroquine from the intracellular digestive vacuole, the site of drug action. Recent studies reveal that PfCRT variants can also affect parasite fitness, protect immature gametocytes against chloroquine action, and alter P. falciparum susceptibility to current first-line therapies. These results highlight the need to be vigilant in screening for the appearance of novel pfcrt alleles that could contribute to new multi-drug resistance phenotypes.

Various pfcrt and pfmdr1 genotypes of Plasmodium falciparum cocirculate with P. malariae, P. ovale spp., and P. vivax in northern Angola

Artemisinin-based combination therapy for malaria has become widely available across Africa. Populations of Plasmodium falciparum that were previously dominated by chloroquine (CQ)-resistant genotypes are now under different drug selection pressures. P. malariae, P. ovale curtisi, and P. ovale wallikeri are sympatric with P. falciparum across the continent and are frequently present as coinfections. The prevalence of human Plasmodium species was determined by PCR using DNA from blood spots collected during a cross-sectional survey in northern Angola. P. falciparum was genotyped at resistance-associated loci in pfcrt and pfmdr1 by real-time PCR or by direct sequencing of amplicons. Of the 3,316 samples collected, 541 (16.3%) contained Plasmodium species infections; 477 (88.2%) of these were P. falciparum alone, 6.5% were P. falciparum and P. malariae together, and 1.1% were P. vivax alone. The majority of the remainder (3.7%) harbored P. ovale curtisi or P. ovale wallikeri alone or in combination with other species. Of 430 P. falciparum isolates genotyped for pfcrt, 61.6% carried the wild-type allele CVMNK at codons 72 to 76, either alone or in combination with the resistant allele CVIET. No other pfcrt allele was found. Wild-type alleles dominated at codons 86, 184, 1034, 1042, and 1246 of the pfmdr1 locus among the sequenced isolates. In contrast to previous studies, P. falciparum in the study area comprises an approximately equal mix of genotypes associated with CQ sensitivity and with CQ resistance, suggesting either lower drug pressure due to poor access to treatment in rural areas or a rapid impact of the policy change away from the use of standard monotherapies.