Abstract
Sulfadoxine-pyrimethamine (SP) is the recommended drug for intermittent preventive treatment of malaria in pregnancy in most of sub-Saharan Africa. Resistance to SP is related to mutations in the dhfr and dhps gene of Plasmodium falciparum. This study determined the prevalence of Pfdhfr and Pfdhps polymorphisms found in asymptomatic pregnant women attending antenatal care in Calabar, Nigeria. From October 2013 to November 2014, asymptomatic pregnant women attending antenatal care clinics were enrolled after obtaining informed consent. Malaria diagnosis testing was done using thick and thin smears. Dried blood spot filter papers were collected. Parasite DNA was extracted from the filter papers using a chelex extraction. Extraction was followed by nested PCR and restriction enzyme digestion. P. falciparum infection was detected by microscopy in 7% (32/459) participants. Twenty-eight P. falciparum isolates were successfully genotyped. In the Pfdhfr gene, the triple mutation was almost fixed; S108N mutation was (100%), N51I (93%) and C59R mutations (93%), whereas the I164L mutation was absent. The prevalence of Pfdhps S436A, A437G, A581G and A613S mutations was 82.1% (23/28), 96.4% (27/28), 71.4% (20/28) and 71.4% (20/28) respectively. The K540E mutation was absent. The prevalence of the Pfdhfr triple mutation IRNI was 92.9% (26/28). The efficacy of SP as IPTp in Southeast Nigeria may be severely threatened. The continuous monitoring of SP molecular markers of resistance is required to assess thresholds. The evaluation of alternative preventive treatment strategies and drug options for preventing malaria in pregnancy may be necessary.
Highlights
IntroductionMalaria remains the most dangerous vector-borne infectious disease in tropical and subtropical countries, causing 219 million clinical episodes and 437,000 deaths only in 2017 (WHO, 2018).The impressive global decrease of malaria incidence observed since 2010 has been considered one of the greatest achievements of the public health sector of the past decade
This assay exists in two forms: i) the in vitro RSA0-3h is performed on cultureadapted parasite lines and is useful in elucidating the molecular basis of artemisinin derivatives (ART) resistance by for instance experimentally validate candidate molecular markers; and ii) the ex vivo ring-stage survival assay (RSA) performed on uncultured parasite isolates collected directly from malaria patients in the field which is recommended for mapping the geographical emergence and spread of ART-resistant parasites in real-time, providing actionable information for national malaria control programmes (Witkowski, et al, 2013, Ménard et al, 2015)
Freshly collected parasite isolates were exposed to pharmacologically relevant concentrations of DHA for 6 h and survival rates were assessed by microscopy after recovery by counting the proportion of viable parasitaemia in comparison to non-exposed isolates (DMSO controls)
Summary
IntroductionMalaria remains the most dangerous vector-borne infectious disease in tropical and subtropical countries, causing 219 million clinical episodes and 437,000 deaths only in 2017 (WHO, 2018).The impressive global decrease of malaria incidence observed since 2010 has been considered one of the greatest achievements of the public health sector of the past decade. In 2018, a 5-year project called TIPTOP (acronym of Transforming Intermittent Preventive Treatment for Optimal Pregnancy) was started in 4 countries of sub-Saharan Africa, including Nigeria This community-based program ( entering phase 2) aims to dramatically increase the number of pregnant women receiving IPTp (≥ 3 doses of SP) of 50% by distributing qualityassured SP in the communities and in the ANC clinics as well as to generate evidence to inform change in policy recommendations across sub-Saharan Africa (WHO, 2019b). Another important promoter of resistance development in both P. falciparum and P. vivax parasites is represented by the introduction of resistant malaria into non-immune populations such as refugees or migrants. Rwanda is geographically close to Uganda, the only African country where high ex vivo RSA survival rates in isolates from slow clearance infections (i.e., infections with parasite clearance half life greater than 5 hours) have been observed (Ikeda et al, 2018)
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