Background and rationale
Malaria, the most common human parasitic disease, is both preventable and treatable, but continues to disproportionately affect children and pregnant women. Malaria continues to be a major health problem in low-income countries. In sub-Saharan Africa, more than 32 million pregnancies occur annually in malaria-endemic regions. In the absence of pregnancy-specific interventions, 12 million live-born deliveries (45% of all live-born deliveries) would be exposed to malaria infection, which would cause an estimated 900 000 low birthweight deliveries due to preterm labour and intrauterine growth retardation.
In Burkina Faso, malaria transmission is seasonal, during the months of August-December, and overlaps with the rainy season (July-October). The peak for malaria cases usually occurs in September-October. Malaria is one of the most common reasons for attending a health facility. The more common vectors are Anopheles gambiae sensu stricto, Anopheles funestus and Anopheles arabiensis. Plasmodium falciparum (P. falciparum) is the predominant malaria parasite and P. malariae and P. ovale are observed in 3-8% and 0.5-2% of malaria cases, respectively, most of them co-infected with Pf. Malaria in pregnancy is known to cause adverse effects on the mother and their offspring.
The WHO recommends the use of long-lasting insecticidal nets throughout pregnancy in malaria-endemic regions in sub-Saharan Africa, as well as intermittent preventive treatment (IPTp) with sulfadoxine–pyrimethamine in the second and third trimesters. Sulfadoxine–pyrimethamine is well tolerated, safe in the second and third trimesters, affordable, widely available, and can be given as a single dose, allowing for directly observed therapy at antenatal clinics. IPTp with sulfadoxine–pyrimethamine is very effective for reducing adverse outcomes of malaria during pregnancy, but is threatened by the emergence of widespread parasite resistance. The WHO also recommends prompt and efficient case management with artemisinin-based combination treatment (ACT) during the second and third trimester of pregnancy. Two keys factors for successful case management are the early detection of malaria, and their treatment with efficient antimalarial drugs. The detection of malaria during pregnancy is a challenge, however, as in endemic areas most infected women are asymptomatic.
In this thesis, the clinical presentation of malaria, the prevention using IPTp, the in vivo and also the ex vivo efficacies of the recommended antimalarial drugs were investigated. The main objectives were, (1) to evaluate the usefulness of clinical signs and symptoms in malaria diagnosis during pregnancy, (2) to determine the prevalence of molecular markers of SP resistance in asymptomatic and symptomatic malaria-infected pregnant women in Burkina Faso, (3) to determine ‘ex vivo’ the current efficacy of antimalarial drugs recommended by the NMCP in Burkina Faso, (4) to determine the efficacy and safety of ACTS used for uncomplicated malaria in pregnant women in Africa, and finally (5) to evaluate the pertinence of the NMCP recommendations for the treatment of malaria in pregnancy in Burkina Faso.
We carried out a longitudinal study in which all pregnant women attending either the routine antenatal care (ANC) or the outpatient clinic were asked to participate. During the visit and after having obtained written informed consent, women were divided into cases or controls. Cases had at least one of the following signs and symptoms: temperature ≥37.5°C (measured by electronic thermometer) or history of fever in the previous 48 hours, headache, pallor, arthromyalgia, convulsions, vomiting, dizziness, malaise, fatigue, enlarged liver, or enlarged spleen. Controls had none of these symptoms. For each case, two controls, matched by parity (0, 1–3, ≥4), gestational age (measured by fundal height) and seasonality (recruited within one month from the corresponding case) were recruited. Also, we determined the prevalence of molecular markers of SP resistance in asymptomatic and symptomatic malaria-infected pregnant women in Burkina Faso.
The second study was part of a multi-centre (Burkina Faso, Ghana, Malawi, and Zambia) trial (ClinicalTrials.gov ID: NCT00852423) investigating the efficacy and safety of four anti-malarial treatments, namely dihydroartemisinin–piperaquine (DHAPQ), mefloquine-artesunate (MQAS), artesunate-amodiaquine (ASAQ) and artemether-lumefantrine (AL), in falciparum malaria-infected pregnant women. Pregnant women were included in the trial if they fulfilled the following criteria: gestation ≥16 weeks, P. falciparum mono-infection at any density with or without symptoms, haemoglobin ≥7 g/dl, residence within the health facility catchment’s area, and willingness to deliver at the health facility. An ex vivo study on the drug sensitivity of isolates from pregnant women was nested into the trial in Burkina Faso. For the ex vivo study the inclusion was limited to women with a parasite density of at least 100/μl.
Usefulness of clinical signs and symptoms for the diagnosis of malaria during pregnancy
Six hundred (200 case and 400 matched controls) pregnant women were included, most of whom were in the second and third trimester of pregnancy. Malaria prevalence by microscopy was 49.0% among cases and 39.5% among controls (p = 0.03). Among malaria-infected women with symptoms, age was significantly related to malaria infection, with women <20 years more at risk than those ≥35 years old.
Fever, history of fever, headache, and dizziness each had a positive predictive value (PPV) around 50%, while for all the others the PPV was much lower. The highest PPVs were found when combining fever and dizziness (61.5%, 95%CI:35–82), and fever and vomiting (66.7%, 95%CI:20–93). If fever had been used to diagnose malaria, 47.2% of the febrile women would have been unnecessarily treated. Also 46.8% of the non-febrile women would have missed treatment for their malaria infection.
Prevalence of molecular markers of SP resistance in asymptomatic and symptomatic malaria-infected pregnant women in Burkina Faso
Among the 600 pregnant women recruited, 256 were diagnosed with malaria by microscopy. After genotyping, 61.2% (156/255) of the samples had the dhfr C59R and/or the S108N (55.7%, 142/255) mutations while only 12.2% (31/255) had the N51I mutation; no I164L mutation was found. There were 6 different dhfr alleles; the prevalence of the dhfr wild type was 30.2% (77/255).
Among the mutant alleles, the double mutation NRNI was the most frequent (35.7%, 91/255), followed by the triple mutation IRNI (11.4%, 29/255). More than a third of the samples (34.2%, 79/231) carried the dhps mutations A437G but none of them had the mutation K540E.
Antimalarials drugs: ex vivo efficacy of antimalarials in pregnancy
A total of 90 isolates (83.3%) had interpretable results for at least one of the study drugs, giving a culture success rate of 80%. Among the drugs currently in use, mefloquine (MQ) had the highest prevalence of resistant isolates (geometric mean IC50 = 1.1 nM; 95% CI 0.8–1.7) with 9.2%, followed by monodesethylamodiaquine (MDAQ) (geometric mean IC50 = 1.5; 95% CI 1.0–2.2) with 8.0%, and then quinine (QN) (geometric mean IC50 = 34.2; 95% CI 24.1–48.5) with 4.4%. Most drugs were equally active against the chloroquine (CQ)-sensitive and CQ-resistant isolates. There was a positive significant correlation between the sensitivity of dihydroartemisinin (DHA) and both MQ and CQ, between CQ and lumefantrine (LM) and between MDAQ and MQ.
Efficacy and safety of ACTs use in pregnant women in Africa
ACTs have proven to be effective in treating uncomplicated malaria in pregnancy. They have shown a good efficacy profile confirming the recommendations for their use. The results of safety, another parameter to take into account, varied between treatments. Women treated with the combinations ASAQ or MQAS had more adverse events than AL and DHAPQ. AL, although efficacious, was associated with a higher risk of re-infections due to the short elimination half-life of LM. DHAPQ had good efficacy, a long post treatment prophylaxis period and an acceptable safety profile.
Conclusions and recommendations
Detection of malaria infections during pregnancy: is clinical diagnosis (screening-based on signs and symptoms) useful?
Signs and symptoms were not discriminative for malaria infections. Restricting treatment to symptomatic pregnant women would be an inadequate strategy to reduce the morbidity and mortality associated with malaria. All pregnant women should be either systematically screened for malaria infection and treated if positive or given SP any time they visit a health facility, provided this is done at least one month apart.
Malaria in pregnancy prevention: efficacy of SP in Burkina Faso
The prevalence of the triple mutation known to confer resistance in vitro to pyrimethamine was relatively low indicating that SP can still be used as IPTp. Assuming that pregnant women are generally infected with low parasite densities, SP should clear malaria infections at the time of administration. For all pregnant women, including the non-infected, SP would protect them for a few weeks.
Antimalarials drugs: ex vivo efficacy of antimalarials in pregnancy
The few resistant isolates to MDAQ suggest that the combination ASAQ is efficacious during pregnancy. Relative low IC50 was also found with two partner drugs of ACT, LM and MQ. This is an indication that the combinations AL and ASMQ are efficacious treatments.
ACTs for the treatment of pregnant women with malaria
DHAPQ and AL have shown good safety and efficacy profiles.
Rationale and pertinence of the national malaria guidelines in Burkina Faso
Pregnant women should be systematically screened for malaria, by RDT or microscopy, when attending a health facility. ASAQ and AL showed good efficacy profile confirming their choice by the NMCP as first line treatment. Finally, SP can still be used as IPTp in our context.