Lucie Raharimalala

Assessment of the efficacy of antimalarial drugs recommended by the National Malaria Control Programme in Madagascar: Up-dated baseline data from randomized and multi-site clinical trials

BackgroundIn order to improve the monitoring of the antimalarial drug resistance in Madagascar, a new national network based on eight sentinel sites was set up. In 2006/2007, a multi-site randomized clinical trial was designed to assess the therapeutic efficacy of chloroquine (CQ), sulphadoxine-pyrimethamine (SP), amodiaquine (AQ) and artesunate plus amodiaquine combination (ASAQ), the antimalarial therapies recommended by the National Malaria Control Programme (NMCP).MethodsChildren between six months and 15 years of age, with uncomplicated falciparum malaria, were enrolled. Primary endpoints were the day-14 and day-28 risks of parasitological failure, either unadjusted or adjusted by genotyping. Risks of clinical and parasitological treatment failure after adjustment by genotyping were estimated using Kaplan-Meier survival analysis. Secondary outcomes included fever clearance, parasite clearance, change in haemoglobin levels between Day 0 and the last day of follow-up, and the incidence of adverse events.ResultsA total of 1,347 of 1,434 patients (93.9%) completed treatment and follow-up to day 28. All treatment regimens, except for the chloroquine (CQ) treatment group, resulted in clinical cure rates above 97.6% by day-14 and 96.7% by day-28 (adjusted by genotyping). Parasite and fever clearance was more rapid with artesunate plus amodiaquine, but the extent of haematological recovery on day-28 did not differ significantly between the four groups. No severe side-effects were observed during the follow-up period.ConclusionThese findings (i) constitute an up-dated baseline data on the efficacy of antimalarial drugs recommended by the NMCP, (ii) show that antimalarial drug resistance remains low in Madagascar, except for CQ, compared to the bordering countries in the Indian Ocean region such as the Comoros Archipelago and (iii) support the current policy of ASAQ as the first-line treatment in uncomplicated falciparum malaria.

Lessons learnt from the six decades of chloroquine use (1945–2005) to control malaria in Madagascar

On the island of Madagascar, malaria was nearly eradicated in the highland areas and malaria transmission was significantly decreased in the coastal areas between the 1940s and 1960s. The success of the control programme was primarily achieved by chloroquine (CQ) use at the community level. CQ was administered to children weekly on a routine basis for malaria prevention in the period 1949-1971. Then, the Malagasy Government was unable to financially support the malaria control programme. The malarial situation worsened in the 1980s, partly due to the shortage of CQ. A malaria epidemic occurred. To deal with this epidemic, massive CQ use was urgently adopted. CQ has remained the first-line drug since 1945, but the prevalence of Plasmodium falciparum carrying the pfcrt mutation associated with CQ resistance remains low (<3%). However, late CQ treatment failure has been reported and the prevalence may be as high as 35% during 14-day follow-up since 1982. In an effort to eliminate malaria as a public health problem, a shift from CQ to artemisinin-based combination therapy has been advocated by a new policy since December 2005. A change of this kind is complex and the lessons learnt from the six decades of CQ use are of the utmost importance to achieve malaria control.

Validity of Lot Quality Assurance Sampling to optimize falciparum malaria surveys in low-transmission areas

To control the reappearance of malaria in the Madagascan highlands, indoor house-spraying of DDT was conducted from 1993 until 1998. Before the end of the insecticide-spraying programme, a surveillance system was set up to allow rapid identification of new malaria epidemics. When the number of suspected clinical malaria cases notified to the surveillance system exceeds a predetermined threshold, a parasitological survey is carried out in the community to confirm whether or not transmission of falciparum malaria is increasing. Owing to the low specificity of the surveillance system, this confirmation stage is essential to guide the activities of the control programme. For this purpose, Lot Quality Assurance Sampling (LQAS), which usually requires smaller sample sizes, seemed to be a valuable alternative to conventional survey methods. In parallel to a conventional study of Plasmodium falciparum prevalence carried out in 1998, we investigated the ability of LQAS to rapidly classify zones according to a predetermined prevalence level. Two prevalence thresholds (5% and 15%) were tested using various sampling plans. A plan (36, 2), meaning that at least 2 individuals found to be positive among a random sample of 36, enabled us to classify a community correctly with a sensitivity of 100% and a specificity of 94%. LQAS is an effective tool for rapid assessment of falciparum malaria prevalence when monitoring malaria transmission.

Madagascan isolates of Plasmodium falciparum showing low sensitivity to artemether in vitro

In Madagascar, although chloroquine (CQ) remains the first-line treatment of choice for malaria, the gradual spread of resistance to this antimalarial drug is of increasing concern. As part of a larger investigation of the effectiveness of the second- and third-line drugs used to treat malaria, the in-vitro susceptibilities of Plasmodium falciparum collected in Madagascar to CQ, mefloquine (MQ) and artemether (ART) were therefore investigated. Median inhibitory concentrations (IC50) were determined for isolates collected from residents of two villages in the foothills of the central highlands. The IC50 for ART ranged from 0.23–17.50 nm [N = 51; geometric mean = 4.02 nm; 95% confidence interval (Cl) = 2.99–5.05 nm], four isolates exhibiting IC50 (> 12 nm) indicative of resistance to this drug. The artemether IC50 were found to be correlated with those of CQ (N = 46; Spearmans r = 0.51; P = 0.0002), which varied widely (0.4–254.3 nm; mean = 23.4 nm; CI = 7.1–39.7 nm; N= 46). Five (11%) of the 46 isolates exposed to CQ in vitro were considered resistant to this drug (i.e. to have IQ50 > 100 nm), with IC50 ranging from 109–245.3 nm (mean =171.6 nm; CI = 110.4–232.8 nm). However, all the CQ-resistant isolates were considered sensitive to ART and vice versa. All the isolates tested also appeared sensitive to MQ (IC50 = 2.21–43.1 nm; mean = 10.5 nm; CI = 7.95–13.07 nm; N= 46), the IC50 for MQ being correlated with those for CQ(N= 46; Spearmans r=0.46; P = 0.001). There was no significant correlation between ART and MQ activities. Although the sample was fairly small, the present results indicate that P. falciparum in Madagascar is generally becoming less sensitive to CQ and ART. The observation of a correlation between the IC50 for these two drugs perhaps indicates that artemisinin derivatives would be better used in combination with antimalarial drugs other than 4-aminoquinolines.

Current absence of pyrimethamine resistance of Plasmodium falciparum in Madagascar

Reported are (i) the in vitro sensitivities to pyrimethamine of 58 primary Plasmodium falciparum isolates collected from the foothill and coastal areas in Madagascar, and (ii) the results of the amplification of the dhfr gene followed by restriction enzyme digestion of codon 108. Testing took place between March 1999 and February 2000 and all the isolates were sensitive to pyrimethamine. The 50% inhibitory concentration (IC50) ranged from 0.1 nM to 242.9 nM (mean IC50 = 30.5 nM, median IC50 = 4.8 nM, 95% confidence interval 17.6-43.4 nM). None of the 58 isolates yielded digestion products after polymerase chain reaction product treatment with BsrI or ScrFI. The results indicate the absence of the dhfr encoding Asn108 and Thr108 among tested clinical isolates. The sensitivity of P. falciparum to pyrimethamine-based antimalarial drugs in Madagascar is discussed.

Longitudinal survey of malaria morbidity over 10 years in Saharevo (Madagascar): further lessons for strengthening malaria control

BackgroundMadagascar has been known for having bio-geo-ecological diversity which is reflected by a complex malaria epidemiology ranging from hyperendemic to malaria-free areas. Malaria-related attacks and infection are frequently recorded both in children and adults living in areas of low malaria transmission. To integrate this variability in the national malaria control policy, extensive epidemiological studies are required to up-date previous records and adjust strategies.MethodsA longitudinal malaria survey was conducted from July 1996 to June 2005 among an average cohort of 214 villagers in Saharevo, located at 900 m above the sea. Saharevo is a typical eastern foothill site at the junction between a costal wet tropical area (equatorial malaria pattern) and a drier high-altitude area (low malaria transmission).ResultsPassive and active malaria detection revealed that malaria transmission in Saharevo follows an abrupt seasonal variation. Interestingly, malaria was confirmed in 45% (1,271/2,794) of malaria-presumed fevers seen at the health centre. All four Plasmodia that infect humans were also found: Plasmodium falciparum; Plasmodium vivax, Plasmodium malariae and Plasmodium ovale. Half of the malaria-presumed fevers could be confirmed over the season with the highest malaria transmission level, although less than a quarter in lower transmission time, highlighting the importance of diagnosis prior to treatment intake. P. falciparum malaria has been predominant (98%). The high prevalence of P. falciparum malaria affects more particularly under 10 years old children in both symptomatic and asymptomatic contexts. Children between two and four years of age experienced an average of 2.6 malaria attacks with P. falciparum per annum. Moreover, estimated incidence of P. falciparum malaria tends to show that half of the attacks (15 attacks) risk to occur during the first 10 years of life for a 60-year-old adult who would have experienced 32 malaria attacks.ConclusionThe incidence of malaria decreased slightly with age but remained important among children and adults in Saharevo. These results support that a premunition against malaria is slowly acquired until adolescence. However, this claims for a weak premunition among villagers in Saharevo and by extension in the whole eastern foothill area of Madagascar. While the Malagasy government turns towards malaria elimination plans nowadays, choices and expectations to up-date and adapt malaria control strategies in the foothill areas are discussed in this paper.

South-East Asian ovalocytosis among the population of the Highlands of Madagascar: a vestige of the island's settlement

In the Madagascar Highlands, 0.76% of children from 168 random primary schools, and 19 of 150 families from 3 villages, had oval-shaped erythrocytes. Most harboured the deletion in the band 3 gene characteristic of South-East Asian ovalocytosis. This genetic trait supports the Indonesian origin of the Madagascar settlement.

PCR characterization of isolates from various endemic areas: diversity and turn over of Plasmodium falciparum populations are correlated with transmission

We have previously investigated the extend of genetic diversity within Plasmodium fakiparum isolates by using an improved cultivation technique for the cloning of parasites (Mazier et al. 1984) and further characterizing those by 4 distinct typing techniques @ruilhe et al. in preparation). Two series of 33 clones derived from 2 isolates obtained in primary attack cases were produced by cloning on the day of sampling and cultivating them together with hepatocytes feeder layers, a method which was found able to promote the growth of parasites not adapted to culture conditions. Drug response and karyotype analysis demonstrated a large degree of diversity among these clones. Restriction Fragment Length Polymorphism, revealed by probing with the pPFrep20 sequence, also confirmed the above results, however showed a high degree of genetic relatedness of the clones, which was unexpected from the results of the other techniques. Finally, amplification by polymerase chain reaction (PCR) of a polymorphic region of 4 genes (see below) revealed respectively 6 and 4 patterns of allelic forms in 24 clones for each isolate. Therefore, due to genetic relatedness of the clones, PCR did not prove to be the most discriminating technique. However, in view of its great sensitivity, it has the major advantage of being able to reveal the Co-existence of distinct parasite populations in an isolate without the need to cultivate parasites in order to produce enough DNA.

Pefloxacin for Falciparum Malaria: Only Modest Success

The spread of chloroquine-resistant Plasmodium falciparum strongly indicated the need for new safe and effective antimalarial drugs. In addition to their antibacterial action, fluoroquinolone antib...

Mefloquine-resistant strains of Plasmodium falciparum in Madagascar: impact on tourists and public health.

Although the national policy for malaria control in Madagascar is to use chloroquine as the first line of treatment, mefloquine has been and is recommended to travellers to the country, both for malaria prevention and cure. The in-vitro susceptibility of Plasmodium falciparum to mefloquine was therefore assessed during a prospective surveillance study in various areas in Madagascar, including the tourist sites of Nosy-be and Sainte Marie. Of the 254 isolates of P. falciparum successfully tested, 232 (90.9%) were sensitive to mefloquine, 12 (4.7%) showed decreased susceptibility (40 nM < IC50 < 50 nM), and 10 (3.9%) were resistant (IC50 > 50 nM). Five (50%) of the resistant strains and nine (75%) of those with decreased susceptibility were from coastal areas or the two tourist sites. The drug pressure that could have induced the resistance observed could therefore be related to the donation of antimalarials, such as mefloquine, by tourists to local populations. The residents of the coastal areas take any donated drugs as self-medication, ignoring recommended doses and durations of treatment. This situation has two main consequences: (1) there is an urgent need to control the abusive and incorrect use of antimalarial drugs in Madagascar, to safeguard the effectiveness of chemotherapy in the future; and (2) these increases in resistance compromise the efficiency of the antimalarial chemoprophylaxis currently recommended to tourists. The use of mefloquine can no longer be considered as a guarantee of protection against malaria in coastal areas and other sites frequented by tourists.