Inland valley rice production systems and malaria infection and disease in the forest region of western Côte d'Ivoire

Background: This study aimed to determine the epidemiological impact of rice cultivation in inland valleys on malaria in the forest region of western Côte d'Ivoire. The importance of malaria was compared in terms of prevalence and parasite density of infections and also in terms of clinical malaria incidence between three agro-ecosystems: (i) uncultivated inland valleys, (R0), (ii) inland valleys with one annual rice cultivation in the rainy season, (R1) and (iii) developed inland valleys with two annual rice cultivation cycles, (R2). Methods: Between May 1998 and March 1999, seven villages of each agro-ecosystem (R0, R1 and R2) were randomly selected among villages pooled by farming system. In these 21 villages, a total of 1,900 people of all age groups were randomly selected and clinically monitored during one year. Clinical and parasitological information was obtained by active case detection of malaria episodes carried out during eight periods of five consecutive days scheduled at six weekly intervals and by cross-sectional surveys. Results: Plasmodium falciparum was the principal parasite observed in the three agro-ecosystems. A level of holoendemicity of malaria was observed in the three agro-ecosystems with more than 75% of children less than 12 months old infected. Geometric mean parasite density in asymptomatic persons varied between 180 and 206 P. falciparum asexual forms per μL of blood and was associated with season and with age, but not with farming system. The mean annual malaria incidence rate reached 0.7 (95% IC 0.5-0.9) malaria episodes per person in R0, 0.7 (95% IC 0.6-0.9) in R1 and 0.6 (95% IC 0.5-0.7) in R2. The burden of malaria was the highest among children under two years of age, with at least four attacks by person-year. Then malaria incidence decreased by half in the two to four-year age group. From the age of five years, the incidence was lower than one attack by person-year. Malaria incidence varied with season with more cases in the rainy season than in the dry season but not with farming system. Conclusion: In the forest area of western Côte d'Ivoire, inland valley rice cultivation was not significantly associated with malaria burden

PFCRT and DHFR-TS Sequences for Monitoring Drug Resistance in Adzopé Area of Côte d’Ivoire After the Withdrawal of Chloroquine and Pyrimethamine

Purpose: Drug resistance is probably the greatest challenge to most malaria-control programmes. The goal of this study was to evaluate polymorphisms in parasite resistance gene markers, pfcft and dhfr, from falciparum malaria isolates collected in Adzopé City, Côte d’Ivoire in 2007. Methods: Blood samples were collected in filter paper from 72 children infected with Plasmodium falciparum living in Adzopé area. Plasmodium falciparum DNA was extracted and nested PCRs were performed using specific primers of pfcrt and dhfr-ts. During the study, chloroquine and sulphadoxinepyrimethamine (which previously were the first-and second-line treatments, respectively, for malaria in Côte d’Ivoire) were not given to the enrolled children, having been withdrawn in 2004. Results: The results revealed the presence of the mutant-type pfcrt and dhfr-ts in 51 (62.2 %) and 29 (35.4 %) samples, respectively. The mutant-type pfcrt alleles consisted of four single mutations (Met74/Asn75/Thr76) and 47 triple mutations (Ile74/Glu75/Thr76). However, the frequency distribution of mutations in dhfr-ts was 35.4 % for dhfr-Asn108, 17 % for dhfr-Ile51 and 21 % for dhfr-Arg59. Conclusion: The results of this study show high presence of chloroquine (CQ) resistance markers while for sulphadoxine-pyrimethamine (SP), a much lower prevalence was detected for the markers under study. Chloroquine remains an inadequate drug for malaria therapy in the study region. Furthermore, in spite of the official withdrawal of CQ and SP in favour of the arteminisin-based combinations (ACTs), it appears the population of this area continues to use the drugs via self-medication

In vitro susceptibility of Plasmodium falciparum to monodesethylamodiaquine, quinine, mefloquine and halofantrine in Abidjan (Côte d'Ivoire)

Background: Malaria is the primary cause of hospitalization in Côte d'Ivoire. Early treatment is one of the strategies to control this illness. However, the spread of resistance of Plasmodium falciparum to antimalarial drugs can seriously compromise this strategy. Objectives: The aim of this study was to assess the in vitro susceptibility of P. falciparum to monodesethylamodiaquine and aminoalcohols in Abidjan (Côte d'Ivoire). Methods: We assessed the in vitro susceptibility of isolates collected from patients with uncomplicated malaria by using the WHO optical microtest technique. Results: The proportions of resistance to monodesethylamodiaquine, méfloquine and halofantrine were 12.5%, 15.6% and 25.9%, respectively. For quinine, none of isolates showed evidence of in vitro resistance. However, two isolates (6.1%) had IC50 values above 300 nM. The IC50 of each drug was positively and significantly correlated to that of the other three drugs, and the correlation was higher between halofantrine and mefloquine. Conclusions: Our results showed that the in vitro chloroquine resistance reported in previous studies has been extended to other antimalarial drugs investigated in this study except for quinine. Therefore, it is necessary to implement a long-term monitoring system of antimalarial drug resistance.Key words: in vitro test, Plasmodium falciparum, monodesethylamodiaquine, quinine, mefloquine, halofantrine, Abidjan (Côte d'Ivoire)

Contribution à l'épidémiologie de la malaria et à son contrôle en Côte d'Ivoire

En Côte-d'Ivoire, le développement de la culture de riz dans les bas-fonds n'a pas d'effet ni sur l'infection ni sur la maladie palustre, en zone de savane comme en zone de forêt. Le parasite Plasmodium falciparum a été trouvé très résistant au traitement par la chloroquine en zone forestière alors qu'il y était sensible en zone de savane. Inversement, le vecteur Anopheles gambiae s.l. a été trouvé résistant aux insecticides pyréthrinoïdes en zone de savane alors qu'il y était sensible en zone forestière. Cette résistance est liée à une mutation du gène kdr. La mise en place au niveau national des combinaisons thérapeutiques à base d'artémisinine a permis de résoudre le problème de la résistance des parasites à la chloroquine. Par ailleurs, il a été démontré que les moustiquaires imprégnées de pyréthrinoïdes utilisées dans la lutte antivectorielle ont conservé leur efficacité contre la morbidité de la malaria dans les zones où An. gambiae s.l. a été trouvé résistant à ces insecticides