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The distribution of M and S molecular forms of Anopheles gambiae sensu stricto across Nigeria was determined. The molecular form of 40 to 45 specimens per locality from 9 localities was determined using mostly the same specimens from our recent study of genetic differentiation of A. gambiae across Nigeria (Onyabe & Conn, 2001). These samples were previously genotyped at 10 microsatellite loci, 5 located within chromosome inversions and 5 outside inversions. Both molecular forms occurred throughout the country, with no apparent relationship to the ecological transition from dry savannah in the north to humid forest in southern Nigeria. In all localities, however, 1 form or the other occurred virtually exclusively. No hybrids between forms were found. Across all loci, F(ST) values were as high within molecular forms as between forms. Regardless of molecular form, F(ST) values calculated across loci within inversions were much higher (range 0.0016 to 0.1988) than those calculated across loci outside inversions (range -0.0035 to 0.0260). Genetic distance was not significantly correlated with geographical distance within either form (P> 0.05). These observations suggest that, in addition to partial reproductive barriers between molecular forms, selection is a major factor shaping genetic differentiation of A. gambiae across Nigeria.

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Background: The therapeutic efficacy of artesunate plus amodiaquine and artemether/ lumefantrine were assessed in an area of Nigeria with high levels of Plasmodium falciparum resistance to chloroquine and sulphadoxine-pyrimethamine.

BackgroundThe use of anti-malarial drug combinations with artemisinin, or with one of its derivatives, is now widely recommended to overcome drug resistance in falciparum malaria. Fixed-dose combination of artemisinin and naphthoquine is a new generation artemisinin combination therapy (ACT) offered as a single dose therapy. The aim of the study was to assess the therapeutic efficacy, safety and tolerability of three dosage schedules of fixed-dose combination of artemisinin (125 mg) and naphthoquine (50 mg) for treating uncomplicated Plasmodium falciparum malaria among adolescents and adults in Calabar, South-east Nigeria.MethodA total of 121 patients aged ≥15 years with uncomplicated P. falciparum malaria were enrolled and randomly assigned to three dosage schedules: (A) 700 mg (four tablets) single dose; (B) 700 mg 12-hourly x two doses; and (C) 1,400 mg (eight tablets) single dose. Patients were observed for 28 days, with clinical, parasitological, and haematological assessments.ResultsA total of 108 patients completed the study. The overall 28-day cure rate was 88.9%. Day 28-cure rates of the three dosage schedules were 85.3%, 93.1% and 88.9% for Group A, B and C respectively. Adverse events were few and mild, the commonest being weakness and headache; there was no serious adverse event.ConclusionConcerns for emergence of parasite resistance due to the use of artemisinin-naphthoquine as single dose regimen is likely to compromise the usefulness of this potentially important combination treatment. A robust multi-centre trial is recommended to evaluate a three-day regimen with potentials to achieve high cure rates while minimizing the risk of emergence of resistant parasite strains.