Indigenous evolution of Plasmodium falciparum pyrimethamine resistance multiple times in Africa.

Objectives: Resistance to pyrimethamine in Plasmodium falciparum is conferred by mutations in the gene encoding dihydrofolate reductase (DHFR). It is known that DHFR double mutants have evolved independently in multiple geographic areas, whereas the triple mutant prevalent in Africa appears to have originated in south-east Asia. In this study, we investigated whether other triple mutants may have evolved independently in Africa.

Failure to detect Plasmodium vivax in West and Central Africa by PCR species typing.

Background: Plasmodium vivax is estimated to affect 75 million people annually. It is reportedly absent, however, from west and central Africa due to the high prevalence of the Duffy negative phenotype in the indigenous populations. Despite this, non-African travellers consistently return to their own countries with P.

Changing patterns of forest malaria among the mobile adult male population in Chumkiri District, Cambodia.

Forest malaria remains a major problem in many parts of Southeast Asia and South America. In Cambodia, where a significant reduction of malaria morbidity and mortality has been observed in the last 20 years, the forest malaria situation was studied in Chumkiri District by analysing the available passive case detection data and conducting malariometric (n=1018) and questionnaire surveys (n=374) in four forest-fringe villages. There has been a decreasing trend of malaria incidence from 2001.

Independent evolution of pyrimethamine resistance in Plasmodium falciparum isolates in Melanesia.

Pyrimethamine resistance in Plasmodium falciparum has previously been shown to have emerged once in Southeast Asia, from where it spread to Africa. Pyrimethamine resistance in this parasite is known to be conferred by mutations in the gene encoding dihydrofolate reductase (dhfr). We have analyzed polymorphisms in dhfr as well as microsatellite haplotypes flanking this gene in a total of 285 isolates from different regions of Melanesia (Papua New Guinea, Vanuatu, and the Solomon Islands) and Southeast Asia (Thailand and Cambodia).

Role of pfmdr1 mutations on chloroquine resistance in Plasmodium falciparum isolates with pfcrt K76T from Papua New Guinea.

The N86Y mutation in pfmdr1 is reported to play an additional role for the chloroquine resistance in Plasmodium falciparum isolates. However, not much has been done to clarify whether this mutation augments the level of chloroquine resistance in the isolates harboring pfcrt K76T mutation. We compared the in vitro chloroquine efficacy between pfcrt K76T mutant parasites with or without N86Y mutation from Papua New Guinea.

Rapid selection of dhfr mutant allele in Plasmodium falciparum isolates after the introduction of sulfadoxine/pyrimethamine in combination with 4-aminoquinolines in Papua New Guinea.

To overcome the declining efficacy of the 4-aminoquinolines in Papua New Guinea, sulfadoxine/pyrimethamine (SP) was combined with the 4-aminoquinolines as the first line treatment for falciparum malaria since 2000. To assess how this change had affected SP resistant gene polymorphisms, we determined allele frequencies of dhfr and dhps in 113 Plasmodium falciparum isolates from Wewak, East Sepik of Papua New Guinea in 2002 and 2003. In dhfr, double mutant (ACNRNVI) was the predominant allele with a prevalence of 91%.

Austronesian origin of the 27-bp deletion of the erythrocyte band 3 gene in East Sepik, Papua New Guinea inferred from mtDNA analysis.

The 27-bp deletion in the erythrocyte band 3 gene (B3Delta27) constitutes a genetic basis for Southeast Asian and Melanesian ovalocytosis. The distribution of B3Delta27 has been interpreted to reflect malaria selection or dispersal of the recent expansion of Austronesian-speaking populations. To explore these two hypotheses, we examined eight malarious populations of the East Sepik Province of Papua New Guinea (PNG) that speak both the Austronesian and Papuan languages.

The involvement of neutrophils in the resistance to Leishmania major infection in susceptible but not in resistant mice.

To understand the immunomodulatory roles of neutrophils in Leishmania major infection, we examined the expression of cytokine and chemokine mRNAs from neutrophils of the infected resistant C3H/HeJ and susceptible BALB/c mice. We also examined the effects of neutrophil depletion on the expression of cytokine by peritoneal macrophages and draining lymph node cells and on the footpad lesions and parasite burdens in these mice. Neutrophils from resistant C3H/HeJ but not from susceptible BALB/c mice expressed mRNAs for IL-12p40, IFN-gamma,TNF-alpha and monokine induced by IFN-gamma(MIG).

Anemia and malaria at different altitudes in the western highlands of Kenya.

Malaria associated severe anemia in children is the most important complication of Plasmodium falciparum infection in sub-Saharan Africa. To evaluate anemia and malaria in an area with recurrent malaria epidemics in the western highlands of Kenya, we conducted cross-sectional surveys in four "lowland" (1440-1660 m) and two "highland" (1960 and 2040 m) villages in 2002. Among 1314 subjects randomly selected from all age groups, the overall prevalence of anemia (hemoglobin, Hb < 11 g/dl) was 14% and P.

Malaria dispersal among islands: human mediated Plasmodium falciparum gene flow in Vanuatu, Melanesia.

A comparison of human and Plasmodium falciparum gene flow patterns in the model island system of Vanuatu, the limit of malaria in the Pacific reveals that human movement is essential for long, but not short distance P. falciparum gene flow. This suggests that long distance movement of humans may accelerate the evolution and spread of drug resistance and therefore exacerbate the global malaria problem.

Analysis of Sepik populations of Papua New Guinea suggests an increase of CYP2C19 null allele frequencies during the colonization of Melanesia.

The cytochrome P450 (CYP) isozyme CYP2C19 metabolizes clinically important drugs, including the anti-malarial proguanil currently used for multi-drug resistant Plasmodium falciparum malaria. CYP2C19 activity varies among geographical regions due to high frequencies of two null alleles (CYP2C19*2/*3) in Asian and especially Pacific populations. Previously, we reported an unprecedentedly high frequency of CYP2C19 poor metabolizers (PM) within populations of Vanuatu, which suggested even higher PM frequencies in Papua New Guinea.

Recovery of chloroquine sensitivity and low prevalence of the Plasmodium falciparum chloroquine resistance transporter gene mutation K76T following the discontinuance of chloroquine use in Malawi.

In 1993, Malawi stopped treating patients with chloroquine for Plasmodium falciparum malaria because of a high treatment failure rate (58%). In 1998, the in vitro resistance rate to chloroquine was 3% in the Salima District of Malawi; in 2000, the in vivo resistance rate was 9%. We assayed two genetic mutations implicated in chloroquine resistance (N86Y in the P.

Evaluation of dot-ELISA for serological diagnosis of amebiasis.

We improved the dot enzyme-linked immunosorbent assay (dot-ELISA) reported by Itoh and Sato, and assessed the usefulness of this test for the diagnosis of amebiasis. The sensitivity of dot-ELISA was compared with that of plate ELISA, the indirect hemagglutination test (IHA), and the indirect fluorescent antibody test (IFA) for the diagnosis of amebiasis. Of 37 serum samples from patients with documented amebiasis, 36 (97.