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Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Genomic DNA of samples from several populations of malaria mosquito Anopheles messeae belonging to the macullipennis Paleoarctic complex was examined using digestion with ten restriction enzymes and electrophoresis in polyacrylamide gel. The patterns of DNA repeat fraction in the EcoRII hydrolysate in two cryptic forms of An. messeae characterized by common inversion polymorphism were shown to be different. The genomic differences in mixed sympatric groups and those between geographically remote populations of the different forms were identical. No interindividual, intrafamilial, inter- and intrapopulation variation was revealed in either form. The electrophoregrams of individuals belonging to the same the B form but having different combinations of inversion chromosomal variants in the karyotypes were identical. Analysis of taxonprints in the forms showed that individuals with the same karyotype may belong to different forms. These results coupled with evidence on the ecological features of and assortative mating in An. messeae populations demonstrated that the examined forms are not conspecific. Our results indicate that taxonprint analysis is the most reliable and precise test for the presence of conspecific forms in a large sympatric zone.
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PMID:[Inversion polymorphism and the divergence of two cryptic forms of Anopheles messeae (Diptera, Culicidae) at the level of genomic DNA repeats]. 1155 31

In Thailand, approximately 8% of patients treated for vivax malaria are found subsequently to have coinfection with Plasmodium falciparum. A P. falciparum histidine rich protein 2 (PfHRP-2) dipstick test was evaluated as a predictor of mixed infections with subpatent P. falciparum in a prospective study of 238 patients admitted to the hospital with acute vivax malaria. Of these, 23 (10%) had subsequent development of falciparum malaria without reexposure. Patients with cryptic P. falciparum infection had a significantly lower mean (standard deviation) hematocrit than those with P. vivax alone: 29.6 (7.6%) versus 37.2 (6.4%) (P < 0.0001). Using microscopic appearance of P. falciparum after the start of treatment as the reference standard, the PfHRP-2 test was 74% sensitive and 99% specific in predicting mixed infections with subpatent P. falciparum parasitemia at presentation. The PfHRP-2 dipstick test may be a useful adjunct to microscopy in areas where mixed infections are common.
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PMID:Identification of cryptic coinfection with Plasmodium falciparum in patients presenting with vivax malaria. 1171 19

Polymerase chain reaction detection revealed cryptic Plasmodium falciparum infections in 21 of 160 samples collected from Thai patients diagnosed (by microscopy) with vivax malaria. The clinical and biological significance of these mixed infections is discussed in the context of chloroquine resistance and the low inoculation rates which characterize malaria epidemiology in Thailand.
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PMID:Cryptic Plasmodium falciparum parasites in clinical P. vivax blood samples from Thailand. 1192 99

The members of the Anopheles punctulatus group are major vectors of malaria and Bancroftian filariasis in the southwest Pacific region. The group is comprised of 12 cryptic species that require DNA-based tools for species identification. From 1984 to 1998 surveys were carried out in northern Australia, Papua New Guinea and on islands in the southwest Pacific to determine the distribution of the A. punctulatus group. The results of these surveys have now been completed and have generated distribution data from more than 1500 localities through this region. Within this region several climatic and geographical barriers were identified that restricted species distribution and gene flow between geographic populations. This information was further assessed in light of a molecular phylogeny derived from the ssrDNA (18S). Subsequently, hypotheses have been generated on the evolution and distribution of the group so that future field and laboratory studies may be approached more systematically. This study suggested that the ability for widespread dispersal was found to have appeared independently in species that show niche-specific habitat preference (Anopheles farauti s.s. and A. punctulatus) and conversely in species that showed diversity in their larval habitat (Anopheles farauti 2). Adaptation to the monsoonal climate of northern Australia and southwest Papua New Guinea was found to have appeared independently in A. farauti s.s., A. farauti 2 and Anopheles farauti 3. Shared or synapomorphic characters were identified as saltwater tolerance (A. farauti s.s. and Anopheles farauti 7) and elevational affinities above 1500 m (Anopheles farauti 5, Anopheles farauti 6 and A. farauti 2).
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PMID:Distribution and evolution of the Anopheles punctulatus group (Diptera: Culicidae) in Australia and Papua New Guinea. 1194 29

Anopheles (Anopheles) sinensis [Wiedemann (1828)] is a member of the hyrcanus species group, and it has been incriminated as the natural or experimental malaria vectors in the Republic of Korea, Japan, China, and Indonesia. In Thailand, however, An. sinensis seems to be of little medical importance. Hybridization tests among the three iso-female lines (isolines) of An. sinensis [i.e., Form A (X, Y1) and Form B (X, Y2) (Thailand strain), and Form B (X, Y2) (Korean strain)] were established based on two distinct types of metaphase chromosomes and geographical differences The chromosomal form of the Korean strain was first identified from this study. Results of reciprocal and back crosses indicated that both karyotypic forms of theAn. sinensis Thailand and Korean strains were genetically compatible, and provided viable progenies and completely synaptic polytene chromosomes. The sequences of the rDNA internal-transcribed spacer 2 (ITS2) and mitochondrial cytochrome c oxidase subunit II (COII) among the An. sinensis strains were nearly identical to each other, and the intraspecific sequence variability was very low (0.0-0.6%). Sequence comparisons among the cryptic inter-species (i.e., An. sinensis, An. lesteri, and An. yatsushiroensis), however, revealed extensive divergence, and the intraspecific variability ranged from 12.2 to 34.6%. Therefore, it is concluded from these results and previous vector ability studies that the An. sinensis Forms A and B exhibit cytological polymorphic races that have different vector abilities in their transmission of malaria, depending on their geographical locations.
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PMID:Intraspecific hybridization of Anopheles sinensis (Diptera: Culicidae) strains from Thailand and Korea. 1244 91

Attempts to reconstruct the phylogenetic history of the Anopheles gambiae cryptic species complex have yielded strongly conflicting results. In particular, An. gambiae, the primary African malaria vector, is variously placed as a sister taxon to either Anopheles arabiensis or Anopheles merus. The recent divergence times for members of this complex complicate phylogenetic analysis, making it difficult to unambiguously implicate interspecific gene flow, versus retained ancestral polymorphism, as the source of conflict. Using sequences at four unlinked loci, which were determined from multiple specimens within each of five species in the complex, we found contrasting patterns of sequence divergence between the X chromosome and the autosomes. The isolation model of speciation assumes a lack of gene flow between species since their separation. This model could not be rejected for An. gambiae and An. arabiensis, although the data fit the model poorly. On the other hand, evidence from gene trees supports genetic introgression of chromosome 2 inversions between An. gambiae and An. arabiensis, and also points to more broad scale genetic exchange of autosomal sequences between this species pair. That such exchange has been relatively recent is suggested not only by the lack of fixed differences at three autosomal loci but also by the sharing of full haplotypes at two of the three loci, which is in contrast to several fixed differences and considerably deeper divergence on the X. The proposed acquisition by An. gambiae of sequences from the more arid-adapted An. arabiensis may have contributed to the spread and ecological dominance of this malaria vector.
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PMID:Semipermeable species boundaries between Anopheles gambiae and Anopheles arabiensis: evidence from multilocus DNA sequence variation. 1294 38

A number of parasitic protists and fungi have adopted extremely specialised characteristics of morphology, biochemistry, and molecular biology, sometimes making it difficult to discern their evolutionary origins. One aspect of several parasitic groups that reflects this is their metabolic organelles, mitochondria and plastids. These organelles are derived from endosymbiosis with an alpha-proteobacterium and a cyanobacterium respectively, and are home to a variety of core metabolic processes. As parasites adapted, new demands, or perhaps a relaxation of demands, frequently led to significant changes in these organelles. At the extreme, the organelles are degenerated and transformed beyond recognition, and are referred to as "cryptic". Generally, there is no prior cytological evidence for a cryptic organelle, and its presence is only discovered through phylogenetic analysis of molecular relicts followed by their localisation to organelle-like structures. Since the organelles are derived from eubacteria, the genes for proteins and RNAs associated with them are generally easily recognisable, and since the metabolic activities retained in these organelles are prokaryotic, or at least very unusual, they often serve as an important target for therapeutics. Cryptic mitochondria are now known in several protist and fungal parasites. In some cases (e.g., Trichomonas), well characterised but evolutionarily enigmatic organelles called hydrogenosomes were shown to be derived from mitochondria. In other cases (e.g., Entamoeba and microsporidia), "amitochondriate" parasites have been shown to harbour a previously undetected mitochondrial organelle. Typically, little is known about the functions of these newly discovered organelles, but recent progress in several groups has revealed a number of potential functions. Cryptic plastids have now been found in a small number of parasites that were not previously suspected to have algal ancestors. One recent case is the discovery that helicosporidian parasites are really highly adapted green alga, but the most spectacular case is the discovery of a plastid in the Apicomplexa. Apicomplexa are very well-studied parasites that include the malaria parasite, Plasmodium, so the discovery of a cryptic plastid in Apicomplexa came as quite a surprise. The apicomplexan plastid is now very well characterised and has been shown to function in the biosynthesis of fatty acids, isopentenyl diphosphate and heme, activities also found in photosynthetic plastids.
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PMID:Cryptic organelles in parasitic protists and fungi. 1471 Oct 83

Plasmodium vivax is the most prevalent malaria infection and is an important cause of morbidity in Central and South America and Asia. P. vivax is generally sensitive to the common antimalarial drugs but high level resistance to chloroquine and/or pyrimethamine has been documented in some geographic locations. In the studies reviewed here, the therapeutic responses to antimalarial and antibacterial drugs in vivax malaria have been assessed in the Bangkok Hospital for Tropical Diseases. The evaluated drugs consisted of the eight most widely used antimalarial drugs and anti-bacterial drugs that possess antimalarial activities (tetracycline, doxycycline, clindamycin or azithromycin). The activities of these drugs in descending order of parasite clearance times were artesunate, artemether, chloroquine, mefloquine, quinine, halofantrine, primaquine, followed by the antibacterial drugs and lastly sulfadoxine-pyrimethamine. Clinical responses to sulfadoxine-pyrimethamine were also poor with evidence of high grade resistance in 42% of the patients. Of the four antibacterial drugs, clindamycin was more effective than azithromycin and can be an alternative to the tetracyclines. Except for chloroquine and mefloquine which have long plasma half lives and may therefore suppress first relapses, the cumulative cure rates for the short acting antimalarial drugs were similar. Double infection with Plasmodium falciparum was common and usually manifested 3-4 weeks following clearance of vivax malaria. The prevalence of cryptic falciparum malaria was 8-15% and was higher in patients treated with less potent antimalarial drugs. Follow-up studies have revealed that the relapse time in Thai patients with vivax malaria is on average only 3 weeks, but can be suppressed by the slowly eliminated antimalarial drugs such as chloroquine and mefloquine. For accurate comparison of relapse/recrudescence rates in vivax malaria, at least 2 month's follow-up is required. It can be concluded that in malarious areas of Thailand, double infection with P. falciparum and P. vivax is common affecting at least 25% of the patients and usually manifests as sequential illnesses. P. vivax in Thailand is sensitive to chloroquine but has acquired high grade resistance to sulfadoxine-pyrimethamine.
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PMID:Therapeutic responses to antimalarial and antibacterial drugs in vivax malaria. 1474 61

Anopheles fluviatilis, one of the major vectors of malaria in India, is a complex of at least three cryptic species provisionally designated as species S, T, and U. Identification of the cryptic species of An. fluviatilis complex is of paramount importance in disease control program due to contrasting differences in their vectorial efficiency, preference for feeding on humans, and resting behavior. Species S, T, and U are morphologically indistinguishable at any stage of their life cycle and can be identified only by the examination of species-specific fixed inversions in the polytene chromosomes. We report an allele-specific polymerase chain reaction assay for the differentiation of members of An. fluviatilis complex, which is based on differences in nucleotide sequences in D3 domain of 28S ribosomal DNA. The assay was evaluated against chromosomally examined individuals from different localities with different sympatric associations and was found to differentiate unambiguously all the members of the complex.
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PMID:Differentiation of members of the Anopheles fluviatilis species complex by an allele-specific polymerase chain reaction based on 28S ribosomal DNA sequences. 1497 94

In central China, Anopheles anthropophagus is considered the primary malaria vector and Anopheles sinensis is a secondary vector. Identification of these two cryptic species would facilitate studies on malaria transmission and the application of control measures. At present, the only reliable morphological markers occur in the egg stage, making this approach impractical for any large scale field studies. In this study, we report on the development of a polymerase chain reaction (PCR)-restriction fragment length polymorphism procedure involving the ribosomal DNA ITS2 region for discrimination of these species. The PCR-amplified product size of the ITS2 was 574 bp for An. anthropophagus and 594 bp for An. sinensis. Diagnostic restriction fragment length polymorphisms appeared with the restriction enzymes RsaI or HinfI. This diagnostic PCR was tested on mosquitoes collected from different locations throughout China. Specimens identified morphologically as An. anthropophagus in the adult and egg stage from one location in Quangdong Province were found to be An. sinensis, while specimens from Liaoning Province, which were variable in their egg morphology, were found to be An. anthropophagus. The presence of An. anthropophagus in Liaoning Province extends the range of this species north to 42 degrees N. The ITS2 spacer sequence was used in a maximum parsimony phylogenetic reconstruction of six members of the Hyrcanus group, two members of the Lesteri subgroup, and one member of the Nigerrimus subgroup, with the resulting molecular groupings at odds with the current morphological groupings.
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PMID:Molecular identification of the malaria vectors Anopheles anthropophagus and Anopheles sinensis (Diptera: Culicidae) in central China using polymerase chain reaction and appraisal of their position within the Hyrcanus group. 1498 40


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