Distinct human immunodeficiency virus type 1 subtype A virus circulating in West Africa: sub-subtype A3.
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Phylogenetic analyses demonstrate significant diversity in worldwide circulating strains of human immunodeficiency virus type 1 (HIV-1). Detailed studies have revealed a complex pattern of intersubtype recombinations, as well as evidence of sub-subtypes circulating in various populations. In this study, we characterized an HIV-1 strain that had previously been identified as a distinct subcluster within the subtype A radiation based on partial sequence data. These viruses were of particular interest given that we recently found that their prevalence was significantly higher in dually infected individuals compared to women who were singly infected with HIV-1. Five viruses isolated from commercial sex workers in Dakar, Senegal, were full-length PCR amplified and sequenced. Phylogenetic analyses indicated that, whereas three of these viruses were closely related and clustered overall within the HIV-1 subtype A radiation, they were distinct from previously characterized sub-subtype A1 and A2 viruses. The clustering pattern was maintained in the individual gag, pol, and env regions of the genome. Distance calculations between these viruses, which we termed A3, and other reference sub-subtype A1 and A2 viruses fell in the range of distances between previously characterized sub-subtype groups. In addition, we found evidence of two A3-containing recombinants in our cohort. These recombinants are mosaics composed of sequence from both sub-subtype A3 and CRF02_AG, the major circulating recombinant form in this West African population. Based on phylogenetic analyses, we propose that the group of viruses found in the Dakar sex worker cohort, previously referred to as HIV-1 A subcluster 2, be referred to as HIV-1 sub-subtype A3. (+info)
PAX4 gene variations predispose to ketosis-prone diabetes.
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Ketosis-prone diabetes (KPD) is a rare form of type 2 diabetes, mostly observed in subjects of west African origin (west Africans and African-Americans), characterized by fulminant and phasic insulin dependence, but lacking markers of autoimmunity observed in type 1 diabetes. PAX4 is a transcription factor essential for the development of insulin-producing pancreatic beta-cells. Recently, a missense mutation (Arg121Trp) of PAX4 has been implicated in early and insulin deficient type 2 diabetes in Japanese subjects. The phenotype similarities between KPD and Japanese carriers of Arg121Trp have prompted us to investigate the role of PAX4 in KPD. We have screened 101 KPD subjects and we have found a new variant in the PAX4 gene (Arg133Trp), specific to the population of west African ancestry, and which predisposes to KPD under a recessive model. Homozygous Arg133Trp PAX4 carriers were found in 4% of subjects with KPD but not in 355 controls or 147 subjects with common type 2 or type 1 diabetes. In vitro, the Arg133Trp variant showed a decreased transcriptional repression of target gene promoters in an alpha-TC1.6 cell line. In addition, one KPD patient was heterozygous for a rare PAX4 variant (Arg37Trp) that was not found in controls and that showed a more severe biochemical phenotype than Arg133Trp. Clinical investigation of the homozygous Arg133Trp carriers and of the Arg37Trp carrier demonstrated a more severe alteration in insulin secretory reserve, during a glucagon-stimulation test, compared to other KPD subjects. Together these data provide the first evidence that ethnic-specific gene variants may contribute to the predisposition to this particular form of diabetes and suggest that KPD, like maturity onset diabetes of the young, is a rare, phenotypically defined but genetically heterogeneous form of type 2 diabetes. (+info)
Towards an understanding of barriers to condom use in rural Benin using the Health Belief Model: a cross sectional survey.
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BACKGROUND: HIV/AIDS is the most dramatic epidemic of the century that has claimed over two decade more than 3 million deaths. Sub Saharan Africa is heavily affected and accounts for nearly 70% of all cases. Despite awareness campaigns, prevention measures and more recently promotion of anti viral regimens, the prevalence of cases and deaths is still rising and the prevalence of systematic condom use remains low, especially in rural areas. This study identifies barriers to condom use based on the Health Belief Model (HBM) in Benin, West Africa. METHODS: The study was a cross-sectional survey conducted from June to July 2002. Two hundred fifty one (251) individuals were interviewed using a structured questionnaire adapted from a standardized WHO/GAP questionnaire. A logistic regression was used to identify factors associated with condom use. RESULTS: In spite of satisfactory knowledge on HIV/AIDS transmission, participants are still at high risk of contracting the infection. Sixty three (63) percents of the interviewees reported being able to recognize infected people, and condom use during the last occasional intercourse was declared by only 36.8% of males and 47.5% of females. Based on the HBM, failure to use condom was related to its perceived lack of efficacy [OR = 9.76 (3.71-30.0)] and perceived quality [OR = 3.61 (1.31-9.91)]. CONCLUSIONS: This study identifies perceived efficacy (incomplete protective effect) and perceived utilization-related problem (any reported problem using condoms) as the main barriers to condom use. Hence, preventions strategies based on increasing perceived risk, perceived severity or adequate knowledge about HIV/AIDS may not be sufficient to induce condom use. These data will be useful in designing and improving HIV/AIDS prevention outreach programs in Sub Saharan Africa. (+info)
Climate drives the meningitis epidemics onset in west Africa.
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BACKGROUND: Every year West African countries within the Sahelo-Sudanian band are afflicted with major meningococcal meningitis (MCM) disease outbreaks, which affect up to 200,000 people, mainly young children, in one of the world's poorest regions. The timing of the epidemic year, which starts in February and ends in late May, and the spatial distribution of disease cases throughout the "Meningitis Belt" strongly indicate a close linkage between the life cycle of the causative agent of MCM and climate variability. However, mechanisms responsible for the observed patterns are still not clearly identified. METHODS AND FINDINGS: By comparing the information on cases and deaths of MCM from World Health Organization weekly reports with atmospheric datasets, we quantified the relationship between the seasonal occurrence of MCM in Mali, a West African country, and large-scale atmospheric circulation. Regional atmospheric indexes based on surface wind speed show a clear link between population dynamics of the disease and climate: the onset of epidemics and the winter maximum defined by the atmospheric index share the same mean week (sixth week of the year; standard deviation, 2 wk) and are highly correlated. CONCLUSIONS: This study is the first that provides a clear, quantitative demonstration of the connections that exist between MCM epidemics and regional climate variability in Africa. Moreover, this statistically robust explanation of the MCM dynamics enables the development of an Early Warning Index for meningitis epidemic onset in West Africa. The development of such an index will undoubtedly help nationwide and international public health institutions and policy makers to better control MCM disease within the so-called westward-eastward pan-African Meningitis Belt. (+info)
Blood parasites of some West African rainforest birds.
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A total of 969 birds representing 121 species of 21 families from the West African nations of Cameroon, Equatorial Guinea and Ivory Coast were examined for haematozoa using thin blood smears; 277 individuals (28.6%) harbored blood parasites. The parasites identified included species of Haemoproteus (7.7% prevalence), Plasmodium (10.7%), Leucocytozoon (4.6%), and Trypanosoma (7.3%). In addition, microfilariae of filariid nematodes were present in 3.6% of the individuals examined. The birds were collected over a period of 12 years, from 1989-2001, from rainforest and ecotone habitats. We report a relatively high prevalence of parasites in colonial nesting birds, and two species of ground nesting birds. In addition, we compared data from bird species collected at a site identical to a previously published study, and did not find significant differences in parasite prevalence between the two years constituting two different seasons. Our results are also compared to other studies in Africa that implement similar and different methodologies. (+info)
Plasma choline and betaine and their relation to plasma homocysteine in normal pregnancy.
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BACKGROUND: Plasma concentrations of total homocysteine (tHcy) decrease during pregnancy. This reduction has been investigated in relation to folate status, but no study has addressed the possible role of betaine and its precursor choline. OBJECTIVE: We investigated the courses of plasma choline and betaine during normal human pregnancy and their relations to plasma tHcy. DESIGN: Blood samples were obtained monthly; the initial samples were taken at gestational week (GW) 9, and the last samples were taken approximately 3 mo postpartum. The study population comprised 50 women of West African descent. Most of the subjects took folic acid irregularly. RESULTS: Plasma choline (geometric x; 95% reference interval) increased continuously during pregnancy, from 6.6 (4.5, 9.7) micromol/L at GW 9 to 10.8 (7.4, 15.6) micromol/L at GW 36. Plasma betaine decreased in the first half of pregnancy, from 16.3 (8.6, 30.8) micromol/L at GW 9 to 10.3 (6.6, 16.2) micromol/L at GW 20 and remained constant thereafter. We confirmed a reduction in plasma tHcy, and the lowest concentration was found in the second trimester. From GW 16 onward, an inverse relation between plasma tHcy and betaine was observed. Multiple regression analysis showed that plasma betaine was a strong predictor of plasma tHcy from GW 20 onward. CONCLUSIONS: The steady increase in choline throughout gestation may ensure choline availability for placental transfer with subsequent use by the growing fetus. Betaine becomes a strong predictor of tHcy during the course of pregnancy. Both of these findings emphasize the importance of choline and betaine status during normal human pregnancy. (+info)
Genetic structure in four West African population groups.
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BACKGROUND: Africa contains the most genetically divergent group of continental populations and several studies have reported that African populations show a high degree of population stratification. In this regard, it is important to investigate the potential for population genetic structure or stratification in genetic epidemiology studies involving multiple African populations. The presences of genetic sub-structure, if not properly accounted for, have been reported to lead to spurious association between a putative risk allele and a disease. Within the context of the Africa America Diabetes Mellitus (AADM) Study (a genetic epidemiologic study of type 2 diabetes mellitus in West Africa), we have investigated population structure or stratification in four ethnic groups in two countries (Akan and Gaa-Adangbe from Ghana, Yoruba and Igbo from Nigeria) using data from 372 autosomal microsatellite loci typed in 493 unrelated persons (986 chromosomes). RESULTS: There was no significant population genetic structure in the overall sample. The smallest probability is associated with an inferred cluster of 1 and little of the posterior probability is associated with a higher number of inferred clusters. The distribution of members of the sample to inferred clusters is consistent with this finding; roughly the same proportion of individuals from each group is assigned to each cluster with little variation between the ethnic groups. Analysis of molecular variance (AMOVA) showed that the between-population component of genetic variance is less than 0.1% in contrast to 99.91% for the within population component. Pair-wise genetic distances between the four ethnic groups were also very similar. Nonetheless, the small between-population genetic variance was sufficient to distinguish the two Ghanaian groups from the two Nigerian groups. CONCLUSION: There was little evidence for significant population substructure in the four major West African ethnic groups represented in the AADM study sample. Ethnicity apparently did not introduce differential allele frequencies that may affect analysis and interpretation of linkage and association studies. These findings, although not entirely surprising given the geographical proximity of these groups, provide important insights into the genetic relationships between the ethnic groups studied and confirm previous results that showed close genetic relationship between most studied West African groups. (+info)
Prioritizing species conservation: does the Cape Verde kite exist?
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The Cape Verde kite (Milvus milvus fasciicauda) is considered to be one of the rarest birds of prey in the world and at significant risk of extinction. For this reason there is great interest in both the taxonomic and the population status of this group. To help resolve its taxonomic status, we provide phylogenetic analyses based on three mitochondrial genes for a sampling of kites in the genus Milvus, including a broad geographical sampling of black kites (Milvus migrans), red kites (Milvus milvus), Cape Verde kite museum specimens collected between 1897 and 1924, and five kites trapped on the Cape Verde Islands during August 2002. We found that the historical Cape Verde kites, including the type specimen, were non-monophyletic and scattered within a larger red kite clade. The recently trapped kites from the Cape Verde Islands were all phylogenetically diagnosed as black kites. Our findings suggest that the traditional Cape Verde kite is not a distinctive evolutionary unit, and the case for species status, as recently suggested by others, is not supported. We do find support for recognition of at least one clade of yellow-billed kites, traditionally considered as a black kite subspecies, as a distinctive phylogenetic species. (+info)