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PubMed1997

Molecular analyses of HIV-1 group O and HIV-2 variants from Africa.

Genetic variation among HIV isolates creates challenges for their detection by serologic and genetic techniques. To characterize the sequence variation and its correlation to serologic diversity of HIV-1 Group O and HIV-2 isolates, samples were identified by differential reactivity in selected commercial and research assays. Analysis of sera from Equatorial Guinea (EG) led to identification of 4 HIV-1 Group O variants. Viral RNA, extracted from these samples was used to PCR amplify overlapping sequences of the entire envelope gene using multiple primer pairs. Sequence analysis indicated that the V3 loop nucleotide and protein sequences aligned more closely with HIVANT70 compared to other Group O sequences. The amino acid sequences at the octameric tip of the V3 loop were RIGPLAWY, RIGPMAWY, or GLGPLAVY. The tetrameric tip GPLA is represented only once in the published 1994 HIV database (Los Alamos) but was present in 2 of 4 of EG samples. The immuno-dominant region (IDR) sequences derived from EG sera were unique in that none of the sequences were completely homologous to other HIV-1 group O variants. Further, the HIV-1 group O sequence variation could be correlated with differential serologic reactivity using IDR peptides. Compared to HIV-1, the sequence information on HIV-2 isolates is relatively limited, though the HIV-2 isolates also show genetic variation similar to HIV-1. To further establish a correlation between the genetic diversity and serologic detection of HIV-2, plasma samples from Western Africa were evaluated. Eight samples were selected based on weak serologic reactivity to env proteins. PCR amplification and sequence analysis of the gag, env V3 loop, and env IDR regions indicated that the samples could be classified as subtypes A (4 samples), B (3 samples) and D (1 sample). Across the subtypes, there was conservation in the IDR region of the sequence WGCAFRQVCHT. This region is absolutely conserved among the majority of currently known HIV-2 and related SIV viruses (1994 HIV database). One subtype B sample had a unique sequence immediately adjacent to the IDR, however, this did not change the serologic detection using a HIV-2 IDR specific monoclonal antibody.

Acquired Immunodeficiency Syndrome↗
PubMed1989

[Animal reservoir of Trypanosoma (Trypanozoon) brucei gambiense in Central africa].

The actual available data, from Central as well as from Western Africa, allow us to assert that animals are naturally carriers of T.b. gambiense. Strains from pigs, sheeps and goats have been isolated. However, the importance of animals in the central-west african sleeping sickness epidemiology is still to be specified.

Africa, Central↗
PubMed2004

Molecular phylogenetics and taxonomy of the African mole-rats, genus Cryptomys and the new genus Coetomys Gray, 1864.

Cryptomys represents the most speciose and widely distributed genus of the Bathyergidae (Mammalia; Rodentia), a family of mole-rats endemic to sub-Saharan Africa. Throughout its range in southern, central, and western Africa, Cryptomys displays diversity in terms of morphology, patterns of behavior, and chromosome number, thus complicating the systematics of the group. A molecular phylogeny was obtained by separate and combined analyses of the mitochondrial 12S rRNA and intron I of the nuclear transthyretin gene for chromosomally and geographically diverse populations of Cryptomys. Our results show that Cryptomys sensu lato is comprised of two distinct and divergent monophyletic clades: hottentotus and mechowi. Based on our analyses, we propose the elevation of the mechowi clade to the genus Coetomys, retaining Cryptomys as the generic epithet of the South African hottentotus clade. This is supported by: (1) reciprocal monophyly of the two lineages based on independent datasets, (2) the level of sequence divergence observed between these lineages relative to other genera (i.e., Bathyergus and Georychus), and (3) different patterns of chromosomal evolution, with Cryptomys sensu stricto being karyotypically conserved (2N=54) and Coetomys exhibiting high karyotypic diversity (2N=40-78).

Animals↗
PubMed2000

Is malnutrition declining? An analysis of changes in levels of child malnutrition since 1980.

Nutritional status is the best global indicator of well-being in children. Although many surveys of children have been conducted since the 1970s, lack of comparability between them has made it difficult to monitor trends in child malnutrition. Cross-sectional data from 241 nationally representative surveys were analysed in a standard way to produce comparable results of low height-for-age (stunting). Multilevel modelling was applied to estimate regional and global trends from 1980 to 2005. The prevalence of stunting has fallen in developing countries from 47% in 1980 to 33% in 2000 (i.e. by 40 million), although progress has been uneven according to regions. Stunting has increased in Eastern Africa, but decreased in South-eastern Asia, South-central Asia and South America; Northern Africa and the Caribbean show modest improvement; and Western Africa and Central America present very little progress. Despite an overall decrease of stunting in developing countries, child malnutrition still remains a major public health problem in these countries. In some countries rates of stunting are rising, while in many others they remain disturbingly high. The data we have presented provide a baseline for assessing progress and help identify countries and regions in need of populationwide interventions. Approaches to lower child malnutrition should be based on successful nutrition programmes and policies.

Child↗
PubMed2002

Chromosomal characterization of Arvicanthis species (Rodentia, Murinae) from western and central Africa: implications for taxonomy.

A chromosome study of unstriped grass rats of the genus Arvicanthis (Rodentia, Murinae) in western and central Africa is presented. The observations extend the data available to 242 specimens from 59 localities. All individuals karyotyped belong to four karyotypic forms, or cytotypes, earlier described as ANI-1, ANI-2, ANI-3, and ANI-4 and are presumed to correspond to four distinct species. In order to provide diagnostic characters for these western and one central African Arvicanthis species, we standardized the chromosomal data available and developed a G- and C-banded chromosome nomenclature that allows easy species identification. Each form is characterized by a distinct geographical distribution, roughly following the biogeographical domains of western Africa, although their precise limits remain to be assessed. The sole area of sympatry detected is the region of the inner delta of the Niger River, where both ANI-1 and ANI-3 can be found. It is proposed that the three western African species ANI-1, ANI-3, and ANI-4 be renamed as A. niloticus, A. ansorgei, and A. rufinus, respectively.

Animals↗
PubMed1997

Demographic, ethnic, and geographic differences between human T cell lymphotropic virus (HTLV) type I-seropositive carriers and persons with HTLV-I Gag-indeterminate Western blots in Central Africa.

Using stringent Western blot (WB) criteria, human T cell lymphotropic virus (HTLV) type I seroprevalence among 3783 persons from representative rural populations of Cameroon averaged 1.1% and was higher in females (1.5%) and in Pygmies (2.0%), increasing with age. Furthermore, an HTLV-I Gag-indeterminate WB profile (HGIP), exhibiting strong reactivities to p19, p26, p28, p32, p36, and pr 53 but lacking both p24 and env reactivity, was observed in 1.6% of the same populations. The prevalence of the HGIP was similar between males and females, did not increase with age, and appeared to cluster in tropical forests of southern Cameroon, especially among Pygmies (reaching 4%). These contrasting epidemiologic features, together with the lack of detection by polymerase chain reaction of HTLV-I sequences in the peripheral blood mononuclear cells of the persons with HGIP, strongly suggest that such a WB profile does not appear to reflect an HTLV-I-related viral infection but possibly an environmental (viral or parasitic) factor endemic in tropical rain forest areas.

Adolescent↗
PubMed2006

History and structure of sub-Saharan populations of Drosophila melanogaster.

Drosophila melanogaster is an important model organism in evolutionary genetics, yet little is known about the population structure and the demographic history of this species within sub-Saharan Africa, which is thought to contain its ancestral range. We surveyed nucleotide variation at four 1-kb fragments in 240 individual lines representing 21 sub-Saharan and 4 Palearctic population samples of D. melanogaster. In agreement with recent studies, we find a small but significant level of genetic differentiation within sub-Saharan Africa. A clear geographic pattern is observed, with eastern and western African populations composing two genetically distinct groups. This pattern may have resulted from a relatively recent establishment of D. melanogaster in western Africa. Eastern populations show greater evidence for long-term stability, consistent with the hypothesis that eastern Africa contains the ancestral range of the species. Three sub-Saharan populations show evidence for cosmopolitan introgression. Apart from those cases, the closest relationships between Palearctic and sub-Saharan populations involve a sample from the rift zone (Uganda), suggesting that the progenitors of Palearctic D. melanogaster might have come from this region. Finally, we find a large excess of singleton polymorphisms in the full data set, which is best explained by a combination of population growth and purifying selection.

Africa South of the Sahara↗
PubMed2001

Molecular systematics and evolutionary history of kalats (genus Sheppardia): a pre-Pleistocene radiation in a group of African forest birds.

The African forest robins (akalats) of the genus Sheppardia are represented by eight forest-dwelling species with restricted distributions in tropical Africa. All but three are strictly montane, inhabiting isolated highland areas in eastern and western Africa. Due to their subtle plumage variation and almost wholly allopatric distribution, determining systematic relationships based upon morphology has proven difficult. However, akalats, due to their distribution, offer an ideal opportunity to test models of speciation within tropical forests. We therefore investigated the phylogeny of species of this genus from presently sampled regions of their distribution using mtDNA sequence analysis. We found that the monophyly of described species, even from disjunct populations, is well supported. However, relationships among species is generally poorly resolved, with support given only to the paired relationships S. montana/S. lowei, S. bocagei/S. gunningi, and S. aequatorialis/S. cyornithopsis. This dataset lent support to S. montana and S. lowei representing a superspecies. All species appear to have evolved rapidly from a common ancestor around the Miocene/Pliocene transition, a time of the last uplift of East Africa's montane region. Surprisingly, intraspecific radiations suggest a far more recent population expansion in the upper Pleistocene, concordant with major climatic variation and vegetational changes. We discuss the implications of our results in the light of previous discussions of the montane speciation model.

Africa↗
PubMed2001

Phylogeography of the human mitochondrial haplogroup L3e: a snapshot of African prehistory and Atlantic slave trade.

The mtDNA haplogroup L3e, which is identified by the restriction site +2349 MboI within the Afro-Eurasian superhaplogroup L3 (-3592 HpaI), is omnipresent in Africa but virtually absent in Eurasia (except for neighbouring areas with limited genetic exchange). L3e was hitherto poorly characterised in terms of HVS-I motifs, as the ancestral HVS-I type of L3e cannot be distinguished from the putative HVS-I ancestor of the entire L3 (differing from the CRS by a transition at np 16223). An MboI screening at np 2349 of a large number of Brazilian and Caribbean mtDNAs (encompassing numerous mtDNAs of African ancestry), now reveals that L3e is subdivided into four principal clades, each characterised by a single mutation in HVS-I, with additional support coming from HVS-II and partial RFLP analysis. The apparently oldest of these clades (transition at np 16327) occurs mainly in central Africa and was probably carried to southern Africa with the Bantu expansion(s). The most frequent clade (transition at np 16320) testifies to a pronounced expansion event in the mid-Holocene and seems to be prominent in many Bantu groups from all of Africa. In contrast, one clade (transition at np 16264) is essentially restricted to Atlantic western Africa (including Cabo Verde). We propose a tentative L3e phylogeny that is based on 197 HVS-I sequences. We conclude that haplogroup L3e originated in central or eastern Africa about 46,000 (+/-14,000) years ago, and was a hitchhiker of much later dispersal and local expansion events, with the rise of food production and iron smelting. Enforced migration of African slaves to the Americas translocated L3e mitochondria, the descendants of which in Brazil and the Caribbean still reflect their different regional African ancestries.

Africa↗
PubMed2004

Ser-249TP53 mutation in tumour and plasma DNA of hepatocellular carcinoma patients from a high incidence area in the Gambia, West Africa.

Hepatocellular carcinoma (HCC) is frequent in areas of high exposure to aflatoxin and high prevalence of HBV infection, such as western Africa and south-east China. A selective mutation in TP53 (AGG-->AGT at codon 249, Arg-->Ser) has been identified as a hotspot in HCCs from such areas, reflecting DNA damage caused by aflatoxin metabolites. Recent studies have shown that circulating free DNA can be retrieved from human plasma, and it is hypothesised that plasma DNA may serve as a source for biomarkers of tumorigenic processes. In our study, we have determined the prevalence of Ser-249 mutation, using a PCR-restriction digestion method, with selective use of short oligonucleotide mass spectrometry analysis (SOMA), in a series of 29 biopsy specimens of HCC from The Gambia in West Africa. Overall, we identified the Ser-249 mutation in 35% (10/29) of the tumours. In parallel, we tested 17 plasma samples from HCC patients with matching tumour tissue. The 249 status concordance between tumour tissues and matched plasma was 88.5%. These results indicate that the Ser-249 mutation is common in HCC in The Gambia (35%), although a higher prevalence has been reported in other regions with high population exposure to aflatoxin (e.g., eastern China: >50%). Moreover, our studies indicate that plasma is a convenient source of liver tumour-derived DNA, thus holding promise for earlier detection and diagnosis of cancer.

Adult↗
PubMed2003

The implications of virus diversity within the SAT 2 serotype for control of foot-and-mouth disease in sub-Saharan Africa.

SAT 2 is the serotype most often associated with outbreaks of foot-and-mouth disease (FMD) in livestock in southern and western Africa and is the only SAT type to have been recorded outside the African continent in the last decade. Its epidemiology is complicated by the presence of African buffalo (Syncerus caffer), which play an important role in virus maintenance and transmission. To assess the level of genetic complexity of this serotype among viruses associated with both domestic livestock and wildlife, complete VP1 gene sequences of 53 viruses from 17 countries and three different host species were analysed. Phylogenetic analysis revealed eleven virus lineages, differing from each other by at least 20 % in pairwise nucleotide comparisons, four of which fall within the southern African region, two in West Africa and the remaining five in central and East Africa. No evidence of recombination between these lineages was detected, and thus we conclude that these are independently evolving virus lineages which occur primarily in discrete geographical localities in accordance with the FMD virus topotype concept. Applied to the whole phylogeny, rates of nucleotide substitution are significantly different between topotypes, but most individual topotypes evolve in accordance with a molecular clock at an average rate of approximately 0.002 substitutions per site per year. This study provides an indication of the intratypic complexity of the SAT 2 serotype at the continental level and emphasizes the value of molecular characterization of diverse FMD field strains for tracing the origin of outbreaks.

Africa South of the Sahara↗
PubMed1999

Epidemiology of primary liver cancer.

Liver cancer (LC) ranks fifth in frequency in the world with an estimated number of 437,000 new cases in 1990. In developing countries, incidence rates are two- to three-fold higher than in developed countries. The geographic areas at highest risk are located in Eastern Asia, with age-adjusted incidence rates (AAIRs) ranking from 27.6 to 36.6 per 100,000 in men; Middle Africa, with AAIRs ranking from 20.8 to 38.1 per 100,000 in men; and some countries of Western Africa, with AAIRs ranking from 30 to 48 per 100,000 in men. The geographic areas at lowest LC risk are Northern Europe, Australia, New Zealand, and the Caucasian populations in North and Latin America, with AAIRs below 5.0 per 100,000 in men. Excess of LC incidence among men compared to women is universal, with sex ratios between 1.5 and 3.0. Significant variations in LC incidence among different ethnic groups living in the same geographical area and among migrants of the same ethnic groups living in different areas have been extensively described. The variability of LC incidence rates between countries and within countries, strongly suggests differences in exposure to risk factors. The role of chronic infection with the Hepatitis B and hepatitis C viruses (HBV and HCV) in the etiology of LC is well established. The attributable risk estimates for LC for each of these hepatotropic viruses vary among countries but the combined effects of persistent HBV or HCV infections account for well over 80% of LC cases worldwide. Other documented risk factors such as aflatoxin exposure in diets, cigarette smoking, alcohol consumption, and oral contraceptives may explain the residual variation between and within countries. Interactions between some risk factors have been postulated, and are subject of active research. New laboratory techniques and biological markers such as polymerase chain reaction detection of HBV DNA and HCV RNA, as well as specific mutations related to aflatoxin exposure may help to provide quantitative estimates of the risk related to each these factors.

Aged↗
PubMedDate not supplied

WHO's role in the development of nursing in the African region.

Over the past 20 years WHO has contributed tremendously to the development and progress of the nursing profession in Africa. Its biggest achievement has been in upgrading the varied and inconsistent nursing education and training programmes introduced prior to 1953 during the colonial period. Then there were no independent states. The British controlled most of eastern and southern Africa and some countries in the west, while the French ruled over most of the colonies in western Africa.

Africa↗
PubMed1997

Use of bovine somatotropin in the tropics: the effect of sometribove on milk production in western, eastern, and southern Africa.

Seven field studies conducted in western, eastern, and southern Africa to determine the effect of a prolonged-release formulation of bovine somatotropin (bST) administered at 14-d intervals on milk production of indigenous, crossbred, and purebred cows are described. Studies in Gambia showed that 334 mg of a prolonged-release formulation of bST increased milk production of N'Dama cattle by 205 ml/d, which represented a 22% increase in milk production, and increased the body weight gain of calves. In small dairy units in Zimbabwe, 500 mg of a prolonged-release formulation of bST increased milk production of crossbreds from 8.0 to 10.0 kg/d. Milk production response of crossbred cows in Kenya increased 2.5 kg/d after the lower dose rate (334 mg); no further increases were observed when the dose rate was increased to 500 mg. A study with Holsteins showed that delaying treatment of 500 mg of a prolonged-release formulation of bST from 90 to 120 or 150 d postpartum resulted in similar milk production responses of 3.5, 3.4, and 3.2 kg/d, respectively. The milk production response (6.1 kg/d) recorded in another study with Holsteins was attributed to an excellent plane of nutrition and delayed treatment initiation. For nonpregnant cows that were classified to be culled, the prolonged-release formulation of bST was efficacious and could potentially be used to extend lactation.

Africa, Eastern↗
PubMed1999

Description of Haemonchus placei (Place, 1893) (Nematoda, Trichostrongylidae, Haemonchinae), identification and intra-specific morphologic variability.

Haemonchus placei in cattle has never been completely described, possibly due to great morphological similarity with small ruminants Haemonchus contortus. It is newly described on one isolate from Argentina. It has clear distinct morphological features from sheep and goats Haemonchus contortus and presents only two female morphotypes (linguiform and knobbed) instead of three recorded in H. contortus. A key is proposed to identify females. Female as well as male Haemonchus placei from New World (Argentina, Mexico, USA) are morphologically different from those of Old World (Africa: Burkina-Faso, Mauritania and Ivory Coast) or Australia, possibly due to local evolution since their introduction several centuries ago from Africa or India. We propose to differentiate three sub-species, H. placei placei in Australia, H. placei africanus in western Africa and H. placei argentinensis in the New World.

Animals↗
PubMed1987

[Chemical resistance of Plasmodium falciparum in Africa. Current situation, implications for chemoprophylaxis].

Resistance of Plasmodium falciparum to antimalarial drugs is a growing worldwide problem in endemic areas. This is particularly obvious with chloroquine resistance which has been spreading throughout Africa since 1978. Initially localized on the Eastern coast of the continent, it has recently reached the Atlantic coast although Western Africa is as yet unaffected. This resistance has most probably arisen in the autochtonous population under the selective pressure of insufficient curative treatments as a result of self medication. It is most prevalent in children of urban areas but is often revealed in non immune expatriates. In addition, moderately resistant parasites in expatriates under chemoprophylaxis may lead to an insidious clinical form with a low or even negative parasitemia which raises diagnostic problems. Prophylactic and therapeutic schemes must take this new situation into account.

Africa↗
PubMed2006

The mammalian fauna associated with an archaic hominin skullcap and later Acheulean artifacts at Elandsfontein, Western Cape Province, South Africa.

The Elandsfontein site, Western Cape Province, South Africa, is well known for an archaic hominin skullcap associated with later Acheulean artifacts. The site has also provided nearly 13,000 mammalian bones that can be identified to skeletal part and taxon. The assemblage derives from 49 species, 15 of which have no historic descendants. Comparisons to radiometrically dated faunas in eastern Africa indicate an age between 1 million and 600 thousand years ago. Unique features of the fauna, including the late occurrence of a dirk-toothed cat and a sivathere, may reflect its geographic origin in a region that was notable historically for its distinctive climate and high degree of biotic endemism. Together, taxonomic composition, geomorphic setting, and pollen extracted from coprolites indicate the proximity of a large marsh or pond, maintained by a higher water table. The small average size of the black-backed jackals implies relatively mild temperatures. The sum of the evidence places bone accumulation during one of the mid-Pleistocene interglacials that were longer and cooler than later ones, including the Holocene. The geomorphic context of the fauna presents no evidence for catastrophe, and most deaths probably resulted from attritional factors that disproportionately killed the young and old. However, only the dental-age profile of long-horned buffalo supports this directly. Field collection methods biased skeletal-part representation, but originally, it probably resembled the pattern in the younger, marsh-edge Acheulean occurrence at Duinefontein 2, 45 km to the south. Excavation there exposed multiple vertebral spreads, which probably mark carcasses from which hominins or large carnivores removed the meatier elements. Bone damage at both sites suggests that, despite abundant artifacts, hominins were much less important than carnivores in the bone accumulation. Together with limited observations from other sites, Elandsfontein and Duinefontein provisionally suggest that Acheulean-age hominins obtained few large mammals, whether by hunting or scavenging.

Animals↗