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PubMed1993

Identification of single specimens of the Anopheles gambiae complex by the polymerase chain reaction.

A ribosomal DNA-polymerase chain reaction (PCR) method has been developed for species identification of individuals of the five most widespread members of the Anopheles gambiae complex, a group of morphologically indistinguishable sibling mosquito species that includes the major vectors of malaria in Africa. The method, which is based on species-specific nucleotide sequences in the ribosomal DNA intergenic spacers, may be used to identify both species and interspecies hybrids, regardless of life stage, using either extracted DNA or fragments of a specimen. Intact portions of a mosquito as small as an egg or the segment of one leg may be placed directly into the PCR mixture for amplification and analysis. The method uses a cocktail of five 20-base oligonucleotides to identify An. gambiae, An. arabiensis, An. quadriannnulatus, and either An. melas in western Africa or An. melas in eastern and southern Africa.

Animals↗

PubMed1995

Cerebral malaria in children.

A retrospective chart review for the 1993 calendar year identified 187 children with cerebral malaria admitted to a large teaching hospital in central Ghana, West Africa. The most common clinical presentation was fever, sensorial depression and convulsions in young children experiencing their first episode of malaria. One-half had splenomegaly. Additional features, seen in decreasing frequency, were hepatomegaly, vomiting, abdominal pain and headache. Long term sequelae were identified in 9% and mortality in 6%. Risk factors for central nervous system disease were negative history for previous malaria (P < 0.005) and a high percentage of parasitemia (P < 0.001). Death or long term sequelae were associated with multiple seizures and prolonged sensorial depression. The incidence of malaria is currently increasing in Western Africa and young children are more likely than older children to develop severe disease.

Adolescent↗

PubMed2001

[Aphthous esophagitis as an atypical manifestation of a primary HIV-infection].

HISTORY: A 56-year-old patient from Burkina Faso (Western Africa), living in Switzerland for 12 years, was referred to hospital because of acute onset of severe painful swallowing. He returned from a 3-week visit to his home country 4 weeks prior to admission. CLINICAL FINDINGS AND INVESTIGATIONS: Whereas clinical and radiological findings were normal, routine laboratory testing showed increased parameters of infection. Endoscopy revealed an aphthous esophagitis, suggesting a viral infection. Biopsy confirmed an active erosive esophagitis. Herpes simplex, cytomegalovirus and candida could not be detected in the biopsy specimens (immunohistochemistry, microbiology) and in serum. Both, the anti-HIV screening-test and the Western blot antibody test for HIV-1 and HIV-2 were negative on admission. Because of the persistent suspicion for an underlying HIV Infection, a combined HIV p24-antigen/ antibody-test was performed, showing an indeterminate result. Following PCR-based tests for HIV-RNA on days 5 and 12 showed 86 100 and 103 700 HIV-1 RNA copies/ml plasma, respectively, revealing the diagnosis of primary HIV-1 infection. Subsequent serological testing (WB) finally documented HIV-1 antibody seroconversion, showing indeterminate and positive results on days 5 and 19, respectively. TREATMENT AND COURSE: Within 5 days all signs of infection returned to normal and as documented by endoscopy on day 12, the esophagitis healed up spontaneously. As the patient intended to go back to his home country and the CD4 cell count was 615 x10(6)/l, no antiviral therapy was initiated. CONCLUSION: This case report is the first demonstrating an atypical symptomatic primary HIV-infection prior to seroconversion, which presented itself exclusively as an aphthous esophagitis with no symptoms of the classic acute retroviral syndrome. Therefore, each clinical suspicion of an underlying HIV-infection should be followed up carefully, even if the patient presents with unusual symptoms.

Acute Disease↗

PubMed2003

Molecular epidemiology of contagious bovine pleuropneumonia by multilocus sequence analysis of Mycoplasma mycoides subspecies mycoides biotype SC strains.

Contagious bovine pleuropneumonia is a bacterial disease caused by Mycoplasma mycoides subsp. mycoides SC (MmmSC), and included in list A of the Office International des Epizooties. It is one of the major constraints to cattle raising in sub-Saharan and south-western Africa and also a threat to all countries currently free of the disease. MmmSC strains were considered very homogeneous until 1995, when various techniques such as enzymatic restriction of whole DNA or Southern blotting showed that this was not the case. These techniques are unfortunately difficult to standardize and require the extraction of DNA from an MmmSC culture. We therefore decided to investigate the possibility of constructing a molecular epidemiology tool based on multilocus sequence analysis (MLSA) with PCR amplification of various loci followed by sequencing. Six loci were found suitable for this purpose and an additional PCR was designed to detect the presence of an 8.8kb deletion described by others in some strains. Fifteen different MLSA profiles were evidenced in our study. They allowed a clear distinction between European, south-western African and sub-Saharan strains. In addition, the results obtained on strain PO1967 confirmed its European origin, even though it does not exhibit the 8.8kb deletion. This new tool for contagious bovine pleuropneumonia may prove particularly useful for identifying MmmSC strains in countries at risk from contamination. It can also easily be refined by adding more strains or other loci of interest.

Africa↗

PubMed2002

Assessment of Helicoverpa Armigera resistance to pyrethroid insecticides in northern Cameroon.

In Central Africa savannas, the noctuid Helicoverpa armigera (Hübner) is a major pest of cotton and vegetable crops (including tomato and okra) which directly affects production by attacking fruit-bearing organs. In order to prevent and anticipate problems, the national cotton company (SODECOTON), with the help of the agricultural research (IRAD-PRASAC), implemented in 1999 a monitoring network for the early detection of resistance of target insects to the main recommended insecticides. Over the last three years, from 1999 up to 2001, assessment of H. armigera susceptibility to pyrethroid insecticides was carried out through both vial tests and topical bioassays. Revealed in southern and western Africa, pyrethroid resistance now seems to affect Central Africa also. Although control failure due to resistance has not yet been reported from the field, these results indicate the presence of resistant genes within H. armigera populations in Northern Cameron. Further laboratory studies confirmed the loss of susceptibility to cypermethrin in wild populations. Priority actions to be developed must focus on the rational and concerted management of pesticide use and the implementation of a regional monitoring network for the early detection of the loss of sensibility of target insects to the main recommended insecticides. At the same time, more fundamental research should be undertaken on the epidemiological profile of resistance in order to define practical ways of reducing the selection pressure.

Abelmoschus↗

PubMed2002

[Intestinal parasites in African asylum seekers: prevalence and risk factors].

OBJECTIVE: To determine the prevalence of potentially pathogenic intestinal parasites in asylum seekers coming from a highly endemic area, and to identify groups of asylum seekers from Africa with a high risk of an intestinal parasitic infestation which is potentially harmful of their own health or that of those in their vicinity. DESIGN: Prospective. METHOD: In the period January 1996-May 1999, 956 asylum seekers from Africa were checked for intestinal parasites by means of a stool examination within one month of arriving in the Netherlands. Independent variables for data analysis were sex, age and area of origin. RESULTS: Pathogenic intestinal parasites were found in 40.6% of the 956 African asylum seekers coming from areas south and east of the Sahara. Double-infection was found in 9.5% and triple-infection in 0.9% of the study population. The most common pathogenic parasite was Trichuris trichiura (13.6%) followed by Entamoeba histolytica/dispar (8.8%), hookworms (7.8%), Schistosoma (7.0%) and Giardia lamblia (5.0%). G. lamblia was the most commonly found potentially pathogenic parasite in children less than 13 years old (19.0%). In the population from Western Africa, 15.6% had a hookworm and 12.8% a Schistosoma. Both these helminthic infestations were three times as prevalent in men as in women. CONCLUSION: Sex, age and area of origin were important indicators for the species of parasite. On the basis of this, risk groups can be selected for screening for potentially pathogenic intestinal parasites.

Adolescent↗

PubMed2000

Reproductive failure in women living in iodine deficient areas of West Africa.

OBJECTIVES: To investigate the association between iodine status and reproductive failure in a population of West African women. DESIGN: Epidemiological survey on iodine deficiency disorders carried out in 1996-1997. SETTING: The iodine deficient areas of Senegal (Casamance and Senegal Oriental). POPULATION: Four thousand nine hundred and eighty women, aged 10 to 50, of whom 1,544 adolescent and 462 pregnant women were examined for thyroid size and urinary iodine excretion. Their iodine status was associated with their fertility rate and reproductive failures. RESULTS: Reproductive failure (defined as repeated miscarriages and stillbirth) was associated with low iodine status, with severe iodine deficiency increasing the risk. Poor nutritional status and illiteracy had a significant effect on the outcome of pregnancy: underweight women had a fourfold higher risk, and those who were illiterate an eightfold higher risk, of failed pregnancy, compared with nutritionally healthy, literature women. CONCLUSIONS: These findings emphasise the need to implement an effective iodine supplementation programme targeted at young and pregnant women in this area of western Africa. They also emphasise the importance of improving the nutritional status of young girls and the crucial role played by education in the prevention of reproductive failure.

Abortion, Spontaneous↗

PubMed2005

Distribution and heterogeneity of hepatitis C genotypes in hepatitis patients in Cameroon.

Hepatitis C virus infects humans world-wide. The virus genome varies greatly and it has several genotypes. HCV infection is highly prevalent in Central Africa and Cameroon. Initial studies on the genetic variability of HCV showed infection with HCV genotypes 1, 2, and 4. We have now sequenced the NS5b and E2 regions of 156 HCV isolates collected from patients presenting for diagnosis in Yaounde and used the data to describe the distribution of HCV genotypes and subtypes in patients with hepatitis in Cameroon. Genotype 1 was more frequent than Genotypes 4 and 2. Genotypes 1 and 4 were highly heterogeneous, containing many subtypes described previously (1b, 1c, 1e, 1h, 1l, 4f, 4t, 4p, 4k) and unsubtyped groups. There was a systematic phylogenetic concordance between NS5b and E2 sequence clustering. The Genotype 2 sequences did not vary. Neither subject age nor gender influenced HCV distribution. HCV Genotypes 1 and 4 are very heterogeneous in Cameroon, perhaps due to ancient infections. The homogeneity of HCV Genotype 2 indicates its more recent introduction from western Africa.

Adult↗

PubMed2002

Evolution of human Polyomavirus JC: implications for the population history of humans.

The polyomavirus JC virus (JCV), the etiological agent of progressive multifocal leukoencephalopathy, is ubiquitous in the human population, infecting children asymptomatically, then persisting in the kidney. The main mode of transmission of JCV is from parents to children through long-term cohabitation. Twelve JCV subtypes that occupy unique domains in Europe, Africa, and Asia have been identified. Here, we attempted to elucidate the evolutionary relationships among JCV strains worldwide using the whole-genome approach with which a highly reliable phylogeny of JCV strains can be reconstructed. Sixty-five complete JCV DNA sequences, derived from various geographical regions and belonging to 11 of the 12 known subtypes, were subjected to phylogenetic analysis using three independent methods: the neighbor-joining, maximum parsimony, and maximum likelihood methods. The trees obtained with these methods consistently indicated that ancestral JCVs were divided into three superclusters, designated as Types A, B, and C. A split in Type A generated two subtypes, EU-a and -b, mainly containing European and Mediterranean strains. The first split in Type B generated Af2 (the major African subtype). Subsequent splits in Type B generated B1-c (a minor European subtype) and all seven Asian subtypes (B1-a, -b, -d, B2, MY, CY, and SC). Type C generated a single subtype (Af1), consisting of strains derived from western Africa. While the present findings provided a basis on which to classify JCV into types or subtypes, they have several implications for the divergence and migration of human populations.

Base Sequence↗

PubMed2006

Molecular dissection of the Y chromosome haplogroup E-M78 (E3b1a): a posteriori evaluation of a microsatellite-network-based approach through six new biallelic markers.

The human Y chromosome haplogroup E-M78 (E3b1a) occurs commonly and is distributed in northern and eastern Africa, western Asia, and all of Europe. Previously, only two rarely observed internal biallelic markers (UEPs) were known within the E-M78 clade. Here we report the identification of six novel UEPs that significantly refine the phylogeny of this haplogroup. Then, we evaluate the correspondence between the newly defined sub-haplogroups and the E-M78 haplotype clusters previously identified by an 11-microsatellite loci-based network encompassing 232 chromosomes (Cruciani et al., 2004). We observed considerable correspondence between the trees generated by the two types of markers, but also noted important discrepancies between microsatellite and UEP findings. Overall, this analysis reveals that the currently visible terminal branches of the Y tree still contain a large amount of information, in terms of undiscovered biallelic markers, and that caution is needed when using the microsatellite alleles as surrogates of unique event polymorphisms.

Africa, Eastern↗

PubMed2000

Effects of selected process parameters in extrusion of yam flour (Dioscorea rotundata) on physicochemical properties of the extrudates.

Raw yam (Dioscorea rotundata) flour was cooked and extruded in a Brabender single-screw laboratory scale extruder. Response surface methodology using an incomplete factorial design was applied with various combinations of barrel temperature [100, 125, 150 degrees C], feed moisture content [18, 22, 26%] and screw speed [100, 150, 200 rpm]. Initial viscosity at 30 degrees C, water solubility index, expansion and hardness were determined. The highest values of initial viscosity were at the highest barrel temperatures and the highest moisture contents. At high feed moisture content and high barrel temperatures the yam extrudate flour showed the greatest values of water solubility index. The physical properties of the extruded product showed that at high temperature the lower the moisture content the greater the expansion index. Hardness was influenced directly by moisture content and inversely by extrusion temperature. The extrusion of yam flour led to the production of snacks and pre-gelatinized flours of diverse properties. Also extruded yam flour can be successfully used in the preparation of 'futu' (pre-cooked compact dough), a yam-based food, popular in Western Africa.

Chemical Phenomena↗

PubMed2007

Cranial ontogeny, diet, and ecogeographic variation in African lorises.

A series of 22 craniodental measurements were obtained for the three subspecies of potto (Perodicticus) and angwantibos (Arctocebus). To describe patterns of variation in Perodicticus, a discriminant function analysis (DFA) was performed with adult data. To investigate the ecogeographic correlates of size variation in Perodicticus, adult cranial dimensions were compared with field data on latitudinal and longitudinal coordinates for available specimens as well as altitudinal data for a more limited sample. Ontogenetic series for larger-bodied Perodicticus and smaller-bodied Arctocebus were compared to test the hypothesis that inter- and intrageneric variation in skull form results from the differential extension/truncation of shared patterns of relative growth, and to assess morphological variation in the masticatory complex of sister taxa with differing dietary habits. Analyses of relative growth indicate that skull proportions in Perodicticus subspecies are largely ontogenetically scaled. In comparisons between Perodicticus and Arctocebus, most facial dimensions also are ontogenetically scaled, with all but one of the seven divergent comparisons (interorbital breadth) representing a feature of the masticatory apparatus. The DFA provided independent support for prior classifications of Perodicticus into three taxa. Size differentiation in African lorises appears to be correlated with altitudinal variation (Bergmann's Rule) as well as character displacement. The smallest pottos, P. p. potto, occupy low-lying coastal habitats in western Africa, whereas the larger, eastern forms inhabit higher, presumably colder elevations. The largest potto, P. p. edwardsi, is sympatric throughout most of its range with the smallest and most insectivorous African lorises (Arctocebus). A basis for intrageneric taxonomic variation in Perodicticus is supported by such nonclinal size variation, as well as divergences in the ontogeny of masticatory proportions corresponding to interspecific variation in dietary proclivities.

Africa↗

PubMed2002

JC virus strains indigenous to northeastern Siberians and Canadian Inuits are unique but evolutionally related to those distributed throughout Europe and Mediterranean areas.

Human polyomavirus JC virus (JCV) isolates around the world are classified into more than 10 geographically distinct genotypes (designated as subtypes). Evolutionary relationships among JCV subtypes were recently examined, and the following pattern of JCV evolution was indicated. The ancestral JCV first divided into three superclusters, designated Types A, B, and C. A split in Type A generated two subtypes, EU-a and -b, containing mainly European and Mediterranean isolates. The split in Type B generated Af 2 (the major African subtype), Bl-c (a minor European subtype), and various Asian subtypes. Type C generated a single subtype (Afl), consisting of isolates derived from western Africa. In this study, JCV isolates prevalent among northeastern Siberians and Canadian Inuits were evaluated in the context of the above-described pattern of JCV evolution. The Siberian/Arctic JCV isolates were classified as belonging mainly to Type A, based on the result of a preliminary phylogenetic analysis. We then examined, using the whole-genome approach, the phylogenetic relationships among worldwide Type A isolates. In neighbor-joining and maximum-likelihood analyses, Type A JCVs worldwide consistently diverged into three subtypes, EU-a, -b, and -c, with high bootstrap probabilities. EU-c was constructed only by northeastern Siberian isolates, derived mainly from Nanais living in the lower Amur River region, and was shown to have been generated by the first split in Type A. Most Siberian/Arctic isolates derived from Chukchis, Koryaks, and Canadian Inuits formed a distinct cluster within the EU-a subtype, with a high bootstrap probability. Based on the present findings, we discuss ancient human migrations, accompanied by Type A JCVs, across Asia and to Arctic areas of North America.

Adult↗

PubMed2002

Simple roost nests confer large energetic savings for sparrow-weavers.

White-browed sparrow-weavers (Plocepasser mahali, body mass 40 g) are group-living passerines adapted to the semi-arid environment of north-eastern and south-western Africa. During winter, the nocturnal ambient temperature of these regions often falls below 0 degrees C. imposing conditions demanding an increase in thermoregulatory heat production. Individuals roost throughout the year in inverted U-shaped roost nests. We investigated the energetic advantages of roosting by measuring nest and ambient temperatures in the field, as well as the resting metabolic rate (RMR) of the birds. The sparrow-weavers exhibited a wide thermoneutral zone (13 degrees C - 32 degrees C). Although RMR at thermoneutrality (40.2 J g.h(-1)) conforms with those of other passerines. the value at 0 degrees C (74.8 J g.h(-1)) is significantly lower than expected. The slope of the line below the lower critical temperature is unexpectedly steep, however, and appears to cause the physiological requirement for nest roosting due to a high cost of thermoregulation at low temperatures, perhaps due to shivering or non-shivering thermogenesis. The nest temperature at 0 degrees C ambient is 5 degrees C. resulting in a saving of some 7% in the energy spent during winter nights when food resources are in short supply compared with the rest of the year.

Acclimatization↗

PubMed2007

Molecular characterization of infectious bursal disease virus (IBDV): diversity of very virulent IBDV in Tanzania.

Nucleotide sequences of the VP2 hypervariable region (VP2-HVR) of 14 infectious bursal disease viruses (IBDVs) isolated in Tanzania from 2001 to 2004 were determined. Phylogenetic analysis showed that the isolates diverged into two genotypes and belonged to the very virulent (VV) type. In the phylogenetic tree, strains in one genotype clustered in a distinct group and were closely related to some strains isolated in western Africa, with nucleotide similarities of 96.1-96.8%, while strains in another genotype were clustered within the European/Asian VV type with nucleotide similarities ranging from 97.5 to 99.3%. Both genotypes were widely distributed throughout Tanzania, and had conserved putative virulence marker amino acids (aa) at positions 222(A), 242(I), 256(I), 294(I) and 299(S). Our findings demonstrate for the first time the existence of both African and European/Asian VV-IBDV variants in Tanzania.

Amino Acid Sequence↗

PubMed1992

PCR amplification of large genomic fragments from human and simian immunodeficiency virus infected cell lines.

Polymerase chain reaction (PCR) has been used to amplify the large fragments from viral genomic DNA of SIV from wild caught, asymptomatic Erythrocebus monkeys from Western Africa (Senegal) and also from HIV-2 infected cell lines. By using consensus primer sequences from highly conserved stretches of gag, pol and env genes, two halves of the viral genome of HIV-2 and SIV (isolated from west African Erythrocebus monkeys) have amplified by PCR. One half spans 5200 bp from within the U3 region of the 5' long terminal repeat (LTR) into pol gene and an overlapping fragment spans 3700 bp from the pol gene into U5 region of 3' LTR. Also fragments ranging from 1-2.3 kb from gag pol and env genes have been successfully amplified. Our data demonstrate that primers used to amplify large segments from viral DNA yield better results if they are derived from a consensus sequence of a highly conserved stretch of the viral genome.

Animals↗

PubMed1981

HLA types in American black juvenile diabetics strong associations with Dw3 and Dw4.

The distributions of HLA-A, -B, -C and -D antigens in 38 black American insulin-dependent juvenile diabetics were studied. Antigens A1, A2, B8 and Cw3 were slightly increased, but the corrected probability values were not statistically significant. As determined by mixed lymphocyte culture, the frequency of Dw3 was 89% in the juvenile diabetics and that of Dw4 was 42% in comparison with 14 and 8%, respectively, in the controls. The relative risks for juvenile diabetes were 52 for Dw3 (p = 10(-8) and 9 for Dw4 (p = 10(-6). Dw2 was significantly decreased in the diabetics (p equals 0.008). All of these deviations in A, B, C and D locus specificities have been previously reported by others in white juvenile diabetics. Because there are white genes in the American black gene pool and juvenile diabetes is rare in blacks in western Africa, many cases of juvenile diabetes in American blacks could be the result of genes ultimately derived from the white genes. This hypothesis is supported by the similar HLA associations in juvenile diabetes in the black and white ethnic groups.

Black People↗

PubMed2005

STR allelic frequencies for an African population sample (Equatorial Guinea) using AmpFlSTR Identifiler and Powerplex 16 kits.

We present allele frequencies and forensic parameters for 17 STRs included in the AmpFlSTR Identifiler (CSF1PO, D2S1338, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D19S433, D21S11, FGA, TH01, TPO and VWA) and Powerplex 16 System (CSF1PO, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D21S11, FGA, Penta D, Penta E, TH01, TPO and VWA) in a sample of 134 unrelated individuals from Equatorial Guinea located in Western Africa, between Cameroon and Gabon. Hardy-Weinberg equilibrium was tested for each locus and the sample was compared with five African databases: Promega's and AB Applied Biosystems African-Americans and samples from Mozambique, from Cabinda (Angola) and Guinea-Bissau.

DNA Fingerprinting↗