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PubMed2002

Antimicrobial activity of some plants used for the treatment of livestock disease in the Eastern Cape, South Africa.

Approximately 75% of rural livestock owners in the Eastern Cape province of South Africa use plants or plant based remedies to treat their livestock. Prominent among these plants are Combretum caffrum, Salix capensis and Schotia latifolia. Water, methanolic and acetonic extracts as well as decoctions of the three plants were screened against ten bacteria and five fungi. The results of the antibacterial assay indicated significant activity against all the Gram-positive bacteria tested with the minimum inhibitory concentrations ranging from 0.1 to 5.0 mg/ml. A few of the extracts showed minimal activity, but the majority of extracts were not active on the Gram-negative bacteria. Generally, all the extracts showed some antifungal activity against the five test fungi. Methanolic extracts exhibited higher fungal growth inhibition, whereas the water extracts showed the least inhibition. It was noteworthy that some water extracts promoted fungal growth.

Animal Diseases↗

PubMed2004

Methods of surveying the incidence and severity of cassava mosaic disease and whitefly vector populations on cassava in Africa: a review.

Field surveys in many cassava growing areas of Africa have assessed the incidence and severity of cassava mosaic disease (CMD), populations of the whitefly vector (Bemisia tabaci), and the distribution of cassava mosaic begomoviruses (CMBs). The methods employed differ greatly between countries and attempts at standardization were made in recent CMD surveys in East and Central Africa, notably in the systemwide Whitefly IPM Project, which provides a paradigm for future work on CMBs and whiteflies on cassava in Africa and also elsewhere. However, there is a need for greater standardization so as to assess the continued expansion of the current CMD pandemic in eastern Africa. Standardized methods will facilitate the collection of reliable data, which can be used to predict future disease spread, develop appropriate management strategies and compare disease development between seasons and locations. In this review, the methods used and the problems encountered during such surveys are discussed and recommendations made on future procedure.

Africa↗

PubMed2003

Extensive female-mediated gene flow from sub-Saharan Africa into near eastern Arab populations.

We have analyzed and compared mitochondrial DNA variation of populations from the Near East and Africa and found a very high frequency of African lineages present in the Yemen Hadramawt: more than a third were of clear sub-Saharan origin. Other Arab populations carried approximately 10% lineages of sub-Saharan origin, whereas non-Arab Near Eastern populations, by contrast, carried few or no such lineages, suggesting that gene flow has been preferentially into Arab populations. Several lines of evidence suggest that most of this gene flow probably occurred within the past approximately 2,500 years. In contrast, there is little evidence for male-mediated gene flow from sub-Saharan Africa in Y-chromosome haplotypes in Arab populations, including the Hadramawt. Taken together, these results are consistent with substantial migration from eastern Africa into Arabia, at least in part as a result of the Arab slave trade, and mainly female assimilation into the Arabian population as a result of miscegenation and manumission.

Africa South of the Sahara↗

PubMed1995

Cancer in the African population of Harare, Zimbabwe, 1990-1992.

The data presented from the population-based cancer registry in Harare, Zimbabwe, represent the first information on the incidence of cancer in Southern Africa for almost 20 years. In the African population in Zimbabwe there are several features in common with other countries in sub-Saharan Africa: high rates of liver, prostate and cervix cancer, low rates of large-bowel cancer and breast cancer. Also, as reported from southern and south-eastern Africa, there are relatively high incidence rates of cancers of the oesophagus, bladder and (in men) lung. The AIDS epidemic has given rise to a striking increase in incidence of Kaposi's sarcoma (now the commonest cancer of African men), but there is not much evidence for an increase in incidence of non-Hodgkin lymphomas nor, although rates are very high, of cervical cancer.

Adolescent↗

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↗

PubMed1999

Complex Shear Wave Velocity Structure Imaged Beneath Africa and Iceland.

A model of three-dimensional shear wave velocity variations in the mantle reveals a tilted low velocity anomaly extending from the core-mantle boundary (CMB) region beneath the southeastern Atlantic Ocean into the upper mantle beneath eastern Africa. This anomaly suggests that Cenozoic flood basalt volcanism in the Afar region and active rifting beneath the East African Rift is linked to an extensive thermal anomaly at the CMB more than 45 degrees away. In contrast, a low velocity anomaly beneath Iceland is confined to the upper mantle.

Journal Article↗

PubMed2000

Short tandem-repeat polymorphism/alu haplotype variation at the PLAT locus: implications for modern human origins.

Two dinucleotide short tandem-repeat polymorphisms (STRPs) and a polymorphic Alu element spanning a 22-kb region of the PLAT locus on chromosome 8p12-q11.2 were typed in 1,287-1,420 individuals originating from 30 geographically diverse human populations, as well as in 29 great apes. These data were analyzed as haplotypes consisting of each of the dinucleotide repeats and the flanking Alu insertion/deletion polymorphism. The global pattern of STRP/Alu haplotype variation and linkage disequilibrium (LD) is informative for the reconstruction of human evolutionary history. Sub-Saharan African populations have high levels of haplotype diversity within and between populations, relative to non-Africans, and have highly divergent patterns of LD. Non-African populations have both a subset of the haplotype diversity present in Africa and a distinct pattern of LD. The pattern of haplotype variation and LD observed at the PLAT locus suggests a recent common ancestry of non-African populations, from a small population originating in eastern Africa. These data indicate that, throughout much of modern human history, sub-Saharan Africa has maintained both a large effective population size and a high level of population substructure. Additionally, Papua New Guinean and Micronesian populations have rare haplotypes observed otherwise only in African populations, suggesting ancient gene flow from Africa into Papua New Guinea, as well as gene flow between Melanesian and Micronesian populations.

Africa South of the Sahara↗

PubMed2001

Environmental change and rates of evolution: the phylogeographic pattern within the hartebeest complex as related to climatic variation.

Global climate fluctuated considerably throughout the Pliocene-Pleistocene period, influencing the evolutionary history of a wide array of species. Using the phylogeographic patterns within the hartebeest (Alcelaphus buselaphus (Pallas, 1766)) complex, we evaluated the evolutionary consequences of such environmental change for a typical large mammal ranging on the African savannah. Our results, as generated from two mitochondrial DNA markers (the D-loop and cytochrome b), suggest an origin of the hartebeest in eastern Africa from where the species has colonized other parts of the continent. Phylogenetic analyses revealed an early diversification into southern and northern hartebeest lineages, an event that may be related to the formation of the Rift Valley lakes. The northern lineage has further diverged into eastern and western lineages, most probably as a result of the expanding central African rainforest belt and subsequent contraction of savannah habitats during a period of global warming. The diversification events appear to have coincided with major climatic changes and are highly correlated in time. These observations strongly suggest that large-scale climatic fluctuations have been a major determinant for the species' evolutionary history and that hartebeest evolution has mainly taken place in isolated yet environmentally favourable refugia during periods of global warming. Indications of sudden population expansion for two putative ancestral hartebeest populations provide further support for a refugia-based explanation of the diversification events. Reciprocal monophyly between southern and northern lineages may suggest that reproductive barriers exist and that the hartebeest complex comprises two different species.

Africa↗

PubMed2001

Genetic diversity of the honeybee in Africa: microsatellite and mitochondrial data.

A total of 738 colonies from 64 localities along the African continent have been analysed using the DraI RFLP of the COI-COII mitochondrial region. Mitochondrial DNA of African honeybees appears to be composed of three highly divergent lineages. The African lineage previously reported (named A) is present in almost all the localities except those from north-eastern Africa. In this area, two newly described lineages (called O and Y), putatively originating from the Near East, are observed in high proportion. This suggests an important differentiation of Ethiopian and Egyptian honeybees from those of other African areas. The A lineage is also present in high proportion in populations from the Iberian Peninsula and Sicily. Furthermore, eight populations from Morocco, Guinea, Malawi and South Africa have been assayed with six microsatellite loci and compared to a set of eight additional populations from Europe and the Middle East. The African populations display higher genetic variability than European populations at all microsatellite loci studied thus far. This suggests that African populations have larger effective sizes than European ones. According to their microsatellite allele frequencies, the eight African populations cluster together, but are divided in two subgroups. These are the populations from Morocco and those from the other African countries. The populations from southern Europe show very low levels of 'Africanization' at nuclear microsatellite loci. Because nuclear and mitochondrial DNA often display discordant patterns of differentiation in the honeybee, the use of both kinds of markers is preferable when assessing the phylogeography of Apis mellifera and to determine the taxonomic status of the subspecies.

Africa↗

PubMed1987

Similarity in ejaculate-endocrine characteristics in captive versus free-ranging cheetahs of two subspecies.

Ejaculate-endocrine characteristics were measured in 23 captive cheetahs (Acinonyx jubatus jubatus) in North American zoos and in 8 free-ranging cheetahs (A.j. raineyi) in eastern Africa (Tanzania). A standardized electroejaculation protocol was used, and numbers of motile spermatozoa were similar (p greater than 0.05) between groups. Of the spermatozoa collected by electroejaculation, 70.6 +/- 3.3% and 75.9 +/- 4.4% were morphologically abnormal in the captive "North American" and in the free-ranging, eastern African populations, respectively. Adrenal activity, as measured by an acute, temporal rise and fall in serum cortisol levels during and after electroejaculation, was no different (p greater than 0.05) between groups. Although serum luteinizing hormone (LH) levels were less (p less than 0.05) in the free-ranging than in the captive animals, serum testosterone concentrations were similar. The data indicate that the comparatively poor reproductive performance of cheetahs maintained in zoological parks is not attributable to a captivity-induced response afflicting the male. Furthermore, there is no evidence that ejaculate/endocrine characteristics differ between the two subspecies. Because adrenal/gonadal activity and the number of pleiomorphic spermatozoa are similar between the test groups, the results suggest that spermatozoal diversity originates as a result of the extreme genetic monomorphism observed universally in the species.

Acinonyx↗

PubMedDate not supplied

Geographic and ethnic distribution of human hemoglobin variants.

The distribution of hemoglobin variants in human populations is of interest to students of hemoglobin as well as geneticists and anthropologists. It has however received relatively little attention and, to the author's knowledge, this is the first attempt to comprehensively tabulate this type of information since Lehmann and Huntsman and Livingstone did so over 15 years ago (429, 430). In the interest of improving both the accuracy and scope of this compilation as well as keeping it current, the author invites investigators to submit to him corrections, references or additional information for inclusion in a future monograph or review article.

Africa, Central↗

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↗

PubMed2025

Influence of genetic factors of humans, mosquitoes and parasites, on the evolution of Plasmodium falciparum infections, malaria transmission and genetic control methods: a review of the literature.

Despite significant progress, malaria remains a public health problem in many regions, particularly in sub-Saharan Africa. This situation is partly explained by the mosquito's resistance to insecticides and the emergence of parasite resistance to antimalarial drugs. Indeed, in spite of the various vectors' controls, insecticide resistance emerges from multi-generational selection and poses worldwide concern. In parallel, artemisinin resistance unfortunately emerged independently in multiple countries in eastern Africa. Since 2014, artemisinin resistance has been observed in 6 countries in Africa and, more concerningly, the evidence from longitudinal molecular surveys in these countries suggests that it is spreading. While phenotypic evidence of treatment failure is still limited, the increasing reports of validated artemisinin resistance mutations are alarming. Unlike the emergence of artemisinin resistance in South-East Asia, our understanding of the genetic determinants of artemisinin resistance and our ability to sequence and map the spread of resistance are significantly greater. In addition to mosquito and parasite genetics affecting malaria evolution, many human individual variants have been identified that are associated with malaria protection, but the most important of all relates to the structure or function of red blood cells, the classical polymorphisms that causes sickle cell trait, α-thalassaemia, G6PD deficiency, and the major red cell blood group variants. In that biological complex context, there is a need to characterize the various genetic factors in Plasmodium falciparum, humans and mosquitoes that are potentially associated with resistance to antimalarial drugs and insecticides, and their involvement in the evolution, severity and transmission of malaria. In this direction, A comprehensive literature review was conducted to capture the objectives highlighted above. The advances in genomic surveillance and emerging genetic control strategies, such as gene drive technology were also considered in this review. We used search engines such as PubMed and Google scholar to retrieve articles useful to the objective of this paper and information on the knowledge of genetic factors and methods that contributed to malaria control were synthesized.

Humans↗

PubMed2006

Socio-economic effects of khat chewing in north eastern Kenya.

BACKGROUND: The khat habit is a widespread phenomenon which has in the past two decades spread to parts of Western Europe and North America from Eastern Africa and the Arabian Peninsula. Although khat has been identified as one of the most commonly abused substances in Kenya, restrictions on cultivation, trade and usage have been non-existent since its legalisation in 1977. OBJECTIVE: To describe the socio-economic effects of khat chewing in Ijara District in the North Eastern Province of Kenya. DESIGN: Cross sectional study. SETTING: Ijara District, North Eastern Kenya. SUBJECTS: Fifty respondents were interviewed. RESULTS: Eighty eight percent of the respondents were khat chewers, and the majority (80%) had family members who engaged in the khat habit. There was a general lack of education on the negative effects of khat chewing. Due to reported mood changes and withdrawal symptoms when not chewing khat, many respondents used more than half of their domestic budgets on khat, but few (28%) perceived this as a waste of resources. Fifty four percent of khat chewers typically started the habit during the day, implying a waste of time for productive work. However, only 40% of the persons interviewed admitted that the drug affected work performance negatively. The khat habit was associated with strain on family relationships, anti-social behaviour and health effects such as insomnia. CONCLUSION: In spite of the negative socio-economic impact of khat in Ijara District, khat consumption remains a widespread habit.

Adolescent↗

PubMed2001

High-resolution analysis of human Y-chromosome variation shows a sharp discontinuity and limited gene flow between northwestern Africa and the Iberian Peninsula.

In the present study we have analyzed 44 Y-chromosome biallelic polymorphisms in population samples from northwestern (NW) Africa and the Iberian Peninsula, which allowed us to place each chromosome unequivocally in a phylogenetic tree based on >150 polymorphisms. The most striking results are that contemporary NW African and Iberian populations were found to have originated from distinctly different patrilineages and that the Strait of Gibraltar seems to have acted as a strong (although not complete) barrier to gene flow. In NW African populations, an Upper Paleolithic colonization that probably had its origin in eastern Africa contributed 75% of the current gene pool. In comparison, approximately 78% of contemporary Iberian Y chromosomes originated in an Upper Paleolithic expansion from western Asia, along the northern rim of the Mediterranean basin. Smaller contributions to these gene pools (constituting 13% of Y chromosomes in NW Africa and 10% of Y chromosomes in Iberia) came from the Middle East during the Neolithic and, during subsequent gene flow, from Sub-Saharan to NW Africa. Finally, bidirectional gene flow across the Strait of Gibraltar has been detected: the genetic contribution of European Y chromosomes to the NW African gene pool is estimated at 4%, and NW African populations may have contributed 7% of Iberian Y chromosomes. The Islamic rule of Spain, which began in a.d. 711 and lasted almost 8 centuries, left only a minor contribution to the current Iberian Y-chromosome pool. The high-resolution analysis of the Y chromosome allows us to separate successive migratory components and to precisely quantify each historical layer.

Africa South of the Sahara↗

PubMed2002

[Trypanosomiasis--a real risk for tourists visiting national parks in Tanzania].

African sleeping sickness is no longer a rare disease among tourists visiting national parks in Tanzania. The disease is caused by a parasite, Trypanosoma brucei, which is transmitted by the tsetse fly. Two species infect humans: Trypanosoma brucci gambiense and Trypanosoma brucei rhodesiense; the last form is re-emerging in parts of Africa. Untreated this disease carries a mortality of nearly 100%. This article describes a case of African sleeping sickness in a tourist visiting Tanzania, which was diagnosed at the Nordic Clinic, Dar es Salaam. The most important symptoms, diagnostic investigations as well as the main principles of treatment are described. Patients with this condition need to be admitted and treated at centres with competence in tropical diseases. African sleeping sickness should be kept in mind in tourists returning to their home country with fever after visits to national parks in Eastern Africa. With early treatment, cure is almost certain. The only way to prevent this condition is through protection against bites of the tsetse fly.

Animals↗

PubMed1993

Chromosomal diagnostic criteria for some members of Simulium damnosum complex in east Africa.

Identification of Simulium damnosum s.l. vectors of onchocerciasis demands adequate knowledge of the chromosomal features that distinguish human-biting members from nonanthropophilic forms. In this study, 955 S. damnosum larvae collected from various geographical locations in Tanzania were chromosomally analyzed. 358 larvae from small mountain streams in the northeast and central regions of Tanzania, were identified as mainly Nyamagasani and Sanje forms, with only one Kiwira form. 378 larvae from plain and lowland rivers, also in the northeast and central regions, were identified as Nkusi, Kisiwani and Kibwezi forms. Chromosomal examination of 219 larvae from the southern highlands zone revealed the presence of Kiwira and Nyamagasani forms. A further 27 larvae of S. damnosum complex collected from 5 rivers in Uganda were identified as Sebwe and Nkusi forms. Chromosomal photomicrographs on which the distinguishing characters were based are provided. These observations are discussed in the light of previous studies carried out on the S. damnosum cytological forms in Eastern Africa.

Animals↗

PubMed2000

Characterization of human CD4(+) T-cell clones recognizing conserved and variable epitopes of the Lassa virus nucleoprotein.

T cells must play the major role in controlling acute human Lassa virus infection, because patients recover from acute Lassa fever in the absence of a measurable neutralizing antibody response. T cells alone seem to protect animals from a lethal Lassa virus challenge, because after experimental vaccination no neutralizing antibodies are detectable. In order to study human T-cell reactivity to single Lassa virus proteins, the nucleoprotein (NP) of Lassa virus, strain Josiah, was cloned, expressed in Escherichia coli, and affinity purified. Peripheral blood mononuclear cells (PBMC) obtained from 8 of 13 healthy, Lassa virus antibody-positive individuals living in the Republic of Guinea, western Africa, were found to proliferate in response to the recombinant protein (proliferation index >/=10). PBMC obtained from one individual with a particularly high proliferative response were used to generate 50 NP-specific T-cell clones (TCC). For six of these the epitopes were mapped with overlapping synthetic peptides derived from the sequence of the NP. These CD4(+) TCC displayed high specific proliferation and produced mainly gamma interferon upon stimulation with NP. Because variation of up to 15% in the amino acid sequences of the structural proteins of naturally occurring Lassa virus variants has been observed, the reactivity of the TCC with peptides derived from the homologous epitopes of the Nigeria strain of Lassa virus and of the eastern Africa arenavirus Mopeia was tested. With the Nigeria strain of Lassa virus the levels of homology were 100% for two of these epitopes and 85% for three of them, whereas homology with the respective Mopeia epitopes ranged from 92 to 69%. Reactivity of the TCC with peptides derived from the variable epitopes of the Nigeria strain and of Mopeia was reduced or completely abolished. This report shows for the first time that seropositive individuals from areas of endemicity have very strong memory CD4(+) T-cell responses against the NP of Lassa virus, which are partly strain specific and partly cross-reactive with other Lassa virus strains. Our findings may have important implications for the strategy of designing recombinant vaccines against this mainly T-cell-controlled human arenavirus infection.

Adolescent↗