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PubMed1992

Numerical taxonomy of Trypanozoon based on polymorphisms in a reduced range of enzymes.

Numerical analyses of Trypanozoon taxonomy are presented, based on the isoenzyme data of Stevens et al. (1992). The previous study used a reduced range of enzymes compared with earlier work; the analyses indicate the value of this rationalized system. Both recently isolated trypanosome stocks and previously studied populations were included, allowing detailed comparison with earlier studies. Relationships between zymodemes were calculated with an improved similarity coefficient program, using Jaccard's coefficient (1908), and by Nei's method (1972). Dendrograms were constructed from the matrices produced with the group-average method. The groupings produced by both numerical methods were in close agreement, and the clusters of related principal zymodemes largely matched the species, subspecies and strain groups proposed by previous workers. Trypanozoon biochemical taxonomy is reviewed and the groupings reinforced by this study are: the mainly East African strain groups, busoga, zambezi, kakumbi, kiboko and sindo; T.b. gambiense and the bouaflé strain group from West Africa, and T. evansi; an intermediate bouaflé/busoga group was also recognized.

Africa, Eastern↗
PubMed1988

Trypanosoma congolense: the distribution of enzymic variants in east and west Africa.

A total of 114 stocks of Trypanosoma congolense originating from Kenya, Uganda, Tanzania, Zambia and Sudan, but including, for comparison, stocks from The Gambia, Liberia, Ivory Coast, Nigeria and Cameroun, were compared by isoenzyme electrophoresis for 6 enzymes. The zymodemes were grouped, both from a dendrogram and using a cladistic method, after calculating the dissimilarity, or distance, between profiles. Previous observations are broadly confirmed, the zymodemes clustering separately according to geographical origin and ecological zone. Thus, one group was composed almost entirely of East African stocks, and another of stocks from both East and West Africa, although each group was of savanna origin. A third group was composed of stocks from the humid, rain-forest zones of West Africa, and was particularly characterized by isoenzyme variants of superoxide dismutase and glucose-phosphate isomerase. Two stocks from the Kenyan coast formed a markedly separate group, which may be taxonomically distinct.

Africa, Eastern↗
PubMed1988

Susceptibility of goats to tsetse-transmitted challenge with Trypanosoma vivax from East and West Africa.

To determine if, as is the case with Trypanosoma brucei and T. congolense, serodemes of T. vivax could be distinguished on the basis of immunity to the metacyclic stages of the parasite, attempts were made to immunize goats by infection with infected tsetse, followed by chemotherapy or eventual 'self-cure'. Thirty goats were infected by tsetse with either clones or stocks of T. vivax from East or West Africa. Twenty-four goats were treated with diminazene aceturate (Berenil, Hoechst A.G.) 2-6 weeks after infection and 6 goats were allowed to self-cure. Infection, followed by treatment, induced immunity to a first homologous challenge by infected tsetse in only 2 of 24 goats (one immune to the East African stock, and the other to a clone of the West African stock). Immunity to a clone of the East African stock was induced in 3 or 4 animals after a second infection and treatment and in the fourth animal of the group following a third infection and treatment. One of 2 goats infected with the clone of the East African stock was immune to challenge at 16 weeks, following self-cure without treatment, and 1 of 4 goats infected with the parent stock was similarly immune when challenged at 40 weeks post-infection. Goats susceptible to infection with East African T. vivax showed evidence of partial immunity by delayed pre-patent periods and depressed parasitaemias after challenge. Goats infected with the relatively more virulent West African T. vivax were, however, completely susceptible to infection after homologous challenge, and showed only a slight delay in pre-patent period. A similar result was obtained in a further 8 goats primed and challenged by large numbers of tsetse (20 or 100 infected tsetse/goat) with the West African T. vivax. In further experiments using a very short treatment interval, infections following challenge were clearly shown to be the result of a lack of immunity rather than relapse following treatment. Lytic antibody activity to cultured metacyclic trypanosomes could not be detected during infection but such activity against bloodstream forms was detected after 2 weeks of infection. It is suggested that the primary reason for the erratic induction of immunity to T. vivax employing this methodology is the low number of metacyclics transmitted by infected tsetse, and thus poor antigenic stimulus encountered by goats upon tsetse challenge.

Africa, Eastern↗
PubMed2000

HIV1 infection in extra-European students in Turin (Italy): epidemiologic pattern and risk factors.

The authors studied a population of 5634 students from various continents to determine possible correlations between risk factors and seroprevalence of HIV infection. In the African sample the seroprevalence rate was 3.5%; the age range from 19 to 30 years was most affected; prevalence differences between the sexes were slight (3.5% for the males vs 3% for the females); the evaluation of the medical history (STDs, malaria, TB and hospital stays) showed no statistically significant association with HIV-1 infection; the central-eastern Africa significantly appeared the most affected.

Adult↗
PubMed2003

Evolution and diversity of HIV-1 in Africa--a review.

The HIV/AIDS pandemic represents a major development crisis for the African continent, which is the worst affected region in the world. Currently, almost 30 of the 42 million people infected with HIV worldwide live in Africa. AIDS in humans is caused by two lentiviruses, HIV-1 and HIV-2, which entered the human population by zoonotic transmissions from at least two different African primate species. Extensive phylogenetic analyses of partial and full-length genome sequences have helped to gain insights into the evolutionary biology and population dynamics of HIV. One of the major characteristics of HIV is its rapid evolution, which has resulted in substantial genetic diversity amongst different isolates, the majority of which are represented in Africa. Genetic variability of HIV and any consequent phenotypic variation poses a significant challenge to disease control and surveillance in different geographic regions of Africa. This review focuses on the origins and evolution of HIV, current classification and diversity of HIV isolates in Africa and provides an extensive account of the geographic distribution of HIV types, groups, and subtypes in each of the 49 African countries. Numerous epidemiological studies have provided a picture of HIV distribution patterns in most countries in Africa, and these show increasing evidence of the importance of HIV-1 recombinants. In particular, this review highlights that our current understanding of HIV distribution in Africa is incomplete and inadequately represents the diversity of the virus, and underscores the need for ongoing surveillance.

Africa, Central↗
PubMed2003

Three serine proteinases from midguts of the hard tick Rhipicephalus appendiculatus; cDNA cloning and preliminary characterization.

Rhipicephalus appendiculatus is one of the most economically important ticks distributed in south central and eastern Africa where little or no progress has been made on attempts to develop a vaccine. We have used a combination of RT-PCR, the 3' and 5'rapid amplification of cDNA ends (RACE) to clone and sequence three cDNAs encoding full-length R. appendiculatus midgut serine proteinases (RAMSP). RT-PCR degenerate primers were designed from amino acid sequences surrounding active sites, His57 and Ser195 conserved among most known serine proteinase-like genes (Mulenga et al. 2001). Northern blotting analysis of total RNA extracted from unfed and partially fed adult ticks revealed that mRNAs for RAMSP-1 and -2 were expressed only in partially fed ticks, while RAMSP-3 mRNA was not only expressed in both unfed and partially fed ticks, it was also up-regulated as tick feeding progressed. Expression analysis by RT-PCR revealed that RAMSP-3 was predominantly expressed in midguts when compared to salivary glands. For RAMSP-1 and -2, they were expressed at equivalent levels in both midguts and salivary glands. Based on key amino acid sequence features as well as similarity comparisons from the database, we speculated that polypeptides encoded by RAMPSP-1 to -3 are structurally more closely related to chymotrypsin- than trypsin-like serine proteinases. We have based our comments on the potential of serine proteinases as candidates for tick vaccines.

Amino Acid Sequence↗
PubMed1999

A dipole mode in the tropical Indian Ocean.

For the tropical Pacific and Atlantic oceans, internal modes of variability that lead to climatic oscillations have been recognized, but in the Indian Ocean region a similar ocean-atmosphere interaction causing interannual climate variability has not yet been found. Here we report an analysis of observational data over the past 40 years, showing a dipole mode in the Indian Ocean: a pattern of internal variability with anomalously low sea surface temperatures off Sumatra and high sea surface temperatures in the western Indian Ocean, with accompanying wind and precipitation anomalies. The spatio-temporal links between sea surface temperatures and winds reveal a strong coupling through the precipitation field and ocean dynamics. This air-sea interaction process is unique and inherent in the Indian Ocean, and is shown to be independent of the El Niño/Southern Oscillation. The discovery of this dipole mode that accounts for about 12% of the sea surface temperature variability in the Indian Ocean--and, in its active years, also causes severe rainfall in eastern Africa and droughts in Indonesia--brightens the prospects for a long-term forecast of rainfall anomalies in the affected countries.

Journal Article↗
PubMed1995

Isolation of novel virus-like sequences associated with human hepatitis.

Two viruses, GB virus A (GBV-A) and GB virus B (GBV-B), were recently identified in the GB hepatitis agent. Human sera containing antibodies that recognize GBV-A and/or GBV-B recombinant proteins were subjected to polymerase chain reaction studies with degenerate oligonucleotides capable of amplifying a segment of the putative helicase genes from GBV-A, GBV-B or hepatitis C virus. Novel sequences related to members of the Flaviviridae were identified in sera from 12 individuals including 4 individuals with hepatitis. The limited nucleotide sequence identity between GBV-A, GBV-B and HCV sequences suggests that a novel virus, tentatively named GB virus C, may be responsible for some cases of non-A, non-B, non-C, non-D, non-E hepatitis.

Adult↗
PubMed2000

Ribosomal DNA internal transcribed spacer (ITS2) sequences differentiate Anopheles funestus and An. rivulorum, and uncover a cryptic taxon.

Differentiation among the closely related Afrotropical species comprising the Funestus Group is difficult by traditional taxonomic measures. Anopheles rivulorum is the second most abundant and widespread species in the Funestus Group, and is occasionally collected indoors along with the dominant member and major malaria vector, An. funestus. The prospect of misidentification of An. rivulorum as An. funestus prompted the development of a rapid, polymerase chain reaction (PCR)-based method for identifying these two species. The ribosomal internal transcribed spacer 2 (ITS2) was amplified from thirty-five specimens of An. rivulorum collected from the extremes of its range: Eastern Africa (Kenya), Southern Africa (South Africa) and Western Africa (Burkina Faso). The ITS2 region of An. rivulorum ( approximately 380 bp) is sufficiently different in size from the ITS2 of An. funestus ( approximately 700 bp) that these species can be distinguished by agarose gel electrophoresis of PCR products without further manipulation. Comparison of the An. rivulorum and An. funestus ITS2 nucleotide sequences revealed such extensive divergence that meaningful alignment was impossible, except for a 25 bp island near the 5' end. Intraspecific sequence comparisons revealed no variation among An. rivulorum individuals collected from the same country. However, sequence divergence was 2% between specimens from South Africa and Kenya, and nearly tenfold higher ( approximately 19%) between specimens from Burkina Faso and either South Africa or Kenya, an unprecedented level of intraspecific ITS2 divergence in Anopheles. Taken together, these data suggest that the Burkina Faso sample is not An. rivulorum, but rather a cryptic taxon within the Funestus Group.

Animals↗
PubMed2001

Traditional tooth bud gouging in a Ugandan family: a report involving three sisters.

It has been reported in the literature that some rural populations of Sub-Saharan and Eastern Africa and other isolated areas around the world, practise gouging or enucleation of primary tooth buds to cure childhood illnesses. The unerupted primary canine tooth bud is believed to be the cause of febrile illness, diarrhoea, and vomiting; prevalent in infants in these areas of the world. Tooth bud gouging has implications for the developing dentition, and is a potential risk to the health and life of the child. Reported prevalence ranges from 22%-90%. From the information in this case report, the practise of tooth bud gouging is no longer confined to rural areas and may well be performed by communities that have emigrated to the UK. The three sisters described, now resident in the UK, suffered tooth gouging in a city clinic in Uganda. The damage caused to the primary and permanent dentition is described and treatment planning and options are suggested for each case to restore structure and function. Appropriate provision of healthcare and education could avoid the potential long-term damage to the health of the child and their developing dentition by the practise of tooth bud gouging, whether it occurs in the developing or developed world.

Child↗
PubMed1999

The cost effectiveness of strategies for the treatment of intestinal parasites in immigrants.

BACKGROUND: Currently, more than 600,000 immigrants enter the United States each year from countries where intestinal parasites are endemic. At entry persons with parasitic infections may be asymptomatic, and stool examinations are not a sensitive method of screening for parasitosis. Albendazole is a new, broad-spectrum antiparasitic drug, which was approved recently by the Food and Drug Administration. International trials have shown albendazole to be safe and effective in eradicating many parasites. In the United States there is now disagreement about whether to screen all immigrants for parasites, treat all immigrants presumptively, or do nothing unless they have symptoms. METHODS: We compared the costs and benefits of no preventive intervention (watchful waiting) with those of universal screening or presumptive treatment with 400 mg of albendazole per day for five days. Those at risk were defined as immigrants to the United States from Asia, the Middle East, sub-Saharan Africa, Eastern Europe, and Latin America and the Caribbean. Cost effectiveness was expressed both in terms of the cost of treatment per disability-adjusted life-year (DALY) averted (one DALY is defined as the loss of one year of healthy life to disease) and in terms of the cost per hospitalization averted. RESULTS: As compared with watchful waiting, presumptive treatment of all immigrants at risk for parasitosis would avert at least 870 DALYs, prevent at least 33 deaths and 374 hospitalizations, and save at least $4.2 million per year. As compared with watchful waiting, screening would cost $159,236 per DALY averted. CONCLUSIONS: Presumptive administration of albendazole to all immigrants at risk for parasitosis would save lives and money. Universal screening, with treatment of persons with positive stool examinations, would save lives but is less cost effective than presumptive treatment.

Albendazole↗
PubMed2006

A stable isotope aridity index for terrestrial environments.

We use the oxygen isotopic composition of tooth enamel from multiple mammalian taxa across eastern Africa to present a proxy for aridity. Here we report tooth enamel delta(18)O values of 14 species from 18 locations and classify them according to their isotopic sensitivity to environmental aridity. The species are placed into two groups, evaporation sensitive (ES) and evaporation insensitive (EI). Tooth enamel delta(18)O values of ES animals increase with aridity, whereas the tooth enamel delta(18)O values of EI animals track local meteoric water delta(18)O values, demonstrating that bioapatite delta(18)O values of animals with different behaviors and physiologies record different aspects of the same environment. The enrichment between tooth enamel delta(18)O values of ES and EI animals records the degree of (18)O enrichment between evaporated water (ingested water or body water) and source water, which increases with environmental aridity. Recognition of the ES-EI distinction creates the opportunity to use the (18)O composition of bioapatite as an index of terrestrial aridity.

Animals↗
PubMed2005

Use of national food balance data to estimate the adequacy of zinc in national food supplies: methodology and regional estimates.

OBJECTIVES: Adequate zinc nutriture is critically important for human health, but the development of programmes to control zinc deficiency is limited by the lack of reliable information on population zinc status. The present analyses were conducted to: (1) estimate the absorbable zinc content of national food supplies; (2) compare this information with theoretical population requirements for zinc; and (3) use these results to predict national risks of inadequate zinc intake. SETTING AND DESIGN: National food balance data were obtained for 176 countries from the Food and Agriculture Organization of the United Nations. The amount of absorbable zinc in these foods was estimated from food composition data, and zinc absorption was predicted using a model developed by the International Zinc Nutrition Consultative Group (IZiNCG). Demographic data were obtained from United Nations estimates, and age- and sex-specific physiological requirements for absorbable zinc were estimated using IZiNCG recommendations. RESULTS AND CONCLUSIONS: The mean per capita absorbable zinc content of national food supplies ranged from 2.98-3.01 mg day(-1) in Western Europe and USA & Canada to 2.09 mg day(-1) in Southeast Asia. The estimated percentage of individuals at risk of inadequate zinc intake ranged from 9.3-9.5% in the regions of North Africa & Eastern Mediterranean and USA & Canada to 33.1% in Southeast Asia. Overall, approximately 20.5% of the world's population is estimated to be at risk of inadequate zinc intake. Data on the absorbable zinc content of national food supplies can be used to determine whether further assessments of population zinc status and development of intervention programmes are warranted.

Biological Availability↗
PubMed1994

Bancroftian filariasis in Kwale District of Kenya. I. Clinical and parasitological survey in an endemic community.

A cross-sectional parasitological and clinical survey for Wuchereria bancrofti infection was carried out in an endemic community of south-eastern Kenya, to obtain background epidemiological information for detailed serological studies on bancroftian filariasis in the same community. Quantitative examination of night blood samples (100 microliters) from 1129 individuals (76% of the population), using the counting chamber technique, revealed circulating microfilariae in 13.7% of the study group. Prevalence increased with age, and was higher in males (15.9%) than in females (11.6%). The geometric mean intensity among infected individuals was 223 microfilariae/ml blood (336 microfilariae/ml for males and 212 microfilariae/ml for females). Approximately 16.5% of the males aged > or = 15 years had hydrocele and 2.4% of the population had elephantiasis. The prevalence of these conditions increased with age; in those aged > or = 50 years, 23.8% of males had hydrocele and 6.1% of the total population had elephantiasis. Acute cases of epididymo-orchitis, adenolymphangitis and funiculitis were also seen. The microfilarial prevalence in males with hydrocele was not significantly different from that in asymptomatic males, but none of the elephantiasis cases had microfilaraemia. The striking difference in microfilaraemia pattern between hydrocele and elephantiasis patients may reflect different mechanisms underlying the development of these two chronic manifestations. The overall prevalences of microfilaraemia and clinical manifestations in this community were moderate when compared with those found in other studies carried out along the coast of eastern Africa.

Adolescent↗