(1/112) Dense populations of a giant sulfur bacterium in Namibian shelf sediments.
A previously unknown giant sulfur bacterium is abundant in sediments underlying the oxygen minimum zone of the Benguela Current upwelling system. The bacterium has a spherical cell that exceeds by up to 100-fold the biovolume of the largest known prokaryotes. On the basis of 16S ribosomal DNA sequence data, these bacteria are closely related to the marine filamentous sulfur bacteria Thioploca, abundant in the upwelling area off Chile and Peru. Similar to Thioploca, the giant bacteria oxidize sulfide with nitrate that is accumulated to =800 millimolar in a central vacuole. (+info)
(2/112) Transmission dynamics of tuberculosis in a high-incidence country: prospective analysis by PCR DNA fingerprinting.
We have prospectively analyzed the DNA fingerprints of Mycobacterium tuberculosis strains from a random sample of patients with newly diagnosed tuberculosis in Windhoek, Namibia. Strains from 263 smear-positive patients in whom tuberculosis was diagnosed during 1 year were evaluated, and the results were correlated with selected epidemiological and clinical data. A total of 163 different IS6110 fingerprint patterns were observed among the 263 isolates. Isolates from a high percentage of patients (47%) were found in 29 separate clusters, with a cluster defined as isolates with 100% matching patterns. The largest cluster included isolates from 39 patients. One predominant strain of M. tuberculosis caused 15% of cases of smear-positive pulmonary tuberculosis in Windhoek. That strain was also prevalent in the north of the country, suggesting that in contrast to other African countries with isolates with high levels of diversity in their DNA fingerprint patterns, only a restricted number of different strains significantly contribute to the tuberculosis problem in Namibia. (+info)
(3/112) Prevalence of hepatitis C virus antibodies and genotypes in asymptomatic, first-time blood donors in Namibia.
Reported is the prevalence of hepatitis C virus (HCV) in Namibia as determined using a third-generation enzyme-linked immunosorbent assay (ELISA) on samples of blood collected from all asymptomatic, first-time blood donors between 1 February and 31 July 1997 (n = 1941). The HCV seroprevalence was 0.9% (95% confidence interval (CI): 0.5-1.5%) and no associations were detected between a positive HCV serostatus and the person's sex, region of residence, or previous hepatitis B exposure or hepatitis B carrier status, as determined by hepatitis B surface antigen (HBsAg). The only significant association in a logistic regression model was an increase in HCV positivity with increasing age (P = 0.04). Viral RNA was amplified from 2 out of 18 (11.1%) specimens that were ELISA positive. Genotyping of these specimens, by restriction fragment length polymorphism (RFLP), showed the presence of genotypes 5 and 1a. The positive predictive value of using HBsAg positivity as a surrogate screening marker for HCV in Namibian blood donors was poor (1.6%), with low sensitivity (16.7%) and specificity (89.3%), and detecting only 3 out of 18 serologically HCV-positive specimens. The results of this first study of the prevalence and epidemiology of HCV infection in Namibia suggest that donor blood should be screened for HCV by ELISA in order to prevent the transmission of hepatitis C virus. (+info)
(4/112) Isotopes, ice ages, and terminal Proterozoic earth history.
Detailed correlations of ancient glacial deposits, based on temporal records of carbon and strontium isotopes in seawater, indicate four (and perhaps five) discrete ice ages in the terminal Proterozoic Eon. The close and repeated stratigraphic relationship between C-isotopic excursions and glaciogenic rocks suggests that unusually high rates of organic carbon burial facilitated glaciation by reducing atmospheric greenhouse capacity. The emerging framework of time and environmental change contributes to the improved resolution of stratigraphic and evolutionary pattern in the early fossil record of animals. (+info)
(5/112) Upwelling intensification as part of the Pliocene-Pleistocene climate transition.
A deep-sea sediment core underlying the Benguela upwelling system off southwest Africa provides a continuous time series of sea surface temperature (SST) for the past 4.5 million years. Our results indicate that temperatures in the region have declined by about 10 degrees C since 3.2 million years ago. Records of paleoproductivity suggest that this cooling was associated with an increase in wind-driven upwelling tied to a shift from relatively stable global warmth during the mid-Pliocene to the high-amplitude glacial-interglacial cycles of the late Quaternary. These observations imply that Atlantic Ocean surface water circulation was radically different during the mid-Pliocene. (+info)
(6/112) An outbreak of hepatitis E in Northern Namibia, 1983.
In 1983 in Namibia's Kavango region, epidemic jaundice affected hundreds of people living in settlements lacking potable water and waste disposal facilities. Many were Angolan refugees. The disease, which after investigation was designated non-A non-B hepatitis, was most common in males (72%), in persons aged 15-39 years, and was usually mild except in pregnant women, who incurred 6 (86%) of the 7 fatal infections. Fifteen years later, archived outbreak-associated samples were analyzed. Hepatitis E virus (HEV) was detected by reverse transcription-polymerase chain reaction in feces from 9 of 16 patients tested. Total Ig and IgM to HEV were quantitated in serum from 24 residents of an affected settlement at the outbreak's end: 42% had IgM diagnostic of recent infection and 25% had elevated total Ig without IgM, consistent with past HEV infection. The Namibia outbreak was typical hepatitis E clinically and epidemiologically. This first report of hepatitis E confirmed by virus detection from southern Africa extends the known range of HEV and highlights its risk for refugees. (+info)
(7/112) Mantophasmatodea: a new insect order with extant members in the Afrotropics.
A new insect order, Mantophasmatodea, is described on the basis of museum specimens of a new genus with two species: Mantophasma zephyra gen. et sp. nov. (one female from Namibia) and M. subsolana sp. nov. (one male from Tanzania). This is the first time since 1914 that a newly described extant insect taxon has proved unplaceable within a recognized order. Mantophasmatodeans are apterous carnivores. Their closest phylogenetic relationships may be to Grylloblattodea (ice-crawlers) and/or Phasmatodea (stick insects), but the morphological evidence is ambiguous. Raptophasma Zompro from Baltic amber is assigned to the Mantophasmatodea, revealing a wider previous range for the lineage. (+info)
(8/112) Proterozoic modular biomineralized metazoan from the Nama Group, Namibia.
We describe a Proterozoic, fully biomineralized metazoan from the Omkyk Member (approximately 549 million years before the present) of the northern Nama Group, Namibia. Namapoikia rietoogensis gen. et sp. nov. is up to 1 meter in diameter and bears a complex and robust biomineralized skeleton; it probably represents a cnidarian or poriferan. Namapoikia encrusts perpendicular to the walls of vertical synsedimentary fissures in microbial reefs. This finding implies that large, modular metazoans with biologically controlled mineralization appeared some 15 million years earlier than previously documented. (+info)