Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Torsten Feldt is active.

Publication


Featured researches published by Torsten Feldt.


Science of The Total Environment | 2014

High levels of PAH-metabolites in urine of e-waste recycling workers from Agbogbloshie, Ghana

Torsten Feldt; Julius N. Fobil; Jürgen Wittsiepe; Michael Wilhelm; Holger Till; Alexander Zoufaly; Gerd D. Burchard; Thomas Göen

The informal recycling of electronic waste (e-waste) is an emerging source of environmental pollution in Africa. Among other toxins, polycyclic aromatic hydrocarbons (PAHs) are a major health concern for exposed individuals. In a cross-sectional study, the levels of PAH metabolites in the urine of individuals working on one of the largest e-waste recycling sites of Africa, and in controls from a suburb of Accra without direct exposure to e-waste recycling activities, were investigated. Socioeconomic data, basic health data and urine samples were collected from 72 exposed individuals and 40 controls. In the urine samples, concentrations of the hydroxylate PAH metabolites (OH-PAH) 1-hydroxyphenanthrene (1-OH-phenanthrene), the sum of 2- and 9-hydroxyphenanthrene (2-/9-OH-phenanthrene), 3-hydroxyphenanthrene (3-OH-phenanthrene), 4-hydroxyphenanthrene (4-OH-phenanthrene) and 1-hydroxypyrene (1-OH-pyrene), as well as cotinine and creatinine, were determined. In the exposed group, median urinary concentrations were 0.85 μg/g creatinine for 1-OH-phenanthrene, 0.54 μg/g creatinine for 2-/9-OH-phenanthrene, 0.99 μg/g creatinine for 3-OH-phenanthrene, 0.22 μg/g creatinine for 4-OH-phenanthrene, and 1.33 μg/g creatinine for 1-OH-pyrene, all being significantly higher compared to the control group (0.55, 0.37, 0.63, 0.11 and 0.54 μg/g creatinine, respectively). Using a multivariate linear regression analysis including sex, cotinine and tobacco smoking as covariates, exposure to e-waste recycling activities was the most important determinant for PAH exposure. On physical examination, pathological findings were rare, but about two thirds of exposed individuals complained about cough, and one quarter about chest pain. In conclusion, we observed significantly higher urinary PAH metabolite concentrations in individuals who were exposed to e-waste recycling compared to controls who were not exposed to e-waste recycling activities. The impact of e-waste recycling on exposure to environmental toxins and health of individuals living in the surroundings of e-waste recycling sites warrant further investigation.


Environment International | 2015

Levels of polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/Fs) and biphenyls (PCBs) in blood of informal e-waste recycling workers from Agbogbloshie, Ghana, and controls

Jürgen Wittsiepe; Julius N. Fobil; Holger Till; Gerd-Dieter Burchard; Michael Wilhelm; Torsten Feldt

The formation and environmental release of highly toxic organohalogen compounds associated with informal recycling of waste electric and electronic equipment (e-waste) is a growing problem at e-waste dumps/recycling sites (EWRSs) in many developing countries worldwide. We chose a cross-sectional study design to measure the internal exposure to polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) as well as polychlorinated biphenyls (PCBs) of individuals working on one of the largest EWRSs of Africa, located at Agbogbloshie, Accra, Ghana, and in controls from a suburb of Accra without direct exposure to EWRS activities. In whole blood samples of 21 age matched male exposed individuals (mean age: 24.7 years, SD 6.0) and 21 male controls (mean age: 24.4 years, SD 5.7) 17 PCDD/F congeners were determined. Moreover three indicator PCB congeners (#138, #153 and #180) were measured in blood of 39 exposed (mean age: 27.5 years, SD 11.7) and 19 non-exposed (mean age: 26.8 years, SD 9.7) patients. Besides a health examination, biometric and demographic data, residential and occupational history, occupational exposures and working conditions were recorded using a standardized questionnaire. In the exposed group, median PCDD/F-concentrations were 6.18 pg/g lipid base WHO2005-TEq (range: 2.1-42.7) and significantly higher compared to the control group with 4.60 pg/g lipid base WHO2005-TEq (range: 1.6-11.6). Concentrations were different for 2,3,7,8-TetraCDD, three HexaCDD and all 10 PCDF congeners, indicating a combustion pattern. Using a multivariate regression analysis exposure to EWRS activities was the most important determinant for PCDD/F exposure. Median PCB levels for the indicator congeners #138, #153 and #180 were 0.011, 0.019 and 0.008 μg/l whole blood (ranges: 0.002-0.18, 0.003-0.16, 0.002-0.078) in the exposed group and, surprisingly, significantly higher in the controls (0.037, 0.062 and 0.022; ranges: 0.005-0.46, 0.010-0.46, 0.004-0.21). In a multivariate regression approach e-waste related activities had no positive influence on internal PCB exposure, but rather the time living in Accra. The internal PCB exposure is in particular notable for a country where PCBs have historically never been produced or used. The impact of EWRS activities on organohalogen compound exposure of individuals working at and living in the surroundings of the Agbogbloshie EWRS, and the surprisingly high PCB exposure of people living in Accra not involved in e-waste activities require further investigation.


Journal of Clinical Virology | 2013

Hepatitis E virus infections in HIV-infected patients in Ghana and Cameroon

Torsten Feldt; Fred Stephen Sarfo; Alexander Zoufaly; Richard Phillips; Gerd D. Burchard; Jan van Lunzen; Johannes Jochum; David Chadwick; Charles Awasom; Lisa Claussen; Christian Drosten; Jan Felix Drexler; Anna Maria Eis-Hübinger

BACKGROUND Chronic hepatitis E virus (HEV) infections have recently been described in HIV-infected patients. Only few data are available for sub-Saharan Africa, where HIV and HEV are highly co-endemic, and where liver pathology is common in HIV-infected individuals. OBJECTIVES To assess the prevalence of HEV viremia, anti-HEV antibodies, and serum aminotransferase levels in HIV patients in Ghana and Cameroon. STUDY DESIGN We retrospectively surveyed a cross-section of patients who were enrolled in cohort studies in Ghana (West Africa), and Cameroon (Central Africa). Plasma samples from 1029 HIV patients from Ghana and 515 patients from Cameroon including 214 children were analyzed for HEV-RNA by two reverse transcription PCR methods. In a subset of 791 patients, anti-HEV IgG and IgM antibodies were analyzed. RESULTS No HEV-RNA was detected in any of the plasma samples of 1544 patients. HEV seroprevalence was high in adult HIV patients from Ghana (45.3%, n=402) and Cameroon (14.2%, n=289), but low in pediatric HIV patients from Cameroon (2.0%, n=100). Elevations of alanine aminotransferase and aspartate aminotransferase levels were common in adult patients from Ghana (20.8% and 25.4%) and Cameroon (38.9% and 69.8%). The prevalence of hepatitis B virus surface antigen was 11.8% and of hepatitis C virus antibodies 2.5% in our adult Cameroonian study population. CONCLUSIONS Acute or chronic HEV infections did not play a role in liver pathology in two HIV cohorts in Ghana and Cameroon. A better understanding of the epidemiology and genotype-specific characteristics of HEV infections in HIV patients in sub-Saharan Africa is needed.


Antiviral Therapy | 2013

Prevalence and determinants of virological failure in HIV-infected children on antiretroviral therapy in rural Cameroon: a cross-sectional study

Alexander Zoufaly; Q. Fillekes; R. Hammerl; N. Nassimi; Johannes Jochum; Jan Felix Drexler; Charles Awasom; F. Sunjoh; Gerd D. Burchard; David M. Burger; J. van Lunzen; Torsten Feldt

BACKGROUND In Africa, success of antiretroviral treatment (ART) seems to lag behind in children compared with adults, and high therapeutic failure rates have been reported. We aimed to identify prevalence and determinants of virological failure in HIV-infected children treated under programmatic conditions. METHODS All patients <18 years on ART presenting to the HIV clinic at the Bamenda Regional Hospital, a secondary referral hospital in rural Cameroon, from September 2010 to August 2011, were enrolled in this cross-sectional study. Clinical data, self-reported adherence, CD4(+) T-cell counts and viral load were recorded. Therapeutic drug monitoring was performed on stored plasma samples. Determinants of virological failure were identified using descriptive statistics and logistic regression. RESULTS A total of 230 children with a mean age of 8.9 years (sd 3.7) were included. At the time of analysis, the mean duration of HAART was 3.5 years (sd 1.7) and 12% had a CD4(+) T-cell count <200 cells/µl. In total, 53% of children experienced virological failure (>200 copies/ml). Among children on nevirapine (NVP), plasma levels were subtherapeutic in 14.2% and supratherapeutic in 42.2%. Determinants of virological failure included male sex, lower CD4(+) T-cell counts, subtherapeutic drug levels, longer time on ART and a deceased mother. Poor adherence was associated with subtherapeutic NVP plasma levels and advanced disease stages (WHO stage 3/4). CONCLUSIONS This study demonstrates high virological failure rates and a high variability of NVP plasma levels among HIV-infected children in a routine ART programme in rural Cameroon. Strategies to improve adherence to ART in HIV-infected children are urgently needed.


International Journal of Std & Aids | 2012

High prevalence of hepatitis B and syphilis co-infections among HIV patients initiating antiretroviral therapy in the north-west region of Cameroon.

Alexander Zoufaly; E F Onyoh; P M Tih; C N Awasom; Torsten Feldt

Hepatitis B virus (HBV) and syphilis co-infections contribute significantly to HIV-associated morbidity and mortality, but the burden of these diseases is not fully appreciated in sub-Saharan Africa, as prevalence data are scarce. Both infections often remain undiagnosed in resource-limited settings because routine testing is not a part of most of the national guidelines. Epidemiological studies provide important information on prevalence and risk factors for such co-infections and can provide guidance for clinical management and for the development of test strategies. We analysed data on baseline characteristics, CD4 cell counts, HBV and syphilis co-infection rates of 690 patients enrolling for antiretroviral therapy in rural Cameroon. The prevalence of both hepatitis B surface antigen (HBsAg, 12.6%, 95% CI 10.1–15.1) and treponemal antibodies (11.4%, 95% CI 8.9–13.7) was high, with significantly higher prevalences for both infections in men; detection of treponemal antibodies increased with age. Although liver enzyme elevations were common, they were not useful to identify HBsAg-positive patients. In this setting, routine serological screening for HBV and syphilis co-infection should be considered to avoid complications and ongoing transmission.


PLOS ONE | 2013

No association between antenatal common mental disorders in low-obstetric risk women and adverse birth outcomes in their offspring: results from the CDS study in Ghana and Côte D'Ivoire.

Nan Guo; Marguerite Te Bonle; John Appiah-Poku; Rebecca Hinz; Dana Barthel; Stefanie Schoppen; Torsten Feldt; Claus Barkmann; Mathurin Koffi; Wibke Loag; Samuel Blay Nguah; Kirsten Alexandra Eberhardt; Harry Tagbor; Eliézer K. N’Goran; Stephan Ehrhardt

Background Evidence linking common mental disorders (CMD) in pregnant women to adverse birth outcomes is inconsistent, and studies often failed to control for pregnancy complications. This study aimed to explore the association between antenatal depression and anxiety symptoms and birth outcomes in a low-obstetric risk sample of mother/child dyads in Ghana and Côte d’Ivoire. Methods In 2010-2011, a prospective cohort of 1030 women in their third trimester in Ghana and Côte d’Ivoire was enrolled. Depression and anxiety were assessed in the third trimester using the Patient Health Questionnaire depression module and the 7-item Generalized Anxiety Disorder scale. 719 mother/child dyads were included in the analysis. We constructed multivariate regression models to estimate the association between CMD and low birth weight (LBW), and preterm birth (PTB) to control for potential confounders. Results The prevalence of depression and anxiety symptoms were 28.9% and 14.2% respectively. The mean birth weight was 3172.1g (SD 440.6) and the prevalence of LBW was 1.7%. The mean gestational age was 39.6 weeks and the proportion of PTB was 4%. Multivariate linear regression revealed no significant association between maternal depression (B=52.2, 95% CI -18.2 122.6, p=0.15) or anxiety (B=17.1, 95% CI -74.6 108.7, p=0.72) and birth weight. Yet, low socio-economic status, female sex of the child, and younger maternal age were associated with lower birth weight. Multivariate logistic regression suggested no significant association between maternal depression (OR: 2.1, 95% CI 0.8 5.6, p=0.15) or anxiety (OR: 1.8, 95% CI 0.6 5.5, p=0.29) with PTB. Conclusions Our data suggests that depression and/or anxiety in the 3rd trimester of pregnancy are not independent predictors of adverse birth outcomes in low obstetric risk women. The role of pregnancy complications as confounders or effect modifiers in studies of maternal CMD and their impact on birth outcomes should be investigated.


Journal of Virology | 2015

A Novel Rhabdovirus Isolated from the Straw-Colored Fruit Bat Eidolon helvum, with Signs of Antibodies in Swine and Humans

Tabea Binger; Augustina Annan; Jan Felix Drexler; Marcel A. Müller; René Kallies; Ernest Adankwah; Robert Wollny; Anne Kopp; Hanna Heidemann; Dickson Dei; Festus Courage Agya-Yao; Sandra Junglen; Torsten Feldt; Andreas Kurth; Samuel Oppong; Yaw Adu-Sarkodie; Christian Drosten

ABSTRACT Bats have been implicated as reservoirs of emerging viruses. Bat species forming large social groups and roosting in proximity to human communities are of particular interest. In this study, we sampled a colony of ca. 350,000 individuals of the straw-colored fruit bat Eidolon helvum in Kumasi, the second largest city of Ghana. A novel rhabdovirus (Kumasi rhabdovirus [KRV]) was isolated in E. helvum cell cultures and passaged to Vero cells as well as interferon-competent human and primate cells (A549 and MA104). Genome composition was typical for a rhabdovirus. KRV was detected in 5.1% of 487 animals, showing association with the spleen but not the brain. Antibody prevalence was 11.5% by immunofluorescence and 6.4% by plaque reduction virus neutralization test (PRNT). Detection throughout 3 sampling years was pronounced in both annual wet seasons, of which only one overlaps the postparturition season. Juvenile bats showed increased viral prevalence. No evidence of infection was obtained in 1,240 female mosquitos (6 different genera) trapped in proximity to the colony to investigate potential vector association. Antibodies were found in 28.9% (5.4% by PRNT) of 107 swine sera but not in similarly large collections of sheep, goat, or cattle sera. The antibody detection rate in human subjects with occupational exposure to the bat colony was 11% (5/45 persons), which was significantly higher than in unexposed adults (0.8% [1/118]; chi square, P < 0.001). KRV is a novel bat-associated rhabdovirus potentially transmitted to humans and swine. Disease associations should be investigated. IMPORTANCE Bats are thought to carry a huge number of as-yet-undiscovered viruses that may pose epidemic threats to humans and livestock. Here we describe a novel dimarhabdovirus which we isolated from a large colony of the straw-colored fruit bat Eidolon helvum in Ghana. As these animals are exposed to humans and several livestock species, we looked for antibodies indicating infection in humans, cattle, swine, sheep, and goats. Signs of infection were found in swine and humans, with increased antibody findings in humans who are occupationally exposed to the bat colony. Our data suggest that it is worthwhile to look for diseases caused by the novel virus in humans and livestock.


Hiv Medicine | 2014

Immune activation despite suppressive highly active antiretroviral therapy is associated with higher risk of viral blips in HIV‐1‐infected individuals

Alexander Zoufaly; Jg Kiepe; Sandra Hertling; Anja Hüfner; Olaf Degen; Torsten Feldt; Stefan Schmiedel; M Kurowski; J van Lunzen

Viral blips are thought to represent random biological variations around a steady state of residual HIV viraemia and to lack clinical significance. We aimed to assess the association of immune activation and the occurrence of blips.


Journal of Antimicrobial Chemotherapy | 2015

Virological failure after 1 year of first-line ART is not associated with HIV minority drug resistance in rural Cameroon

Alexander Zoufaly; Johannes Jochum; R. Hammerl; N. Nassimi; Y. Raymond; Gerd D. Burchard; Stefan Schmiedel; Jan Felix Drexler; N. K. Campbell; N. Taka; Charles Awasom; Karin J. Metzner; J van Lunzen; Torsten Feldt

OBJECTIVES The aim of this study was to describe clinical and virological outcomes in therapy-naive HIV-1-positive patients treated in a routine ART programme in rural Cameroon. METHODS In a prospective cohort, 300 consecutive patients starting first-line ART were enrolled and followed for 12 months. Among 238 patients with available viral load data at Month 12, logistic regression was used to analyse risk factors for virological failure (≥1000 HIV RNA copies/mL) including clinical, immunological and virological parameters, as well as data on drug adherence. Population sequencing was performed to detect the presence of drug-resistance mutations in patients with virological failure at Month 12; minority drug-resistance mutations at baseline were analysed using next-generation sequencing in these patients and matched controls. RESULTS At Month 12, 38/238 (16%) patients experienced virological failure (≥1000 HIV RNA copies/mL). Patients with virological failure were younger, had lower CD4 cell counts and were more often WHO stage 3 or 4 at baseline. Sixty-three percent of patients with virological failure developed at least one drug-resistance mutation. The M184V (n = 18) and K103N (n = 10) mutations were most common. At baseline, 6/30 patients (20%) experiencing virological failure and 6/35 (17%) matched controls had evidence of minority drug-resistance mutations using next-generation sequencing (P = 0.77). Lower CD4 count at baseline (OR per 100 cells/mm(3) lower 1.41, 95% CI 1.02-1.96, P = 0.04) and poorer adherence (OR per 1% lower 1.05, 95% CI 1.02-1.08, P < 0.001) were associated with a higher risk of virological failure. Unavailability of ART at the treatment centre was the single most common cause for incomplete adherence. CONCLUSIONS Virological failure after 1 year of ART was not associated with minority drug resistance at baseline but with incomplete adherence. Strategies to assure adherence and uninterrupted drug supplies are pivotal factors for therapy success.


Journal of Virology | 2016

CD25+FoxP3+ memory CD4 T cells are frequent targets of HIV infection in vivo

Mkunde Chachage; Georgios Pollakis; Edmund Osei Kuffour; Kerstin Haase; Asli Bauer; Yuka Nadai; Lilli Podola; Petra Clowes; Matthias Schiemann; Lynette Henkel; Dieter Hoffmann; Sarah Joseph; Sabin Bhuju; Leonard Maboko; Fred Stephen Sarfo; Kirsten Alexandra Eberhardt; Michael Hoelscher; Torsten Feldt; Elmar Saathoff; Christof Geldmacher

ABSTRACT Interleukin 2 (IL-2) signaling through the IL-2 receptor alpha chain (CD25) facilitates HIV replication in vitro and facilitates homeostatic proliferation of CD25+ FoxP3+ CD4+ T cells. CD25+ FoxP3+ CD4+ T cells may therefore constitute a suitable subset for HIV infection and plasma virion production. CD25+ FoxP3+ CD4+ T cell frequencies, absolute numbers, and the expression of CCR5 and cell cycle marker Ki67 were studied in peripheral blood from HIV+ and HIV− study volunteers. Different memory CD4+ T cell subsets were then sorted for quantification of cell-associated HIV DNA and phylogenetic analyses of the highly variable EnvV1V3 region in comparison to plasma-derived virus sequences. In HIV+ subjects, 51% (median) of CD25+ FoxP3+ CD4+ T cells expressed the HIV coreceptor CCR5. Very high frequencies of Ki67+ cells were detected in CD25+ FoxP3+ memory CD4+ T cells (median, 27.6%) in comparison to CD25− FoxP3− memory CD4+ T cells (median, 4.1%; P < 0.0001). HIV DNA content was 15-fold higher in CD25+ FoxP3+ memory CD4+ T cells than in CD25− FoxP3− T cells (P = 0.003). EnvV1V3 sequences derived from CD25+ FoxP3+ memory CD4+ T cells did not preferentially cluster with plasma-derived sequences. Quasi-identical cell-plasma sequence pairs were rare, and their proportion decreased with the estimated HIV infection duration. These data suggest that specific cellular characteristics of CD25+ FoxP3+ memory CD4+ T cells might facilitate efficient HIV infection in vivo and passage of HIV DNA to cell progeny in the absence of active viral replication. The contribution of this cell population to plasma virion production remains unclear. IMPORTANCE Despite recent advances in the understanding of AIDS virus pathogenesis, which cell subsets support HIV infection and replication in vivo is incompletely understood. In vitro, the IL-2 signaling pathway and IL-2-dependent cell cycle induction are essential for HIV infection of stimulated T cells. CD25+ FoxP3+ memory CD4 T cells, often referred to as regulatory CD4 T cells, depend on IL-2 signaling for homeostatic proliferation in vivo. Our results show that CD25+ FoxP3+ memory CD4+ T cells often express the HIV coreceptor CCR5, are significantly more proliferative, and contain more HIV DNA than CD25− FoxP3− memory CD4 T cell subsets. The specific cellular characteristics of CD25+ FoxP3+ memory CD4+ T cells probably facilitate efficient HIV infection in vivo and passage of HIV DNA to cell progeny in the absence of active viral replication. However, the contribution of this cell subset to plasma viremia remains unclear.

Collaboration


Dive into the Torsten Feldt's collaboration.

Top Co-Authors

Avatar
Top Co-Authors

Avatar

Gerd D. Burchard

Bernhard Nocht Institute for Tropical Medicine

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Kirsten Alexandra Eberhardt

Bernhard Nocht Institute for Tropical Medicine

View shared research outputs
Top Co-Authors

Avatar

Jan Felix Drexler

Humboldt University of Berlin

View shared research outputs
Top Co-Authors

Avatar

Mark Oette

University of Düsseldorf

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Fred Stephen Sarfo

Kwame Nkrumah University of Science and Technology

View shared research outputs
Top Co-Authors

Avatar

Samuel Blay Nguah

Komfo Anokye Teaching Hospital

View shared research outputs
Researchain Logo
Decentralizing Knowledge