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Marcel Tanner

Publications and source records attributed to Marcel Tanner.

At least 19 recordsLinked to original sources
PubMed2007

Adaptation of the ultrasensitive HIV-1 p24 antigen assay to dried blood spot testing.

Implementation of molecular tests for the assessment of pediatric HIV-1 infection in resource-limited countries is difficult because of technical complexity and costs. Alternatives like the ultrasensitive HIV-1 p24 antigen enzyme-linked immunosorbent assay have therefore been proposed. We have now adapted this test to dried blood spot (DBS) plasma p24 antigen (p24). High background activity was recognized as originating from endogenous peroxidase and eliminated by H2O2 quenching. The assay was evaluated with 72 pediatric specimens from Tanzania and with 210 pediatric or adult specimens from Switzerland. A real-time polymerase chain reaction assay for DBS DNA and/or plasma RNA identified HIV-1 infection in 38 Tanzanian children. HIV-1 subtypes included 18 C, 9 A1, 8 D, 1 AC, 1 J-like, and 1 unidentified. The detection rates for the different assays were as follows: DBS-p24, 32 (84%) of 38 samples; DBS DNA, 30 (79%) of 38 samples; plasma-p24, 23 (85%) of 27 samples; and plasma RNA, 30 (100%) of 30 samples. False-negative DBS-p24 was associated with subtype D (P < 0.01). DBS-p24 detection for non-D subtypes was 93% (95% confidence interval: 81% to 99%), and for subtype C, it was 94% (95% confidence interval: 76% to 99%). Specificity among 193 HIV-negative DBS samples was 100%. Correlation of DBS-p24 and plasma-p24 concentrations was excellent (R = 0.83, P < 0.0001). DBS-p24 is thus a promising alternative to molecular tests for HIV-1 in subtype C regions. It should now be evaluated in large studies of children for accurate assessment of diagnostic sensitivity.

Adolescent↗
PubMed2006

Evaluation of the in vivo activity of tribendimidine against Schistosoma mansoni, Fasciola hepatica, Clonorchis sinensis, and Opisthorchis viverrini.

We examined the in vivo activity of tribendimidine against selected trematodes. A single 150-mg/kg dose of tribendimidine achieved a 99.1% reduction of Clonorchis sinensis in rats. A 400-mg/kg dose of tribendimidine reduced Opisthorchis viverrini in hamsters by 95.7%. High doses of tribendimidine showed no activity against Schistosoma mansoni and Fasciola hepatica.

Animals↗
PubMed2006

Effect of temperature on the development of Schistosoma japonicum within Oncomelania hupensis, and hibernation of O. hupensis.

The objectives of this investigation were to assess the effect of temperature on the development of Schistosoma japonicum harboured in Oncomelania hupensis and to determine the lowest temperature threshold at which the hibernation of O. hupensis occurs. In the first experiment, adult infection-free O. hupensis, collected from Jiangsu province in eastern China, were infected with S. japonicum miracidia and raised at different temperatures under laboratory conditions. The development of miracidia until the release of cercariae was monitored employing the cercarial shedding method. In the second experiment, batches of O. hupensis were kept at temperatures below 13 degrees C with the temperature gradually reduced. Snail activity was assessed by a pin puncture method. We found a positive relationship between the development of S. japonicum within O. hupensis and temperature. In snails kept at 15.3 degrees C, S. japonicum arrested their development, while the fastest development occurred at 30 degrees C. The temperature at which half of the snails were in hibernation (ET(50)) was 6.4 degrees C. Our results underscore the pivotal role temperature plays on the biological activity of O. hupensis and the development of S. japonicum within the intermediate host. These findings are likely to have implications for the transmission of schistosomiasis in a warmer future China.

Animals↗
PubMed2006

The synthetic peroxide OZ78 is effective against Echinostoma caproni and Fasciola hepatica.

OBJECTIVES: The trematocidal properties of a synthetic peroxide, 1,2,4-trioxolane (OZ78) were determined both in vivo and in vitro. METHODS: Two weeks post-infection Echinostoma caproni-infected mice were administered single oral doses of 400-1000 mg/kg OZ78. Fasciola hepatica-infected rats were treated orally with 50-400 mg/kg OZ78 3 and 8-9 weeks post-infection. Worm burden reductions were assessed against untreated control animals. Adult F. hepatica were observed by scanning electron microscopy (SEM) after recovery from the bile duct of a rat 3 days after administration of a single oral dose of 100 mg/kg OZ78 and after in vitro exposure to concentrations of 1, 10 and 100 microg/mL OZ78. RESULTS: In the E. caproni-mouse model 100% worm burden reductions were achieved with a single oral dose of 1000 mg/kg OZ78. A single dose of 100 mg/kg OZ78 resulted in worm burden reductions of 100% against juvenile and adult F. hepatica. F. hepatica recovered from rats 3 days post-treatment displayed feeble activity and some flukes had died. Typical features revealed by SEM included extensive blebbing and sloughing. Exposure of F. hepatica to 10-100 microg/mL OZ78 in vitro resulted in the death of all trematodes. F. hepatica showed focal blebbing and sloughing of the tegument at all concentrations investigated. CONCLUSIONS: Our data indicate that OZ78 is highly efficacious against F. hepatica and E. caproni and provide a sound platform for identification of a synthetic peroxide drug development candidate against major trematode infections.

Adamantane↗
PubMed2006

Effect of artesunate and artemether against Clonorchis sinensis and Opisthorchis viverrini in rodent models.

Food-borne trematodiasis is an emerging public health problem and there is a need to develop novel treatment options. We examined the in vivo efficacy of single oral doses of artesunate and artemether administered to rodents experimentally infected with either Clonorchis sinensis or Opisthorchis viverrini. Rats infected with adult C. sinensis were administered artesunate or artemether at doses of 75, 150 or 300 mg/kg. Hamsters infected with adult O. viverrini were administered artesunate or artemether at doses of 200, 400 or 600 mg/kg. Treatment efficacy was assessed according to reductions in worm burden compared with infected but untreated control animals. Worm burden reductions of 98.6-100% were found in C. sinensis-infected rats after a single dose of artesunate and artemether at 150 mg/kg. Administration of artesunate and artemether at a dose of 400mg/kg to O. viverrini-infected hamsters resulted in worm burden reductions of 77.6% and 65.5%, respectively. However, both drugs showed toxic effects when administered to O. viverrini-infected hamsters at a dose > or =400mg/kg. Our study demonstrates that artesunate and artemether possess excellent clonorchicidal activities in vivo. These findings provide a foundation for subsequent clinical trials. More laboratory investigations are warranted to investigate further the opisthorchicidal properties of the artemisinins.

Animals↗
PubMed2006

Community-based surveillance of malaria vector larval habitats: a baseline study in urban Dar es Salaam, Tanzania.

BACKGROUND: As the population of Africa rapidly urbanizes it may be possible to protect large populations from malaria by controlling aquatic stages of mosquitoes. Here we present a baseline evaluation of the ability of community members to detect mosquito larval habitats with minimal training and supervision in the first weeks of an operational urban malaria control program. METHODS: The Urban Malaria Control Programme of Dar es Salaam recruited and provided preliminary training to teams of Community-Owned Resource Persons (CORPs) who performed weekly surveys of mosquito breeding sites. Two trained mosquito biologists accompanied each of these teams for one week and evaluated the sensitivity of this system for detecting potential Anopheles habitats. RESULTS: Overall, 42.4% of 986 habitats surveyed by an inspection team had previously been identified by CORPs. Agricultural habitats were detected less often than other habitats (30.8% detected, Odds Ratio [95%CI] = 0.46 [0.29-0.73], P = 0.001). Non-agricultural artificial habitats were less suitable than other habitats (29.3% occupancy, OR = 0.69 [0.46-1.03], P = 0.066) but still constituted 45% (169/289) of occupied habitats because of their abundance (51 % of all habitats). CONCLUSION: The levels of coverage achieved by modestly trained and supported CORPs at the start of the Dar es Salaam UMCP were insufficient to enable effective suppression of malaria transmission through larval control. Further operational research is required to develop surveillance systems that are practical, affordable, effective and acceptable so that community-based integrated vector management can be implemented in cities across Africa.

Animals↗
PubMed2006

Rapid Urban Malaria Appraisal (RUMA) IV: epidemiology of urban malaria in Cotonou (Benin).

BACKGROUND: An estimated 40 % of the population in Benin lives in urban areas. The purpose of the study was to estimate malaria endemicity and the fraction of malaria-attributable fevers in health facilities in Cotonou. METHODS: A health care system evaluation and a series of school parasitaemia surveys and health facility-based surveys were carried out during the dry season in of 2003, applying standard Rapid Urban Malaria Appraisal (RUMA) methodology. This study was part of a multi-site assessment supported by the Roll Back Malaria Partnership. RESULTS: The field work was carried out in February-March 2003. In 2002 and out of 289,342 consultations in the public health facilities of Cotonou there were 100,257 reported simple malaria cases (34.6%) and 12,195 complicated malaria cases (4.2%). In the school parasitaemia surveys, a malaria infection was found in 5.2 % of all samples. The prevalence rates of parasitaemia in the centre, intermediate and periphery zones were 2.6%, 9.0% and 2.5%, respectively. In the health facility surveys the malaria infection rates in presenting fever cases were 0% (under one year old), 6.8% (one to five years old), 0% (> five to 15 years old) and 0.9% (over 15 years old), while these rates in the control group were 1.4%, 2.8%, 1.3% and 2.0%. The malaria-attributable fractions among presenting fever cases were 0.04 in the one to five years old and zero in the three other age groups. Hence, malaria played only a small role in fever episodes at the end of the dry season. In total, 69.2% of patients used a mosquito net the night before the survey and 35.1% used an insecticide-treated net, which was shown to be protective for an infection (OR = 0.23, 95% CI 0.07-0.78). Travelling to a rural area (5.8% of all respondents) did not increase the infection risk. CONCLUSION: The homogenously low malaria prevalence might be associated with urban transformation and/or a high bednet usage. Over-diagnosis of malaria and over-treatment with antimalarials was found to be a serious problem.

Adolescent↗
PubMed2006

Effect of artemether administered alone or in combination with praziquantel to mice infected with Plasmodium berghei or Schistosoma mansoni or both.

The artemisinins have become key drugs for the treatment and control of malaria, particularly within artemisinin-based combination therapies. Since the artemisinins also exhibit antischistosomal properties, their use in areas where malaria and schistosomiasis are co-endemic may have an effect on both diseases and co-infection might alter drug efficacy. We assessed the antimalarial and antischistosomal efficacies of artemether in mice infected with Plasmodium berghei or Schistosoma mansoni or both parasites concurrently. Three oral doses of 400 mg/kg artemether at 14-day intervals reduced total and female S. mansoni worm burdens by 98.7-100%, regardless of a concurrent P. berghei infection. When four daily doses of 55 mg/kg artemether were administered, which is a standard treatment schedule to cure P. berghei-infected mice, significantly lower total and female S. mansoni worm burden reductions were observed (73.1-89.2%). Artemether, administered at both of the above-mentioned treatment schemes, showed excellent antimalarial efficacy with no indications of delayed clearance of P. berghei or recrudescence, also in mice co-infected with S. mansoni. Co-infection with P. berghei had no effect on S. mansoni worm burden reductions following artemether-praziquantel combinations. Our findings point to the need for epidemiological studies in areas where malaria and schistosomiasis co-exist and where artemisinin-based combination therapies are introduced, since artemisinin-based combination therapies as part of a malaria control package may have ancillary benefits against schistosomiasis.

Animals↗
PubMed2006

An integrated approach for risk profiling and spatial prediction of Schistosoma mansoni-hookworm coinfection.

Multiple-species parasitic infections are pervasive in the developing world, yet resources for their control are scarce. We present an integrated approach for risk profiling and spatial prediction of coinfection with Schistosoma mansoni and hookworm for western Côte d'Ivoire. Our approach combines demographic, environmental, and socioeconomic data; incorporates them into a geographic information system; and employs spatial statistics. Demographic and socioeconomic data were obtained from education registries and from a questionnaire administered to schoolchildren. Environmental data were derived from remotely sensed satellite images and digitized ground maps. Parasitologic data, obtained from fecal examination by using two different diagnostic approaches, served as the outcome measure. Bayesian variogram models were used to assess risk factors and spatial variation of S. mansoni-hookworm coinfection in relation to demographic, environmental, and socioeconomic variables. Coinfections were found in 680 of 3,578 schoolchildren (19.0%) with complete data records. The prevalence of monoinfections with either hookworm or S. mansoni was 24.3% and 24.1%, respectively. Multinomial Bayesian spatial models showed that age, sex, socioeconomic status, and elevation were good predictors for the spatial distribution of S. mansoni-hookworm coinfection. We conclude that our integrated approach, employing a diversity of data sources, geographic information system and remote sensing technologies, and Bayesian spatial statistics, is a powerful tool for risk profiling and spatial prediction of S. mansoni-hookworm coinfection. More generally, this approach facilitates risk mapping and prediction of other parasite combinations and multiparasitism, and hence can guide integrated disease control programs in resource-constrained settings.

Adolescent↗
PubMed2006

Rapid Urban Malaria Appraisal (RUMA) III: epidemiology of urban malaria in the municipality of Yopougon (Abidjan).

BACKGROUND: Currently, there is a significant lack of knowledge concerning urban malaria patterns in general and in Abidjan in particular. The prevalence of malaria, its distribution in the city and the fractions of fevers attributable to malaria in the health facilities have not been previously investigated. METHODS: A health facility-based survey and health care system evaluation was carried out in a peripheral municipality of Abidjan (Yopougon) during the rainy season of 2002, applying a standardized Rapid Urban Malaria Appraisal (RUMA) methodology. RESULTS: According to national statistics, approximately 240,000 malaria cases (both clinical cases and laboratory confirmed cases) were reported by health facilities in the whole of Abidjan in 2001. They accounted for 40% of all consultations. In the health facilities of the Yopougon municipality, the malaria infection rates in fever cases for different age groups were 22.1% (under one year-olds), 42.8% (one to five years-olds), 42.0% (> five to 15 years-olds) and 26.8% (over 15 years-olds), while those in the control group were 13.0%. 26.7%, 21.8% and 14.6%, respectively. The fractions of malaria-attributable fever were 0.12, 0.22, 0.27 and 0.13 in the same age groups. Parasitaemia was homogenously detected in different areas of Yopougon. Among all children, 10.1% used a mosquito net (treated or not) the night before the survey and this was protective (OR = 0.52, 95% CI 0.29-0.97). Travel to rural areas within the last three months was frequent (31% of all respondents) and associated with a malaria infection (OR = 1.75, 95% CI 1.25-2.45). CONCLUSION: Rapid urbanization has changed malaria epidemiology in Abidjan and endemicity was found to be moderate in Yopougon. Routine health statistics are not fully reliable to assess the burden of disease, and the low level of the fractions of malaria-attributable fevers indicated substantial over-treatment of malaria.

Adolescent↗
PubMed2006

Rapid Urban Malaria Appraisal (RUMA) II: epidemiology of urban malaria in Dar es Salaam (Tanzania).

BACKGROUND: The thinking behind malaria research and control strategies stems largely from experience gained in rural areas and needs to be adapted to the urban environment. METHODS: A rapid assessment of urban malaria was conducted in Dar es Salaam in June-August, 2003 using a standard Rapid Urban Malaria Appraisal (RUMA) methodology. This study was part of a multi-site study in sub-Saharan Africa supported by the Roll Back Malaria Partnership. RESULTS: Overall, around one million cases of malaria are reported every year by health facilities. However, school surveys in Dar es Salaam during a dry spell in 2003 showed that the prevalence of malaria parasites was low: 0.8%, 1.4%, 2.7% and 3.7% in the centre, intermediate, periphery and surrounding rural areas, respectively. Health facilities surveys showed that only 37/717 (5.2%) of presenting fever cases and 22/781 (2.8%) of non-fever cases were positive by blood slide. As a result, malaria-attributable fractions for fever episodes were low in all age groups and there was an important over-reporting of malaria cases. Increased malarial infection rates were seen in persons who travelled to rural areas within the past three months. A remarkably high coverage of insecticide-treated nets and a corresponding reduction in malarial infection risk were found. CONCLUSION: The number of clinical malaria cases was much lower than routine reporting suggested. Improved malaria diagnosis and re-defined clinical guidelines are urgently required to avoid over-treatment with antimalarials.

Adolescent↗
PubMed2006

Artesunate and artemether are effective fasciolicides in the rat model and in vitro.

OBJECTIVES: To study the fasciocidal properties of artesunate and artemether in the rat model and in vitro. METHODS: Adult Fasciola hepatica were exposed in vitro to 1, 10 and 100 microg/mL of artesunate, artemether and dihydroartemisinin for 72 h. Female Wistar rats were administered a single oral dose of artesunate and artemether (100-400 mg/kg) commencing 3 or 10-14 weeks post-infection and worm burden reductions were assessed against infected but untreated control rats. F. hepatica were also observed by scanning electron microscopy (SEM) after recovery from bile ducts of rats given a single oral dose of 200 mg/kg artesunate 24 and 72 h post-treatment. RESULTS: F. hepatica exposed for 72 h to 10 microg/mL of artesunate, artemether and dihydroartemisinin in vitro showed poor mobility, swelling of the worm body, roughness, damage of the tegument and blebbing. Exposure to drug concentrations of 100 microg/mL resulted in the death of all F. hepatica by 72 h. One hundred per cent worm burden reductions were achieved in rats infected with adult F. hepatica after treatment with artesunate and artemether at 400 and 200 mg/kg, respectively. Administration of artesunate and artemether at a dose of 200 mg/kg to rats harbouring juvenile F. hepatica resulted in worm burden reductions of 46% and 82%, respectively. F. hepatica recovered from rats' bile ducts 24 h after administration of 200 mg/kg artesunate showed normal activity and SEM observations revealed that there was no visible damage. Seventy-two hours post-treatment F. hepatica displayed very poor mobility and there was focal swelling of the tegument and spines. CONCLUSIONS: Artesunate and artemether exhibit promising fasciocidal activities, with the latter showing better tolerability by the hosts.

Animals↗
PubMed2006

Ecologists can enable communities to implement malaria vector control in Africa.

BACKGROUND: Integrated vector management (IVM) for malaria control requires ecological skills that are very scarce and rarely applied in Africa today. Partnerships between communities and academic ecologists can address this capacity deficit, modernize the evidence base for such approaches and enable future scale up. METHODS: Community-based IVM programmes were initiated in two contrasting settings. On Rusinga Island, Western Kenya, community outreach to a marginalized rural community was achieved by University of Nairobi through a community-based organization. In Dar es Salaam, Tanzania, Ilala Municipality established an IVM programme at grassroots level, which was subsequently upgraded and expanded into a pilot scale Urban Malaria Control Programme with support from national academic institutes. RESULTS: Both programmes now access relevant expertise, funding and policy makers while the academic partners benefit from direct experience of community-based implementation and operational research opportunities. The communities now access up-to-date malaria-related knowledge and skills for translation into local action. Similarly, the academic partners have acquired better understanding of community needs and how to address them. CONCLUSION: Until sufficient evidence is provided, community-based IVM remains an operational research activity. Researchers can never directly support every community in Africa so community-based IVM strategies and tactics will need to be incorporated into undergraduate teaching programmes to generate sufficient numbers of practitioners for national scale programmes. Academic ecologists at African institutions are uniquely positioned to enable the application of practical environmental and entomological skills for malaria control by communities at grassroots level and should be supported to fulfil this neglected role.

Africa↗
PubMed2006

Schistosomiasis and water resources development: systematic review, meta-analysis, and estimates of people at risk.

An estimated 779 million people are at risk of schistosomiasis, of whom 106 million (13.6%) live in irrigation schemes or in close proximity to large dam reservoirs. We identified 58 studies that examined the relation between water resources development projects and schistosomiasis, primarily in African settings. We present a systematic literature review and meta-analysis with the following objectives: (1) to update at-risk populations of schistosomiasis and number of people infected in endemic countries, and (2) to quantify the risk of water resources development and management on schistosomiasis. Using 35 datasets from 24 African studies, our meta-analysis showed pooled random risk ratios of 2.4 and 2.6 for urinary and intestinal schistosomiasis, respectively, among people living adjacent to dam reservoirs. The risk ratio estimate for studies evaluating the effect of irrigation on urinary schistosomiasis was in the range 0.02-7.3 (summary estimate 1.1) and that on intestinal schistosomiasis in the range 0.49-23.0 (summary estimate 4.7). Geographic stratification showed important spatial differences, idiosyncratic to the type of water resources development. We conclude that the development and management of water resources is an important risk factor for schistosomiasis, and hence strategies to mitigate negative effects should become integral parts in the planning, implementation, and operation of future water projects.

Africa↗
PubMed2006

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Acquired Immunodeficiency Syndrome↗
PubMed2006

Urban malaria in the Sahel: prevalence and seasonality of presumptive malaria and parasitaemia at primary care level in Chad.

OBJECTIVE: To assess malaria prevalence rates and seasonal patterns among clinically diagnosed malaria cases at the level of primary care facilities in an urban Sahelian setting. METHOD: Screening all patients consulting two private and two governmental providers on a randomly selected weekday over a period of 9 months. Patients with presumptive malaria underwent a blood test. RESULTS: Of 1658 patients included in the survey, 47% were clinically diagnosed and treated as malaria cases. Malaria was more often diagnosed by private providers. There were no clear seasonal patterns in presumptive malaria. A 30% of clinically diagnosed cases were positive for Plasmodium (all falciparum) by thick film examination. Thus, false positive cases constituted more than 70% of the clinically diagnosed malaria cases. The highest positive prevalence rates were found at the end and shortly after the rainy season (44%-47%) and the lowest during the dry season (2%). CONCLUSIONS: Clinical diagnosis of malaria has a very low positive predicted value in this low endemicity urban setting, and its low specificity leads to inappropriate care for a large proportion of patients. This has a major impact on economic costs for health services and households. In the Sahel, systematic use of microscopy-based diagnosis and/or rapid diagnostic tests should be considered to appropriately manage malaria and non-malaria cases.

Adolescent↗
PubMed2006

Mycobacterium bovis isolates from tuberculous lesions in Chadian zebu carcasses.

This slaughterhouse study in Chad shows higher proportions of Mycobacterium bovis isolates among Mbororo than Arabe zebu cattle. Spoligotyping shows a homogenetic population structure for M. bovis and lack of spacer 30, as were found in neighboring Cameroon and Nigeria. This finding suggests transborder and ongoing transmission between cattle.

Abattoirs↗