| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Ahlberg, Sara, et al.
(författare)
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A Risk Assessment of Aflatoxin M1 Exposure in Low and Mid-Income Dairy Consumers in Kenya
- 2018
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Ingår i: Toxins. - : MDPI. - 2072-6651 .- 2072-6651. ; 10:9
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Tidskriftsartikel (refereegranskat)abstract
- Aflatoxin M-1 (AFM(1)), a human carcinogen, is found in milk products and may have potentially severe health impacts on milk consumers. We assessed the risk of cancer and stunting as a result of AFM(1) consumption in Nairobi, Kenya, using worst case assumptions of toxicity and data from previous studies. Almost all (99.5%) milk was contaminated with AFM(1). Cancer risk caused by AFM(1) was lower among consumers purchasing from formal markets (0.003 cases per 100,000) than for low-income consumers (0.006 cases per 100,000) purchasing from informal markets. Overall cancer risk (0.004 cases per 100,000) from AFM(1) alone was low. Stunting is multifactorial, but assuming only AFM(1) consumption was the determinant, consumption of milk contaminated with AFM(1) levels found in this study could contribute to 2.1% of children below three years in middle-income families, and 2.4% in low-income families, being stunted. Overall, 2.7% of children could hypothetically be stunted due to AFM(1) exposure from milk. Based on our results AFM(1) levels found in milk could contribute to an average of -0.340 height for age z-score reduction in growth. The exposure to AFM(1) from milk is 46 ng/day on average, but children bear higher exposure of 3.5 ng/kg bodyweight (bw)/day compared to adults, at 0.8 ng/kg bw/day. Our paper shows that concern over aflatoxins in milk in Nairobi is disproportionate if only risk of cancer is considered, but that the effect on stunting children might be much more significant from a public health perspective; however, there is still insufficient data on the health effects of AFM(1).
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| 3. |
- Alonso, Silvia, et al.
(författare)
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Prevalence of tuberculosis, brucellosis and trypanosomiasis in cattle in Tanzania : a systematic review and meta-analysis.
- 2016
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Ingår i: Animal Health Research Reviews. - 1466-2523 .- 1475-2654. ; 17:1, s. 16-27
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Tidskriftsartikel (refereegranskat)abstract
- A meta-analysis was performed to derive prevalence estimates for Brucella spp., Mycobacterium spp. and Trypanosoma spp. in cattle in Tanzania using data derived from a systematic review of zoonotic hazards in cattle production systems. Articles published before 2012 reporting prevalence and considered at least moderate in quality were included in the analysis. Results showed high heterogeneity between studies, with wide ranges in the reported prevalence: Brucella (0.3-60.8%), Mycobacterium (0.1-13.2%) and Trypanosoma (0.82-33.3%). Overall meta-analytic mean prevalence estimates were 8.2% (95% CI 6.5-10.2), 1.28% (95% CI 0.35-4.58) and 10.3% (95% CI 6.20-16.70) respectively, for Brucella spp., Mycobacterium spp. and Trypanosoma spp. Time and region were predictors of variability of Brucella spp. prevalence, while diagnostic test was a strong predictor of Mycobacterium spp. prevalence, with higher prevalence estimates given by skin tests compared with post-mortem inspection. None of the studied factors were associated with prevalence of Trypanosoma spp. The small sample sizes, range of study locations, study designs and diagnostics used, contributed to high variability among prevalence estimates. Larger and more robust prevalence studies are needed to adequately support risk assessment and management of animal and public health threats.
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| 4. |
- Alonso, Silvia, et al.
(författare)
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Where literature is scarce : observations and lessons learnt from four systematic reviews of zoonoses in African countries.
- 2016
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Ingår i: Animal Health Research Reviews. - 1466-2523 .- 1475-2654. ; 17:1, s. 28-38
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Tidskriftsartikel (refereegranskat)abstract
- The success of a systematic review depends on the availability, accessibility and quality of literature related to the review question. This paper presents the literature found in four systematic reviews conducted for a selection of zoonotic hazards in four livestock value chains in Africa, as well as setting out the challenges in conducting the reviews. The protocol was designed following international standards, and addressed four questions around prevalence, risk factors, control options and impact of various hazards and populations. Searches were conducted in four online databases. Articles were screened for relevance, and quality was assessed before data extraction. Literature on zoonotic hazards was in general scarce and access to full articles was limited. Overall, 25-40% of papers were considered poor quality. The diversity of approaches and designs in the studies compromised the ability to generate summarized estimates. We found that the emphasis of veterinary research has been on livestock problems rather than public health issues, although this seems to be shifting in the last decade; we also found there are limited studies on impact and control. While increasing literature is being published around zoonoses in Africa, this is still inadequate to appropriately inform policy and guide research efforts.
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| 5. |
- Anyango, Gladys, et al.
(författare)
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A survey of aflatoxin M1 contamination in raw milk produced in urban and peri-urban areas of Kisumu County, Kenya
- 2018
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Ingår i: Infection Ecology & Epidemiology. - : Taylor & Francis. - 2000-8686 .- 2000-8686. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACTBackground: Food safety is of increasing global concern, and a OneHealth issue requiring attention of many disciplines. Aflatoxins are toxins produced by fungi and found in foods and feeds, and exposure causes negative health effects in humans and animals. When lactating animals consume aflatoxin B1, the metabolite (AFM1) is transferred to milk.Methods: A cross-sectional study was designed to determine characteristics of smallholder dairy farming in urban and peri-urban areas of Kisumu and quantify AFM1 in milk. Data was collected from 97 randomly selected dairy farms on farming practices, milk production, and awareness about aflatoxins. Collected milk samples were analyzed using enzyme-linked immunosorbent assay for AFM1.Results: Average milk produced was 13 liters per day per household and mainly used for household consumption and sold to neighbours. Farmers mainly fed cows on forage and concentrates (62.9%). Levels of AFM1 ranged from below the detection limit to 151 ppt, with a mean of 29.67 p...
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| 6. |
- Anyango, Gladys, et al.
(författare)
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Effectiveness of Training and Use of Novasil Binder in Mitigating Aflatoxins in Cow Milk Produced in Smallholder Farms in Urban and Periurban Areas of Kenya
- 2021
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Ingår i: Toxins. - : MDPI. - 2072-6651 .- 2072-6651. ; 13:4
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Tidskriftsartikel (refereegranskat)abstract
- Aflatoxins, which commonly contaminate animal feeds and human food, present a major public health challenge in sub-Saharan Africa. After ingestion by cows, aflatoxin B1 is metabolized to aflatoxin M1 (AFM1), some of which is excreted in milk. This study involved smallholder dairy farms in urban and periurban areas of Nairobi and Kisumu, Kenya. The objective was to determine the effectiveness of training and providing farmers with aflatoxin binder (NovaSil(R)) on AFM1 contamination in raw milk. A baseline survey was undertaken and 30 farmers whose milk had AFM1 levels above 20 ppt were randomly selected for inclusion in the study. Of these, 20 farmers were part of the intervention, and were given training on the usage of the NovaSil(R) binder, while 10 served as a control group. All farmers were visited biweekly for three months for interviews and milk samples were collected to measure the AFM1 levels. The AFM1 levels were quantified by enzyme linked immunosorbent assay. The NovaSil(R) binder significantly reduced AFM1 concentrations in the raw milk produced by the farmers in the intervention group over the duration of the study (p < 0.01). The control farms were more likely to have milk with AFM1 levels exceeding the regulatory limit of 50 ppt compared to the intervention farms (p < 0.001) (odds ratio = 6.5). The farmers in the intervention group perceived that there was an improvement in milk yield, and in cow health and appetite. These farmers also felt that the milk they sold, as well as the one they used at home, was safer. In conclusion, the use of binders by dairy farmers can be effective in reducing AFM1 in milk. Further research is needed to understand their effectiveness, especially when used in smallholder settings.
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| 7. |
- Begum, Ruhena, et al.
(författare)
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Heavy metal contamination in retailed food in Bangladesh : a dietary public health risk assessment
- 2023
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Ingår i: Frontiers in Sustainable Food Systems. - : Frontiers Media S.A.. - 2571-581X. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- IntroductionContamination with heavy and toxic metals along the food value chain is a public health concern in Bangladesh. MethodsIn this study, 608 fish and chicken samples from traditional and modern retail outlets in urban, peri-urban, and rural areas were collected and analyzed for chromium (Cr), cadmium (Cd), and lead (Pb) contamination, using atomic absorption spectrometry method. The daily intake, target hazard quotient and the target carcinogenic risk (for lead only) as a result of fish and chicken consumption was calculated based on mean results, and by Monte Carlo simulation in @Risk with 100,000 iterations (quantitative risk assessment). ResultsCr and Cd were detected in 80-86% of both chicken meat and fish samples, while Pb positivity found in chicken meat and fish was 54.9 and 23.3%, respectively. The mean concentration (+/- SD) of Cr, Cd, and Pb in chicken meat were 0.66 +/- 0.93, 0.02 +/- 0.03, and 0.09 +/- 0.10 mg/kg, respectively; and in fish were 0.49 +/- 0.62, 0.02 +/- 0.03, and 0.06 +/- 0.09 mg/kg, respectively. The estimated daily intakes of Cr, Cd, and Pb from chicken and fish were lower than the maximum tolerable daily intake in all studied areas. In addition, the target carcinogenic risk for Pb in chicken was lower than the negligible range, which indicated the risk of cancer due to exposure to Pb through chicken meat and fish consumption was very low. DiscussionThe present study concludes that consumption of chicken meat and fish in Bangladesh, currently at very low levels, is unlikely to constitute a major health risk for humans in respect to these metals. However, continuous market surveillance for heavy metals in food stuff is recommended, especially since consumers may increase their meat intake.
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| 8. |
- Bett, Bernard, et al.
(författare)
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Climate Change and Infectious Livestock Diseases : The Case of Rift Valley Fever and Tick-Borne Diseases
- 2019
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Ingår i: The Climate-Smart Agriculture Papers. - Cham : Springer. - 9783319927978 - 9783319927985 ; , s. 29-37
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Bokkapitel (refereegranskat)abstract
- Climate change influences the occurrence and transmission of a wide range of livestock diseases through multiple pathways. Diseases caused by pathogens that spent part of their life cycle outside the host (e.g. in vectors or the environment) are more sensitive in this regard, compared to those caused by obligate pathogens. In this chapter, we use two well-studied vector-borne diseases—Rift Valley fever (RVF) and tick-borne diseases (TBDs)—as case studies to describe direct pathways through which climate change influences infectious disease-risk in East and southern Africa. The first case study demonstrates that changes in the distribution and frequency of above-normal precipitation increases the frequency of RVF epidemics. The second case study suggests that an increase in temperature would cause shifts in the spatial distribution of TBDs, with cooler and wetter areas expected to experience heightened risk with climate change. These diseases already cause severe losses in agricultural productivity, food security and socio-economic development wherever they occur, and an increase in their incidence or geographical coverage would intensify these losses. We further illustrate some of the control measures that can be used to manage these diseases and recommend that more research should be done to better understand the impacts of climate change on livestock diseases as well as on the effectiveness of the available intervention measures.
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| 9. |
- Bett, Bernard, et al.
(författare)
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Effects of flood irrigation on the risk of selected zoonotic pathogens in an arid and semi-arid area in the eastern Kenya
- 2017
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Ingår i: PLOS ONE. - : PUBLIC LIBRARY SCIENCE. - 1932-6203. ; 12:5
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Tidskriftsartikel (refereegranskat)abstract
- To investigate the effects of irrigation on land cover changes and the risk of selected zoonotic pathogens, we carried out a study in irrigated, pastoral and riverine areas in the eastern Kenya. Activities implemented included secondary data analyses to determine land use and land cover (LULC) changes as well as human, livestock and wildlife population trends; entomological surveys to characterize mosquitoes population densities and species distribution by habitat and season; and serological surveys in people to determine the risk of Rift Valley fever virus (RVFV), West Nile fever virus (WNV), dengue fever virus (DFV), Leptospira spp. and Brucella spp. Results demonstrate a drastic decline in vegetation cover over R approximate to 25 years particularly in the irrigated areas where cropland increased by about 1,400% and non-farm land (under closed trees, open to closed herbaceous vegetation, bushlands and open trees) reduced by 30-100%. The irrigated areas had high densities of Aedes mcintoshi, Culexspp. and Mansonia spp. (important vectors for multiple arboviruses) during the wet and dry season while pastoral areas had high densities of Ae. tricholabis specifically in the wet season. The seroprevalences of RVFV, WNV and DFV were higher in the irrigated compared to the pastoral areas while those for Leptospira spp and Brucella spp. were higher in the pastoral compared to the irrigated areas. It is likely that people in the pastoral areas get exposed to Leptospira spp by using water fetched from reservoirs that are shared with livestock and wildlife, and to Brucella spp. by consuming raw or partially cooked animal source foods such as milk and meat. This study suggests that irrigation increases the risk of mosquito-borne infections while at the same time providing a protective effect against zoonotic pathogens that thrive in areas with high livestock population densities.
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| 10. |
- Bett, Bernard, et al.
(författare)
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Spatiotemporal analysis of historical records (2001-2012) on dengue fever in Vietnam and development of a statistical model for forecasting risk
- 2019
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 14:11
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Dengue fever is the most widespread infectious disease of humans transmitted by Aedes mosquitoes. It is the leading cause of hospitalization and death in children in the Southeast Asia and western Pacific regions. We analyzed surveillance records from health centers in Vietnam collected between 2001-2012 to determine seasonal trends, develop risk maps and an incidence forecasting model.METHODS: The data were analyzed using a hierarchical spatial Bayesian model that approximates its posterior parameter distributions using the integrated Laplace approximation algorithm (INLA). Meteorological, altitude and land cover (LC) data were used as predictors. The data were grouped by province (n = 63) and month (n = 144) and divided into training (2001-2009) and validation (2010-2012) sets. Thirteen meteorological variables, 7 land cover data and altitude were considered as predictors. Only significant predictors were kept in the final multivariable model. Eleven dummy variables representing month were also fitted to account for seasonal effects. Spatial and temporal effects were accounted for using Besag-York-Mollie (BYM) and autoregressive (1) models. Their levels of significance were analyzed using deviance information criterion (DIC). The model was validated based on the Theil's coefficient which compared predicted and observed incidence estimated using the validation data. Dengue incidence predictions for 2010-2012 were also used to generate risk maps.RESULTS: The mean monthly dengue incidence during the period was 6.94 cases (SD 14.49) per 100,000 people. Analyses on the temporal trends of the disease showed regular seasonal epidemics that were interrupted every 3 years (specifically in July 2004, July 2007 and September 2010) by major fluctuations in incidence. Monthly mean minimum temperature, rainfall, area under urban settlement/build-up areas and altitude were significant in the final model. Minimum temperature and rainfall had non-linear effects and lagging them by two months provided a better fitting model compared to using unlagged variables. Forecasts for the validation period closely mirrored the observed data and accurately captured the troughs and peaks of dengue incidence trajectories. A favorable Theil's coefficient of inequality of 0.22 was generated.CONCLUSIONS: The study identified temperature, rainfall, altitude and area under urban settlement as being significant predictors of dengue incidence. The statistical model fitted the data well based on Theil's coefficient of inequality, and risk maps generated from its predictions identified most of the high-risk provinces throughout the country.
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