With the second highest gross domestic product in Africa, South Africa is known to have a high pesticide usage, including the highly persistent and banned group of organochlorine pesticides (OCPs). ...South Africa is also one of few countries to still actively spray DDT as malaria vector control. The aim of the study was to determine the degree to which aquatic biota in selected rivers of the world renowned Kruger National Park (KNP) are exposed to by use of OCPs in the catchments outside the KNP and how this exposure relates to human health. Tigerfish (Hydrocynus vittatus) are economically important apex predators and was selected as bioindicator for this study. Fish were sampled from the KNP sections of the Luvuvhu, Letaba and Olifants rivers during the high and low flow periods from 2010 to 2011 within the KNP and 19 OCPs were determined in muscle tissue using GC-ECD techniques. Significant flow related and spatial OCP bioaccumulation was observed. Tigerfish from the Luvuvhu River displayed the highest OCP bioaccumulation. Concentrations of the majority of the OCPs including the DDTs were the highest levels ever recorded from South African freshwater systems and in many cases the concentrations were higher than most contaminated areas from around the world. The concentrations found in H. vittatus muscle also exceeded maximum residue levels in edible fat as set by the European Union. The health risk assessment also demonstrated that the levels of OCPs pose very high cancer risks to the local populations consuming tigerfish, as high as 2 in 10 increased risk factor. This is of concern not only when managing the water resources of the conservation area but also for surrounding communities consuming freshwater fish. Contaminants enter the park from outside the borders and pose potential risks to the mandated conservation of aquatic biota within the KNP.
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•First record of OCPs in top predator tigerfish from rivers in Kruger National Park•Pesticides used for vector control bioaccumulate at very high levels in fish from conservation areas•Both rivers flowing through the Kruger National Park are polluted by OCPs originating from the catchment.•OCP bioaccumulation is the highest reported for Africa.•Significant human cancer risk is associated with the consumption of fish from these rivers.
To avoid delay in oncological treatment, a 6-weeks norm for time to treatment has been agreed on in The Netherlands. However, the impact of the COVID-19 pandemic on health systems resulted in reduced ...capacity for regular surgical care. In this study, we investigated the impact of the COVID-19 pandemic on time to treatment in surgical oncology in The Netherlands.
A population-based analysis of data derived from five surgical audits, including patients who underwent surgery for lung cancer, colorectal cancer, upper gastro-intestinal, and hepato-pancreato-biliary (HPB) malignancies, was performed. The COVID-19 cohort of 2020 was compared to the historic cohorts of 2018 and 2019. Primary endpoints were time to treatment initiation and the proportion of patients whose treatment started within 6 weeks. The secondary objective was to evaluate the differences in characteristics and tumour stage distribution between patients treated before and during the COVID-19 pandemic.
A total of 14,567 surgical cancer patients were included in this study, of these 3292 treatments were started during the COVID-19 pandemic. The median time to treatment decreased during the pandemic (26 vs. 27 days,
< 0.001) and the proportion of patients whose treatment started within 6 weeks increased (76% vs. 73%,
< 0.001). In a multivariate logistic regression analysis, adjusting for patient characteristics, no significant difference in post-operative outcomes between patients who started treatment before or after 6 weeks was found. Overall, the number of procedures performed per week decreased by 8.1% during the pandemic. This reduction was most profound for patients with stage I lung carcinoma and colorectal carcinoma. There were fewer patients with pulmonary comorbidities in the pandemic cohort (11% vs. 13%,
= 0.003).
Despite pressure on the capacity of the healthcare system during the COVID-19 pandemic, a larger proportion of surgical oncological patients started treatment within six weeks, possibly due to prioritisation of cancer care and reductions in elective procedures. However, during the pandemic, a decrease in the number of surgical oncological procedures performed in The Netherlands was observed, especially for patients with stage I disease.
Dichlorodiphenyltrichloroethane (DDT) is an organochlorine insecticide used worldwide. Several studies have reported the toxic effects of DDT and its metabolites on steroid hormone biosynthesis; ...however, its environmental effects are not well understood. This study examined wild rats collected in DDT-sprayed areas of South Africa and quantified plasma metabolites using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS). Fold change analysis of the metabolome revealed the effect of DDT on bile acid biosynthesis. Gene expression of the related enzyme in rat liver samples was also quantified. Significant association was found between DDT and gene expression levels related to constitutive androstane receptor mediated enzymes, such as Cyp2b1 in rat livers. However, our results could not fully demonstrate that enzymes related to bile acid biosynthesis were strongly affected by DDT. The correlation between DDT concentration and gene expression involved in steroid hormone synthesis in testis was also evaluated; however, no significant correlation was found. The disturbance of metabolic enzymes occurred in rat liver in the target area. Our results suggest that DDT exposure affects gene expression in wild rats living in DDT-sprayed areas. Therefore, there is a need for DDT toxicity evaluation in mammals living in DDT-sprayed areas. We could not find an effective biomarker that could reflect the mechanism of DDT exposure; however, this approach can provide new insights for future research to evaluate DDT effects in sprayed areas.
The physical and chemical characteristics of surface sediments from a leading conservation area, namely the Kruger National Park, were determined in order to identify potential stressors in the ...systems that may contribute to overall deterioration in sediment quality within the reserve, leading to potential threats to the aquatic biota conserved within these stretches of river. Sediment samples were collected during four surveys (two low flow and two high flow) from 2009 to 2011. Samples were analysed for organic content, grain size determination, metals and various organochlorine pesticides. Results indicated that the Olifants River sediments did not show any great improvement over the years and point towards the continued input of pollutants into this system. Sediment quality in the Luvuvhu and Letaba Rivers is better than that of sediments from the Olifants River in terms of metals, but metal concentrations are still comparable and point towards anthropogenic inputs of metals into these rivers. Even though the data indicate that these systems are being contaminated with both metals and organochlorine pesticides (OCPs), levels were still below contaminated sediments from around the globe. Sediment Quality Index scores showed that the sediment quality of these rivers is in a relatively good state. High metal concentrations were the drivers behind lowered sediment quality, and in some cases certain OCPs played a role. Both metals and OCP concentrations were highly correlated with finer grain sizes. Sediment assessments are not routinely applied in South Africa resulting in very little reference or background data available for the area. The metal concentrations for the study area were generally lower than those for other studies in more polluted regions. The study also contributes to the available knowledge on surrounding metal pollution in riverine sediments in South Africa.
•South Africa's largest floodplain not been assessed for OCPs for three decades.•High OCP concentration found in other aquatic ecosystems of eastern South Africa.•OCPs and stable isotopes assessed in ...ecologically and economically important fishes.•High levels of γ-HCH (Lindane) in all species sampled•Trophic transfer of DDT demonstrated major ecological and human health risks.
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•Vanadium exposure causes the inhibition of AChE, SOD and CAT in frogs.•Biomarkers revealed differing trends between acute and chronic exposures.•MT, AChE, SOD, CAT, and GSH responses were more ...pronounced in chronic exposures.•Acute V exposure affected CEA, Ec, Ea, glucose, lipid and protein content most.
Vanadium is a metal whose toxicity towards terrestrial and aquatic species has been under-reported to date.. The biochemical responses of vanadium in amphibian species have not been determined. To establish the effects of vanadium (V) on exposed adult Xenopus laevis, acute and chronic exposures were conducted, and biomarker analyses were performed on liver and muscle tissues from exposed frogs. Biomarkers of exposure, such as acetylcholinesterase (AChE) and metallothioneins (MT), were analysed. Biomarkers of effect were also analysed to determine possible increases in reactive oxygen species (ROS), and the effect of the exposure on the energy balance in the organisms. These included superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH), protein carbonyls (PC), malondialdehyde (MDA), and cellular energy allocation (CEA) (energy available, energy consumption, lipids, proteins and glucose). In acute exposures, the energy balances in organisms were distinctly affected, possibly due to insulin mimetic properties of V. In chronic exposures, MT, AChE, SOD, CAT and GSH responses were more pronounced. Although AChE is generally inhibited by pollutant exposure, in this study, it was stimulated. There were significant inhibitions of SOD and CAT, previously observed in frog species. PC levels increased in the highest acute exposure concentration, indicating protein damage. The IBR.v2 revealed the biochemical responses of V more effectively than traditional statistical analysis.
This study investigated the use of an exotic fish species 'Oreochromis niloticus' as a bio-indicator organism in active biomonitoring of Yellow Jacket and Mazowe rivers, Zimbabwe, receiving acid mine ...drainage from Iron Duke Mine. The Yellow Jacket River flows through Iron Duke Pyrite Mine while the Mazowe River passes through the Mazowe factory and estate shop that receives runoff from intensive agricultural activities. Active biomonitoring (ABM) exposures were conducted for 6 weeks in effluent-contaminated sections of the rivers during high flow, from February to March 2013. A set of biomarkers of exposure and effect (glutathione S-transferase, catalase and metallothioneins) were selected and their responses determined in 'O. niloticus' liver, gills and muscle. We hypothesized that the increase in activities of GST, CAT and MT in exposed fish, in comparison to control fish, can be used to assess river water quality using 'O. niloticus'. Biomarker expression was measured after 4 and 6 weeks and compared against control fish kept under laboratory conditions without contaminants. Concentrations of zinc, cadmium, chromium, nickel, lead, copper, manganese, arsenic and iron were measured in flowing water, riverbed sediments and muscle tissue of actively biomonitored 'O. niloticus'. Key water quality parameters, including dissolved oxygen and conductivity, clearly showed a pollution gradient from Iron Duke Mine. Expression of CAT and GST was highest in the liver, compared to gills and muscles, after 4 and 6 weeks of exposure, and their expression was lower (p < 0.05) in control fish. The expression of the enzymes was not significantly different after 6 weeks compared to 4 weeks. Increased enzyme expressions at Site 1, which is upstream from Iron Duke Mine, were comparable to enzyme expressions at Sites 3, 4, 5 and 6, which correlated with increased zinc concentrations in the exposed fish muscle tissue. The general order of metal concentrations was sediments > water > fish, except for zinc, which had the highest bioconcentration factors. Using the GST, CAT and MT we concluded that Mazowe and Yellow Jacket rivers are contaminated and that these oxidative stress biomarkers can successfully be used in assessing pollution from point sources such as acid mine drainage, as well as diffuse sources of pollutants such as commercial agriculture.
Vanadium (V) is a transition metal that is found in low concentrations in aquatic ecosystems. These levels increase due to anthropogenic activities. The mortality and teratogenicity effects of V ...remain unexplored in amphibian species. To address this gap in the knowledge base, a standard Frog Embryo Teratogenic Index –
Xenopus
(FETAX) assessment was conducted. Vanadium pentoxide (V
2
O
5
) was chosen for its known toxicity in other aquatic biota and its solubility in water. A range-finding test was conducted in two different mediums, V
2
O
5
in distilled water (VDH2O) and V
2
O
5
in FETAX medium (VMED), to determine concentration ranges where effects occurred. Thereafter, definitive tests were conducted using two separate breeding pairs, with two replicate dishes per concentration containing 15 embryos each. Multiple endpoints were assessed including mortality, malformations, minimum concentration to inhibit growth (MCIG), and the teratogenic index (TI). Mortality and malformation effects occurred at different ranges, and therefore, the exposures were conducted in low dose and high dose ranges. The high dose range for mortality effects was conducted at 0, 10, 20, 40, 80, and 160 mg/L of V. The low dose exposures to assess malformation effects were conducted at 0.0001, 0.00025, 0.0005, 0.00075, and 0.001 mg/L. Binary logistic regression was used to determine the LC50 and EC50 for the two sets of definitive tests. The LC50s were determined to be 46.10 mg/L and 26.91 mg/L for VDH
2
O and 34.50 and 25.25 for VMED for the two breeding pairs respectively. The EC50 was calculated as 0.00053 mg/L and 0.00037 mg/L for VDH2O and 0.00036 mg/L and 0.00017 mg/L for VMED for the two definitive tests respectively. The TI was calculated as 86,981 and 72,729 for VDH2O and 95,833 and 148,526 for VMED. Ultimately, there were severe malformation effects in embryos exposed to low doses of V and V was determined to be a very strong teratogen.
Stable isotope analyses, specifically δ
C and δ
N, are useful tools increasingly used to understand ecosystem function, food web structures, and consumer diets. Although the iconic tigerfish ...Hydrocynus vittatus is regarded as an apex predator in southern African freshwater systems, little information is available regarding their feeding behavior and how this may change with growth or differ between ecosystems, with most information stemming from stomach content analyses (SCA). The aim of the present study was to address this lack of information through a baseline study of the diet of large and small tigerfish in various lentic and lotic ecosystems in South Africa using stable isotope methods. Fish and various food web components and food sources were collected from two river and two lake ecosystems in South Africa. The δ
C and δ
N values for all samples were determined and multivariate analyses and Bayesian analytical techniques applied to determine the feeding ecology of H. vittatus and how this may differ with size and habitat type. Analyses revealed a substantial difference in the type and abundance of food sources contributing to the diet of H. vittatus between ecosystems, most prominently between the lotic systems, where less dietary specialization was observed, and lentic systems where more specialization was observed. Furthermore, there was a distinct difference in diet between small and large tigerfish, especially in the lotic system, indicating an ontogenetic diet shift as tigerfish grow and further supporting previous SCA studies. This is the first study of its kind on the African continent for H. vittatus and the findings illustrate the value of stable isotope analysis in providing in-depth information into the feeding ecology of consumers and how this may differ between size classes and habitat types.
Ethiopia and South Africa are among the few countries to still implement indoor residual spraying with dichloro-diphenyl-trichloroethane (DDT) for malaria vector control. In this study, we ...investigated the levels and ecological risks of DDT and its metabolites in liver tissues of house rat, as a sentinel animal, for providing an early warning system for public health and wildlife intervention from Ethiopia and South Africa. The results showed that ΣDDT concentration ranged from 127 to 9155 μg/kg wet weight, and the distribution order of DDT and its metabolites in the analyzed liver samples was
p,p
′-DDD >
p,p
′-DDE >>
p,p
′-DDT, o
,p
′-DDT, and o
,p
′-DDD. The risk assessment indicated a potential adverse impact on humans, especially for pregnant women and children, because they spend majority of their time in a DDT-sprayed house. The ecological assessment also showed a concern for birds of prey and amphibians like frogs. This study is the first report on DDT contamination in liver tissues of house rats from Ethiopia and South Africa, and henceforth, the data will serve as a reference data for future studies.
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