DDT exposure of frogs: A case study from Limpopo Province, South Africa

Viljoen, Ignatius M.; Bornman, Riana; Bouwman, Hindrik

doi:10.1016/j.chemosphere.2016.06.023

Cited by 13 publications

(17 citation statements)

References 54 publications

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“…Different EDCs also elicit an effect through different modes of actions. The majority of ED related studies in South Africa have investigated disruption of reproductive systems ( Barnhoorn et al , 2010 ; Kruger et al , 2013 ; Arukwe et al , 2016 ; Viljoen et al , 2016 ; Leusch et al , 2018 ) ( Table 1 ) and when EDCs elicit an effect on the reproductive system, the response (mode of action) can either be (anti-)oestrogenic or (anti-)androgenic ( Archer and Van Wyk, 2015 ).…”

Section: Endocrine Disrupting Effects Observed In South African Watermentioning

confidence: 99%

“…Endocrine disrupting effects have also been observed in frog species. Viljoen et al (2016) reported on the asymmetric testicular morphology of frogs that naturally occur in dams and ponds in Limpopo where DDT is still sprayed for malaria control. This phenomenon was attributed to possible ED caused by DDT ( Table 1 ).…”

Section: Endocrine Disrupting Effects Observed In South African Watermentioning

confidence: 99%

“…As a consequence of freshwater pollution, aquatic species are exposed to these pollutants through their food and surface areas (skin and/or gills) ( Olujimi et al , 2010 ; Mahmood et al , 2016 ). This allows researchers to use many aquatic species including freshwater shrimp ( Caridina nilotica ) ( Mensah et al , 2012 ), African sharptooth catfish ( Clarias gariepinus ) ( Pheiffer et al , 2018 ), Mozambique tilapia ( Oreochromis mossambicus ) ( Truter et al , 2016 ) and African clawed frog ( Xenopus laevis ) ( Van Wyk et al , 2003 ; Viljoen et al , 2016 ) as indicators of effects of agrochemical pollution. Since pesticides are chronically present in the environment at low concentrations, humans and wildlife are consistently exposed ( Damalas and Eleftherohorinos, 2011 ).…”

Section: Introductionmentioning

confidence: 99%

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Agrochemicals in freshwater systems and their potential as endocrine disrupting chemicals: A South African context

Horak

Horn

Pieters

2021

Environmental Pollution

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South Africa is the largest agrochemical user in sub-Saharan Africa, with over 3 000 registered pesticide products. Although they reduce crop losses, these chemicals reach non-target aquatic environments via leaching, spray drift or run-off. In this review, attention is paid to legacy and current-use pesticides reported in literature for the freshwater environment of South Africa and to the extent these are linked to endocrine disruption. Although banned, residues of many legacy organochlorine pesticides (endosulfan and dichlorodiphenyltrichloroethane (DDT)) are still detected in South African watercourses and wildlife. Several current-use pesticides (triazine herbicides, glyphosate-based herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D) and chlorpyrifos) have also been reported. Agrochemicals can interfere with normal hormone function of non-target organism leading to various endocrine disrupting (ED) effects: intersex, reduced spermatogenesis, asymmetric urogenital papillae, testicular lesions and infertile eggs. Although studies investigating the occurrence of agrochemicals and/or ED effects in freshwater aquatic environments in South Africa have increased, few studies determined both the levels of agricultural pesticides present and associated ED effects. The majority of studies conducted are either laboratory-based employing in vitro or in vivo bioassays to determine ED effects of agrochemicals or studies that investigate environmental concentrations of pesticides. However, a combined approach of bioassays and chemical screening will provide a more comprehensive overview of agrochemical pollution of water systems in South Africa and the risks associated with long-term chronic exposure.

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Section: Endocrine Disrupting Effects Observed In South African Watermentioning

confidence: 99%

Section: Endocrine Disrupting Effects Observed In South African Watermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Agrochemicals in freshwater systems and their potential as endocrine disrupting chemicals: A South African context

Horak

Horn

Pieters

2021

Environmental Pollution

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“…None of the frogs analysed had accumulated DDT or metabolite concentrations above limit of detection (0.01 μg/g), except one individual which had 0.054 μg/g wm p,p-DDE. Viljoen et al (2016) measured DDT in X. laevis and X. muelleri fat bodies in an area sprayed with DDT for MVC through means of IRS in the Limpopo Province of South Africa. All DDT metabolites detected showed higher accumulation at sprayed sites compared to reference sites.…”

Section: Organochlorinesmentioning

confidence: 99%

Current Status and Future Prognosis of Malaria Vector Control Pesticide Ecotoxicology and Xenopus sp.

Wolmarans

Bervoets

Meire

et al. 2019

Reviews of Environmental Contamination and Toxicology

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Whilst frogs are generally considered as good indicators of environmental change, they are not widely utilised as indicators in ecological studies. With much of current research relying on model organisms as proxies for other animals or even humans, toxicology data on these model organisms is important for higher tier risk assessment studies and ecological modelling. The issue at hand is that for some topics, even when looking at model organisms, this empirical data does not seem to be as common as expected when doing literature research. Malaria vector control (MVC) is often a sensitive subject due to the paradox surrounding it (Bouwman et al. 2011). The lack of toxicological data mentioned feeds into the issues complicating debates on the chemical vector control interventions. Although being in use for decades, there are still many unknowns regarding the environmental impact of these pesticides. Informed decision making and policies require that this information first be available. The main research problem investigated in this review is this lack of toxicological and biomonitoring data available for one of the model organisms (Xenopus laevis) representative of aquatic ecosystems, and to a lesser extent, anurans. Species from the Xenopus genus are endemic to Africa and their distribution includes many areas where malaria vector control is applied. Reliable toxicology data on these frogs regarding malaria vector control pesticides (MVCPs) would strengthen the use of these animals as bioindicators.

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“…Despite widespread discontinuation of DDT spraying many countries still regularly use DDT (See van den Berg 2009). Concentrations of DDT have been detected in fish, water and sediment samples across a number of different systems (Gerber et al 2016;Viljoen et al 2016;Wolmarans et al 2018). However, there is disturbingly little data available on the myriad potential effects of DDT on the ecology of freshwater systems.…”

Section: Introductionmentioning

confidence: 99%

Assessing predator-prey interactions in a chemically altered aquatic environment: the effects of DDT on Xenopus laevis and Culex sp. larvae interactions and behaviour

et al. 2019

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Behavioural assays are used as a tool to understand ecotoxicological effects on organisms, but are often not applied in an ecologically relevant context. Assessment of the effect of chemical contaminants on behaviours relating to fitness and trophic interactions for example, requires incorporating predator-prey interactions to create impact assessments. Dichlorodiphenyltrichloroethane (DDT) is a controlled substance but is still regularly used as a form of mosquito control. There is little explicit information on the effect of DDT on animal behaviour and the consequent effects upon trophic interactions. This study uses a 3 × 2 factorial design to assess the feeding behaviour of Xenopus laevis toward Culex sp. larvae when supplied with different prey cues. We also assess the behavioural responses of mosquito larvae when supplied with no threat cue and predator threat cues when exposed to 0 µg/L, 2 µg/L and 20 µg/L DDT. There was a significant "DDT exposure" x "prey cue" interaction whereby DDT significantly decreased the foraging behaviour of X. laevis towards live prey cues, however there was no effect of DDT on X. laevis response to olfactory prey cues. Dichlorodiphenyltrichloroethane exposure caused mosquito larvae to appear hyperactive regardless of DDT concentration. Mosquito larvae antipredator response was significantly dampened when exposed to 2 µg/L DDT, however when exposed to 20 µg/L the antipredator responses were not impaired. Our results indicate a complex interplay in trophic interactions under DDT exposure, wherein effects are mediated depending on species and concentration. There are possible implications regarding reduced anti-predator behaviour in the prey species but also reduced foraging capacity in the predator, which could drive changes in ecosystem energy pathways. We demonstrate that in order to quantify effects of pesticides upon trophic interactions it is necessary to consider ecologically relevant behaviours of both predator and prey species.

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DDT exposure of frogs: A case study from Limpopo Province, South Africa

Cited by 13 publications

References 54 publications

Agrochemicals in freshwater systems and their potential as endocrine disrupting chemicals: A South African context

Agrochemicals in freshwater systems and their potential as endocrine disrupting chemicals: A South African context

Current Status and Future Prognosis of Malaria Vector Control Pesticide Ecotoxicology and Xenopus sp.

Assessing predator-prey interactions in a chemically altered aquatic environment: the effects of DDT on Xenopus laevis and Culex sp. larvae interactions and behaviour

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