PhD / An important component of fish health is an optimally functioning reproductive system. The Luvuvhu River Catchment in the Limpopo Province, South Africa, is a tropical, high-risk malaria area where 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT), an endocrine disrupting chemical (EDC), has been used annually since 1945 as a malaria vector control. DDT is known to affect testes morphology and motility of fish sperm. As such, testicular histology and sperm motility (kinematic) parameters were studied as reproductive indicators of the reproductive capacity for two wild, indigenous fish species (Oreochromis mossambicus and Clarias gariepinus) from the currently DDT sprayed area. Three field studies were carried out over two years (2007 – 2008), including two high flow (HF) periods and one low flow (LF) period [HF 1 (March 07), LF (October 07), HF 2 (February 08)]. Both species were sampled from three sites on the Luvuvhu River for testicular histology and computer assisted sperm analysis (CASA), during all three field studies. The sites included a reference site outside the DDT sprayed area, Albasini Dam (AD), and two exposed sites within the DDT sprayed area, Xikundu Weir (XW) and Nandoni Dam (ND). CASA, based on open-source software, was used for the first time in South Africa to assess sperm kinematic parameters of indigenous fish species in field conditions. These included percent motile sperm (% MOT), curvilinear velocity (VCL μm s-1), velocity of an average path (VAP μm s-1), straight line velocity (VSL μm s-1), linearity (LIN %), progression (PROG μm), and average efficiency (AVE. EFF.). Water and sediment samples were collected during all field studies from the three sites for metal and EDC analysis. Controlled laboratory studies were also carried out on the sperm of both species, externally sourced from aquaculture farms equipped to breed and raise fish in toxicant free water. The laboratory studies involved in vitro exposure of spermatozoa to two different, but environmentally relevant, concentrations of both DDT (DDT 1: 0.27 μg L-1; DDT 2: 0.5 μg L-1) and 1,1-dihloro-2,2-bis(p-chlorophenyl)ethylene (DDE) (DDE 1: 0.11 μg L-1; DDE 2: 1.0 μg L-1) with the aim to provide data to support the possible outcomes found in the field studies using CASA. Furthermore, peroxidation of sperm lipids was assayed by production of malondialdehyde (MDA) after in vitro exposure of spermatozoa to DDT and DDE. DDT and its metabolites were found in varying concentrations in the water from all three sites (0.1 μg L-1 – 1.2 μg L-1). Levels of dieldrin (3.5 μg L-1) and lindane (9.4 μg L-1) residues were also found at XW in HF 2. The histological results revealed alterations to testis tissue of both species at all three sites. The testes were assessed through the identification of alterations and an organ index was calculated: Testes Index (IT). The index is indicative of the histological response in the respective tissue type. O. mossambicus at XW had the highest mean IT value during LF (7.45 ± 5.73) and for all field studies combined (5.47 ± 4.63), primarily due to the occurrence of testicular oocytes (intersex), where the frequency of prevalence was 72.73% and 58.82% respectively. These results were statistically higher than the laboratory control (C) group. The CASA results showed statistical differences primarily for O. mossambicus, where motility parameters were lower at XW when compared to AD. Laboratory exposures found a decrease in sperm motility (% MOT) between the control (C) group and the DDT 1, DDE 1 and DDE 2 exposed groups for C. gariepinus. No significant differences were seen for lipid peroxidation (MDA). On the other hand, no significant differences were seen in CASA parameters between the control and exposed laboratory groups for O. mossambicus, but there was an increase in MDA production from the control to the DDT 1 exposure group.

The insecticide dichloro-diphenyl-trichloroethane (DDT) is widely used in indoor residual spraying (IRS) for malaria control owing to its longer residual efficacy compared to other World Health Organization (WHO) alternatives. It was envisaged that by investigating mechanisms of degradation of these alternative insecticides, a better understanding would be obtained on strategies of stabilising them and rendering their efficacy comparable with or better than DDT, hence providing less controversial and more acceptable and effective alternative insecticide formulations to DDT. This study sought to investigate the reasons behind the reported longer lasting behaviour of DDT by exposing all the WHO approved insecticides to high temperature, high humidity and ultra-violet light. Interactions between the insecticides and some mineral powders in the presence of an aqueous medium were also tested. Simple insecticidal paints were made using slurries of these mineral powders whilst some insecticides were dispersed into a conventional acrylic paint binder. These formulations were then spray painted on neat and manure coated mud plaques, representative of the material typically used in rural mud houses, at twice the upper limit of the WHO recommended dosage range. DDT was applied directly onto mud plaques at four times the WHO recommended concentration and on manure plaques at twice WHO recommended concentration. All plaques were subjected to accelerated ageing conditions of 40 °C and a relative humidity of 90%. In the accelerated ageing tests, Fourier transform infra-red (FTIR) interferograms showed that pyrethroids were the most stable insecticides compared to carbamates and DDT. High temperature oxidation, ultra violet light and humidity were ruled out as the cause of failure of the alternative insecticides. Gas chromatography (GC) interferograms showed that phosphogypsum stabilised the insecticides the most against alkaline degradation. Bioassay testing showed that the period of efficacy of these formulations was comparable to that of DDT sprayed at 4 times the upper limit of the WHO recommended dosage range. Bioassay testing also showed that these insecticidal “paint” formulations stabilised the insecticides on cattle manure coated surfaces as compared to DDT sprayed directly on similar surfaces. Bioassay experiments indicated that incorporating insecticides into a conventional paint binder or adsorbing them onto phosphogypsum provided effective life spans, under accelerated ageing conditions, comparable to or exceeding that of DDT directly applied to typical soil substrates. Best results were obtained with propoxur in standard acrylic emulsion paint. Similarly, insecticides adsorbed on phosphogypsum and sprayed on cattle manure coated surfaces provided superior lifespans compared with DDT sprayed directly on a similar surface. Copyright / Dissertation (MEng)--University of Pretoria, 2012. / Chemical Engineering / unrestricted

Please read the abstract in the section 00front of this document / Thesis (DPhil (Entomology))--University of Pretoria, 2005. / Zoology and Entomology / unrestricted

The chemical fate and biological impacts of cyfluthrin in aquatic ecosystems were investigated using microcosms (1.9 m^3 concrete tanks) during 1989. Results were compared to a concurrent pesticide registration study using mesocosms (634.7 m^3 earthen ponds). Ten spray drift and five soil runoff simulations were conducted. Pesticide loadings were scaled by system volume, with the same experimental design in ponds and microcosms. Aqueous cyfluthrin concentrations and sediment residue values were generally higher in microcosms, while aqueous half-life was shorter in the smaller systems.

The Sacramento River watershed provides important rearing habitat for key aquatic species, including juvenile Chinook salmon (Oncorhynchus tshawytscha). Salmon rearing in the watershed may inhabit the mainstem river channel or a corresponding floodplain, the Yolo Bypass, before migrating to the ocean. Studies of juvenile salmon have indicated that floodplain rearing may be beneficial in terms of growth and survival, likely related to different trophic pathways of the river and floodplain. However, fish also encounter many anthropogenic stressors in these habitats, such as pesticides, which have well-documented use and environmental presence in the region. Rearing individuals are potentially exposed to pesticides via trophic transfer, which may vary based on utilized food webs due to hydrophobic pesticide fate and transport. To examine the food web structure of each system and the potential for pesticide exposure through dietary routes, a two-year field study was completed. First, to characterize dietary contributions, a three-tiered approach incorporating stable isotopes (δ13C, δ15N and δ34S), essential fatty acids and gut content analyses was employed. Subsequently, pesticides were extracted from prey items and salmon and analyzed to determine contaminant residues. Stable isotope analyses indicated that critically important components of juvenile Chinook diet were amphipoda and adult diptera in 2019 and 2020, respectively. Amphipoda groups had higher concentrations of the fatty acid docosahexaenoic acid (DHA), an important component for fish development, than juvenile diptera or oligochaeta. Diptera (larvae and adults) were frequently found in juvenile Chinook stomachs from both areas and years. Throughout the pesticide examination, organochlorines including the DDT group (p,p’-DDT, p,p’-DDD and p,p’-DDE) were prevalent in all examined biota. There were a significantly greater number of pyrethroid and phenylpyrazole detections and concentrations in zooplankton as compared to macroinvertebrates (Poisson regression, p < 0.05) across regions and years. Additionally, significantly higher concentrations of organochlorines were exhibited in floodplain rearing fish as compared to the Sacramento River (ANOVA, p < 0.05). These findings suggest that juvenile Chinook feeding primarily on zooplankton may be exposed to a greater range of pesticides than those exhibiting benthic feeding, but these pelagic prey were not demonstrated as a major dietary item during the two-year study. Additionally, the previously inferred benefits of floodplain rearing may come at a cost of increased organochlorine exposure. This research has allowed for a robust assessment of potential trophic transfer of pesticides to juvenile salmon, which may help inform future floodplain restoration efforts.

Epidemiological studies implicate pesticide exposure as a possible etiologic factor in idiopathic Parkinson's Disease, which results from degeneration of nigrostriatal neurons, along with reduced levels of the neurotransmitter, dopamine. Behavioral and neurochemical analyses in C57BL6 mice were performed following a subchronic dosing regime with the organochlorine insecticide heptachlor or the pyrethroid deltamethrin. Results were compared to those induced by the established parkinsonian neurotoxicant, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). At the end of the treatment period, mice were assessed for effects on behavior, as well as levels of striatal dopamine, nerve terminal respiration, and synaptosomal dopamine transport. The primary behavioral effect of deltamethrin was incoordination, while heptachlor caused hyperexcitability and increased locomotion. The major neurochemical effect observed for both compounds was upregulation of the presynaptic dopamine transporter (DAT) by 70% and 100% for deltamethrin and heptachlor, respectively. The insecticides exerted only modest effects on striatal levels of dopamine and its metabolite, dihydroxyphenylacetic acid. However, doses of heptachlor higher than those which caused induction of DAT (e.g. greater than or equal to 25 mg/kg), when administered subchronically, were found to cause convulsions in some animals and caused marked, dose-dependent depression of basal striatal tissue respiration rates. No synergism was observed between the effects of insecticides and MPTP. Enhanced transport was thought to be a compensatory effect from increased release of transmitters by the insecticides, <i>in vivo</i>. Striatal dopamine, GABA and glutamate nerve terminals were differentially sensitive to the releasing effects of heptachlor compared to cortical serotonin terminals, and responded in the following rank order of sensitivity: dopamine > GABA > glutamate > serotonin. Additional experiments to characterize the mechanism(s) by which cyclodienes facilitate release of neurotransmitters in synaptosomes demonstrated a lack of distinct Ca²⁺ component and no involvement of retrograde DAT activity, suggesting that released label was of vesicular origin, but did not require Ca²⁺. Insecticidal toxicants, such as organochlorines and pyrethroids, which augment dopamine release and increase the maximal rate of dopamine uptake, may inundate the cytosol of nigrostriatal neurons with high concentrations of free dopamine, which has been shown by other researchers to induce apoptosis and may thereby contribute to the development of Parkinson's disease. Funding for this work was provided under grant number HHHREP 94-01 by the Hawaii Heptachlor Foundation, a non-profit organization. The Hawaii Heptachlor Foundation may be contacted at the following address: Ocean View Center PH#3, 707 Richards St., Honolulu, HI 96813. / Ph. D.

A field experiment tested the effectiveness of carbaryl and two pyrethroid insecticides, cyfluthrin and esfenvalerate, in protecting high-value Engelmann spruce trees from attack by Dendroctonus rufipennis Kirby. Carbaryl suspension at the 2% registered rate and a reduced rate of 1 % were both effective in protecting Engelmann spruce from attack by D. rufipennis through two pheromone baiting periods and 24 months following insecticide application . Cyfluthrin at 0.025% rate and esfenvalerate at 0.025 and 0.05% rates provided effective protection through one pheromone baiting and 12 months following insecticide application. Only cyfluthrin at 0.008% rate was judged ineffective protection 12 months following insecticide application. A laboratory evaluation utilizing a 32-h bioassay on D. rufipennis adults determined all three insecticides were toxic by contact. Carbaryl and piperonyl butoxide bioassays testing synergism were inconclusive. The methodology presented provides a means for forest land managers to quantify insecticide toxicity and monitor for resistance development.

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Background: The relationships between both obesity and diabetes and the exposure to insecticides, specifically organophosphates and pyrethroids, in the adult Canadian population are not well-understood. Methods: Urinary concentrations of 4 organophosphate metabolites (DEP, DEPT, DMP, and DMPT) and of 4 pyrethroid metabolites (cis-DBCA, cis-DCCA, 3-PBA, and trans-DCCA) were measured for 1,147 adult Canadians aged between 18-79 years old. The geometric means and medians of both creatinine-adjusted and unadjusted urinary insecticide metabolites were estimated. Multiple linear regression and logistic regression analyses were employed to examine the associations between the insecticide metabolite concentrations and obesity and diabetes measures. Results: Both insecticides had detectable levels in over 70% of CHMS respondents. Most metabolites demonstrated a negative significant relationship between their urinary concentrations and BMI as well as waist circumference. No significant relationship was found in regard to HbA1c levels or for diabetes. Conclusion: Organophosphate and pyrethroid metabolites were detected in more than 70% of Canadian adults. Our data showed no evidence that organophosphate and pyrethroid exposures increase the risks of obesity and diabetes in adults. These results should be interpreted with caution as diet may play a large confounding role in the relationships of study.