Browsing by Author "Mnkandla, Sanele"
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- ItemAn Assessment of the Extent of Bovine Milk Pollution by DDT used in Public Health in Zimbabwe(Scientia Research Library, 2016) Basopo, N.; Brock, Gerome; Mnkandla, SaneleIndoor residual spraying of dichlorodiphenyltrichloroethane (DDT) has been widely used in the control of malaria, and has been appreciated for its low cost and high effectiveness. Prolonged use, however, has adverse effects as DDT and its metabolites persist for long in the environment, resulting in human and animal contamination. Contamination in animals such as cattle may result from consuming contaminated water, feed and fodder. The aim of the study was to evaluate the extent of contamination of DDT and its metabolites in cow’s milk from five towns in Zimbabwe. Samples were collected from farms around Bulawayo, Chiredzi, Esigodini, Harare and Mutare with a total of n=24 samples. The pesticide residues were extracted using the quick, easy, cheap, rugged and safe (Quechers®) method and solid phase extraction and analysed using gas chromatography with electron capture detector. Total DDT was detected in all samples at levels higher than the maximum allowable residue limit. Harare and Mutare samples had the highest DDT levels of 0.38 μg/ml and 0.26 μg/ml respectively, as compared with samples from other regions (0.08-0.13 μg/ml). The DDT metabolite residues,1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (DDD) and 1,1-dichloro- 2,2-bis(p-dichlorodiphenyl)ethylene (DDE), were also detected at varying levels in the samples. The results show the presence of DDT and its metabolite contaminants in bovine milk, posing a serious health risk to consumers. Alternatives to DDT may therefore need to be employed in the control of the malaria vector.
- ItemThe Effects of Sub Lethal Levels of Lead on Acetylcholinesterase Activity in the Rock Pigeon, (Columba Livia)(Zimbabwe Journal of Science & Technology, 2017) Muusha, Yeukai; Mnkandla, Sanele; Basopo, N.Lead is one of the most abundant heavy metals that has become widely distributed and mobilised in the environment. It exists in various forms which are bioavailable to many organisms including birds, causing physiological changes upon exposure. The aim of this study was to investigate the effects of sub lethal levels of lead on acetylcholinesterase activity in the Rock pigeon (Columba livia). Twelve free range and two pen reared (control) pigeons were collected from breeders around the city of Bulawayo and placed in separate cages. Six free range and one pen reared birds were exposed to 1.25 ppm lead acetate spiked feed and water for 72 hrs, whilst the remaining birds served as the unexposed control. Spiked feed and water were changed daily. Both the exposed and unexposed birds were sacrificed and the muscle, heart and liver tissues isolated and assayed for acetylcholinesterase activity. There was significant inhibition of enzyme activity in all tissue samples obtained from lead exposed free range birds when compared to their unexposed counterparts. In the lead exposed free range birds, muscle and liver acetylcholinesterase activity was below 0.005 μg/min/mg protein while that of the heart was in the 0.02-0.07 μg/min/mg protein range. Enzyme activity was greater than 0.1 μg/min/mg protein in the unexposed free range birds. Comparing the acetylcholinesterase activity of the lead exposed pen reared control, with that of the lead exposed free range birds, the latter demonstrated significant inhibition (p<0.05). The results therefore highlight the inhibitory effect of sub lethal levels of lead on acetylcholinesterase activity which could also be possibly enhanced by prior exposure to other environmental contaminants.
- ItemToxicological Effects of Differently Polluted Dam Waters Spiked with Pesticides on Freshwater Snails Lymnaea Natalensis(Canadian Center of Science and Education, 2016) Mnkandla, Sanele; Basopo, N.; Tapfuma, Donald; Delfina, Majaya RachelPesticides extensively used in agricultural fields to ensure high quality crop yields indirectly find their way to aquatic bodies where they affect aquatic biota. We investigated the effects of pesticides in different dam waters on esterase enzyme activity of the freshwater snail species Lymnaea natalensis. Groups of adult snails were exposed to 0.006 ppm chlorpyrifos and 0.003 ppm aldicarb in polluted water from Umguza dam and relatively pristine water from Hillside dam for 14 days. Carboxylesterase, acetylcholinesterase and arylesterase activities were measured. Both pesticides caused significant inhibition of esterase activity after the 14 day exposure period, with exposures to Umguza dam water showing higher inhibition as compared to exposures to Hillside dam water. Aldicarb and chlorpyrifos both showed a time-dependent inhibition of enzyme activity, the former causing a higher inhibitory effect as compared to the latter. Acetylcholinesterase was inhibited up to 80% following exposure to aldicarb while exposure to chlorpyrifos in Umguza water caused only 40% inhibition. Carboxylesterases were similarly inhibited with higher inhibition observed in snails exposed to Umguza dam water when compared to snails exposed to Hillside dam water, while arylesterases were inhibited in the range 80-90%, with an exception of chlorpyrifos spiked Hillside dam water which caused 45% inhibition. Contaminated Umguza dam water also appeared to enhance the effects of pesticides when compared to the relatively pristine Hillside dam water. Alteration of esterase activity can be used as an early warning signal indicating exposure to environmental pollutants. The results of this study therefore, highlight the adverse effects of pesticides on non-target aquatic organisms, evidenced by the inhibition of esterase activity.