Modeling Genetic Defects as a Molecular Biomarker in Evaluating Environmental Impacts Dichlorvos on Pullet Chicks.
ABSTRACT
Environmental pollution and poisoning owing to the widespread use of pesticides in agricultural and domestic pest control may be detrimental to the health of handlers, non-target organisms and iv consumers.
In this study, genetic defect was used as a molecular biomarker in evaluating the environmental impacts of dichlorvos, a widely used pesticide in Nigeria, on poultry birds (Gallus domestic).
Seven-week-old pullets with an average weight of 557.5 ± 9.5 g divided into four groups of ten birds each were fed on commercial poultry feed contaminated with 0.01, 0.02 and 0.04% (w/v) dichlorvos.
The control group had no pesticide added into their feed. The birds were exposed for ten weeks after which they were sacrificed and the liver taken for analysis.
Electrophoresis of isolated liver DNA in 0.8% agarose gels gave variations in band intensity between the control DNA sample and DNA from exposed birds.
These variations in band intensity were more pronounced in the RAPD-PCR products amplified with OPE-01 primer, where there is complete disappearance of DNA bands in the birds exposed to 0.04% pesticide.
Thermal denaturation of the DNA from the exposed birds resulted in a significant reduction (p< 0.01) in the DNA melting temperature from 87.2oC to 81.7oC while the GC/AT ratio was also significantly reduced (p<0.01) from 0.77 in the control to 0.42 in exposed birds respectively.
The percentage weight gain of the birds over the 10-week period was significantly higher (p<0.05) in the control (126.50%) when compared with the birds fed on pesticide contaminated diet (68.75%, 65.10% and 28.10% respectively), but increase in liver weight was not significant (p>0.05).
INTRODUCTION
The use of pesticides in agriculture has become important considering the huge losses farmers experience due to the ravaging effects of agricultural pests. The large scale use of pesticides in agriculture has proven effective in controlling and minimizing losses due to pests.
Experts agree that removal of pesticides from crop protection will result to an immediate drop in food supplies (NAS, 1975). Pesticides have also found application in other areas for example in controlling wood destroying insects like termites and disease control.
Despite the immense benefits that can be derived from the use of pesticides, continuous and indiscriminate use of pesticides has caused severe environmental problems and is a health hazard for humans and animals (Perring and Mellanby, 1975; Partanen et al., 1999).
The U.S. Environmental protection Agency (EPA) states that, “By their very nature, most pesticides create some risk or harm to humans or the environment because they are designed to kill or otherwise adversely affect living organisms” (U.S.EPA, 2002).
Bioaccumulation of pesticides in the food chain can lead to potentially adverse effects in humans due to their putative toxic effect (Palmeira, 1999). There is a need to devise an accurate and effective way of monitoring the effects of pesticide exposure to humans and the environment.
Until recently, the most common end -point measured when evaluating toxicity of chemicals focuses on mortality values (Otijolu and Onwurah, 2007). Mortality values can only provide a measure of short-term acute toxicity and are not always useful for predicting the ecological consequences of exposure to a particular chemical (Neuhauser et al., 1984).
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