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 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 domestica). 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). There was also a reduction in feed intake by the birds exposed to pesticides. Egg laying was delayed in the hens exposed to pesticides by as much as eighteen weeks. The ages of the hens at first egg  lay were 18 weeks for the control, 23 weeks for hens fed on 0.01 and 0.02% contaminated diet and 36 weeks for those fed on 0.04% contaminated diet. The average daily egg production was reduced from 5 eggs in the control group to 1 egg in 0.04%contaminated group.  The protein contents of the egg (yolk and albumin) and cholesterol level of the egg yolk were lower in birds exposed to pesticide. There was a general reduction of liver (cytoplasmic and membrane bound) cholesterol, triglycerides and total lipids in the birds fed on pesticide contaminated diet as well as reduction (p<0.05) in GSH levels and GST activity. There was also a significant increase (p<0.05) in lipid peroxidation in the birds exposed to the pesticide. Results of this study suggests that dichlorvos exposure has genotoxic effects in addition to other physiological and biochemical effects on poultry birds.