Immunopathological effects of fenvalerate on cell mediated immune response in sheep

Fenvalerate is an insecticide of synthetic pyrethroid group and is used on a large scale for control of insect pests in agriculture and ectoparasites in veterinary practice. To assess the effect of fenvalerate on cell mediated immune response in sheep, 8 lambs, six months old were used in two groups of 4 lambs each. All the Iambs were vaccinated with Brucella melitensis rev. 1 at day zero and day 90. One group was given fenvalerate daily orally at dose rate of 1.25 mg/kg body weight for six months. The lymphocyte stimulation test, total leucocytic count and absolute lymphocytic count were performed from blood collected at 10 days interval. Delayed type hypersensitivity (DTH) reaction was assessed at 6 months of observation. A significant suppression in total leucocytic count, absolute lymphocyte count, lympqocyte stimulation and DTH reaction was observed in fenvalerate fed lambs in comparison to control lambs indicating immunosuppressive effect of the pesticide.