Clinical Signs and Organ Pathology in Rats Exposed To Graded Doses of Pyrethroids-Containing Mosquito Coil Smoke and Aerosolized Insecticidal Sprays

Morphological changes in tissues/organs of weanling Albino ratsexposed to graded doses of popular brands of pyrethroids-containing insecticides - mosquito coil and aerosolized spray were studied over a period of 18 days. Rats were exposed to 0.4, 0.8, 1.2 and 1.6mg/kg BW of active ingredients in aerosolized insecticidal spray for 15, 30, 45 and 60 seconds, in two divided doses daily for 18 days. Control rats were not exposed. Early clinical signs include irritability, head shaking and scratching of nostrils; these later gave way to sneezing, gurgling, fine muscular tremors, ruffled fur, lethargy and depression. No self-death was recorded in all the exposed and control groups. Gross changes were not apparent in most organs, but for pulmonary oedema and slight hepatomegaly and palor of kidneys in rats exposed to high doses of the fumes sacrificed on days 12, 15 and 18 post-exposure. Histopathology revealed varying degrees of vacuolar degeneration and necrosis of hepatocyctes, myocardiac degeneration, glomerular and tubular degeneration and necrosis, meningitis, neuronophagia, demyelination of neuronal axons and exudative pnuemonia. Others include blood vascular damage, haemorrhages, vasculitis and thrombosis in many organs, and Kuppfer and intestinal goblet cells hyperplasia. The severity of the lesions was dose and time dependent. The lesions observed suggest interference with tissue energy metabolism and widespread vascular damage and multi-organ degeneration and necrosis. The implications of the consistent and uncontrolled use of pyrethroids-containing insecticides on farm and market produce and in human inhabitants and their effects on public health and biodiversity conservation are discussed.

Keywords
Pyrethroids, insecticides, rats, tissue pathology, public health hazard