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

Abstract

Morphological changes in tissues/organs of weanling Albino rats exposed 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.