The Thai Journal of Veterinary Medicine


Trifluralin, a herbicide, was observed for it's side effects when used, extralabel, as an ectoparasiticide in shrimp farming. Black tiger shrimp were exposed to trifluralin at a therapeutic level, commonly employed in shrimp farming, 0.1 or 0.2 ppm, for up to 96 hrs. Shrimp were examined 96 hrs after the primary dosage of trifluralin. The total haemocyte count in the exposed shrimp was not different from the control, unexposed shrimp. A significant reduction of muscle acetylcholinesterase was found in all exposed shrimp (p<0.05). Some of the exposed shrimp also demonstrated clinical signs of cholinergic overload characterized as abnormal movement. This study suggests sublethal effects when trifluralin is used for the treatment of shrimp ectoparasitic disease.

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