PYRETHROID POISONING OF FISH - CASE-REPOR T AND REVIEW ARTICLE

The authors have summarized the literature on the effects of pyrethroi ds on fish. Based on that, mechanisms of the action of synthetic pyret hroids have been outlined together with the pathomorphological alterat ions observed in fish. Factors influencing the development of acute to xicosis (chemical composition and configuration of pyrethroid, biologi cal, environmental and other effects) have been analyzed. Data of the laboratory toxic levels for the Hungarian fishes have been summarized in a Table. Ecological consequences being effective after the practica l use of pyrethroids have also been treated. Four cases of mass fish d eterioration caused by pyrethroid poisoning have been reported. The re port is remarkable because description of similar cases has not been f ound in the literature. In two cases alphametrin, in one case each del tametrin and cipermetrin containing preparations were used as pesticid es for spraying the neighboring vegetation. Two to four days later was observed the havaria. The fish showed nervous symptoms, described cir cles near to the water surface. Contamination of the branchiae with mu d indicated that the movement of fish slowed down and thus the self cl eaning capacity of branchiae decreased. In certain cases, the fish sho wed ''pipe smoking'' and the animals were ''apathic'', akynetic before death, they could be catched with naked hands. Generally, external al terations could not be observed on the fish, however skin haemorrhages were observed in one of the alphametrin poisoning cases. The present cases also confirm that gross and histopathological lesions are not pa thognostic in case of pyrethroid poisonings. It has been pointed out t hat factors influencing the pyrethioid residual level in fish and fish cadavers are still unknown, thus the diagnostic criteria of havaria c aused by pyrethroids are not solved. Therefor the detection or exclusi on of cause and effect relation between the use of pesticides containi ng pyrethroid and a mass death near to that region can only be establi shed after the exclusion of all known causes of fish havaria and consi deration of all the laboratory examinations of fish cadavers, as well as lo cal circumstances.