The use of parasites as bioindicators of pesticide exposure

Organisms used in risk assessment of pesticides must be the most sensitive ones to pesticides exposure. The aim of this study was to observe the effect of two commercial pesticide products (containing glyphosate and tolylfluanid) to larval stages of parasites Cooperia curticei, Ostertagia circumcincta, Haemonchus contortus and Trichostrongylus axei. There were two concentrations tested for each product vs. control group. Larvae (500 individuals/Petri dish) were incubated at 27°C and observed daily for 42 days.

We found out that T. axei larvae are the most resistant ones to tolylfluanid exposure - there was no statistical significance in any concentration tested after 42 days of tolylfluanid exposure. 100% of dead larvae were found on 33^rd day of experiment at higher concentration, resp. on 37^th day at lower tested concentration of glyphosate. C. curticei, O. circumcincta and H. contortus showed similar statistical significance in both pesticides tested (there was high statistical significance (p<0.0001) at both concentrations of glyphosate and only at higher tested concentration of tolylfluanid). C. curticei and H. contortus larvae were found dead, spiral shaped and without movement at all concentrations tested, spiral shape was not observed in other two tested larvae. O. circumcincta larvae reacted to pesticides exposure very quickly; rapid death was recorded on second day of experiment at both concentrations of glyphosate and at higher tested concentration of tolylfluanid. From four tested small ruminant parasites (L3), O. circumcincta larvae seem to be the most sensitive ones and need further research.