Safety and Effectiveness of Trichlorfon in Prevention of Lernaeosis and Its Comparison with Plant Extracts in Lernaeosis Control

This study was carried out to evaluate the safety and effectiveness of trichlorfon in prevention of lernaeosis among hatchery-reared cyprinids. Also, it compared with plant extracts (carvacrol and cymene mixture and thyme) in lernaeosis control. At the Abo-Saleh fish hatchery in BeniSuef, Egypt, the trichlorfon bioconcentrations of cyprinids fries and fingerlings, as well as soil, water and plant samples were examined for 2 years. Trichlorfon was detected in fingerlings, water and plant samples, except soil sampled 1 hr after trichlorfon was applied to the fish pond. The highest concentration of trichlorfon was in fish, followed by water and plant samples. No trichlorfon was detected in fingerlings, water, plant and soil sampled after 5 days and 5 months. Fingerlings and brooders of cyprinids were examined in situ for clinical abnormalities and prevalence of lernaeosis. In addition, the intensity of the lernaea infestation was determined. Macroscopic Lernaea cyprinacea females were seen attached to the skin and fins associated with swollen hyperemic nodules and open wounds. Lernaeosis appeared sporadically during examination seasons with a high intensity. Under experimental condition, trichlorfon succeeded in controlling lernaeosis among Ctenophyrngedon idella fingerlings, as it eliminated 100% of Lernaea cyprinacea in comparison with 74.28% and 50.2% in carvacrol and cymene mixture and thyme treated fish respectively.