Unfortunately ivermectin has been losing its effectiveness against large roundworms in CHICKENS due to its overuse as a miteacide. It certainly will not kill cecal worms.Thanks dawn, seems like I have run into several problems this winter. The worms were definitely large round worms. The quantity that were expelled was alarming and these girls have been wormed before. I used Ivermect for cattle last time and put a few drops on their necks. I do not think it did much and yet many people swear by it. I can usually see results immediately with the Wazine. I'll wait a couple of months and give them the Wazine again.