Worms in droppings just after deworming - what does it mean?

[mangobingo]

We deworm/delouse our flock every few months using Ivermectin, a few drops on the skin separated by 10 days or so. This time, just after giving them their second dose, we found a big watery poo with a disgusting long worm in it. What does that mean? Are they shedding dead worms because of the treatment, or does it mean that they're full of worms and the treatment isn't working? How would we know if the parasites had become resistant to Ivermectin and the deworming isn't actually doing anything?

Thanks a lot!

 

[centrarchid]

Means they are shedding the worms, most likely just killed / immobilized by dewormer. If load was heavy, then birds should quickly become thrifty and put weight back on.