You start some of the most interesting threads!Of course!!!

Sorry I am unable to identify your slide in question, but thanks for letting me share and learn along the way.

I've seen ALL the signs folks SWEAR is worms (except actual worms).. from the chickens.. yellow frothy droppings, muddy bumm, messy eggs.. From the dogs.. scoot paddling across the floor.

Fecal floats done at my vet come back clean EVERY time SO far.. 10 years on with NO "preventative measures (aside from good nutrition and waste removal)!

Floats at the vet cost me $25 a pop.. so I bought my own microscope as at the time having goats, dogs, chickens, and whatever chicken math brings, etc the cost quickly adds up even using the "group" float method for each species..
Only one acre total including house, barn, etc.. had 72+ birds, 2 large goats, 3 medium dogs.. sandy soil, 60+ inches of rain per year, temp range 38F low in winter to 70F high in summer. Humidity year round 60%+.
Anxiety and over thinking have slowed the onset of running my own floats.. but through planning and continued learning I WILL get there.. just like I eventually got to harvesting my own humanely raised chicken!

@Chicalina that's pretty funny that you see resistance to the wormer by the keepers!

I'm ALL for using something that works IF needed, natural or not. I'm of the mind that you can't prevent what you don't have and also that natural doesn't always mean good.. think arsenic is natural.. I won't ever worm an already ill bird without verifying need.. why throw poisons into their system that may not help them?
Just using a broad spectrum wormer without knowing need just continues to put $ in the pockets of big pharma.. Pass. That's one reason I am resistant, though most others mentioned already are my basic truths as well.
Good gut health can be achieved without vermx or other supplements simply through good nutrition (not diminished by excess treats) which supports the entire immune system.

Consider doing a float before and after your worm prevention treatment and share your findings. Doing it a couple times throughout the year during different seasons could help determine YOUR parasite load.