With the last flock I just gave them a pumpkin with the seeds about 3 times a year and never had worms or coccidiosis.
Pumpkin doesn't work as wormer... did you do fecal floats to confirm before or after counts? Tape worms and large round worms are the only ones that will EVER be seen in droppings (and then maybe only under heavy load), as all others stay living in the intestines and only their microscopic oocysts (eggs) will pass. PLEASE... if you do treat with pumpkin this time around... get before and after floats and report your results back here... tag me with @ in front of my user name. I seek to know the TRUTH not an old wives tale... and so far NOBODY who "treats" worms with pumpkin or DE is willing to... My offer is to pay for half... There is already clinical studies showing DE ineffective as a wormer. I truly mean no ugliness and my desire is to help people not to give them a false sense of security just because they don't understand biology and don't "see worms".
Also coccidia are in every chicken poo... they are ONLY a problem when too many of the microscopic oocysts have been ingested. It can happen to anyone at anytime... but usually accentuated by over crowding or warm/humid conditions... similar to a brooder or certain weather patterns. Accidental droppings in the waterer spreads coccidiosis (an overgrowth bloom) fast.
I personally never ever treat anything just on a schedule. I will check for everything on a schedule... every few weeks for parasites a physical check of multiple birds AFTER DARK with a flash light is most effective since SOME mites only come out to feed at night and don't actually live on the bird. And a couple fecal floats per year to check worm load AND species... since it's pointless to treat for what you don't have while maybe not treating what you do and not all wormers treat all worms... treating without cause is a recipe for resistance to the drugs and making them not work when you really need them too. Also note that some mites are microscopic and you will never see them, but only the evidence of them... Like Scaly leg mites and depluming.
DE is stuff I hate. Consider it over rated, overused, and ineffective in MANY environments AND on many parasites... plus it's indiscriminate and will take bees and all in addition to being strip mined. I also consider it a health hazard to my birds and my family. The dust cloud when they are bathing is on par with a tractor plowing a field and I see it explode every time they shake out there after.
http://www.the-chicken-chick.com/the-cut-dry-truth-about-diatomaceous/
http://www.the-chicken-chick.com/diatomaceous-earth-de-benefitrisk/
Listen, I'm ALL for natural and organic IF it works. But when the health of my birds is at stake, I won't fool around.
If I NEED to treat for lice or mites... which I never did for 9 years in a different location... I use permethrin spray. It's safe, effective, affordable, labeled for use in chickens, and no withdrawal time for eggs. It's the synthetic version of Pyrethrum which is a chrysanthemum extract. But to me organic or not... poison IS poison, think lead, arsenic type stuff. There are other product like elector psp, and IC3 that are good alternatives.
The worm load will depend on your pasture situation. Some places have higher populations than others. I practice good pasture management for prevention. Since it is new to you, maybe you can do a float at different times of year the first year or... see how your count looks and then if it seem like you do have a heavy season... maybe then treat on a schedule... trying to switch up the drug you use to prevent parasite resistance.
With enough birds... for me, I decided most the poo I remove gets hauled off in the trash can. It really isn't garden gold. You might consider deep litter method in your run?? I tried to make mine like the forest floor... inviting good microbes and bugs to come clean up and compete for space with the nasties. I still pick up what poo I see... but the build of leaves, grass clippings, pine needles and so on really keeps things dry and flies down. Could also consider making a fly trap... inverted cone part into a soda bottle with attractant like raw meat scrap (waste) or surprisingly a slice of apple.
Funny enough... you mention using DE especially in hot months... I believe (but always here to learn) that lice and mites are more cool weather pests... I KNOW the lice is according to my vet and for MY area. Hot weather here actually equals LESS cleaning for me... because everything dries out pretty fast. In cool weather, I have to clean way more often to keep things acceptable. But I know each situation is unique... as so finding and knowing what works for YOU in YOUR location is key.
I am no expert... these are my opinion based on my experience, research, and understanding... after about 9 years and a few hundred birds.
You are already seeking the truth about different treatment.

You have come to the right place! You will still get many varied opinions and still have to sort through the muck ( I see a LOT of misinformation spread EVERY day) and decide what truly makes sense to YOU.
I prefer barn lime or Sweet PDZ if I need to keep odor down.
Ask a long question... get a LONG answer. Like MOST here, I'm a BIT passionate.
Good luck and best wishes with your flock!
