Tuesday, May 5, 2015

The DE Debate

Andrea asked me if I have ever tried Diatomaceous Earth (DE) to eliminate ticks.  The short answer is yes, I've tried it.  Did it work on the ticks?  Unfortunately, not in any way that I ever found useful.  I have not ever tried to use it as a perimeter dust though.  With 20 acres to cover, that is just not feasible.  I rather doubt that it would work well that way, at least not in my wet/humid climate.  It might be more effective in a drier region.

DE works in two ways (maybe):
  1. It draws moisture out of anything it comes in contact with, including insects, which kills them.  Once the DE is wet, it stops working.  
  2. The second mode of action is a bit more questionable, there does not seem to be any clear consensus as to the veracity of this.....DE is made of microscopic diatoms, which have very sharp edges.  This abrasiveness cuts up tiny insects and kills them. (notice the little scale at the bottom right that says 10 microns, that is about the thickness of a piece of paper.  I'm going to come back to that in just a bit)

Ticks are very susceptible to changes in humidity, if it is too dry they die, so DE should work well on them.  However, getting enough onto the tick to be effective is the challenge that I have not been able to master.

Spreading enough DE around the property that it might help is just not doable for me.  It is especially not feasible as it would get washed into the ground during the first rain.  Even without rain, it would absorb so much moisture from the ground itself that it would be rendered useless within minutes.  Once it is really wet, it clumps up and even its abrasiveness is rendered useless.

I have used DE to dust the animals directly as well as in chicken coops and in the garden.  It works great for treating lice and mites on donkeys, horses, cattle, chickens, etc.  I did not see that it helped keep ticks or flies off.

The trouble/blessing with it is that it is such a fine powder that it settles down into the hair next to the skin.  That may be why it works so well for lice and mites, but ticks just crawl over the top of it.  Also, I find 99% of the ticks attached under the chin, between the front legs and in the inner thighs.  The DE just won't stay there.  I even tried putting it into a solution and spraying it on, but it had no noticeable effect that way.  I have found live ticks attached right through a layer of DE.

A couple of the the things I do not like about using DE on the animals is that it is a definite irritant to eyes and lungs and it really dries out the skin.  That last can be a good thing for the donkeys when it is extremely humid as they are meant for a dry climate and are prone to fungal infections, but used routinely, it is too much.

If anyone more clever than me comes up with a successful way of using DE to control ticks, please do let me know.  I would appreciate it.


Since I get asked about feeding DE, using it as a wormer or feed-thru fly control at least 6 or 8 times a year and we're on the subject....

When DE first started gaining popularity 12-15(?) years ago, we were all set to jump on the band wagon.  It sounded like the greatest thing since sliced bread - a natural, organic pesticide, wormer, miracle cure that parasites could never develop a resistance to.  And, for the external parasites I already mentioned, it is all that.

Since that time, I've learned a lot more about DE and the entire premise of using it to treat internal parasites now seems ridiculously faulty to me.  The first mode of action, as a desiccant, becomes moot as soon as it hits the stomach full of fluid.  As for the second mode of action...If it actually DOES work that way, I just can't see how it would be safe to feed in doses large enough to actually kill parasites.  Maybe its because of my job as a histotech, but that idea just scares me. and here's why:

The photo below was taken through a microscope.  It is a piece of normal small intestine

Those finger-like projections are where 90% of nutrient absorption takes place and they line the entire length of the small intestine.  This tissue section is cut at 5 microns thick (remember the scale in the first photo?), to put that into perspective, a red blood cell averages about 7 microns.  Lining the outer edges of those fingers are super tiny cilia that are so small they can't be seen here.  If you look REALLY close at the top of this photo, you will see that the outer edge of fingers appear to have a faint, pink fuzz - that is called the brush boarder and is made of those tiny cilia.  They are like little Velcro "hairs" that reach out and "grab" individual nutrients.

Remember those big, sharp diatoms in the first photo?  If DE really is that abrasive, what do you suppose they might do to these tiny, delicate, crucial structures when fed in sufficient quantity to "shred" worms?  The way I see it, if it is safe to feed than it is not going to kill worms through sheer abrasion.  If it does kill worms that way, how can it be safe to feed?

DE is considered safe as a food additive and is used as an anti-caking agent in feeds.  However, it is generally used in very small amounts in feeds that are themselves supposed to be fed in small amounts.  A large enough quantity of DE to kill parasites through sheer abrasion while inside the GI tract....nope that just doesn't make sense to me.

I personally know several horses who were routinely fed DE to control worms.  They all suffered for it and at least two youngsters nearly died of anemia caused by extremely heavy parasitism. To my eye, horses who have been fed "therapeutic" doses of DE for a long time have an unthrifty look to them.  They often have diarrhea and their hair coats look long and dull.  Whether from worms or the DE itself, I couldn't say.

My opinion, for what it's worth to  you....Use DE to dust for lice.  Use it to dust the bedding litter in chicken coops to kill mites.  Use it in the garden to kill aphids and slugs, but don't use it to kill worms.  If the propaganda gets to be too much and you absolutely MUST try it, do regular fecal egg counts and if your critter starts acting listless and lethargic, stop feeding it and call your vet ASAP.


  1. Thanks for the info! Glad to have your first-hand account. I hadn't tried it yet, and I guess I'll save it for the garden.

    About tick control, at least in dogs, I recently tried NexGard treats, after a spot on treatment didn't work at all. I'm not seeing any ticks at all anymore. I was worried about feeding them something like that, but I haven't seen any I'll-effects so far. Granted, they've only had the one dose.

  2. Once again, a very useful discussion! One of my horse mentors has been touting DE and making exactly these claims. I told her we needed some untreated comparison fecals before I would agree to feed it routinely. She'll never let go of this idea without the controls. Guess I better get on that.

  3. What is depicted in the first, black and white, photo? Is that DE itself? Looks like lace doilies.

  4. Not to be contradicting or anything, but I must tell all you blog readers that personally I HATE ivermectin! It discourages dung beetles and all sorts of other beneficial soil life. It is potentially deadly to dogs, particularly collies. I will no longer have the stuff on my farm. I rarely ever used it before. I must have accidentally given Kris some misinformation, as I have not used DE mixed with kelp since prior to 1995, when I had my dairy. Kris is much smarter than me about the scientific aspects of DE, but I like it. I use it with great success on cattle in the winter for lice, which they usually get even though they are allowed to be outside whenever they like. This winter, they never had trouble with lice, so I did not use it. I used it early last summer with great success on my squash plants, and it did a real number on those squash bugs. In the winter of 2013/2014, I had a calf that I felt was doing poorly, and I did use some pour-on ivermectin, which I now regret doing, and I did not see any improvement. Hate the stuff. Mostly I just ignore internal parasites, which is amazing, but I think I avoid problems with them because I have both sheep and cattle on this farm. I have never wormed my sheep and amazingly they look great, which I do not take credit for at all, but am very happy about.

  5. I use DE for mites and that's it. I takes a few days to work but still better than chemicals. I never believed the hype of it doing anything internally and I don't even like getting it on my hands or breathing it. So it just has one job here - ridding the goats of mites that the rats or mice bring in. The better job the cats do with the mice the less DE is necessary at all. Good post!

  6. Great and informative post! Thanks for your research. The vet I work for routinely advises against the use of DE. We too, have seen GI tract damage from people routinely feeding the stuff to their horses, and long-term it has been known to do serious damage through the thinning of intestinal walls - not a good thing. Also, we do fecal egg counts routinely through our local lab on horses that are on DE, and those dewormed using the common de-worming drugs like oxibendazole, pyrantel pamoate and ivermectin. The amount of parasites in horses being fed DE are almost always higher than the horses dewormed with the common drugs. So, for me and my horses I would never, ever use DE internally. It does far too much damage and does very little to kill the parasites. Used correctly (proper dose/weight) all the de-worming drugs on the market are extremely safe and are beneficial in preventing colic and improved thriftiness of the animal. And...ivermectin is safely used in dogs (not Collies). Proper dosing is critical in dogs, much more so than in horses. Common sense prevails (hopefully) in all things, over-dosing is detrimental long-term and the less animals on the property means less parasites being picked up from the ground. Lots of animals on a small acreage = many more parasites. Cold climates make it more difficult for parasites to live as well, warmer climates = more parasites. Hope this helps some too!

  7. I've just seen this post and felt I needed to add my DE story. I tried it on 2 golden retrievers for worming. Fecal egg counts done prior to starting (negative) then at 3mthly intervals. By the third fecal egg count at 6mths on DE both dogs had worms. One of my girls also developed a partial bowel obstruction during this time. Was it due to DE? I can't say but I am suspicious. Fortunately the obstruction resolved without surgery. No more DE orally in this house. Yes, I'll dust bugs on plants with it though I can't say whether it really works or not. One thing I have found it helped with - a small "hot spot" on one of my dogs. Just a thumb nail size area where a blackberry thorn had broken the skin and caused enough discomfort to get the dog licking (and licking and licking....). We all know how those little hot spots can grow in a matter of hours if not treated. It was a Saturday evening - so I tried some DE on the area hoping it would dry it out enough to keep things stable until Monday when I could get to the vet. The cone of shame went on the pup. By Monday morning no hot spot just a dry scaly area that soon healed altogether. Yes, of course the lack of continual licking helped settle the area BUT I've never had them heal so quickly just with the cone of shame. I'm thinking the drying powers of DE may have contributed to the rapid healing. Fortunately, I haven't had the opportunity to try it again but no doubt there is another hot spot in our future somewhere. It will be interesting to see if DE works again.