It's a long time since we discussed this, but given the impending withdrawal of permethrin, readers might be interested in some info I've dug up recently on pyrethrum.
So, it's "one of the safest and most widely used natural pesticides in the world... Pyrethrins (the active chemicals in the powder) are incredibly potent neurotoxins - just not to humans... We now know how pyrethrum works as an insecticide: pyrethrins bind to important protein passageways (voltage-gated sodium channels) for sodium ions in nerve cells. When pyrethrins bind to these proteins, the nerve cells wildly overfire, causing involuntary muscle contractions, paralysis and even death. This physiological reaction sounds bad, and it is indeed problematic for invertebrates like insects, molluscs, arachnids, and some vertebrates, like fish. But natural pyrethrins are not very toxic to other vertebrates, like humans and birds."
Hence we can use it safely on chickens; humans and birds.
"... A single ancient change in the DNA of insects makes their nerve cells a hundred times more sensitive to pyrethrins than ours. By contrast, cats and fish are sensitive to pyrethrins because they lack one of the liver enzymes we humans use to detoxify pyrethrins." So the cat owners amongst us might want to note, if they didn't know it already, that using pyrethrum may present a risk to their feline friend(s).
Source: N Whiteman Most delicious poison 2023:15-17.
Hopefully someone with a scientific background can explain it better than I, but I think that permethrin is a chemical reproduction of natural pyrethrin. So they may well work in the same kind of manner and permethrin is also deadly to cats. In fact, the number of substances cats can not process is very important compared to most mammals.
As you know I'm using pyrethrum powder in my flock now for a lice infestation ; but I also used for one of my ex-batt's, Blanche, who is close to death and turned out to be totally infested, a canine permethrin and fipronil droplet applicator. To be clear I don't approve the use of this product at all , but I wasn't ready to see my dying chicken covered in hundreds of lice and unable to fight them.
Well, the efficiency is definitely not the same. I'm on my second and third application of the pyrethrum powder, depending on the chicken's degrees of infestation. The number of lice is clearly decreasing, but on the few chickens that had what could really be called an infestation, I still see some lice. On Blanche, the hen that had the permethrin and fipronil combo, I saw maybe dozens of live lice for a few days ; now the only lice I see on her are dead. The product is persistent enough to kill the lice that hatched days after application.
I am definitely not advertising it's use, especially for the Fipronil. It's persistence, while making it more efficient, is also a major reason of the environmental problem. But, I think that if I used pyrethrum powder as a natural alternative exactly following the instructions on the label (two single applications of 2 g a week apart) some of the chickens would definitely still have too many lice to deal with by themselves.
I intend to do more applications for the chickens who still have lice I can see ; I will also use DT and ashes in the dustbath ; and I have a dimethicone spray that the chickens really hate but which I might eventually use on one or two of them.
The insistence for commercial structures on switching between different molecules and type of products is, I believe, also a necessity for backyard chicken keepers.
And folks, for those of you who inspect your chickens more or less regularly, don't forget to look underneath them. The lice were all hidden on their bellies and legs. I had been inspecting necks, vents and underneath the wings with no clue of what was going on.
My two remaining ex-batts. Blanche is in front attempting to dustbathe.
Mélisse is one of the hens that had lice even though she is young and healthy.
