In the interest of accuracy, allow me to expand on what I wrote earlier
about pyrethrin, and correct a couple of mistakes or bad choices of
wording:

    --------------------------

Pyrethrin is generally considered safe, when used as directed, for
use on pets. It is frequently recommended by veterinarians for use
on ferrets. Marshall flea and tick products for ferrets contain a
pyrethrin derivative called resmethrin. Pyrethrin has been used many
thousands of times, at least, on ferrets with good results. From here
on, by "pyrethrin" I mean either plain pyrethrin or resmethrin.

It is probably better to avoid other forms of pyrethrin. Cats are
known to have reactions to permethrin and possibly ferrets as well.
Definitely stay away from any product containing additives or
"synergistic compounds", such as piperonyl butoxide, sesamex, piperonyl
cyclonene, carbamates, carbamyls. It is likely that additives are
actually responsible for many of the health problems that have been
attributed to pyrethrin. In the words of one source, these additives
"potentiate mammalian toxicity". In other words, they may make the
product more poisonous to insects but then they are more poisonous to
mammals, too.

It may be that ferrets in general are more sensitive to pyrethrin than
some other animals are. There is some evidence for this. But it must be
pointed out that even if so, pyrethrin is still less toxic than most
alternatives you are likely to find.*

The choice is yours. There are in fact reports of ferret illness and
death from the use of pyrethrin. At the same time, it is not clear that
it was pyrethrin itself that was the culprit in most of these cases; it
may have been from additives. Further, it has been in common use for a
long time, and reported problems have been rare.

**IF** you decide to use pyrethrin, I recommend the following
precautions, which I will explain more fully than last time:

(1) Use plain pyrethrin or resmethrin. Avoid other pyrethrin
derivatives. In particular, never use permethrin on your ferret. And
"synergistic" additives are definitely out. See the list I gave above
and if any of those things are on the label, don't use it. Obviously
not all chemicals can be listed here; use your judgment.

(2) Pyrethrin should be used outside if possible, for several good
reasons.

First, pyrethrin is not just an insecticide, it also repels the pests.
Fleas, ticks, bedbugs, and mites generally prefer to bite your pets
because they have fur and a higher body temperature than humans. But
if they are repelled from your animals, they will bite the next best
thing: you. Taking things outside gives them an opportunity to just
leave instead. Especially if you spray and then leave the area for a
while.

Second, using insecticides inside can cause concentrations that are
not intended or according to directions. Always use insecticide with
caution, and use only in well-ventilated areas. If for some reason
you feel you need to apply a pyrethrin-based product to your general
household or any large part of it, you should open windows for
ventilation and go elsewhere for a few hours, to give it time to
work and then break down. Best to err on the side of caution.

Third, light and oxygen cause pyrethrin to break down faster. Pyrethrin
kills pests quickly, but it also breaks down very quickly. These are
both good things. It will generally break down in air and be rendered
non-toxic (even to insects) within about 4 hours. Taking things outside
into the sunlight and the breeze will speed up the breakdown process,
as well as giving the vermin a chance to exit to somewhere besides your
own pants.

So take the items outside, including your pets, and spray them there.
(For a ferret, maybe find a way to confine it outside like one of those
portable play-area fence things.) Then walk away and leave them be for
a while. Earlier I wrote 15 minutes but a half hour would probably be
even better. This is not enough time for all the pyrethrin to break
down, but it helps, and it is enough time for it to do whatever work
it is going to do.

Bedding and other such materials should then be laundered with warm or
hot water and detergent.

I mentioned mattresses last time, but I could have been clearer: since
you can't launder these items, after treatment with pyrethrin you
should leave them out in the air and sun for a good couple of hours.
But keep in mind that if you leave them out long enough for the
pyrethrin to degrade completely, the pests might well just crawl back
to where they were before. So while you might take them inside, open
a window and you probably don't want to cover them or use them for
several hours afterward.

(3) PLEASE follow the directions. Any household chemical is usually
safe if used as directed, but many can be hazardous if they are not.

(4) One application of pyrethrin is usually not enough to get rid of a
severe pest problem. It kills the adults, but not eggs. It generally
has to be done again after a couple of weeks. There are products that
claim to kill the eggs, too... but those are the very additives I was
warning against.

I do not claim that pyrethrin is safe for your ferret. You must decide
that on your own. There have been reported cases of problems, and it is
possible that pyrethrin was indeed the cause; that is impossible for me
to say. All I can say is that it has been used a lot, for a long time,
and that the vast majority of the time it has been safe and effective.

      --------------------------


* This added later: I was referring to alternatives you can find on the
shelf, but it appears this has changed. While looking up this
information I ran across some other, newer products that are reportedly
safer for ferrets, but they haven't been around nearly as long so one
must be cautious about such conclusions.

One of the newer products is "fipronil", which is sold under the brand
names Frontline®, Frontline Plus®, and Top Spot®. Another of the newer
products deemed to be "safer" is Advantage®. Advantage works
differently from the others.

For general advice about treatment and control, please see here:

<http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/71600.htm#aTreatment%20and%20Control>

Note: that page is aimed mainly at treatment of cats and dogs, but in
the ferret section of the manual it states that ferret treatment should
be the same as for a cat.

For symptoms of insecticide poisoning, please see here:
<http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/211604.htm>

However, it should be noted that contrary to that entry, permethrin
appears to be less safe in cats and ferrets than pyrethrin.

There may be more authoritative texts for ferrets than the Merck
Veterinary Manual, but they tend to be expensive and their content
is not available online.

Lonny Eachus

============

[Posted in FML 7194]