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Posted by WK on November 04, 2002 at 23:59:47:
In Reply to: Re: au contraire.... posted by noleary on November 04, 2002 at 10:25:15:
Both of these compounds fall under a class of insectisides called pyrethrins. Now, without getting into extremely detailed chemical analyses and toxicity studies, it appears that black knight is more concentrated, by a factor of 4 ( assuming that slightly different derivates of the same class of compound have the same insect toxicity).
Pyrethroids do differ in toxicity across the class. For example, the 'isomer of promethrin' contained in PAM can vary significantly in toxicity depending on whether it is the cis or trans isomer. Pyrethroids also vary greatly with respect to half life, meaning they vary with respect to accumulation (in environment & body tissues) potential. This is one reason making it difficult to draw conclusions about pyrethroid products and dosing toxicities.
Pyrethroids kill insects and similar inverts by interfering with nerve conduction. Specifically, they affect sodium channels in nerve cell membranes. Mammals are not as sensitive to these pyrethroid neurotoxins because their sodium channels are more varied in makeup and structure (unlike insects). Even though some of these mammalian Na channels are susceptible to pyrethroids, most are not, meaning mammalian nerve conduction is not greatly affected by "normal" pyrethroid concentrations. I don't know if pyrethroids have been studied in the reptilian system with respect to effects on Na channels.
Interestingly, a single mutation resulting in substitution of one amino acid in the protein making up the Na channel can alter the channel's susceptibility to pyrethroids - making it resistant, or, on the other hand, exquisitely sensitive. Maybe this is the reason behind varied reports of herp susceptibility (i.e. BrandonN friend lost boa to pyrethroid, Pro Exotics Robyn loses none out of 2000), and not something inherent to either BK or PAM. Snakes could develop a mutation in their sodium receptors that makes them very sensitive to pyrethroids, resulting in death when they are exposed. This is just speculation on my part, but I'm just trying to illustrate a point.
I hope everyone sees from this that it would be difficult to draw meaningful conclusions about the comparative safety of pyrethrin mite treatments without some real studies. These, to my knowledge, are currently lacking.
Personally, I get the Spectracide Bug Stop from Walmart that contains a pyrethroid (huge bottle, three bucks - why is it that everything skyrockets in price when it is labeled a "herp product"?). Seems to work well for me.
Cheers,
WK
