caterpillar disease

I've come across a problem in different seasons with Hyalophora caterpillars that begin to exude a blackish liquid from the mouth, languish, then expire.
This has occurred using different food plants, either sleeved on branches, or caged with a potted plant. It happens outdoors and indoors as well, there seems to
be no common thread, except the result, a dead and probably contagious caterpillar.
Sometimes it has killed every larva, even larva separated by what I would have thought a safe distance, other times it will take only one, I've seen it at the final instars,
and most recently the third instar, but that's as young as I've seen a caterpillar get this frustrating malady.
Perhaps this happens with other species, it's just that I have most of my rearing experience with the Hyalophora.
Any input would be appreciated, at least for now, this has only occurred with relatively common species, but losses are always a frustration.

kevin

Hi Rudi,
unfortunately, yes. This is a second, or third instar Hyalophora euryalus.
I have received some email from another breeder who seemed to have this pinned down, more or less, the pathogen
is apparently unknown, but not unfamiliar.
The breeder who emailed me detailed a focused method he uses with a disinfectant chemical, spray misters and a fogger
he uses in a clean breeding room, having given up on outdoor rearing, not an option for everyone, but seemingly very useful
information, some of which I can easily incorporate into my rearing efforts.
kind regards, Kevin