Lab rats won't necessarily be more prone to myco or anything else unless they're 1.) a specific strain known/bred to be susceptible, or 2.) "germ-free" (delivered via caesarean section and raised in a sterile environment). Generally you can't get germ-free rats as a pet owner, because they know these rats don't do well outside the lab and also because they're expensive as balls to produce. And the others... well, to be honest, I'd think if anything they
might be more resistant simply due to the fact that they live in conditions which facilitate the spread of germs (they don't live in huge colonies all together, but there ARE lots of rats in one room, so aerosolised microorganisms/viruses can travel easily), and the sick ones don't get bred or get euthanased. I wouldn't say you'd get longer-lived/healthier rats from labs than pet rats, though, particularly as laboratory research rarely uses rats older than a year, so they have no specific need for animals who stay healthy into old age.
That said, I have a friend who regularly adopts ex-lab rats from a local university, and she has always had great success with them. The three I've met have been friendly, lovely creatures, just as healthy and as un-healthy as non-lab rats (they had sniffles on and off or as they got older, and one died of a suspected stroke or heart attack, suddenly with no warning at 29 months, but like I say... no different from non-lab animals). This is in Australia, where the ethics standards for lab animals are quite high - I read over the specifications for rats a few months ago, actually, and it's incredibly comprehensive! (Check it out -
http://www.animalethics.org.au/__da...2512/housing-rats-scientific-institutions.pdf It's a fascinating read! Did you know that you shouldn't have computers in the same room as your rats? Or that albino rats can suffer degenerative changes in their eyes from only 60 lux of light? [For reference, 50 lux is supposedly the level of "family room lights" and 320-500 lux is "office lighting," according to the wiki article.])
My experience is with Australian labs/lab rats; other countries may be different. If you're interested, though, it's probably worth calling your nearest university to see what you can find out. Each lab is run independently (a "lab" in a university is under the direction of a single head researcher, so there can be many labs at a single university), so if you manage to track someone down and you get a "no," ask them if they can give you contact details for any other labs which work with rats who might be interested.
Then, if you do manage to find a potential "yes," ask lots of questions - what strain are the rats (write it down so you can google it later - some strains are known by number/letter codes like SD-Tg(P23H)1Lav), what characterises the strain, what research are they doing, what specific experiment(s) have the rats been used in, will this experiment have any effect on the rats' lifespan/health/quality of life, how old are the rats/how old will they be when they're released, what sex are they, is there anything else you should know about them, etc.
The lab my friend gets her rats from is only too happy to give healthy rats away, as the other option is euthanasia at the end of the experiments. In some cases they can't offer the animals for adoption, but the possibility exists for many others. Worth looking into if you're interested.
