http://cbsnewyork.com/healthwatch/health_story_125132159.html

Secure breeding environments and appropriate good-health measures are key. Wild rats and mice (and other wildlife) are capable of sharing their creepy-crawlies with their domestic cousins. Furthermore, these domesticated rats and mice will share them with other animals at their intended destinations and then, ultimately, with you!

Oxyuriasis - Syphacia muris (pinworms):
     Rat is natural host.
     Transmission fecal-oral, self-cleaning.

Oxyuriasis - Syphacia obvelata (pinworms):
     Mouse, hamster, gerbil is natural host.
     Can affect rats (when housed in same room).
     Transmission fecal-oral, self-cleaning.

Oxyuriasis - Aspiculuris tetraptera (pinworms):
     Mouse, rat (?) is natural host.
     Transmission fecal-oral.

Acariasis - Radfordia ensifera (fur mites):
     Rat is natural host.
     Transmission eggs (results in barbering, secondary skin infections, ulcers).

Acariasis - Radfordia affinis (fur mites):
     Mouse is natural host.
     Transmission eggs (results in barbering, secondary skin infections, ulcers).

Pneumocystosis - Pneumocystis carinii:
     Mammal is natural host.
     Transmission inhalation of spores (it’s a fungus).

Trichophyton mentagrophytes (ringworm):
     Wild rat is natural host.
     Can affect rats, mice, guinea pigs, cats, dogs, humans.
     Transmission direct contact.

Hymenolepis nana (tapeworm):
     Wild mouse is natural host.
     Can affect mice, humans.
     Transmission fecal-oral(?).

We can’t prevent bacteria from being, but we can limit the harm done. Poor breeding practices and facilities contribute to greater risk. Clean bedding and ample space (the more overcrowded, the more likely they are to attack cagemates) alone would reduce such risk to them, to other animals, and to us!

Murine Respiratory Mycoplasmosis:
     Rat and mouse is natural host.
     Can affect hamsters, guinea pigs.
     Transmission airborne.

Pseudotuberculosis:
     Rat and mouse is natural host.
     Can affect hamsters, guinea pigs.
     Transmission fecal-oral.

CAR bacillus:
     Rat, mouse, rabbit is natural host.
     Transmission direct contact

Tyzzer’s Disease - Clostridium piliforme:
     Japanese waltzing mice is natural host.
     Can affect numerous rodent species, rabbits, carnivores, horses, monkeys, and humans.
     Transmission fecal-oral (spores).

Staphylococcosis:
     Rodent (all) is natural host.
     Transmission dirty bedding.

Streptobacillus moniliformis (rat bite fever):
     Wild rat is natural host.
     Can affect rats, mice, cats, humans.
     Transmission bite wounds, scratches, aerosol exposure.

Leptospira icterohemorrhagiae:
     Wild rat is natural host.
     Can affect rats, humans.
     Transmission skin wounds, contact, dirty bedding.

Viruses happen and we can’t do much about that, but we should be concerned about knowingly sending sick animals to their intended destinations! They can get everyone sick and that can become quite costly!

Parvovirus - RV:
     Rat (and wild) is natural host.
     Can affect hamsters, mice, kittens.
     Transmission fecal-oral, urine, milk, direct contact, aerosol exposure.

Paramyxovirus - Sendai Virus (SV):
     Rat and mouse is natural host (moreso mouse).
     Can affect hamsters, guinea pigs, rabbits, marmosets(???).
     Transmission airborne, direct contact, aerosol exposure.

Paramyxovirus - Pneumonia Virus of Mice (PVM):
     Mouse is natural host (moreso mouse).
     Can affect rats, hamsters, gerbils, guinea pigs, rabbits, mongooses(???), and perhaps monkeys and humans.
     Transmission direct contact.

Reovirus - Infectious Diarrhea of Infant Rats (IDIR):
     Rat is natural host (moreso mouse).
     Can affect humans.
     Transmission oral-fecal.

Lymphocytic Choriomeningitis Virus (LCMV):
     Wild mouse is natural host.
     Can affect mice, hamsters, humans.
     Transmission fecal-oral.

Hemorrhagic Fever with Renal Syndrome (HFRS):
     Wild rat is natural host.
     Can affect humans.
     Transmission dirty bedding, saliva, respiratory.

Why is the connection between feeder rats and fancy rats so important? The USDA has already created one completely artificial distinction between rats of the genus Rattus and mice of the genus Mus bred for use in research - and everyone else. Laboratory rats and mice are identical to non-laboratory rats and mice; however, the research community insisted on creating two categories of animal to keep the Animal Welfare Act (AWA) out of laboratories.

Now, another special interest group wants to slice rats of the genus Rattus and mice of the genus Mus into yet another independant category, ‘feeder’, in order to keep the AWA out of mass breeder warehouses - rodent puppy mills.

So, we have the same animals, Rattus norvegicus and Mus Musculus, already divided arbitrarily into ‘bred for use in research’ and not ‘bred for use in research’ in order to satisfy one special interest. In order to satisfy yet another special interest, the group will be divided again into ‘feeders’ and ‘non-feeders’. Despite the fact that feeder and pet rats are not only biologically identical animals: they come from the same source.

What a regulatory nightmare! The same animal, regulated under at least three different standards, depending on a completely arbitrary designation made by profit-making entities.

If you ever thought that the “fancy” rat or mouse bin and “feeder” rat or mouse bin at your favorite pet store meant something, think again! Most of the time this distinction is the result of human intervention: Someone somewhere found one rat or mouse to be more appealing than the other (and thus worth more moeny than the other) - the more appealing of the two became friend (fancy) while the other became fodder.

Why does this matter? Because fancy and food come from the same sources. People who breed rats and mice for food aren’t naive - they know that they can get more money for a “fancy” rat or mouse than they can for an unappealing “food” rat. There’s one such example here:
http://www.RemarkableRodents.com
Although appealing because they produce a great variety daily, it seems likely that their excessive production is not solely appreciated by the rat and mouse lovers of the world (and while you’re there, don’t forget to scroll down and see their breeding setup - 33 1/3 rats per tub!):
Remarkable Rodents Variety and Tubs
Why are some “fancy"? Check out the prices:
Remarkable Rodents Prices

As another example, this was found on Kingsnake:

And another, from Backwoods Farm, Inc. website:

the ‘pet’ rats. . .
* dark skin hairless - $8.95
* masked hairless - $9.95
* hairless masked dumbo - $10.95

and the live ‘feeder’ rats. . .
* small - $2.00
* medium - $3.00
* large - $4.00
* JUMBO! - $5.00

Most mass rat/mouse breeders breed other animals and are already licensed and inspected by the USDA. As such, it is unlikely that additional cost would be incurred on that front, I would think, since a regularly scheduled inspection would allow the USDA to inspect all animals on the premises at once.