Opossums carry diseases such as leptospirosis, tuberculosis, relapsing fever, tularemia, spotted fever, toxoplasmosis, coccidiosis, trichomoniasis, and Chagas disease. They may also be infested with fleas, ticks, mites, and lice. Opossums are hosts for cat and dog fleas, especially in urban environments.
Well, that may be somewhat true, but only part of the truth… As you do have to consider the source here (Integrated “Pest” Management)… Yet again, for example, opossums actually serve to KILL an enormous amount of ticks (and thus fight debilitating LYME disease)!
Yes, they will carry many hungry ticks like any furry creature like a sponge…but then they’ll eat 96.5% of those same ticks before they can detach on their own. So they’re not tick vectors…they’re actually tick traps! A KEY distinction that that “pest” site completely ignores! As if ticks aren’t MASSIVE “pests” and Lyme disease isn’t far more epidemic amongst humans than all those other rare diseases they listed (minus trichomoniasis) COMBINED???
only 3.5 percent of ticks on opossums survived to drop off. Why? It turns out that the fastidious opossums were killing their ticks in the process of grooming—scratching, licking and chewing away at ticks in their fur. Examination of opossum feces confirmed that some of the ticks had been eaten.
This is significant because during late summer, when ticks are most abundant, the average opossum may be walking around with roughly 200 ticks on its body, according to the researchers. Based on their study results, they calculate that a single opossum might kill an astonishing 4,000 ticks in a week, a number that “really got our attention,” says Ostfeld. By “hoovering up and killing” so many ticks, he says, opossums are “not only protecting themselves, they’re protecting us because we know that human risk is a function of the abundance of infected ticks out in the environment.”
That said yes, of course, if they can carry fleas, they can carry disease…
But that also goes for all of peoples’ domestic pets too, so it’s not fair to only scapegoat wildlife.
And what are the actual frequency of transmission rates for such diseases??? Every animal (including humans) can carry diseases, too - but you have to factor in transmission rates and actual risk to gain a more useful perspective.
Anyhow, guess you have to weigh the pros and cons in your situation, and glad you at least put some thought into it! 
PS - A few more fun facts about opossums is that they have the most teeth (50) of any North American mammal, immunity to many toxins and venoms, opposable “thumbs,” prehensile tails, and forked penises!
