wingsandsword
Legend
I'm curious - why not? Nothing in the SRD spell description prevents it from being used on an sentient parasite. I can use swords and fireballs on sentient creatures, but not Remove Disease?
I'd be quite okay with Remove Disease destroying a sentient parasite. If it counts as a Disease for infection rules, then Remove Disease should destroy it. Then again, I saw a lighthearted game where a Cleric cast Remove Disease on a trashy bar wench and she vanished entirely.
The way I see it, if it's a infectious bacteria, virus, fungus, or prion, or parasitic protozoa causing the infection, Remove Disease kills it dead. If it's magically augmented (like in the example of some Fey plot) it may require a higher level caster, but the spell itself should work.
Or, if you simply don't have that many clerics in the game world, there may not be enough of them 5th level and over to cover the problem.
Personally, I would go with this. 5th Level Clerics aren't supposed to be horribly common. In my campaigns, a 5th level NPC Cleric would probably be the parish priest at a small temple, or a more senior functionary in a larger cathedral. The rank-and-file of the Clergy are 1st and 2nd level, maybe 3rd level at most. Most towns would only have a handful of Cleric of 5th level (or higher) and they might get 1 or 2 3rd level spells per day. Assuming they only prepare/memorize Remove Disease (or Cure Disease, edition-dependent), they can cure a couple of people a day. . .which may include themselves.
Basically, you can use Clerical magic for miracles to save a few people, but basic sanitation, hygiene, and Heal skill checks will do a lot more for the masses than magic. Use the Magic to fix up the worst cases, with people near death whom non-magical healers can't help, quarantine the ill, and good cleanliness using plenty of soap and alcohol for disinfection will stop a normal plague in a D&D world.