[metalliqaz]

We use "disease" for maladies caused by infections (virus, bacteria), and we use "disease" for maladies caused by genetics (cancer), caused by chemicals (lung disease), and so forth. So yeah, a parasite certainly would qualify I think.

[I_dream_of_Geni]

And (weirdly, I think) a few years back they called alcoholism and smoking diseases, which, well, really??