Plent pox split from its ancestor plent fever. It has run rampant in the Raptor limestone caves and has killed off the cavehog and Raptorian bearhog. It also spread outside the cave to the rainforest and scrub, but due to the much larger populations of these mobile plents, they were able to survive. However their numbers diminished greatly.
The plent pox is spread via the air and causes mobile plents to cough uncontrollable through their butt nostril. Once infected the effects are weakness, sneezing, excess mucus, chills, delirium and eventfully a high fever that can lead to death. One can tell if a plent has this not only from the described symptoms but visible bright green spots all over the body. These spots can become very itchy over time and cause great discomfort for the plent.
The insidious part about it is that it can stay dormant in a plent's systems for days without showing symptoms, thus spreading itself from just breathing near another plent. Thankfully those that do survive it will likely never get the pox ever again.