As the title suggests, looking to convert this creature into PF2e:
https://www.aonprd.com/MonsterDisplay.aspx?ItemName=Rot%20Grub%20Swarm
Thought about how to implement the infestation mechanic as an affliction for a Level 7 creature, and here's what I came up with (basically treating an infestation as a disease that behaves like a poison for mechanical purposes):
Creatures that are not composed of flesh are immune to this ability. This ability otherwise ignores immunity to disease.
A living creature that takes damage from this ability becomes drained with a value equal to the Stage of the infestation as the rot grubs burrow through and consume its flesh.
After the maximum duration expires, the sated rot grubs crawl away.
Energy damage (except vitality) dealt to the victim reduces the Stage of the affliction by 1 for every 5 points of damage taken. Additionally, any effect that counteracts a disease can counteract a rot grub infestation (counteract rank 4, DC 23).
Saving Throw DC 22 Fortitude; Maximum Duration 6 rounds
Stage 1: 1d6 piercing damage (1 round)
Stage 2: 2d6 piercing damage (1 round)
Stage 3: 3d6 piercing damage (1 round)
Stage 4: 4d6 piercing damage (1 round)
I'm wondering if the damage or number of stages needs adjusting for a Level 7 affliction, but balanced around the idea it's caused by a sluggish swarm.
Beyond this affliction, the rest of the stat block looks like this:
Traits: Large, Animal, Swarm
Initiative +13
Perception +13; no vision, scent (imprecise) 30 feet, tremorsense (imprecise) 30 feet
Attributes: Str +2, Dex +4, Con +6, Int -5, Wis +4, Cha -2
AC: 25
Saves: Fort +18, Reflex +14, Will +12
HP: 85
Immunities: precision, swarm mind
Weaknesses: area 7, splash 7
Resistances: bludgeoning 7, piercing 7, slashing 3
Speed: 10 feet
Swarming bites [one-action] Each creature in the rot grub swarm's area takes 3d6 piercing damage (DC 22 basic Reflex). A creature that fails the saving throw is also exposed to Rot Grub Infestation.