Gorillas build leaf nests to sleep in. Do the lice which parasitise gorillas, Pthirus gorilla, remain in gorilla leaf nests after gorillas migrate to new regions (and abandon the old nests)?
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From the Wikipedia page on Pthirus gorillae: "Researchers theorize that humans acquired the parasite while butchering or scavenging on gorilla corpses, or sleeping in the abandoned sleeping nests of gorillas".
So yes, they are believed to remain.