Answer: Pinworm (Enterobius vermicularis eggs.
A few of you noticed that I gave the answer away on the close up image! Thanks for writing in to let me know and share your thoughts.
As you all probably know, this is an extremely rare presentation of pinworm infection. Typically, deposition of eggs by the female work in the perianal skin folds causes intense itching. It is only when the worm and/or eggs ends up in a place where they shouldn't be (e.g. genital tract, colon diverticulum or fissure) that an abscess can form, and complications arise, such as seen in this case.
The diagnosis is made by identifying the characteristic eggs, measuring approximately 50-60 microns in greatest dimension.
Salbrent had asked: "Can you tell if this is recent infection or an older one?"
I believe this manifestation (the abscess) is acute, since the inflammatory response consists of neutrophils, and there is no evidence of granulation tissue or fibrosis. As far as the infection itself however, I'm not sure if it's possible to say how long it's been going on. The adult worms only live for a few months, but autoinfection is common, so it's possible that the infection has been around longer than a few months.