Dirofilaria repens is a filarial nematode that affects dogs and other carnivores. As with other filaria species, mosquitoes transmit infectious microfilariae.
Humans may become infected as aberrant hosts which usually manifest as a single subcutaneous nodule. However, subcutaneous migration of the worm may be seen.
Infections have been reported from various regions of the world, mainly from Europe, Africa, and Asia.
This brings me to an interesting case reported in The New England Journal of Medicine, which describe a migrating case:
A 32-year-old woman presented to an ophthalmologist with a 2-week history of nodules that moved around her face. She had first noted a nodule below her left eye. Five days later, it had moved to above her left eye, and 10 days after that to the upper lip.
The nodules occasionally caused a localized itching and burning sensation, but otherwise she had no symptoms.
She had recently traveled to a rural area outside Moscow and recalled being frequently bitten by mosquitoes.
A physical examination showed a superficial moving oblong nodule at the left upper eyelid. A parasite was fixed with forceps and removed surgically. The parasite was identified by means of a polymerase-chain-reaction assay as Dirofilaria repens.
See photos at the NEJM