Ocular dirofilariasis is a very rare parasitic disease that can occur following a mosquito bite. Mosquitoes can transmit parasite larvae from infected dogs and cats to humans.

The parasite does not complete its full life cycle in humans, but its larvae can enter the tissues of the eye, the eyelids or beneath the conjunctiva — the thin membrane covering the eye. It is in this area that the parasite is most commonly found.

An Unusual Case at the Filatov Institute

Specialists from the Pathological Anatomy Unit of the Centre for Laboratory Research at the SI ‘V.P. Filatov Institute of Eye Diseases and Tissue Therapy of the NAMS of Ukraine’, led by the Head of the Unit, Oleksandr Valentynovych Artyomov,MD, PhD, encountered an extremely rare case.

In a 7-year-old boy, the physicians identified a small nodule in the lower portion of the conjunctiva of the right eye. Its appearance was suggestive of a small neoplasm or a foreign body that had remained within the tissues for an extended period.

During surgery, the lesion, measuring only 3 × 2 mm, appeared as a small grayish-pink nodule. Thin whitish structures resembling threads could be seen inside it.

It was the laboratory analysis that enabled the true cause to be established.

What Did the Doctors Find?

During the histological examination, the specialists observed characteristic signs of dirofilariasis — a parasitic infection caused by the dirofilaria larva.

Importantly, in this case, the parasite was at an early stage of development. The child’s body had formed a protective inflammatory reaction  around it, known as a granuloma. As a result, the parasite remained small and did not develop into an adult nematode.

Why Is This Case Important?

This case demonstrates that not every small lesion of the eye is a tumor or a foreign body. In rare cases, the cause may be a parasitic infection.

Human dirofilariasis is uncommon, and its clinical manifestations may resemble those or other diseases. Therefore, accurate diagnosis depends not only on clinical examination and surgery but also on thorough laboratory and histological examination of the excised tissue.

This clinical case once again demonstrates the importance of ophthalmologists’ expertise and the capabilities of modern laboratory diagnostics.