Dirofilaria repens microfilariae from a human node fine-needle aspirate: a case report

Area of Science:

• Veterinary Medicine
• Parasitology
• Human Infectious Diseases

Background:

• Human dirofilariosis is an underrecognized zoonotic infection, often presenting as an abortive illness in endemic regions.
• This report details a rare instance of human dirofilariosis caused by Dirofilaria repens, the first documented case in Italy.

Observation:

• A 30-year-old woman presented with migratory swelling, a subcutaneous nodule, and joint discomfort, initially suspected to be a travel-related illness.
• Ultrasound revealed a mobile filamentous structure within a subcutaneous lesion, and fine-needle aspiration detected microfilariae.
• Initial identification of microfilariae was Mansonella ozzardi, but subsequent molecular analysis confirmed Dirofilaria repens.

Findings:

• Microfilariae were detected in a fine-needle aspirate of a subcutaneous nodule, but not in peripheral blood (no microfilaraemia).
• Despite the absence of peripheral microfilariae, molecular and morphological analyses confirmed the presence of mature Dirofilaria repens.
• This indicates that adult Dirofilaria repens worms can achieve complete development and fertilization within a human host.

Implications:

• This case challenges the established understanding that Dirofilaria worms typically undergo abortive development in humans.
• It suggests that complete parasitic development and reproduction of Dirofilaria repens are possible in human hosts, even without patent infection.
• Further research is warranted to understand the full spectrum of human dirofilariosis and its implications for public health in endemic and non-endemic areas.