Microfilaria in Human Subcutaneous Dirofilariasis: A Case Report

Abstract

Human subcutaneous dirofilariasis, a rare zoonosis is being increasingly reported from various parts of the world. Most of the reported cases have lesions in and around the eye. The adult female dirofilariae release microfilaria into the definitive host's blood. Various mosquitoes that serve as intermediate hosts such as Culex, Aedes and Anopheles take up the microfilariae (mf-L1) while feeding on an infected host. Microfilariae develop in the mosquitoes. The transmission to dogs or other hosts including humans occurs through mosquito bite during subsequent blood meal. Humans may be infected as aberrant (accidental) hosts, mainly by D. repens and D. immitis. D. repens usually resides subcutaneously, while D. immitis frequently ends up in the human lung. In human infections usually just one larva develops, which does not reach sexual maturity. In India, almost all reported cases of dirofilariasis in humans have involvement of face in the form of ocular dirofilariasis with a few reports on subcutaneous dirofilariasis. We report a case of human subcutaneous dirofilariasis, from western India, involving leg and showing microfilaria in tissue indicating presence of gravid female dirofilaria (sexual maturity). To the best of our knowledge, it is among rare cases of subcutaneous dirofilariasis wherein microfilariae have developed in human host.

The Mitochondrial Genomes of the Zoonotic Canine Filarial Parasites Dirofilaria (Nochtiella) repens and Candidatus Dirofilaria (Nochtiella) Honkongensis Provide Evidence for Presence of Cryptic Species

“…In humans as accidental hosts, Dirofilaria spp. usually do not complete their entire life cycle, although a few cases of infections with circulating microfilaria (MF) have been reported [ 11 , 12 ]. Pulmonary dirofilariosis appears to be the most common clinical presentation in humans infected with D .…”

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

“…The described case is remarkable for at least three reasons: firstly, from a biological point of view, since in humans rarely more than one adult develops, and only exceptionally mature worms meet, mate and generate active microfilariae (unusual immunotolerance of the unsuitable host). Secondly, the new-borne larvae remained inside the nodule without reaching the peripheral blood, as previously reported in only three cases [ 12 – 14 ], which makes the infection not fully patent . Finally, this is the first case of human dirofilariosis diagnosed in Italy based on microfilariae (by microscopy and molecular assays), therefore laboratories must carefully consider this diagnostic possibility when dealing with microfilariae.…”

Dirofilaria repens transmission in southeastern Finland

“…Genchi et al [ 11 ] state that, usually, D. repens parasites do not mature to adults in humans, but knew of three microfilaremic humans in Europe and one in Iran. Later, an Indian case was also reported [ 39 ].…”