Rare Case of Orbital Granuloma Caused by Coexisting Male and Female Dirofilaria repens Worms: Implications for Human Host Status

Abstract

Introduction: Dirofilariasis is a ubiquitous zoonotic infection mainly involves the canine animals. Mosquitoes acts as intermediate hosts. Humans are accidental hosts and considered dead end of the parasite transmission. D. repens typically involve the subcutaneous region presenting as a soft tissue granuloma. Possible emergence of humans as definitive host is discussed. Presentation of Case: This case report involves a 45year old male from Puducherry, India with orbital soft tissue granuloma caused by Dirofilaria repens. Histopathology of the granuloma shows presence of both male and female worms co-existing in a single lesion. The clinical, radiological, and histopathological findings are presented providing insights into this rare condition. Discussion: Humans are considered as unsuitable hosts for D.repens infestation. The larvae deposited in the subcutaneous tissue are unable to reach maturation because of the hosts defending immune system which arrests their growth leading to the development of a granuloma. Diagnosis of the condition often occurs when the dead or damaged nematodes are isolated from the patient's excised tissue. D. repens typically involve as single worm infestation in humans. Presence of both male and female worm co-existing in a single lesion is an unusual presentation. Conclusion: This case report underscores the need for awareness of rare parasitic infestations such as dirofilariasis which can mimic as soft tissue orbital granulomas, should be included in the differential diagnosis of orbital mass lesions. The unique finding of dirofilarial couple encysted in a granuloma provides evidence, humans may be emerging as a definitive host to D. repens.