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Year : 2011  |  Volume : 54  |  Issue : 2  |  Page : 428-430
A case of Dirofilaria immitis presenting as an intramuscular soft tissue mass

1 Department of Pathology, K.S. Hegde Medical Academy, Nithyanand Nagar, Derelakatte, Mangalore, Karnataka, India
2 Department of Surgery, K.S. Hegde Medical Academy, Nithyanand Nagar, Derelakatte, Mangalore, Karnataka, India

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Date of Web Publication27-May-2011

How to cite this article:
Teerthanath S, Hariprasad S. A case of Dirofilaria immitis presenting as an intramuscular soft tissue mass. Indian J Pathol Microbiol 2011;54:428-30

How to cite this URL:
Teerthanath S, Hariprasad S. A case of Dirofilaria immitis presenting as an intramuscular soft tissue mass. Indian J Pathol Microbiol [serial online] 2011 [cited 2021 May 14];54:428-30. Available from: https://www.ijpmonline.org/text.asp?2011/54/2/428/81620


Zoonotic filariasis, an accidental infection in human beings, is on the rise in certain parts of Southern India and is considered as an emerging zoonotic infection. Cases of zoonotic filariasis caused by filarial nematodes transmitted mostly by zooanthrophilic vectors occur worldwide, apparently with increasing incidence. [1] Human dirofilariasis has not been widely recognized in India, but there is probably a focus of infection in Kerala and the disease is relatively common in Sri Lanka, which is geographically closer to southern India. [2] There has been an increased occurrence of filarial worms in the subcutaneous tissues and subconjunctival space of human beings belonging to different areas of the state of Kerala. [2],[3] Dirofilaria infestation can manifest as a soft tissue mass, which should not be mistaken for a soft tissue tumor. Surgical exploration and an accurate diagnosis are very essential to prevent unnecessary drug abuse. We report a rare case of dirofilariasis presenting as an intramuscular swelling in a 27-year-old male from Kasargod, Kerala.

A 27-year-old presented with the complaints of swelling over his right forearm with tenderness since 6 months, which gradually increased to the present size. The patient did not give history of trauma or similar swelling in the past. On examination, a firm swelling measuring 3 × 2 cm, oval-shaped situated 6 cm below the right elbow. There was no evidence of digital neurovascular defect. Clinical diagnosis of an intramuscular neoplasm was made. Surgical exploration revealed a soft tissue swelling arising from the brachioradial muscle with a 16 cm thread-like worm entangled in it. The patient was later checked for microfilaremia by blood smear examination, and was found to be amicrofilaremic. The hematologic and biochemical investigations were within normal limits. Enzyme-linked immunosorbent assay for filarial antigen was negative.

The worm [Figure 1] was long, white, thread-like cylindrical measuring 15 cm in length and a maximum diameter of 0.25 mm. Microscopically the worm showed a slightly curved and pointed cephalic end, which was unarmed. The caudal end is bluntly rounded and well pronounced. On glycerine wet mount [Figure 2], the worm revealed a short esophagus, short tail with a patent anus, which is suggestive of the worm belonging to the family Dirofilaria. It showed a thick and smooth cuticle with 2-3 distinct layers. Muscles were separated into dorsal and ventral bands. Indistinct longitudinal ridges with cross-striations were seen. The body cavity did not contain a female reproductive system. The anus was subterminal and rounded with spicule and three pairs of large caudal papillae, one of which is postanal. Morphologically, based on the size (15 cm) and the longitudinal ridges, and cross-striations the worm was diagnosed as a male worm belonging to the species Dirofilaria immitis. The histopathologic examination of the formalin-fixed soft tissue revealed mature adult worm having longitudinal ridges, between the skeletal muscle fibers, surrounded by dense infiltration by eosinophils, histiocytes, and foreign body giant cell reaction [Figure 2].
Figure 1: Gross specimen of the worm and soft tissue mass

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Figure 2: Vertical and transverse section of Dirofilaria immitis surrounded by dense infiltration by inflammatory cells (H and E, ×100). Inset: Glycerine wet mount of the worm showing cross-striation (upper left) and cross-section of the worm showing cuticular ridges (H and E, ×400) (lower left)

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Zoonotic filariasis occurs when humans are accidentally infected by filariae normally found in animals. [3] D. immitis and Dirofilaria of the subgenus Nochtiella (repens, tenuis, ursi, subdermata) are parasites of mammals (dogs mainly) occasionally transmitted to humans. Clinical manifestations after infection include nodules in subcutaneous tissues, muscles, and visceral organs. [4] Three cases of D. repens presenting as a subcutaneous nodule have been reported in north of Iran, of which one case presented with swelling in the frontal region was reported by Athari, while Siavashi and Maseud reported two cases of D. repens infections, one causing a small nodule on the 5th finger and the other in the wrist. [5] The size, nature of the cuticles, ridges, and arrangement of the striations discussed here are indicative of D. immitis. Dirofilaria should be considered as a differential diagnosis for migratory subcutaneous swellings and conjunctival nodules in Kerala and elsewhere in Southern India. [6],[7] Humans are an accidental dead-end host. In human infection, parasite development is impaired and microfilaria is not produced. [7] However, it is important to identify the nematode as Dirofilaria to avoid treatment with antihelmintic drugs. Surgical removal of the worm is the recommended treatment.

   References Top

1.Orihel TC, Eberhard ML. Zoonotic filariasis. Clin Microbiol Rev 1998;11:366-81.  Back to cited text no. 1
2.George M, Kurian C. Conjunctival abscess due to Dirofilaria conjunctivae. J Indian Med Assoc 1978;71:123-4.  Back to cited text no. 2
3.Sabu L, Devada K, Subramanian H. Dirofilariosis in dogs and humans in Kerala. Indian J Med Res 2005;121:691-3.  Back to cited text no. 3
4.Raniel Y, Machamudov Z, Garzozi HJ. Subconjunctival Infection with Dirofilaria repens. Isr Med Assoc J 2006;8:139.  Back to cited text no. 4
5.Jamshidi A, Jamshidi M, Mobedi I, Khosroara M. Periocular dirofilariasis in a young woman: A case report. Korean J Parasitol 2008;46:265-7.  Back to cited text no. 5
6.Nath R, Gogoi R, Bordoloi N, Gogoi T. Ocular dirofilariasis. Indian J Pathol Microbiol 2010;53:157-9.  Back to cited text no. 6
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7.Sekhar HS, Srinivasa H, Batru RR, Mathai E, Shariff S, Macaden RS. Human ocular dirofilariasis in Kerala Southern India. Indian J Pathol Microbiol 2000;43:77-9.  Back to cited text no. 7
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Correspondence Address:
S Teerthanath
Department Of Pathology, K.S. Hegde Medical Academy, Nithyanand Nagar, Derelakatte, Mangalore- 575 018, Karnataka State
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0377-4929.81620

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